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ABCS 207:
PRINCIPLES OF EVOLUTION
COURSE GOALS
• To explain the principles of evolution
and give students a good foundation in
understanding biological phenomena
and the application of evolutionary
theory to economic development
LEARNING OUTCOMES
• At the end of the course students would
have received adequate knowledge and
understanding of the basic concepts that
would enable them to interpret
biological data and observations and
reasoning in biology.
Reading List
• Ridley, M. (1993). Evolution. Blackwell Scientific
Publications, Inc.
• Futuyma, D. J. (1986). Evolutionary Biology. 2nd Ed.
Sinauer Associates, Inc
• Keeton, W. T. and Gould, J. L. (1993). Biological
Science. 5th Ed. W. W. Norton & Company, Inc
• Gould, S. J. (2002). The Structure of Evolutionary
Theory. Belknap Harvard
• Newson, L. and Richerson, P. (2021). A Story of Us: A
New Look at Human Evolution. Oxford University
Press.
LECTURE SCHEDULE
Week
Topic
Comments
DR MILLICENT COBBLAH
1
Introduction and Pre-course assessment
To shape future lectures
2
Terms, definitions, terminologies and the concept of life
To enable understanding of terms during the course
3
Pre-Darwinian evolution and Darwin's Theory of Evolution
Quiz
4
•
Revision of Darwin's Theory - Synthetic Theory of Evolution.
•
•
•
Species concepts
Provide factual basis of evolution.
To understand the importance of species in biodiversity
conservation.
5
Processes and patterns of evolution
To explain where life’s diversity come from
6
Documentary on Charles Darwin: The tree of life
It summarises the course so far
7
Interim Assessment
To assess students understanding of course so far
8
PROF. ROSINA KYEREMATEN
Evolution - The Evidence
Demonstrate the available data in support of evolution
9
Application of evolutionary principles in agriculture
Importance of understanding the principles for development
10
Application evolutionary principles in health & conservation & other areas
Importance of understanding the principles for development
11
Introduction to human evolution &Strategies for adaptation and survival in humans
12
Strategies for adaptation and survival in non-humans
13
Interim assessment
Final test as part of continuous assessment as required
EVOLUTION
• Evolution in the broadest sense means change –
galaxies, languages, political systems all change/evolve
• Biological/Organic Evolution
Genetic change in the properties of populations of
organisms that transcends the lifetime of a single
individual
• Evolution is the change in the inherited characteristics
of biological populations over successive generations
EVOLUTION
• Individual organisms do not evolve
• The changes in populations that are considered
evolutionary are inheritable
• Biological evolution may be slight or substantial
• Evolution is an ‘unrolling’ i.e. species change with time
• Evolution can occur through emigration or immigration
Creationism
• This is the religious belief that nature, and aspects
such as the universe, Earth, life, and humans,
originated with supernatural acts of divine creation.
• In its broadest sense, creationism includes
a continuum of religious views, which vary in their
acceptance or rejection of scientific
explanations such as evolution that describe the
origin and development of natural phenomena
Humanity
Biological species
Young Earth creationism
Directly created by God.
Intelligent design
Theistic evolution (evolutionary
creationism
Age of Universe
Less than 10,000 years old.
Reshaped by global flood.
Less than 10,000 years old, but
some hold this view only for our
Solar System.
Scientifically accepted age.
Reshaped by global flood.
Scientifically accepted age.
Scientifically accepted age.
Directly created by
God. Macroevolution does not
occur.
Gap creationism
Progressive creationism
Earth
Directly created by God, based
on primate anatomy.
Direct creation + evolution. No
single common ancestor.
Scientifically accepted age. No
global flood.
Proponents hold various beliefs.
Divine intervention at some point
in the past, as evidenced by what
intelligent-design creationists call
"irreducible complexity." Some
adherents accept common
descent, others do not.
Some claim the existence of Earth
is the result of divine
Scientifically accepted age.
intervention.
Evolution from primates.
Evolution from single common
ancestor.
Scientifically accepted age. No
global flood.
Scientifically accepted age.
EVOLUTION – THE EVIDENCE
All organisms have descended with modification
from common ancestors
Evident in:
• fossil records
• geographical distribution of species,
• comparative anatomy and embryology
• vestigial structures
• modification of domesticated organisms
EVOLUTION – THE EVIDENCE
The Fossil Record
• The only direct evidence of evolutionary history
• Shows ancestral intermediates
• Specimens are usually considered to be fossils if they
are over 10,000 years old.
• The oldest fossils are around 3.48 billion years old to
4.1 billion years old.
EVOLUTION – THE EVIDENCE
The Fossil Record
• Fossil remains found in the sedimentary rocks
deposited in ages past give glimpses of the ancestry
of living organisms
• The earliest archaeological record of human
agriculture eg. is about 12,000 years old – <1/8000
of the time since Tyrannosaurus rex, though in the
time frame of evolution T. rex was a late comer
EVOLUTION – THE EVIDENCE
The Fossil Record
• Whole communities of organisms quite different
from those of today have arisen and perished since
the days of the dinosaurs:
•
•
•
•
continents have moved,
sea levels have risen and dropped,
climates have changed,
glaciers have scoured the continents etc.
• The enormous changes in both the physical and
biotic environment have occurred continually for
billions of years
EVOLUTION – THE EVIDENCE
• Organisms are fossilized only under exceptionally
favorable conditions, or unless they occupy habitats
such as swamps or estuaries where their remains can be
buried in sediments
• Sediments become compacted into rock and persist without
metamorphosis or erosion for millions of years.
• Strata can be assigned to geological periods or stages
within periods on the basis of their fossil content.
• Radioactive decay has made it possible to obtain
absolute ages of rocks
EVOLUTION – THE EVIDENCE
• Radioactive dating is based on the constant rate
of decay of unstable parent nuclides into
daughter nuclides
• Eg. half the potassium-40 nuclides incorporated into a
rock during its formation will decay to argon-40 in 1300
million years – the ratio of parent to daughter nuclides
measures the age of the rock – estimation procedure has
an error of a few percent
• The oldest rocks on earth have been
radiometrically dated at 3.8 billion years
EVOLUTION – THE EVIDENCE
• The earliest fossil indication of life is in South African
rocks dated at 3.4 - 3.1 billion years old
• – contains forms that resemble bacteria including
Cyanobacteria (blue-green bacteria or “algae”) and
Stromatolites (mound-like structures still formed by
cyanobacteria in Australia)
• The first complex, multicellular animals known as the
Ediacaran fauna are dated at about 640Myr B.P.
• – included traces of burrows and tracks and a number of softbodied animals (annelid worms, coelenterates and soft –bodies
arthropods)
EVOLUTION – THE EVIDENCE
• The environment in which organisms have evolved
has undergone vast changes – astronomical
influences, dynamics of the earth itself and the
activities of organisms have all played a role
• The arrangement of the seas and land masses have
changed over time due to plate tectonics
FOSSILS
FOSSILS – 130my dinasaur
FOSSILS
FOSSILS
Fossils – 518my Sea Creature
Fossils – Phytosaur: 200my
EVOLUTION – THE EVIDENCE
Geographical Distribution of Species –Biogeography
• Explains how species and higher taxa are
distributed as they are and why the biota varies
from one region to another
• Although a few species are virtually cosmopolitan,
the geographic range of every species is limited to
varying degrees – most higher taxa are endemic or
restricted to particular geographic regions. Eg. Polar
bear
EVOLUTION – THE EVIDENCE
Biogeography
• Biogeography is important as a branch of
geography that sheds light on the natural habitats
around the world.
• It is also essential in understanding why species are
in their present locations and in developing and
protecting the world's natural habitats.
EVOLUTION – THE EVIDENCE
Historical Biogeography
• Distribution of species is the consequence of past
events such as continental drift – explains why
some groups and not others occur in a certain
geoegraphical area/region
• Also known as paleobiogeography - studies the past
distributions of species.
EVOLUTION – THE EVIDENCE
Historical Biogeography
• It looks at their evolutionary history and past
climate change for eg. to determine why a certain
species may have developed in a particular area.
• Eg. the historical approach would say there are
more species in the tropics than at high latitudes
because the tropics experienced less severe climate
change during glacial periods
• led to fewer extinctions and more stable populations
over time.
EVOLUTION – THE EVIDENCE
Historical Biogeography
• Paleobiogeography includes plate tectonics. This
type of research uses fossils to show the movement
of species across space via moving continental
plates.
• Paleobiogeography also takes varying climate as a
result of the physical land being in different places
into account for the presence of different plants
and animals.
EVOLUTION – THE EVIDENCE
Ecological Biogeography
• Ecological biogeography looks at the current
/contemporary factors responsible for the distribution
of plants and animals.
• The most common fields of research within ecological
biogeography are climatic equability, primary
productivity, and habitat heterogeneity (distribution of
habitats).
• It explains the local distribution of groups in a
geographical area/region
EVOLUTION – THE EVIDENCE
Ecological Biogeography
• Climatic equability looks at the variation between
daily and annual temperatures.
• It is harder to survive in areas with high variation
between day and night and seasonal temperatures.
• Because of this, there are fewer species at high latitudes
because more adaptations are needed to be able to
survive there.
EVOLUTION – THE EVIDENCE
Ecological Biogeography
• In contrast, the tropics have a steadier climate with
fewer variations in temperature.
• This means plants eg. do not need to spend their energy
on being dormant and then regenerating their leaves
and/or flowers, they do not need a flowering season,
and they do not need to adapt to extreme hot or cold
conditions.
Tree in Spring, Summer, Autumn
and Winter
EVOLUTION – THE EVIDENCE
Ecological Biogeography
• Habitat heterogeneity leads to the presence of
more biodiversity (a greater number of species
present).
Conservation Biogeography
• This is the protection and/or restoration of nature
and its flora and fauna.
EVOLUTION – THE EVIDENCE
• Environment cannot account for either similarity or
dissimilarity, since similar environments can harbor
entirely different species groups
• "Affinity" (=similarity) of groups on the same continent
(or sea) is closer than between continents (or seas)
• Geographical barriers usually divide these different
groups, and there is a correlation between degree of
difference and rate of migration or ability to disperse
across the barriers –mountain ranges, edges of deserts
Evolution – The Evidence
• Disjunct locations/distribution for the same extant
species: Good evidence for creation?
(Evolution proposes Single Centers for the origins of
species, so Discontinuous Distributions need to be
explained) Eg. Africa, Australia and South America all have
lungfishes and ratite birds
• Many difficulties remain to be solved, esp. the very
distinct, but distantly related forms in the Southern
hemisphere (e.g., marsupial versus placental mammals)
Evolution – The Evidence
Disjunct locations/distribution for the same extant
species:
The Mammal Placentals and Their
Related Marsupials
The Tapir Tapirus terrestris
(South American) and
Tapirus indicus (Malayan )
Evolution – The Evidence
• Four species of Tapir are sparse and
extremely fragmented with most
distribution in southern America (3
species) and one species in Malaya
and Sumatra.
• Malayan tapir: Malaya and
Sumatra (Formerly: Burma and
parts of Thailand)
• Baird's tapir: Belize, Costa Rica,
Guatemala, southern Mexico,
Honduras, Nicaragua, Republic of
Panama
• Lowland tapir: Broadest range of
the 4 species: Most South
American rain forests
• Mountain tapir: High elevations in
Andean regions of Columbia,
Ecuador and Peru
Evolution – The Evidence
• Fresh water distributions
Because freshwater is isolated, one might expect
restricted ranges; but this is not the case (in fact, they
often have distributions even broader than
terrestrials): How is this explained?
1.
Distribution of Fish
2.
Distribution of Shellfish (molluscs)
3.
Distribution of Plants (often very wide
ranges)
Evolution – The Evidence
Evolution – The Evidence
Evolution – The Evidence
• Distribution of species on oceanic islands
Darwin considered this evidence as especially strong in its support of
descent with modification
A. The total number of species on oceanic islands is small compared to
the number on an equal area of continent
B. Proportion of endemic species is very high
C. Endemic species often possess characters that are adaptive
elsewhere, but are useless characters on the island
D. Endemic species often show (new) adaptive traits not possessed by
any of their relatives
Zoogeographic Regions
Causes of Geographical
Distributions
• Dispersal – a taxon’s distribution and present range
can be achieved by dispersal from the region from
which it originally evolved
• Vicariance – the existing distribution of a taxon or
group may arise from a formerly continuous
distribution that has become fragmented by some
external factor such as the separation of one
landmass or body of water into two, such that
members of this biota become separated and
evolve differently
Evolution – The Evidence
Comparative Anatomy and Embryology
• Early evolutionist such as Lamarck used comparative anatomy to
determine relationships between species.
• Organisms with similar structures, they argued, must have
acquired these traits from a common ancestor.
• Today, comparative anatomy can serve as the first line of
reasoning in determining the relatedness of species.
• However, there are many hidden dangers that make it necessary
to support evidence from comparative anatomy with evidence
from other fields of study.
Evolution – The Evidence
• A major problem in determining evolutionary
relationships based on comparative anatomy can be
seen when we look at a commonly found structure: the
wing.
• Wings are present in a number of very different groups
of organisms - birds, bats and insects all have wings,
but what does this say about how closely related the
three groups are?
• It is tempting to say that the three groups must have
had a common winged ancestor.
Evolution – The Evidence
• This is however not true - the wings of bats and
birds are both derived from the forelimb of a
common, probably wingless, ancestor.
• Both have wings with bone structures similar to the
forelimbs of ancestral and current tetrapod or fourlegged, animals.
• Such traits that are derived from a trait found in a
common ancestor are called homologous traits.
Evolution – The Evidence
•
All tetrapods have a pentadactyle (5-digit) limb structure. The fore limb of a bird, human, whale and bats are all
constructed from the same bones even though they perform different functions
Evolution – The Evidence
• Structurally speaking, though, the wings of bats
and birds have little in common with those of
insects.
• Bird wings and insect wings are an analogous trait,
or a trait that has developed independently in two
groups of organisms from unrelated ancestral traits.
Convergence
Evolution – The Evidence
Embryology
• Another difficulty in comparing traits between
species rests on the fact that homologous structures
not present in the adult organism often do appear in
some stage of embryonic development.
• In this way, the embryo serves as a microcosm for
evolution, passing through many of the stages of
evolution to produce the current state of the
organism.
• Species that bear little resemblance in their adult
form may have strikingly similar embryonic stages.
Evolution – The Evidence
• For example, in humans, the embryo passes
through a stage in which it has gill structures like
those of the fish from which all terrestrial animals
evolved.
• For a large portion of its development the human
embryo also possesses a tail, much like those of our
close primate relatives.
Vestigial Structures
• Structures and characteristics found in existing
species that have no known function
• Provide evidence of common ancestry
• As species evolve, their structures change
• The structure/organ is adapted for a new use eg.
Penguins
• The structure/organ will no longer have a use eg. Whale
pelvis/snake feet
Vestigial Structures
Amphiuma
Evolution – The Evidence
• This tail is usually
reabsorbed before birth,
but occasionally children
are born with the
ancestral structure intact.
• Tails and even gills could
be considered
homologous traits
between humans and
primates or humans and
fish, even though they are
not present in the adult
organism.
IMPORTANCE OF EVOLUTION
• Evolution plays an important role not only
for present day humans but all living things
today.
• To understand the importance of evolution,
we must gather some understanding of the
meaning of evolution.
Application Of Evolutionary
Principles To Agriculture
• Through genetic
engineering and artificial
selection, the principles
of evolution are used in
agriculture for breeding
crops and animals with
desirable features to
help solve the problem
of food security
Application Of Evolutionary
Principles To Agriculture
• As agriculture developed,
the environment of the
agricultural field has
become increasingly
differentiated from that
of the natural
environments in which
plants and animals
originally evolved.
Application Of Evolutionary
Principles To Agriculture
Similarly for animals:
• domestication created a more predictable environment
with increased resource availability during harsh times
and
• protection from predators,
• but increased threats from contagious diseases,
• all subtly influencing the evolutionary make-up of our
livestock.
Application Of Evolutionary Principles
To Agriculture
• Over the last few thousand years, domestication, selection
and hybridisation, both unconscious and conscious, have
also led to significant changes in the appearance of plants
and animals and their nutritional value.
• Examples are seen in virtually all plant and animal species
that are farmed.
(A)The tomato self pruning (sp) mutant (right) has a compact ‘determinate’ growth
habit with a burst of flowering and fruit production (inset) compared to the
continuous ‘indeterminate’ vine-like growth of classical cultivars (left) and their wild
ancestors
(B) Similar benefits for soybean came from mutations in the orthologous gene
(determinate stem, dt1)
(C) The cotton sp mutant (Gbsp) has determinate shoots that result in the ‘clustered
boll’ trait. All three mutants provide shorter stature with multiple agronomic
adaptations.
Application Of Evolutionary
Principles To Agriculture
• Extensive selection in farmyard fowls (chickens, ducks, geese and
turkeys), and in pigs, sheep and cattle have given rise to very
many distinctive breeds that differ in milk production, flesh
texture and flavour, and obvious appearance, as well as in less
obvious traits, such as patterns of social behaviour.
Belgian Blue Cow
Application Of Evolutionary
Principles To Agriculture
• In horticulture, this
diversity is often highly
prized in the form of
different varieties that
are preserved for
subtle variations in
flavour, texture or
simply appearance
• Eg. in potato, tomato,
apple
Application Of Evolutionary
Principles To Agriculture
• Extensive agriculture has also
seen similar major changes
that have resulted in
significant increases in yield
and productivity.
• The emergence of modern
high-yielding hybrid maize
from its close relative
teosinte, and the subsequent
application of a number of
induced mutations and the
introduction of an F1 hybrid
system.
Discovery of new stem cell pathway
indicates route to much higher yields
The two maize varieties on the left combine to produce a high-yielding hybrid,
center (B73/W22); hybrids grown from "weak alleles" of the FEA3 gene yield
ears with significantly higher yields (the two ears on the right).
Application Of Evolutionary
Principles To Agriculture
Application Of Evolutionary
Principles To Agriculture
Biotechnology
• Biotechnology has progressed to
creating things that do not exist in
nature.
• However, even these advances
have some connection with
evolutionary biology.
• An example is the use of the most
profuse tools in biotechnology—
using enzymes to splice pieces of
DNA at particular locations.
Application Of Evolutionary
Principles To Agriculture
• These are the basis for what has been made
possible through molecular evolution
through the second half of the 20th century.
• These enzymes used to splice DNA for our
own purposes actually evolved in bacteria to
protect them from attacks by viruses.
Application Of Evolutionary
Principles To Agriculture
• Splicing enzymes—enzymes that cut DNA in particular
places—are formidable weapons that natural
selection evolved in bacteria to protect them from
viral attacks.
• Work very nicely because those enzymes can
recognize the viral host DNA as distinct from bacterial
DNA.
• Molecular biologists have discovered this little class
of enzymes, and are now using them for all sorts of
interesting science
Application Of Evolutionary
Principles To Medicine
Medicine
• Rapid evolution of viruses has led to emerging
diseases like H1N1 "swine flu" and HIV AIDS and
the novelle SARS-CoV-2 (COVID 19) that threaten
human health.
• Evolution has also led to antibiotic resistance in
some bacteria.
• Knowledge in evolution has helped scientists
identify lifesaving drugs.
Importance of Evolution
• For instance, the Pacific Yew tree was once the only
source of taxol, a remarkable drug used to fight cancers of
the lung, ovaries and breast.
• This endangered tree grows very slowly - 4 to 6 trees
would be destroyed to produce just one dose of taxol.
• The evolutionary history of the Yew tree was used to trace
other trees in its family line, discovering taxol-like
compounds in more common trees.
• This helped scientists find a replacement to the tree, thus
increasing the supply of taxol to cancer patients.
Importance of Evolution
Education
• The study of evolution helps to make teaching in certain
areas/fields of science such as embryology and genetics
easier and less difficult.
• It also helps to make understanding of these subject areas
easier.
Other areas
• Software engineering basically uses genetic algorithms
(simple codes which evolve by mutating themselves), this
process was borrowed from evolutionary biologists.
• Forensics interprets and analyse DNA evidence in forensic
cases and this depends on the principles of evolution.
HUMAN EVOLUTION
• This is the process by which human beings developed
on Earth from now-extinct primates.
• Zoologically, humans are Homo sapiens, a culturebearing, upright-walking species that lives on the
ground and very likely first evolved in Africa about
315,000 years ago.
HUMAN EVOLUTION
• We are now the only living members of what many
zoologists refer to as the human tribe Hominini
• There is abundant fossil evidence to indicate that
we were preceded for millions of years by other
hominins, such as Ardipithecus, Australopithecus,
and other species of Homo, and that our species
also lived for a time contemporaneously with at
least one other member of our genus,
H. neanderthalensis (the Neanderthals).
HUMAN EVOLUTION
• We and our predecessors have always shared Earth
with other ape-like primates, from the modernday gorilla to the long-extinct Dryopithecus.
• That we and the extinct hominins are somehow related
and that we and the apes, both living and extinct, are
also somehow related is accepted by anthropologists
and biologists everywhere.
• Yet the exact nature of our evolutionary relationships
has been the subject of debate and investigation since
the great British naturalist Charles Darwin published his
monumental books On the Origin of Species (1859)
and The Descent of Man (1871).
HUMAN EVOLUTION
• Darwin never claimed, that “man was descended
from the apes,” and modern scientists would view
such a statement as a useless simplification—just
as they would dismiss any popular notions that a
certain extinct species is the “missing link” between
humans and the apes.
• There is theoretically, however, a common ancestor
that existed millions of years ago.
HUMAN EVOLUTION
• This ancestral species does not constitute a
“missing link” along a lineage but rather a node for
divergence into separate lineages.
• This ancient primate has not been identified and
may never be known with certainty, because fossil
relationships are unclear even within the human
lineage, which is more recent.
HUMAN EVOLUTION
• The human “family tree” may be better described
as a “family bush,” within which it is impossible to
connect a full chronological series of species,
leading to Homo sapiens, that experts can agree
upon.
HUMAN EVOLUTION
HUMAN EVOLUTION
• The trove of fossils from Africa and Eurasia indicates that,
unlike today, more than one species of our family has lived
at the same time for most of human history.
• The nature of specific fossil specimens and species can be
accurately described, as can the location where they were
found and the period of time when they lived;
• But questions of how species lived and why they might
have either died out or evolved into other species can only
be addressed by formulating scenarios, albeit scientifically
informed ones.
HUMAN EVOLUTION
• These scenarios are based on contextual information gleaned
from localities where the fossils were collected.
• In devising such scenarios and filling in the human family bush,
researchers must consult a large and diverse array of fossils,
• They must also employ refined excavation methods and
records, geochemical dating techniques, and data from other
specialized fields such as genetics, ecology and paleoecology,
and ethology (animal behaviour)
— in short, all the tools of the
multidisciplinary science of paleoanthropology.
HUMAN EVOLUTION
HUMAN EVOLUTION
• It is generally agreed that the taproot of the human family
shrub is to be found among apelike species of the
Middle Miocene Epoch (roughly 16–11.6 mya) or Late
Miocene Epoch (11.6–5.3 mya).
• Genetic data based on molecular clock estimates support a
Late Miocene ancestry.
• Various Eurasian and African Miocene primates have been
advocated as possible ancestors to the early hominins,
which came on the scene during the Pliocene Epoch (5.3–
2.6 mya).
HUMAN EVOLUTION
Though there is no consensus among experts, the
primates suggested include:
• Kenyapithecus,
• Griphopithecus,
• Dryopithecus,
• Graecopithecus (Ouranopithecus),
• Samburupithecus,
• Sahelanthropus, and Orrorin.
HUMAN EVOLUTION
• Kenyapithecus inhabited Kenya and Griphopithecus
lived in central Europe and Turkey from about 16–
14 mya.
• Dryopithecus is best known from western and
central Europe, where it lived from 13 to possibly 8
mya.
• Graecopithecus lived in northern and
southern Greece about 9 mya, at roughly the same
time as Samburupithecus in northern Kenya.
HUMAN EVOLUTION
• Sahelanthropus inhabited Chad between 7 and 6 million
years ago.
• Orrorin was from central Kenya 6 mya.
• Among these, the most likely ancestor of great apes and
humans may be either Kenyapithecus or Griphopithecus.
The Divergence of Humans and Great Apes
from a Common Ancestor.
HUMAN EVOLUTION
• Results of some molecular studies, show
chimpanzees, bonobos, and humans to be more
closely related to one another than any of them is
to gorillas
• Orangutans (Pongo) are more distantly related.
HUMAN EVOLUTION
• The Miocene Epoch was characterized by major
global climatic changes that led to more seasonal
conditions with increasingly colder winters north of
the Equator.
• By the Late Miocene, in many regions inhabited by
apelike primates, evergreen broad-leaved forests were
replaced by open woodlands, shrublands, grasslands,
and mosaic habitats, sometimes with denser-canopied
forests bordering lakes, rivers, and streams.
HUMAN EVOLUTION
• Such diverse environments stimulated
novel adaptations involving locomotion in many types
of animals, including primates.
• In addition, there were a larger variety and greater
numbers of antelope, pigs, monkeys, giraffes, elephants,
and other animals for adventurous hominins to
scavenge and perhaps kill.
HUMAN EVOLUTION
• But large cats, dogs, and hyenas also flourished in the
new environments; they not only would provide meat
for scavenging hominins but also would compete with
and probably prey upon them.
• Ancestors of humans were not strictly or even heavily
carnivorous.
• Their diet relied on tough, abrasive vegetation,
including seeds, stems, nuts, fruits, leaves, and tubers,
evidenced by primate remains bearing large premolar
and molar teeth with thick enamel.
HUMAN EVOLUTION
• Behaviour and morphology associated with locomotion
also responded to the shift from arboreal to terrestrial
life.
• The development of bipedalism enabled hominins to
establish new niches in forests, closed woodlands, open
woodlands, and even more open areas over a span of at
least 4.5 million years.
• Indeed, obligate terrestrial bipedalism (that is, the ability
and necessity of walking only on the lower limbs) is the
defining trait required for classification in the human
tribe, Hominini.
HUMAN EVOLUTION
• Bipedalism is not unique to humans, though our
particular form of it is.
• Whereas most other mammalian bipeds hop or
waddle, we stride.
• H. sapiens is the only mammal that
is adapted exclusively to bipedal striding.
HUMAN EVOLUTION
• Unlike most other mammalian orders,
the primates have hind-limb-dominated locomotion.
• Accordingly, human bipedalism is a natural
development from the basic arboreal primate body
plan, in which the hind limbs are used to move about
and sitting upright is common during feeding and rest.
HUMAN EVOLUTION
• Human feet are distinct from those of apes
and monkeys.
• This is not surprising, since in humans the feet must
support and propel the entire body on their own
instead of sharing the load with the forelimbs.
• In humans the heel is very robust, and the great toe
is permanently aligned with the four diminutive
lateral toes.
HUMAN EVOLUTION
• Unlike other primate feet, which have a mobile
midfoot, the human foot possesses (if not requires)
a stable arch to give it strength.
• Accordingly, human footprints are unique and are
readily distinguished from those of other animals.
The Fossil Evidence
• By 3.5 million years ago at least
one hominin species, Au. afarensis, was an adept
walker.
• In addition to anatomic evidence from this time, there
is also a 27.5-metre (90-foot) trackway produced by
three individuals who walked at a leisurely pace on
moist volcanic ash at Laetoli in northern Tanzania.
The Fossil Evidence
• In all observable features of foot shape and walking
pattern, they are astonishingly similar to those of
habitually barefoot people who live in the tropics
today.
• Nevertheless, although the feet of the Laetoli
hominins appear to be strikingly human, one
should not assume that other parts of their bodies
were as similar to ours.
A trail of footprints, probably left
by Australopithecus afarensis individuals
some 3.5 million years ago, at Laetoli,
northern Tanzania.
Hominid Fossil Excavation Sites
Australopith Fossil Locations
Approximate time ranges of sites yielding
australopith fossils.
Cranial Capacity of Members of
the Human Lineage
Relative Cranial Capacity
Neanderthal (Homo neanderthalensis)
Hominid Evolution