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Lesson 1 Activity: Small Group Discussion on Misconceptions of Evolution
Each group will choose a different misconception, read about it individually and discuss in
small groups (20-30 min). Then each group will share with the rest of the class. <Misconceptions
not covered can be assigned for homework – answer the same question and for one of the
misconceptions also come up with an example that is not used in the text> <This sheet can be
printed for each student>
Each group will share: (10-15 min per group)
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The misconception they chose
Why this conception incorrect (what is wrong with the reasoning?)
What is still unclear or questions they have as a group
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Students from other groups will then be allowed to ask questions (each group is required
to ask at least 1 question to another group during the activity)
MISCONCEPTION 1: Evolutionary theory implies that life evolved (and continues to
evolve) randomly, or by chance.
CORRECTION: Chance and randomness do factor into evolution and the history of life
in many different ways; however, some important mechanisms of evolution are nonrandom and these make the overall process non-random. For example, consider the
process of natural selection, which results in adaptations — features of organisms that
appear to suit the environment in which the organisms live (e.g., the fit between a flower
and its pollinator, the coordinated response of the immune system to pathogens, and the
ability of bats to echolocate). Such amazing adaptations clearly did not come about "by
chance." They evolved via a combination of random and non-random processes. The
process of mutation, which generates genetic variation, is random, but selection is nonrandom. Selection favored variants that were better able to survive and reproduce (e.g.,
to be pollinated, to fend off pathogens, or to navigate in the dark). Over many generations
of random mutation and non-random selection, complex adaptations evolved. To say that
evolution happens "by chance" ignores half of the picture. To learn more about the
process of natural selection, visit our article on this topic. To learn more about random
mutation, visit our article on DNA and mutations.
MISCONCEPTION 2: Evolution results in progress; organisms are always getting better
through evolution.
CORRECTION: One important mechanism of evolution, natural selection, does result
in the evolution of improved abilities to survive and reproduce; however, this does not
mean that evolution is progressive — for several reasons. First, as described in a
misconception below (link to "Natural selection produces organisms perfectly suited to
their environments"), natural selection does not produce organisms perfectly suited to
their environments. It often allows the survival of individuals with a range of traits —
individuals that are "good enough" to survive. Hence, evolutionary change is not always
necessary for species to persist. Many taxa (like some mosses, fungi, sharks, opossums,
and crayfish) have changed little physically over great expanses of time. Second, there
are other mechanisms of evolution that don't cause adaptive change. Mutation, migration,
and genetic drift may cause populations to evolve in ways that are actually harmful
overall or make them less suitable for their environments. Finally, the whole idea of
"progress" doesn't make sense when it comes to evolution. Climates change, rivers shift
course, new competitors invade — and an organism with traits that are beneficial in one
situation may be poorly equipped for survival when the environment changes. And even
if we focus on a single environment and habitat, the idea of how to measure "progress" is
skewed by the perspective of the observer. From a plant's perspective, the best measure
of progress might be photosynthetic ability; from a spider's it might be the efficiency of a
venom delivery system; from a human's, cognitive ability. It is tempting to see evolution
as a grand progressive ladder with Homo sapiens emerging at the top. But evolution
produces a tree, not a ladder — and we are just one of many twigs on the tree.
MISCONCEPTION 3: Individual organisms can evolve during a single lifespan.
CORRECTION: Evolutionary change is based on changes in the genetic makeup of
populations over time. Populations, not individual organisms, evolve. Changes in an
individual over the course of its lifetime may be developmental (e.g., a male bird growing
more colorful plumage as it reaches sexual maturity) or may be caused by how the
environment affects an organism (e.g., a bird losing feathers because it is infected with
many parasites); however, these shifts are not caused by changes in its genes. While it
would be handy if there were a way for environmental changes to cause adaptive changes
in our genes — who wouldn't want a gene for malaria resistance to come along with a
vacation to Mozambique? — evolution just doesn't work that way. New gene variants
(i.e., alleles) are produced by random mutation, and over the course of many generations,
natural selection may favor advantageous variants, causing them to become more
common in the population.
MISCONCEPTION 4: Evolution only occurs slowly and gradually.
CORRECTION: Evolution occurs slowly and gradually,
but it can also occur rapidly. We have many examples of
slow and steady evolution — for example, the gradual
evolution of whales from their land-dwelling, mammalian
ancestors, as documented in the fossil record. But we also
know of many cases in which evolution has occurred
rapidly. For example, we have a detailed fossil record
showing how some species of single-celled organism, called
foraminiferans, evolved new body shapes in the blink of a
geological eye, as shown to the right.
Similarly, we can observe rapid evolution going on around us all the time. Over the past
50 years, we've observed squirrels evolve new breeding times in response to climate
change, a fish species evolve resistance to toxins dumped into the Hudson River, and a
host of microbes evolve resistance to new drugs we've developed. Many different factors
can foster rapid evolution — small population size, short generation time, big shifts in
environmental conditions — and the evidence makes it clear that this has happened many
times. To learn more about the pace of evolution, visit Evolution 101. To learn more
about rapid evolution in response to human-caused changes in the environment, visit our
news story on climate change , our news story on the evolution of PCB-resistant fish, or
our research profile on the evolution of fish size in response to our fishing practices.
MISCONCEPTION 5: Humans are not currently evolving.
CORRECTION: Humans are now able to modify our environments with technology.
We have invented medical treatments, agricultural practices, and economic structures that
significantly alter the challenges to reproduction and survival faced by modern humans.
So, for example, because we can now treat diabetes with insulin, the gene versions that
contribute to juvenile diabetes are no longer strongly selected against in developed
countries. Some have argued that such technological advances mean that we've opted out
of the evolutionary game and set ourselves beyond the reach of natural selection —
essentially, that we've stopped evolving. However, this is not the case. Humans still face
challenges to survival and reproduction, just not the same ones that we did 20,000 years
ago. The direction, but not the fact of our evolution has changed. For example, modern
humans living in densely populated areas face greater risks of epidemic diseases than did
our hunter-gatherer ancestors (who did not come into close contact with so many people
on a daily basis) — and this situation favors the spread of gene versions that protect
against these diseases. Scientists have uncovered many such cases of recent human
evolution. Explore these links to learn about:
— genetic evidence regarding recent human evolution
— the recent evolution of adaptations that allow humans to thrive at high altitudes
— the recent evolution of human genetic traits that protect against malaria
— the recent evolution of lactose tolerance in humans
MISCONCEPTION 6: Natural selection involves organisms trying to adapt.
CORRECTION: Natural selection leads to the adaptation of species over time, but the
process does not involve effort, trying, or wanting. Natural selection naturally results
from genetic variation in a population and the fact that some of those variants may be
able to leave more offspring in the next generation than other variants. That genetic
variation is generated by random mutation — a process that is unaffected by what
organisms in the population want or what they are "trying" to do. Either an individual has
genes that are good enough to survive and reproduce, or it does not; it can't get the right
genes by "trying." For example bacteria do not evolve resistance to our antibiotics
because they "try" so hard. Instead, resistance evolves because random mutation happens
to generate some individuals that are better able to survive the antibiotic, and these
individuals can reproduce more than others, leaving behind more resistant bacteria. To
learn more about the process of natural selection, visit our article on this topic. To learn
more about random mutation, visit our article on DNA and mutations.
MISCONCEPTION 7: The fittest organisms in a population are those that are strongest,
healthiest, fastest, and/or largest.
CORRECTION: In evolutionary terms, fitness has a very different meaning than the
everyday meaning of the word. An organism's evolutionary fitness does not indicate its
health, but rather its ability to get its genes into the next generation. The more fertile
offspring an organism leaves in the next generation, the fitter it is. This doesn't always
correlate with strength, speed, or size. For example, a puny male bird with bright tail
feathers might leave behind more offspring than a stronger, duller male, and a spindly
plant with big seed pods may leave behind more offspring than a larger specimen —
meaning that the puny bird and the spindly plant have higher evolutionary fitness than
their stronger, larger counterparts. To learn more about evolutionary fitness, visit
Evolution 101.
MISCONCEPTION 8: All traits of organisms are adaptations.
CORRECTION: Because living things have so many impressive adaptations (incredible
camouflage, sneaky means of catching prey, flowers that attract just the right pollinators,
etc.), it's easy to assume that all features of organisms must be adaptive in some way —
to notice something about an organism and automatically wonder, "Now, what's that
for?" While some traits are adaptive, it's important to keep in mind that many traits are
not adaptations at all. Some may be the chance results of history. For example, the color
of blood is not adaptive. There's no reason that having red blood is any better than having
green blood or blue blood. Blood's redness is a by-product of its chemistry, which causes
it to reflect red light. The chemistry of blood may be an adaptation, but blood's color is
not an adaptation. To read more about explanations for traits that are not adaptive, visit
our module on misconceptions about natural selection and adaptation. To learn more
about what traits are adaptations, visit another page in the same module.