Download Life Changes - Miami Museum of Science

Life Changes:
Essentials for museum professionals
Prepared for the New York Hall of Science
by the University of California Museum of Paleontology
Contents
I. Exhibit overview and rationale............................................................................................................... 3
II. Key concepts and questions ................................................................................................................... 4
 What is the theory of evolution? ................................................................................................ 4
 How does evolution happen? ...................................................................................................... 5
 What does it mean to say that dinosaurs and birds are related?............................................ 6
 How did dinosaurs evolve into birds?........................................................................................ 7
 How did we end up with so many different kinds of birds today? ......................................... 9
 How do scientists study evolution? How do we know that evolution has occurred? ......... 10
 Why is evolution so important? ............................................................................................... 12
III. Short FAQs.......................................................................................................................................... 13
IV. Correcting misconceptions ................................................................................................................. 16
V. Avoiding potential pitfalls.................................................................................................................... 22
VI. Dealing with controversy in the museum.......................................................................................... 24
VII. Factsheets: .......................................................................................................................................... 26
 Kiwi factsheet............................................................................................................................. 26
 Hawaiian honeycreeper factsheet ............................................................................................ 27
 Peppered moth factsheet........................................................................................................... 28
 Archaeopteryx factsheet ........................................................................................................... 29
 Bambiraptor factsheet .............................................................................................................. 30
 Feathered (but non-avian!) dinosaur factsheet....................................................................... 31
 Tree of life factsheet .................................................................................................................. 32
 Timeline of evolution factsheet................................................................................................. 34
VII. Background information links ......................................................................................................... 35
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
2
I. Exhibit overview and rationale
***to be provided by NYHS
Learning goals
Not everyone who experiences the exhibit will learn the same things from it. Here is a summary of the
key evolutionary concepts that we hope visitors of different ages can learn through their experiences with
this exhibit.
5- to 7-Year olds and up:
o The natural world is diverse; there are many different species.
o Individual organisms of the same species vary from one to the next.
o This variation can be adaptive in particular environments and improve the organism's chances of
survival.
o Different species of organisms are adapted to different environments.
o Parents and offspring look alike.
o Dinosaurs and birds are related.
o Dinosaurs and birds share common features.
8- to 9-year olds and up:
o If the environment changes (e.g., different source of food; temperature change) only those
organisms that possess features that are adaptive in the changed environment will survive.
o The surviving organisms will pass those features to their offspring.
o Those offspring will vary—not all of them will possess those adaptive features.
o Dinosaurs lived a long time ago.
10- to 12-year olds and up:
o Those animals with features that increase their chances of survival in a particular environment are
more likely to pass these features onto their offspring.
o Over many generations, this will lead to changes in the population.
o Birds evolved from dinosaurs.
o Features shared between birds and dinosaurs are evidence of their common ancestry.
o Dinosaurs lived millions of years ago.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
3
II. Key concepts and questions
Here are some quick answers to key questions that visitors may ask regarding Life Changes.
 What is the theory of evolution?
Biological evolution, simply put, is
descent with modification. This definition
encompasses small-scale evolution
(changes in gene frequency in a population
from one generation to the next) and largescale evolution (the descent of different
lineages—like kiwis and penguins—from a
common ancestor over many generations).
Biological evolution is not simply a matter
of change over time. Lots of things change over time: trees lose their leaves, mountain ranges rise and
erode, but they aren't examples of biological evolution because they don't involve descent through genetic
inheritance.
gene frequency – proportion of gene versions in a population that are of a particular type.
common ancestor – an ancestral lineage that two or more descendent lineages have in common.
The central ideas of evolutionary theory are that life has a history — it has changed over time —
and that different species share common ancestors, just as you and your cousins share a common
grandmother. Through the process of descent with modification, the common ancestor of life on Earth
gave rise to the fantastic diversity that we see documented in the fossil record and around us today.
Evolution means that we're all distant cousins: humans and oak trees, hummingbirds and whales.
Evolution is a scientific theory—but in science, the word theory means much more than a guess or a
hunch. Scientific theories are broad explanations for a wide range of phenomena, and in order to be
accepted by the scientific community (as evolution is), they must be supported by many lines of
evidence, help us understand a wide range of observations, and make predictions in new situations.
Evolution is the very best scientific explanation for the diversity and history of life, and there is no
controversy in the scientific community over its acceptance.
> To learn more about nature of science and how evolution fits into this framework, see
http://evolution.berkeley.edu/evolibrary/article/nature_01
Exhibit examples: Small-scale evolutionary change is represented in several ways in the exhibit.
Dinosaurs with feathers do better than dinosaurs without feathers. They leave behind more offspring—
which happen to inherit their parents’ feathers. As this process continues over many generations,
feathered dinosaurs become more and more frequent in the population. Similarly, the discovery box Who
survives shows how small-scale evolution can occur in a population of moths. Large-scale evolutionary
change is emphasized by other aspects of the exhibit: the evolution of birds from dinosaurs, the evolution
of the suite of unique characters that make kiwis kiwis, and the diversification of honeycreepers from a
common ancestor in the Honeycreeper Puzzle.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
4
 How does evolution happen?
Natural selection is one of the key mechanisms of evolution (though there are others). Natural selection
is responsible for the close fit between organisms (e.g., a drought-tolerant cactus) and their
environments (e.g., the Sonoran desert). Natural selection involves four ingredients (VIST) and results
in adaptation (A):
V = Variation: All life forms vary genetically within a population.
I = Inheritance: Genetic traits are inherited from parents and are passed on to offspring.
S = Selection: Organisms with favorable traits are more likely to survive and pass on their genes.
T = Time: Over time, this results in . . .
A = Adaptation: A trait that increases the survival and reproduction of its bearers.
To see how it works, imagine a population of grounddwelling birds:
1. There is variation. Some birds have short beaks and
some birds have longer, pointier beaks
2. There is selection. The longer-beaked birds can catch
more bugs, get more nourishment, and produce more
offspring than short-beaked birds.
3. There is inheritance. Beak length has a genetic basis,
so the offspring of long-beaked birds also have long
beaks.
4. Over time, the more advantageous trait, long beaks,
which allows the birds to have more offspring, becomes
more common in the population. If this process
continues, eventually, all individuals in the population
will be long-beaked.
If you have variation, selection, and inheritance, you will
have evolution by natural selection as an outcome. Over short periods of time, this process increases the
frequency of favorable gene versions in a population. Over long periods of time, these small changes
can accumulate, resulting in the evolution of new complex adaptations and new species.
> To learn more about natural selection and other mechanisms of evolution, see
http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_14
Exhibit examples: Natural selection is represented in several ways in the exhibit: the spread of feathers in
the dinosaur population, the evolution of kiwi adaptations suited to ground-dwelling, the evolution of the
moth population in Who survives, the evolution of honeycreeper traits suited to their environments, and
the evolution of bird beaks specialized for different foods. The components of VISTA are emphasized by
different discovery boxes and different aspects of the exhibit.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
5
 What does it mean to say that dinosaurs and birds are related?
The process of evolution produces a branching pattern of relationships between species. As lineages
evolve and split and modifications are inherited, their evolutionary paths diverge. This means that
different species share common ancestors. So when we say that dinosaurs and birds are related, we mean
that they share common evolutionary ancestors—just as you and your cousins share common ancestors
(e.g., your grandparents). In fact, birds evolved from dinosaurs. The first organisms we’d call birds
evolved more than 150 million years ago from a group of dinosaurs known as the Maniraptorans.
By studying species' inherited characteristics and other historical evidence, we can reconstruct
evolutionary relationships and represent them on a “family tree,” called a phylogeny. This is a
phylogeny showing how birds are related to other dinosaurs:
You can see that the relationship between birds and dinosaurs is close. In fact, because of how biologists
classify organisms, technically, birds are dinosaurs. That’s because biologists classify organisms based
on their evolutionary histories. They only gives names to branches of the tree of life—groupings called
clades. Since birds evolved from dinosaurs, there’s just no way to clip a single branch from the tree above
that includes Triceratops and T. rex, but excludes birds. That means that birds are on the dinosaur branch
(i.e., in the dinosaur clade)—and hence, are a type of dinosaur. This is cool because it means that
dinosaurs are not extinct! In fact, there might be dinosaurs nesting in your tree at this very moment.
Scientists call dinosaurs that are not birds “non-avian dinosaurs”—and they are extinct.
clade - grouping that include an ancestor and all the organisms (whether living or extinct) descended from that ancestor.
> To learn more about family trees in evolution, see our factsheet on the tree of life (pg. 32) and
http://evolution.berkeley.edu/evolibrary/article/phylogenetics_01
Exhibit examples: The evolution of birds from dinosaurs is explained in Charlie’s and Kiwi’s story.
Some of the evidence supporting this relationship is also shown in the display highlighting structures that
dinosaurs, Archaeopteryx, and modern birds all share.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
6
 How did dinosaurs evolve into birds?
Dinosaurs evolved into birds in little steps over millions of years. The features that we recognize as
key characteristics of modern birds—feathers, the wishbone, hollow leg bones, an s-shaped neck, etc.—
did not evolve all at once. This phylogeny shows where in the evolutionary history of birds and other
dinosaurs different features evolved. The lineage in which the feature first evolved is marked with a dash.
That lineage passed the trait on to its descendents.
From the phylogeny, you can see that not all of the traits necessary for flight evolved at once—for
example, birds’ ancestors evolved a lighter skeleton through hollow vertebrae and leg bones long before
they evolved feathers. This means that the traits useful for flying must have first evolved in some
other context (e.g., under natural selection for some other function) and were later co-opted for
flight. Natural selection is an excellent thief, taking features that evolved in one context and using them
for new functions.
Exhibit examples: The display highlighting structures that dinosaurs, Archaeopteryx, and modern birds
all share includes the small meat-eating dinosaur Bambiraptor. This dinosaur had feathers but could not
fly, demonstrating that feathers must have evolved in some context other than that of flight.
The most obvious trait necessary for flight is wings. How did they evolve? Like other complex
adaptations, wings must have evolved in small steps, becoming larger and more wing-like over the course
of many thousands of generations. In the early part of this evolutionary transition, wings wouldn’t have
been any good at flying but must have served some adaptive function. There are many hypotheses about
why wings might have offered a survival and reproductive advantage in their early stages:
o They may have been useful in capturing small prey.
o They may have helped with leaping into the air.
o They may have helped with running up steep slopes.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
7
o They may have been used to attract the attention of potential mates.
o They may have used for gliding.
Scientists are still gathering evidence to try to figure out which of these explanations is most likely to be
correct.
hypothesis – a proposed explanation for a fairly narrow set of phenomena, usually based on prior experience, scientific
background knowledge, preliminary observations, and logic. A hypothesis must be testable with evidence from the natural
world. If an explanation can't be tested with experimental results, observation, or some other means, then it is not a scientific
hypothesis.
Along the same lines, feathers evolved in small steps. Based on fossil evidence, we think that the first
feathers were simple affairs—little more than fuzz. But through many generations of random mutation
and natural selection, they evolved into more elaborate structures. Scientists are still investigating the
genetic changes that could have helped form early feathers and are making progress in this area. Feathers
evolved in dinosaurs long before any of them had evolved the ability to fly or even wings—so in their
early stages, feathers must have been useful for some other function. Insulation and thermoregulation are
good hypotheses for the original function of feathers, but this question is still being actively investigated.
> To learn more about the evolution of complex innovations, see
http://evolution.berkeley.edu/evolibrary/article//evo_53 and
http://evolution.berkeley.edu/evolibrary/article/side_0/complexnovelties_01
> To learn more about the early evolution of feathers, see our factsheets on Bambiraptor and feathered
dinosaurs (pgs. 30-31).
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
8
 How did we end up with so many different kinds of birds today?
Two hundred million years ago, birds did not yet exist. Today, they are the most diverse terrestrial
vertebrates, with around 10,000 known species. How did this happen? Through speciation. The
ancestral bird branch—the dinosaur lineage that scientists consider to be the first bird—split, or speciated,
into two separate lineages. These descendent lineages split again and again, and those descendents
diversified further. Many of the major splits in the bird clade occurred during the Cretaceous alongside
non-Avian dinosaurs like T. rex. Despite many extinctions along the way, birds eventually diversified
into the wide array of bird species on Earth today.
Exactly how does speciation or
lineage-splitting occur? Scientists
think that geographic isolation
is a common way for the
process of speciation to begin:
rivers change course, mountains
rise, continents drift, organisms
migrate, and what was once a
continuous population is divided
into two or more smaller
populations. This barrier
prevents two parts of a population from mating with one another. While they are isolated, the two parts of
the population evolve genetic differences from one another—often because the habitats they each occupy
are different and natural selection favors different traits in the two groups. Eventually, after many
generations, the two groups have evolved so many differences that, even if they are reunited, they
would not or could not successfully mate with one another. These need not be huge genetic
differences. A small change in the timing, location, or rituals of mating could be enough. But still, some
difference is necessary. At this point, speciation has occurred.
Speciation may be facilitated if there are many unfilled niches available—perhaps because a mass
extinction has left them open or because a lineage has evolved a key innovation that allows it to take
advantage of resources and space that other organisms cannot. It is easy to imagine that flight was a key
innovation that facilitated the diversification of birds. Scientists are currently studying this time in birds’
evolutionary history to try to learn more about how and why they diversified.
species – members of populations that actually or potentially interbreed. In this sense, a species is the largest gene pool
possible under natural conditions
mass extinction – event in which many different lineages go extinct around the same time. Mass extinctions involved higher
rates of extinction than the usual rate of background extinction that is going on all the time.
> To learn more about speciation and macroevolution, see
http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_40 and
http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_47
Exhibit examples: Speciation is responsible for the diversity of birds and other dinosaurs showcased in
the exhibit. It is particularly salient to the diversity of closely related birds seen in the honeycreeper
puzzle.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
9
 How do scientists study evolution? How do we know that evolution has
occurred?
We can’t directly observe the past, but we can gather evidence available today in order to figure out what
happened in the past—much as crime scene investigators collect evidence to try to figure out how and
why a particular crime was committed. Overwhelming evidence supports the idea that life has existed
for billions of years and has changed over time. Scientists continue to argue about details of evolution,
but the question of whether life has evolved was answered in the affirmative at least two centuries ago.
Here are a few of the lines of evidence that have convinced us of this fact:
o The fossil record. The fossil record provides snapshots of the past that, when assembled, illustrate
a panorama of evolutionary change over the past four billion years. For example, paleontologists
have found many examples of fossil organisms that show the intermediate states between an
ancestral form and that of its descendants.
o Homologies. Evolutionary theory predicts that related organisms will share similarities that are
inherited by different lineages from their common ancestor. Similar characteristics due to
relatedness are known as homologies. Homologies can be revealed by comparing the anatomies of
different living things, looking at cellular similarities and differences, studying embryological
development, and studying vestigial structures within individual organisms. We observe
homologies across the tree of life.
vestigial structure – a feature that an organism inherited from its ancestor but that is now less elaborate and functional than in
the ancestor. Usually, vestigial structures are formed when a lineage experiences a different set of selective pressures than its
ancestors, and selection to maintain the elaboration and function of the feature ends or is greatly reduced.
o Dating techniques. The ages of the Earth and its inhabitants have
been determined through two complementary lines of evidence:
relative dating and radiometric dating. Relative dating places
fossils in a temporal sequence by noting their positions in layers of
rocks. Radiometric dating relies on the decay of radioactive
elements, such as uranium, potassium, rubidium, and carbon. Very
old rocks must be radiometrically dated using volcanic material.
By dating volcanic ash layers both above and below a fossilbearing layer, as shown in the diagram, you can determine “older
than X, but younger than Y” dates for fossils. Sedimentary rocks
less than 50,000 years old can be dated using their radioactive
carbon content.
o Geography. The distribution of living things on the globe provides
information about the history of life and of the Earth. This
evidence is consistent not just with the evolution of life, but also
with the movement of continental plates around the world.
o Observations of modern organisms. There are many ways we can look at present-day
organisms, as well as recent history, to better understand what has occurred through deep time: (1)
Artificial selection in agriculture or laboratories provides a model for natural selection. (2)
Looking at interactions of organisms in ecosystems helps us to understand how populations adapt
over time. (3) Experiments demonstrate selection and adaptive advantage. (4) And finally, we can
observe evidence of evolution in the way that the diversity of life is arrayed. Evolutionary theory
leads us to expect that living things should be arrayed in nested hierarchies of groups within
groups within groups, delineated by the characteristics they inherited from their ancestors. This is
indeed what we observe in the living world and is strong evidence supporting evolutionary theory.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
10
The following lines of evidence have been particularly important in helping scientists figure out that birds
evolved from dinosaurs and how this occurred:
o Studies of fossil birds and dinosaurs
o Anatomical studies of birds, dinosaurs, and other organisms
o Genetic studies of modern birds
o Observations of modern bird behavior
o Studies of bird movement
o Knowledge of aerodynamics
Exhibit examples: The exhibit includes information on several lines of evidence relevant to evolutionary
theory: the fossil Archaeopteryx, the homologies shared by Bambiraptor, Archaeopteryx, and modern
birds, and the homologies between bird and bat wings (in the We can fly discovery box).
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
11
 Why is evolution so important?
Evolution is of practical importance. Because biological systems evolve, solutions to biological
problems that don’t take evolution into account are likely to fail. Here are just a few ways that
evolution helps us solve practical problems:
o In medicine. Because both disease-causing organisms and their victims evolve, understanding
evolution can make a big difference in how we treat disease. For example, bacteria and viruses
reproduce rapidly and so evolve rapidly. These short generation times mean that natural selection
acts quickly. In each pathogen generation, new mutations and gene combinations are generated
that then pass through the selective filter of our drugs and immune response. Over the course of
many pathogen generations (a small fraction of a single human lifetime), they adapt to our
defenses, evolving right out from under our antibiotic and antiviral drugs. By understanding these
pathogens as evolving entities, scientists are developing new drugs to treat them and providing
doctors and patients with guidelines for extending the useful life of our existing drugs.
o In agriculture. Crops, livestock, pests, and crop diseases evolve—so in the field of agriculture,
just as in medical science, evolution matters. For example, understanding the evolutionary history
of domestic crops and other organisms helps scientists identify valuable stores of genetic
variation. Corn viruses can seriously damage crops unless resistant varieties are grown. So where
do we get resistant varieties? Many are genetically engineered using genes found in closely
related plant species. In this case, an evolutionary perspective—one that considers the history of
corn—can point scientists searching for these genes towards the closest living relative of modern
corn, teosinte. Using genes from the teosinte species Zea diploperennis, scientists have developed
several virus-resistant domestic corn varieties.
o In conservation. Understanding evolution can also help us protect Earth’s dwindling biodiversity.
For example, determining the population size at which a species becomes threatened is important
for our conservation efforts. Without evolutionary theory, one might imagine that a fairly small
population—just enough to breed—would be sufficient to repopulate a species. However,
according to evolutionary theory, very small populations face two dangers—inbreeding depression
and low genetic variation—that might keep them from recovering, despite our best efforts to
preserve them. Taking evolution into account allows us to plan our conservation efforts more
realistically.
mutation – a change in a DNA sequence, usually occurring because of errors in DNA copying or repair. Mutation is the
ultimate source of genetic variation.
inbreeding depression – decreased health and reproductive capacity experienced by the offspring produced through the mating
of close relatives.
genetic variation – loosely, a measure of the genetic differences within populations or species. For example, a population with
many different versions of a particular gene may be said to have a lot of genetic variation for that gene. Genetic variation is
essential for natural selection to operate since natural selection can only increase or decrease frequency of gene versions
already in the population.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
12
III. Short FAQs
 How long does it take for evolution to happen?
It depends on which organism is evolving and what kind of evolution you are interested in. Here are a
few examples:
• Shift in gene frequency in bacterial populations (e.g., evolution into a largely antibiotic
resistant strain): hours or days
• Shift in gene frequency in human populations (e.g., evolution favoring genes that let
individuals digest milk): hundreds or thousands of years
• Early stages of speciation in flies: 200 years
• Evolutionary transition from fish ancestors to walking vertebrates: tens of millions of years
 How did life start?
Three and a half billion years ago, life originated in a series of small steps, each building upon the
complexity that evolved previously. First, simple organic molecules formed, possibly near an oceanic
hydrothermal vent or a hot spring. Then, molecules that could copy themselves evolved and began to
undergo natural selection. Eventually those replicating molecules became enclosed within a cell
membrane and evolved into organisms we would recognize as alive. Science can help us reconstruct the
steps and natural processes through which life evolved.
 How do we get new species?
Though there many ways that new species can arise, biologists think that the following process is
common: a population is split into two sub-populations by some geographic barrier, the two subpopulations evolve in isolation, and eventually the sub-populations evolve so many differences that—
even if they were reunited—they would not or could not successfully mate with one another. At this
point, speciation has occurred: a single ancestral species has evolved into two separate daughter species.
 Where does new variation come from?
The ultimate source of genetic variation is random mutation. Mutations are "random" in the sense that the
sort of mutation that occurs cannot generally be predicted based upon the needs of the organism. So, for
example, in the exhibit, the gene variants that caused some baby dinosaurs to have fuzz originally arose
through the process of random mutation. However, once the gene variant was present in the population, it
spread through the nonrandom process of natural selection. The offspring of two parents are all slightly
different from one another because they each got slightly different combinations of gene versions from
their parents—but the ultimate source of those gene versions is random mutation.
 What’s the difference between microevolution and macroevolution?
Microevolution is what biologists call evolutionary change that occurs within a single population or
species (e.g., an increase in the frequency of dinosaurs with tiny feathers from one generation to the next).
Macroevolution is what biologists call evolutionary change that occurs on a scale that transcends the
boundaries of a single species (e.g., the evolution and radiation of the dinosaur lineage into many different
species of non-avian dinosaurs and birds). Despite their differences, evolution at both of these levels relies
on the same, established mechanisms of evolutionary change: mutation, migration, genetic drift, and
natural selection.
genetic drift – random changes in the gene frequencies of a population from generation to generation. This happens as a result
of sampling error — some individuals just happen to reproduce more than others, not because they are “better,” but just
because they got lucky. This process causes gene frequencies in a population to drift around over time. Some genes may even
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
13
“drift out” of a population (i.e., just by chance, some gene may reach a frequency of zero). In general, genetic drift has the
effect of decreasing genetic variation within a population.
 Who came up with the idea of evolution?
Charles Darwin championed the idea that species evolved from common ancestors, and he and Alfred
Russel Wallace came up with the idea of natural selection as a mechanism of evolution, but other
evolutionary ideas were around long before Darwin and Wallace. For example, in the 1700s, GeorgesLouis Leclerc Buffon argued that life was extremely old and had changed over time, and in the early
1800s, Jean Baptiste Lamarck proposed several ideas about the mechanisms through which life might
evolve.
 Do scientists still think that Darwin was right?
Many lines of evidence and decades of research support Darwin’s central ideas—that evolution occurs
through natural selection and that different species share common ancestors. In fact, Darwin’s writing
anticipated many of the key components of modern evolutionary theory. However, scientists now think
that Darwin was wrong about some things (e.g., his ideas about the mechanism of inheritance). And, of
course, Darwin didn’t anticipate all parts of modern evolutionary theory (e.g., genetic drift). As scientists
find new lines of evidence and new ways of explaining that evidence, their ideas about the how the world
works change. This is a normal part of science—so the fact that scientists now reject some aspects of
Darwin’s thinking about evolution is not surprising and reflects normal scientific progress.
 What happened to the dinosaurs?
Some dinosaurs evolved into birds and remain alive today. However, many dinosaur lineages—along
with tons of other sorts of organisms—went extinct about 65 million years ago at the end of the
Cretaceous period. Their extinction was probably related to a massive asteroid that struck Earth and that
may have thrown up a sun-blotting cloud of dust and ignited wildfires and/or oil deposits. Around the
same time, the earth was also experiencing climate change and significant volcanic activity that may have
further contributed to the extinctions.
 Did humans evolve from chimpanzees?
No. Humans did not evolve from chimpanzees. Humans and chimps are both modern organisms. Our
relationship is more like that of cousins than that of children to their parents. We share a recent common
ancestor with one another. That ancestor was neither chimp nor human—but it was an ape. This means
that, technically, humans are considered to be apes—just as we are considered to be primates, mammals,
vertebrates, and animals.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
14
 Are humans still evolving?
Since evolution is simply changes in gene frequency in a population from one generation to the next, the
answer to this question is almost certainly “yes.” At the very least, the frequencies of different gene
versions change a small amount each generation due to genetic drift. However, more significant
evolutionary change may be occurring as well. For example, genes for resistance to HIV may be
spreading in some populations, and other genes correlated with producing fewer offspring may be
decreasing in frequency. Though this is an area of active research, one thing is for certain: modern
humans have changed the ways that natural selection can act on us. Our ability to mediate our
environments with technology—to keep ourselves warm, to treat diabetes with insulin, and to provide
food for those without farming, hunting, or gathering skills, amongst a myriad of other cultural
innovations—has changed our evolutionary landscape. So, for example, because of the availability of
insulin in many developed countries, the gene versions that contribute to juvenile diabetes are no longer
strongly selected against. But this sort of technological innovation doesn’t necessarily mean that we've
stopped evolving. It may just be indicative of the changing rules of the evolutionary game that we humans
are playing today.
 Is evolution against religion?
The idea that one always has to choose between science and religion is incorrect. Of course, some
religious beliefs explicitly contradict science (e.g., the belief that the world and all life on it were created
in six literal days); however, most religious groups have no conflict with the theory of evolution or other
scientific findings. In fact, many religious people, including theologians, feel that a deeper understanding
of nature actually enriches their faith. Moreover, in the scientific community there are thousands of
scientists who are devoutly religious and also accept evolution.
 Why doesn’t this exhibit discuss God’s role in evolution or creationism?
Religion and science are very different things. In science, only natural causes are used to explain natural
phenomena, while religion deals with beliefs that are beyond the natural world. Creationism deals with
supernatural explanations and so is not a part of science. Because this is a science exhibit in a science
museum, it is only appropriate to address scientific explanations. This exhibit is not a denouncement of
religion; in fact, many people have no problem at all reconciling acceptance of evolution with religious
faith and find that an understanding of science enriches their appreciation of the natural world.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
15
IV. Correcting misconceptions
Many visitors are likely to have misconceptions about how evolution works and what its implications are.
Evolution can be tricky to understand for many reasons:
• it may occur over huge lengths of time that we have no direct experience with
• it involves changes in species, which may seem like fixed entities on human timescales
• it depends on variation within a population, but that variation is often subtle and non-obvious
• it results in adaptations that are well suited for their function, but does not rely on a conscious agent
trying, wanting, or intending those adaptive changes to occur
To make your job even more difficult, some Creationist groups actively promote misconceptions.
As a docent, you can help clarify these issues by familiarizing yourself with some common
misconceptions and following these tips:
• Actively listen to visitors’ viewpoints.
• As you offer explanations, be sure to recognize what is correct or reasonable about the visitor’s
viewpoint. A learner can modify and rebuild their existing conceptions into more productive and
accurate concepts.
• Avoid telling visitors that they are simply “wrong.”
• Multiple concrete examples often help learners grasp abstract concepts.
• Avoid reinforcing misconceptions. Don’t use intentional language (e.g., needs, wants, tries) to
explain how adaptations came about.
• Be respectful but clear about how science works and what is and is not science.
• Recognize when to end the conversation.
 Misconception: Evolution means that life changed randomly or by chance.
Response: Chance is certainly a factor in evolution, but there are also non-random evolutionary
mechanisms. Random mutation is the ultimate source of genetic variation; however, natural selection is
not random. For example, some aquatic animals are more likely to survive and reproduce if they can
move quickly through water. Speed helps them to capture prey and escape danger. Animals such as
sharks, tuna, dolphins and ichthyosaurs have evolved streamlined body shapes that allow them to swim
fast. As they evolved, individuals with more streamlined bodies were more likely to survive and
reproduce. Individuals that survive and reproduce better in their environment will have more offspring
(displaying the same traits) in the next generation. That's non-random selection. To say that evolution
happens “by chance” ignores half of the picture.
Exhibit examples: Feathered dinosaurs didn’t evolve randomly. The genes for feathers spread because
feathered dinosaurs were able to leave behind more offspring than those without feathers. That’s not
random.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
16
 Misconception: Natural selection involves organisms “trying” or “wanting” to adapt.
Response: Natural selection leads to adaptation, but the process doesn't involve “trying.” Natural
selection relies on heritable genetic variation and selection among variants present in a population. Either
an individual has genes that are good enough to survive and reproduce, or it does not — but it can't get the
right genes by “trying.”
Exhibit examples: Feathered dinosaurs didn’t try to acquire feathers. It doesn’t matter how much an
unfeathered dinosaur might need them or want them; it can only get feathers if it happens to inherit the
genes for feathers from its parents. Trying, wanting, and needing have nothing to do with it.
 Misconception: Acquired characteristics can be inherited.
Response: Traits that organisms acquire through interactions with the environment (e.g., strong muscles
through exercise, short hair through a haircut, the ability to speak Swahili through Swahili lessons) are not
passed on to offspring. Only traits encoded somewhere in the parents’ genes can be inherited, and
interacting with the environment in these ways (exercising, visiting a barber, Swahili lessons) cannot
affect the content of one’s genes. You might wonder then, where new genetic traits come from if not the
environment. New genetic traits can only be acquired through mutation and recombination. Random
mutation alters the DNA of reproductive cells, and recombination creates new combinations of genes
within those cells. The offspring that are produced by those cells will then carry new gene versions or
new combination of genes, and this may affect what traits they have. The new traits have nothing to do
with the sort of environment the parent has experienced, but are instead the product of random processes.
The new traits may or may not be a good fit for the environment. If they are a good fit, natural selection
will increase their frequency in subsequent generations, and if they are not, their bearers are unlikely to
produce many offspring.
Exhibit examples: In Charlie’s story, baby dinosaurs get feathers because they inherit them from their
parents, not because they experience cold weather. Similarly, the moths in Who survives don’t become
dark or light because of the color of the tree bark they sit on. Furthermore, a number of the discovery
boxes emphasize that genetic inheritance is the reason that offspring have the traits they do.
recombination – a process in which pairs of chromosomes swap DNA with one another. This happens during gamete
formation. A single parent cell (containing two sets of chromosomes) will form four daughter cells (with one complete set of
chromosomes each). In the process of forming these daughter cells, recombination happens so that the chromosomes the
daughter cells have are “mosaic,” composed of different pieces of the parent cells' chromosomes. Recombination is important
for evolution because it brings new combinations of genes together — a source of variation for natural selection to act upon.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
17
 Misconception: Genes can skip generations.
Response: You’ve probably observed traits that seem to “skip” generations (e.g., a grandma and
granddaughter both have red hair while the mother has brown hair), but this doesn’t mean that the genes
that encode those traits are jumping around. We all inherit half of our genetic material from our mothers
and half from our fathers. Whether or not the traits encoded in our genes actually show up in our bodies
often depends on exactly what combination of gene versions we get from our parents. You might carry
one gene for red hair (that you inherited from your mom)—but if you inherited a gene for brown hair
from your dad, you won’t have red hair. In other words, you can “carry” the gene for red hair without
actually having red hair. The gene itself is still there—it didn’t “skip” you. Genes can “go stealth” for
many generations if they never happen to wind up in combination with the right gene version. So a greatgreat-great-grandma might pass the gene for red hair on to her great-great-great-granddaughter without
the trait showing up in any of the intervening generations.
Exhibit examples: One of the discovery boxes (Pieces of the past) mentions features that skip
generations. Other discovery boxes deal with genetic inheritance. It is important that you, as a docent,
keep in mind the actual mechanisms behind inheritance to help visitors overcome their misconceptions.
 Misconception: Evolution is transformative; individual organisms evolve.
Response: Populations evolve over the
course of generations; individuals do not
evolve within the course of single lifetime.
Of course, an individual may change over
the course of his or her life through growth
and development—but this is different from
biological evolution. In biological
evolution the frequency of different traits in
a population changes from generation to
generation.
Exhibit examples: Charlie’s story
clearly illustrates that the evolution of
feathers takes place over the course of
many generations, not an individual’s
lifetime. Furthermore, text in the main
exhibit is designed to clarify this point.
 Misconception: Evolution is like a
climb up a ladder of progress;
organisms are always getting better.
Response: It is true that natural selection
weeds out individuals that are unfit in a
particular situation, but for evolution, “good
enough” is good enough. No organism has
to be perfect. For example, many groups of
organisms (like some mosses, protists,
fungi, sharks, opossums, and crayfish) have changed little over great expanses of time. They are not
marching up a ladder of progress. Rather, they are fit enough to survive and reproduce, and that is all that
is necessary to ensure their existence. Other taxa may have changed and diversified a great deal — but
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
18
that doesn't mean they got “better.” After all, climates change, rivers shift course, new competitors invade
— and what was “better” a million years ago, may not be “better” today. What works well in one location
might not work so well in another. There is no universal scale that we can use to measure which
organisms are “better” than others.
Exhibit examples: The relative scale of what is “better” in evolutionary terms is illustrated by Charlie’s
story. Flying is obviously advantageous for many birds, but wasn’t “better” for kiwis. Many of the other
exhibit features emphasize that what is advantageous depends on the situation the organism is in (e.g., the
“best” color for moths depends on the color of the tree bark and the “best” beak shape for birds depends
on the food sources available).
 Misconception: Evolution always leads to increased complexity.
Response: Not necessarily. Sometimes it does. Sometimes it doesn’t. If we simply compare the forms
of life that were probably around 3.5 billion years ago to the life forms that are around today, it is obvious
that the “average” level of complexity is higher today than it was at life's origins. (Although this is
probably just because, when life started out, it was at its lowest limit of complexity. It had nowhere to go
but up!) On the other hand, there are many cases of simplification in evolution—for example, some
insects have lost their wings through the course of their evolutionary history. And keep in mind that a lot
of “simple” organisms are still around and are incredibly successful. The entire history of life could be
referred to as the “Age of Bacteria” because bacteria have been, and still are, ubiquitous since the
beginning of life on Earth.
Exhibit examples: Though the ability to fly is arguably more advanced or “complex” than not being able
to fly, some birds (including the kiwi) have lost this ability through evolution.
 Misconception: Natural selection gives organisms what they “need.”
Response: Natural selection has no intentions or senses; it cannot sense what a species “needs.” If a
population happens to have the genetic variation that allows some individuals to survive a particular
challenge better than others, then those individuals will have more offspring in the next generation, and
the population will evolve. If that genetic variation is not in the population, the population may still
survive (but not evolve much) or it may die out. But it will not be granted what it “needs” by natural
selection.
Exhibit examples: In Charlie’s story, baby dinosaurs get feathers because they inherit them from their
parents, not because they need them for protection from cold weather. Similarly, the moths in Who
survives don’t become dark or light because they need that color for camouflage.
 Misconception: Evolution is “just” a theory.
Response: Scientific theories are explanations that are based on lines of evidence, enable valid
predictions, and have been tested in many ways. In contrast, there is also a popular definition of theory —
a “guess” or “hunch.” These conflicting definitions often cause unnecessary confusion about evolution.
 Misconception: Evolution is a theory in crisis and is collapsing as scientists lose confidence in it.
Response: Scientists do not debate whether evolution (descent with modification) took place, but they do
argue about how it took place. Details of the processes and mechanisms are vigorously debated.
Antievolutionists may hear the debates about how evolution occurs and misinterpret them as debates
about whether evolution occurs. Evolution is sound science and is treated accordingly by scientists and
scholars worldwide.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
19
 Misconception: Gaps in the fossil record disprove evolution.
Response: The fact that some transitional fossils are not preserved does not disprove evolution.
Evolutionary biologists do not expect that all transitional forms will be found and realize that many
species leave no fossils at all. Lots of organisms don't fossilize well, and the environmental conditions for
forming good fossils are not that common. So, scientists actually expect that for many evolutionary
changes, there will be gaps in the record. Also, scientists have found many transitional fossils. For
example, there are many fossils of transitional organisms between whales and their terrestrial mammal
ancestors.
Exhibit examples: Paleontologists have discovered many fossils of transitional organisms that help us
understand how modern birds evolved from their non-flying dinosaur ancestors. Archaeopteryx and
Bambiraptor are examples.
 Misconception: Evolutionary theory is incomplete and is currently unable to give a total
explanation of life.
Response: Evolutionary science is a work in progress. New discoveries are made and explanations are
adjusted when necessary. And in this respect, evolution is just like all other sciences. Research continues
to add to our knowledge. While we don't know everything about evolution (or any other scientific
discipline, for that matter), we do know a great deal about the history of life, the pattern of lineagesplitting through time, and the mechanisms that have caused these changes. And more will be learned in
the future. To date, evolution is the only well-supported explanation for life's diversity.
Exhibit examples: It is true that scientists continue to investigate many questions regarding bird
evolution—but that is the normal way that science works. The existence of open questions in this field
does not mean that scientists have any doubts about the overarching theory of evolution.
 Misconception: The theory of evolution is flawed, but scientists won’t admit it.
Response: Scientists have examined the supposed “flaws” that creationists claim exist in evolutionary
theory and have found no support for these claims. These “flaws” are based on misunderstandings of
evolutionary theory or misrepresentations of evidence. Scientists continue to refine the theory of
evolution, but that doesn't mean it is “flawed.” Science is a very competitive endeavor and if “flaws” were
discovered, scientists would be more than glad to point them out.
Some of Darwin’s ideas have been rejected or modified since his time. For example, we now know that
Darwin’s ideas about the mechanism of inheritance were simply wrong, and his idea that evolution
generally proceeds at a slow, deliberate pace has been modified to include the idea that evolution can
proceed at a relatively rapid pace under some circumstances. In this sense, “Darwinism” is continually
being modified. Modification of theories to make them more representative of how things work is the role
of scientists and of science itself.
Thus far, however, there have been no credible challenges to the basic Darwinian principles that evolution
proceeds primarily by the mechanism of natural selection acting upon variation in populations and that
different species share common ancestors. Scientists have not rejected Darwin's natural selection, but
have improved and expanded it as more information has become available.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
20
 Misconception: Evolution is not science because it is not observable or testable.
Response: Evolution is observable and testable. The misconception here is that science is limited to
controlled experiments that are conducted in laboratories by people in white lab coats. Actually, much of
science is accomplished by gathering evidence from the real world and inferring how things work.
Astronomers cannot hold stars in their hands and geologists cannot go back in time, but in both cases
scientists can learn a great deal by using multiple lines of evidence to make valid and useful inferences
about their objects of study. The same is true of the study of the evolutionary history of life on Earth, and
as a matter of fact, some mechanisms of evolution are studied through direct experimentation, as they are
in more familiar sciences.
Exhibit examples: The evolutionary ideas presented in this exhibit have been thoroughly tested. In fact
some of the lines of evidence that test them (fossils of transitional forms, homologous structures) are
presented here.
 Misconception: Evolution leads to immoral behavior. If children are taught that they are
animals, they will behave like animals.
Response: We humans share anatomical and biochemical traits with other animals, and there are many
behaviors that we share — we care for our young, we form cooperative groups, etc. There are other
behaviors that are specific to particular animals. In this sense, humans act like humans, slugs act like
slugs, and squirrels act like squirrels. It is unlikely that children, upon learning that they are related to all
other animals, will start to behave like jellyfish or raccoons. Evolution does not make ethical statements
about right and wrong. It simply helps us understand how life has changed and continues to change over
time. It is up to us, as societies and individuals, to decide what constitutes ethical and moral behavior.
 Misconception: Evolution supports the idea that 'might makes right' and rationalizes the
oppression of some people by others.
Response: In the nineteenth and early twentieth centuries, a philosophy called “Social Darwinism” arose
from a misguided effort to apply lessons from biological evolution to society. According to this view,
society should allow the weak and less fit to fail and die, and that this is not only good policy, but morally
right. Supposedly, evolution by natural selection provided support for these ideas. Pre-existing prejudices
were rationalized by the notion that colonized nations, poor people, or disadvantaged minorities must
have deserved their situations because they were “less fit” than those who were better off. This
misapplication of science was used to promote social and political agendas. The “science” of Social
Darwinism was refuted. Biological evolution has stood the test of time, but Social Darwinism has not.
 Misconception: Evolution and religion are incompatible.
Response: Religion and science are very different things. In science, only natural causes are used to
explain natural phenomena, while religion deals with beliefs that are beyond the natural world. The
misconception that one always has to choose between science and religion is incorrect. Of course, some
religious beliefs explicitly contradict science (e.g., the belief that the world and all life on it were created
in six literal days); however, most religious groups have no conflict with the theory of evolution or other
scientific findings. In fact, many religious people, including theologians, feel that a deeper understanding
of nature actually enriches their faith. Moreover, in the scientific community there are thousands of
scientists who are devoutly religious and also accept evolution.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
21
V. Avoiding potential pitfalls
As a docent, guide, or museum professional, visitors look to you as an authority on the material in the
exhibit. When you talk about evolution with visitors, try to avoid these language pitfalls:
 Function not purpose. The purpose of a hammer is to pound nails. One function of a hand is to hold
a hammer. Designed tools have purposes, but evolved structures and behaviors of living things have
functions. Talking about the “purpose” of feathers suggests that they were designed by someone.
 Adapted not designed. Use of the word “design” may imply that living things are designed and that
there is a plan at work. The use of terms like “structure” and “adaptation” are more appropriate. For
example, “How is a kiwi designed to eat insects?” could be replaced by, “How is a kiwi adapted to
eating insects?” or, “What structures and behaviors aid a kiwi in eating insects?”
 Specialized not advanced/ancestral not primitive. “Advanced” and “primitive” remind us of
progress or steps on a ladder—but that’s not how evolution works. Opossums, for example, have
retained some traits of the ancestral marsupial, but they are not primitive mammals. They are well
adapted to their omnivorous lifestyle and are every bit as successful as other modern mammals.
Similarly, it would be incorrect to describe non-avian dinosaurs as primitive and birds as advanced.
Instead, you can just say that birds evolved from dinosaur ancestors, while recognizing that many
dinosaur lineages evolved specialized traits that suited their lifestyles.
 Theory vs. hypothesis. A theory is a broad, natural explanation for a wide range of phenomena.
Theories are concise, coherent, systematic, predictive, and broadly applicable, often integrating and
generalizing many hypotheses. Gravitational theory, for example, attempts to explain the nature of
gravity. Cell theory explains the workings of cells. Evolutionary theory explains the history of life on
Earth. Theories accepted by the scientific community (as evolution is) are generally strongly
supported by many different lines of evidence, but may be modified with new evidence and
perspectives. A hypothesis, on the other hand, is a proposed explanation for a fairly narrow set of
phenomena. Hypotheses may come and go by the thousands, but theories often remain to be tested
and modified for decades or centuries. To describe evolution as “just” a theory misleads people about
the status of theories in science and the importance of evolution to an accurate scientific
understanding of biology.
 Believe vs. accept. In the museum, you may be asked “Do you believe in evolution?” Since we
associate the word belief with faith, this can be a tricky question. Scientists generally prefer the term
accept which implies that the idea in question is supported by evidence. If asked this question, you
might explain the difference between believe and accept and say that you accept the fact that the Earth
is very old and life has changed over billions of years because that is what the evidence tells us.
 Adapt vs. learn. Colloquially, we might say that we adapt to cold weather by putting on more
clothing. Unfortunately, visitors may apply this definition to evolution, resulting in the erroneous
impression that evolution consists of individuals changing their behavior or learning over the course
of a lifetime. By using the word adapt only when referring to actual evolutionary change, you can
avoid this pitfall. Along the same lines, don’t say that some dinosaurs “learned” to fly, when you
really mean that they evolved the ability to fly.
 Ancestor vs. relative When we fail to distinguish between an ancestor and a relative, we set visitors
up for confusion. For example, humans and chimps are related, but humans did not evolve from
chimps any more than chimps evolved from humans. Similarly, birds do have dinosaur ancestors—
but not all dinosaurs are in birds’ ancestral lineage. For example, pigeons and T. rex are evolutionary
cousins; pigeons did not evolve from T. rex.
 Evolution vs. development. Development is the process that occurs as a living thing grows up.
Evolution is a change of gene frequency in a population over generations. It is more correct to say
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
22
that some dinosaurs evolved the ability to fly than that they developed the ability to
fly.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
23
VI. Dealing with controversy in the museum
 Why the controversy?
There is no scientific controversy over evolution: biologists agree that evolution is the most useful
and well-supported explanation for life’s diversity and history available. However, some
organizations in this country actively promote the rejection of evolution. These groups and like-minded
individuals have created a social controversy over evolution. Social objections to evolutionary theory
frequently cite its supposed incompatibility with belief in supernatural beings, like God, and the fear that
people will see the explanations offered by evolutionary theory as replacements for the potential role of a
supernatural being in generating the diversity of life.
The most important thing to remember in all this is that there doesn’t have to be a conflict between
evolution and religion. Many scientists both believe in higher powers and accept evolution, and many
religious groups have made explicit statements regarding the compatibility of their views with
evolutionary theory and their support for evolution education. In general, scientific theories (including
evolution) offer explanations for the natural world around us, while religion deals with the
supernatural world; the two deal with separate domains. The tools of science can only help us learn
about the natural world; they cannot inform us about the nature of the supernatural and what supernatural
entities may or may not exist, which are matters of personal faith.
 What beliefs might be encountered?
Most controversy you are likely to encounter will come from Creationists. There are a variety of groups
that promote different versions of Creationism. Here are a few of the most common sorts of beliefs:
o that the Earth and all of its species were created in their current forms less than 10,000 years
ago.
o that different “kinds” of animals (e.g., cats) were created and then evolved into different
species over long periods of time.
o that humans were created, but other organisms evolved.
o that a supernatural being has intervened in evolution
Intelligent Design (ID) is a Creationist movement that masquerades as science. ID proponents claim
that structural complexity cannot arise through natural causes (like evolution), but requires the direct hand
of a designer. They claim that structures such as bacterial flagella, events such as the origin of life, and
major innovations such as the establishment of the basic animal body forms are too complex to be
explained naturally. Thus, ID demands that a role be left for the intelligent designer, implied but not
always stated to be God.
Intelligent Design isn’t science for a variety of reasons. Science deals with the natural world, but ID
relies on the existence of a designer—i.e., a supernatural being. Science deals with testable ideas, but
since ID involves an unpredictable supernatural being, it is not testable. Science relies on feedback from
the scientific community, but ID proponents reject the feedback of the scientific community and largely
fail to participate in that community. Scientific ideas lead to ongoing research, but ID has not inspired
ongoing scientific research. The scientific community, the United States judicial system, many religious
organizations, and educational groups across the country have identified ID as a religious movement and
not as science.
 Strategies
• Learn about evolution. Review the information in this guide and in other resources. Get comfortable
explaining it to others.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
24
•
•
•
•
•
•
Don’t avoid using the word evolution. This is a science museum and evolution is an accepted
scientific theory. By treating the subject matter-of-factly, you help communicate the scientific
consensus on evolution to visitors.
Actively listen to visitors’ viewpoints. Create an environment for a respectful exchange of views.
Be respectful but clear about how science works and what is and is not science.
Don’t get frustrated, defensive, or try to win an argument with a devoted Creationist. If the
atmosphere of a conversation becomes tense or charged, acknowledge that you have different views or
that a science museum is not the place to have a philosophical or religious debate, and leave the area.
Always be respectful.
Recognize when to end the conversation.
Recognize probes designed to frustrate you. Some Creationist groups rely on a set of arguments that
misinterpret scientific evidence and ideas. However, few people who use these arguments understand
their details. If you hear something like the probes below, a response asking the person to explain his
or her meaning or the details of the argument may defuse the situation.
Common Creationist probes:
• Wasn’t the Miller-Urey experiment on the origins of life wrong?
• Doesn’t the second law of thermodynamics make the evolution of complex organisms impossible?
• Don’t the Cambrian explosion fossils show that major animal groups originated fully formed without
precursors?
• Isn’t the idea of homology (that organisms often share traits because they were inherited from a
common ancestor) circular or tautological?
• Don’t mutations destroy information? How could mutations lead to new genetic information?
• I heard that those drawings of similar vertebrate embryos were faked and that the early
developmental stages of different vertebrate groups are not very similar.
• If we evolved from monkeys, why are there still monkeys?
• Isn’t the bacteria flagellum irreducibly complex?
• Why do scientists claim that Archaeopteryx is the missing link between dinosaurs and birds when it’s
not?
• Weren’t the peppered moth photos staged?
• I heard that Darwin’s finches on the Galapagos evolved during droughts but then reversed their
evolution once the drought was over. So there was no net evolution . . .
• Mutant fruit flies with an extra pair of wings are sometimes used as an example of evolution, but those
mutant wings have no muscles and aren’t functional.
• Scientists are still arguing about which species are human ancestors. If they can’t get their story
straight, why should we believe them?
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
25
VII. Factsheets:
 Kiwi factsheet
Species: Recent genetic studies suggest that there
are five species of kiwi. All share the genus name
Apteryx, which means “no wing.”
Appearance: Species vary in size but most are
the size of a chicken. They have big feet, tiny
wings with a claw at the tip, fuzzy hair-like
feathers, and a long beak.
Habitat: All species live on the islands of New
Zealand. They live in forests and shrublands.
Ecology: Kiwis cannot fly. During the day, they rest in burrows in the
ground. At night, they go out to forage, using their long beaks, sense of
smell, and possibly also an ability to detect vibrations in the ground, to
find insects, worms, and other small animals that live in the soil. Kiwis
form mating pairs, and at least one species seems to mate for life. In some
species, the males do most of the work of incubating and brooding the
eggs and young chicks, but in other species, males and females share the
work.
Evolution: Genetic studies suggest that the kiwi lineage split from other birds about 68 million years
ago—around the time that non-avian dinosaurs went extinct. Modern kiwi lineages (the species alive
today) seem to have begun to diverge from one another about 8 million years ago. Kiwis are closely
related to rheas, emus, ostriches, cassowaries, the extinct moa, and the extinct elephant-bird from
Madagascar. Early studies based on anatomy suggested that tiny kiwis and giant moas (another New
Zealand native) were close cousins; however, scientists recently extracted DNA from 1400-year-old moa
skeletons, and found that kiwis seem to be more closely related to Australian emus and cassowaries than
they are to New Zealand moas.
Conservation: All kiwi species are threatened, and some species are critically endangered with less than
500 individuals. Kiwi numbers are in decline because of habitat loss, human activity, and, significantly,
the invasion of predators like stoats, ferrets, cats, and dogs.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
26
 Hawaiian honeycreeper factsheet
Species: Hawaiian honeycreepers form a clade called
Drepanidinae. There are around 25 species of honeycreeper
alive today—but before humans moved to Hawaii and triggered a
wave of extinctions, there were more than 50 species.
Appearance: The Hawaiian honeycreepers are small birds, often
with brightly colored plumage in some striking combination of
black, brown, red, yellow, and/or white. Different
species display remarkable variation in bill shape and
size, ranging from long, thin, curving bills to short, robust
bills. These bill shapes are adapted to the feeding habits
of the different species
Habitat: The Hawaiian honeycreepers are native to and
found only in the Hawaiian Islands. Different species
occupy different habitats within the islands.
Ecology: Hawaiian honeycreepers make their livings in
a variety of ways. Some species specialize on seeds,
some on particular plants, some on fruits, some on insect
larvae, some on snails, and some on nectar.
Evolution: Many lines of evidence suggest that Hawaiian
honeycreepers evolved from a finch ancestor. Around five million years ago, the honeycreepers’
ancestors invaded the still-forming Hawaiian Islands and began diversifying into different species.
Species of the evolving honeycreeper clade invaded new islands as they were formed by volcanic activity.
The honeycreepers are notable as an extreme example of an adaptive radiation on islands. From just one
ancestral species, the honeycreepers diversified into many species with different feeding adaptations,
colors, and ecological niches. Some species may have even coevolved beak shapes with the flowers that
they sip nectar from.
adaptive radiation – an event in which a lineage rapidly diversifies with the newly formed lineages evolving different
adaptations.
coevolution – a process in which two or more different species reciprocally affect each other's evolution. For example, species
A evolves, which causes species B to evolve, which causes species A to evolve, which causes species B to evolve, etc.
Conservation: The Hawaiian honeycreepers are imperiled. They have already suffered severe extinction.
Many went extinct shortly after Polynesians arrived on Hawaii, and they are currently experiencing a
second wave of extinction. Of the 25 or so species alive today, 18 are endangered because of habitat loss,
human activity, the invasion of predators, and disease. The introduction of mosquitoes carrying avian
malaria has been a particular challenge to honeycreeper survival.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
27
 Peppered moth factsheet
Species: Biston betularia
Ecology: The peppered moth is common in England. It often
rests on tree trunks and tree branches where it may be caught
by the birds that are able to spot it against the tree.
The story: Before the industrial revolution, the light-colored
form of the moth (called ‘typica’) was most common in
England. They blended in well against light-colored tree
trunks. Any dark-colored mutants (called ‘carbonaria’) that
arose would have been selected against because they would
have been easy for birds to spot and eat. However, during
the industrial revolution, factories between London and
Manchester began to spew out soot that darkened the trees.
Consequently, in the 1850s, the dark-colored form became
more common. The genes for dark color now had an
advantage and the lighter form was selected against. By
1895, the dark form dominated the moth population in the
areas affected by the pollution. Recently, pollution control
laws have significantly improved air quality in the area. Consequently, the trees are lighter and the lightcolored form is on the rise again. This is a classic example of natural selection in action. In just 150
years, we’ve directly observed the evolution of a population from one form to another and back again.
The science: Experiments and observations performed by Bernard Kettlewell in the 1950s suggested that
the basic story described above was indeed an accurate picture of the moths’ evolution. Since then, other
researchers (e.g., Michael Majerus) have studied the moths further. That research, again, backs up the
basic story described above and additionally suggests that migration of the moths is an important factor in
determining which moths are found where. However, Majerus also noticed that some of Kettlewell’s
original experiments were not very well designed.
Misinterpretation: Some creationist publications have (probably willfully) misinterpreted criticisms of
Kettlewell’s experimental technique as suggesting that the moth example is “wrong” or “faked.” This is
not true. Scientists who have improved on Kettlewell’s experimental technique have studied the moths
and found support for the basic explanation of moth evolution that Kettlewell put forth. In addition,
they’ve elaborated on the explanation so that we now know even more about how the moths have
evolved.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
28
 Archaeopteryx factsheet
Species: Archaeopteryx lithographica (Archaeo = ancient,
pteryx = wing)
Discovery: This fossil bird was first found in 1861 in a
quarry in Germany. It was extremely well preserved—even
its feathers. Since then several other Archaeopteryx fossils
have been discovered.
Appearance: So far, specimens have been found that range
from sparrow-sized to pigeon-sized. Archaeopteryx had a
long tail, relatively long legs, teeth, and claws at the tips of
its wings. Scientists don’t know what color it was.
Significance: Having lived about 150 million years ago,
Archaeopteryx is the earliest bird yet discovered. Furthermore,
it has features that clearly demonstrate that it evolved from
dinosaurs. It shares over 100 anatomical features with
dinosaurs. Thus, it is a great example of a transitional form—it
has features of both dinosaurs and modern birds and helps us
understand how and why different bird traits might have
evolved. However, it is NOT the ancestor of all modern birds.
It is a very early branch on the bird family tree, but is not the
root of that tree.
Flight: Although it is currently thought that Archaeopteryx
could sustain powered flight, it was probably not a strong flyer;
it may well have run, leaped, glided, and flapped all in the
same day.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
29
 Bambiraptor factsheet
Name: The full name of this
dinosaur is Bambiraptor
feinbergi. It is named after
Bambi from the Disney movie
because of its small size. The
root rapt means “to seize”—
which is probably what
Bambiraptor did to its prey.
Discovery: Bambiraptor was
found in Montana in 1995 by a 14-year-old
boy. So far, we’ve only found one example of
Bambiraptor—but luckily the fossil was
remarkably complete, so we have a good
picture of what this animal looked like.
Appearance: With its tail, Bambiraptor was
almost three feet long—but was just one foot
tall and weighed 4.4 lbs. However, the fossil
we have is likely from an animal that was not
fully grown, so they may have gotten bigger
than this. It was probably covered in
feathers—though it couldn’t fly. It also
appears to have had a pretty large brain for its
size (almost as large as that of modern birds),
and deadly claws.
Ecology: Bambiraptor probably made its living as a hunter of small mammals and reptiles.
Significance: Bambiraptor is a Dromaeosaur dinosaur—a type of Maniraptoran dinosaur that is thought
to be the closest relative of birds. It lived about 75 million years ago.
Feathers: Scientists think that Bambiraptor was covered in feathers, even though these weren’t
preserved in the single specimen we have. Why would we think this? The principle of parsimony. We
know that birds have feathers. And we know that some Maniraptoran dinosaurs not so closely related to
birds had feathers because the feathers were preserved as fossils. The simplest explanation for this is that
feathers evolved early in the history of the Maniraptorans and were inherited by all these different groups.
Since Bambiraptor is so closely related to birds, it is very likely that it too inherited feathers. Some
scientists even think that T. rex may have had feathers!
parsimony – a principle stating that the simplest explanation accounting for the observations is the preferred explanation.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
30
 Feathered (but non-avian!) dinosaur factsheet
Since birds are dinosaurs, it should be obvious that plenty of dinosaurs have feathers—but did you know
that many non-avian dinosaurs had feathers as well? Dinosaurs evolved feathers long before any
dinosaurs evolved into birds. For example, Bambiraptor (see previous factsheet) probably had feathers—
though these were not preserved in the fossils we’ve found so far. In the past 20 years, however,
paleontologists have found many remarkable fossils of non-avian dinosaurs that do preserve evidence of
their delicate feathers. Most of these fossils have been found in South America and Asia (especially
China). Here, we’ll review just a few of the dinosaurs known from their fossils to have had feathers.
Dilong paradoxus, a 125
million year old
Tyrannosaurid from China.
This five foot long dinosaur
would have walked around
on two legs. It was shaped a
bit like T. rex, but had a
longer neck, longer arms, and
shorter legs relative to its
body. It had filamentous,
branched feathers found on fossils of its tail and jawbone. Dilong’s feathers suggest that T. rex (another
Tyrannosaurid) might have also had feathers—but perhaps only as a baby and juvenile.
Sinornithosaurus millenii, a 125
million year old dromaeosaur
dinosaur from China.
Sinornithosaurus was a small
bipedal dinosaur with a skull about
five inches long. It was completely
covered with downy feathers, some
of which were branched and some
of which were single filaments.
Velociraptor mongoliensis, a 75 million year old dromaeosaur dinosaur from Mongolia. This animal was
about five feet long and would have weighted about 33 lbs (Jurassic Park got this wrong—and also failed
to showcase their feathers!). Velociraptor has not yet been found in rocks that would have preserved its
feathers, but we know that it
had fairly modern feathers
(with a quill and everything)
from its bones. Its forearms
had “quill knobs”—structures
to which feathers attach. The
pictures at right show a
Velociraptor forearm (A and
B) above a turkey vulture
forearm (C and D) for
comparison.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
31
 Tree of life factsheet
Biologists represent evolutionary relationships on family trees called phylogenies. This factsheet reviews
the basics of understanding phylogenies.
Reading trees: The root of the tree represents the
ancestral lineage, and the tips of the branches represent
the descendents of that ancestor. Depending on how
many branches the tree depicts, the descendents at the
tips might represent different populations of a species,
different species, or different clades, each composed of
many species. As you move from the root to the tips of the tree,
you are moving forward in time. When a lineage splits
(speciation), it is represented as a branching point.
Phylogenies trace patterns of shared ancestry among lineages.
Each lineage has a part of its history that is unique to it alone and parts that are shared with other lineages.
Similarly, each lineage has ancestors that are unique to that lineage and ancestors that are shared with
other lineages — common ancestors.
Understanding clades: Evolutionary trees depict clades. A clade is a group of organisms that includes
an ancestor and all descendents of that ancestor. Clades are nested within one another — they form a
nested hierarchy. A clade may include many thousands of species or just a few.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
32
Misinterpreting phylogenies: When reading a phylogeny, it is important to keep three things in mind:
1. Evolution produces a pattern of relationships among lineages that is tree-like, not ladder-like.
2. Just because we tend to read phylogenies from left to right, there is no correlation with level of
"advancement."
3. For any speciation event on a phylogeny, the choice of which lineage goes to the right and which
goes to the left is arbitrary. The following phylogenies are equivalent:
Building phylogenies: Biologists reconstruct the evolutionary history of a group of organisms by
collecting and analyzing evidence. This evidence takes the form of characters—heritable traits that can be
compared across organisms, such as physical characteristics (morphology), genetic sequences, and
behavioral traits. To build a phylogenetic tree, biologists collect data about the characters of each
organism they are interested in and then analyze those data to figure out the pattern of evolutionary
relationships most consistent with the data.
Phylogenies are essentially hypotheses about the relationships among groups of organisms. That means
that phylogenies may change if we discover new evidence (i.e., learn more about the characters of a group
of organisms) or if we interpret existing evidence in new ways.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
33
 Timeline of evolution factsheet
If you wanted to squeeze the 3.5 billion years of the history of life on Earth into a single minute, you
would have to wait about 50 seconds for multicellular life to evolve, another four seconds for vertebrates
to invade the land, and another four seconds for flowers to evolve — and only in the last 0.002 seconds
would “modern” humans arise. Evolutionary time is deep!
The timeline below shows some of the major events in life's history—but keep in mind that most of that
history occurred before the first multi-cellular organisms evolved 555 million years ago.
Years
ago
Event
130,000
Anatomically modern humans evolve. Seventy thousand years later, their descendents
create cave paintings — early expressions of consciousness.
4 million
In Africa, an early hominid, affectionately named “Lucy” by scientists, lives. The ice
ages begin, and many large mammals go extinct.
65 million
A massive asteroid hits the Yucatan Peninsula, and ammonites and non-avian dinosaurs
go extinct. Birds and mammals are among the survivors.
130 million
As the continents drift toward their present positions, the earliest flowers evolve, and
dinosaurs dominate the landscape. In the sea, bony fish diversify.
225 million
Dinosaurs and mammals evolve. Pangaea has begun to break apart.
248 million
Over 90% of marine life and 70% of terrestrial life go extinct during the Earth's largest
mass extinction. Ammonites are among the survivors.
250 million
The supercontinent called Pangaea forms. Conifer-like forests, reptiles, and synapsids
(the ancestors of mammals) are common.
360 million
Four-limbed vertebrates move onto the land as seed plants and large forests appear. The
Earth's oceans support vast reef systems.
420 million
Land plants evolve, drastically changing Earth's landscape and creating new habitats.
450 million
Arthropods move onto the land. Their descendants evolve into scorpions, spiders, mites,
and millipedes.
500 million
Fish-like vertebrates evolve. Invertebrates, such as trilobites, crinoids, brachiopids, and
cephalopods, are common in the oceans.
555 million
Multi-cellular marine organisms are common. The diverse assortment of life includes
bizarre-looking animals like Wiwaxia.
3.5 billion
Unicellular life evolves. Photosynthetic bacteria begin to release oxygen into the
atmosphere.
3.8 billion
Replicating molecules (the precursors of DNA) form.
4.6 billion
The Earth forms and is bombarded by meteorites and comets.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
34
VII. Background information links
It’s not possible to provide a full introduction to evolutionary theory in this short guide. However, more
extensive background information is freely available online. The following resources from
Understanding Evolution (http://evolution.berkeley.edu/) are particularly relevant to the topics dealt with
in this exhibit. Just use an Internet browser to get to the first page of each tutorial, and then click the
“next” button to read additional pages in each tutorial.
•
•
•
•
•
•
•
•
The nature of science and evolution (http://evolution.berkeley.edu/evolibrary/article/nature_01).
Review what science is and how it works.
Lines of evidence relevant to evolution
(http://evolution.berkeley.edu/evolibrary/article/0_0_0/lines_01). The theory of evolution is
broadly accepted by scientists — and for good reason! Learn about the diverse and numerous
lines of evidence that support the theory of evolution.
Evolutionary trees (http://evolution.berkeley.edu/evolibrary/article/phylogenetics_01). Learn
about phylogenetic systematics, the study of the evolutionary relationships among organisms, and
how the field is shaping biological research today.
Mechanisms of evolution (http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_14). Learn
about the basic processes that have shaped life and produced its amazing diversity.
Microevolution (http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_36). Microevolution
is going on around us all the time. Find out how small-scale evolutionary change occurs.
Speciation (http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_40). Figuring out what
species are is not as easy as one might think. Find out how biologists define species and how new
species evolve.
Macroevolution (http://evolution.berkeley.edu/evolibrary/article/0_0_0/evo_47). Explore the
processes behind major radiations and extinctions and other grand patterns in the history of life.
The evolution of complex innovations (http://evolution.berkeley.edu/evolibrary/article//evo_53
and http://evolution.berkeley.edu/evolibrary/article/side_0/complexnovelties_01). Learn how
complex innovations, like wings and eyes, evolve from much simpler beginnings.
© 2009 The University of California Museum of Paleontology, Berkeley, and the Regents of the University of California ●
Understanding Evolution, www.evolution.berkeley.edu
35