1 Lecture 7 Lecture Summary In this lecture will continue the text’s discussion of bipedalism. This lecture will also provide some further information on the early hominids: Ardipithecus, Australopithecus, and Homo and their associated biocultural evolution. Bipedalism Perhaps the most crucial change in early hominid evolution was the development of bipedal locomotion – walking on two legs. We know from the fossil record that other important changes such as the expansion of the brain, modification of the female pelvis to allow bigger-brained babies to be born, and significant reduction of the face, teeth, and jaws, did not occur until about 2 million years after the emergence of bipedalism. Be familiar with the specific anatomical features associated with bipedalism as described in chapter 6 of your text. Why did we evolve to become bipedal? There are at least 6 different models that have been proposed to account for the evolution of bipedalism: 1.) Carrying model – bipedalism could have allowed our ancestors to search for and collect food in greater safety and with greater efficiency by freeing the arms and hands. Mothers could carry their children. They could carry sticks and rocks to throw at predators and scavengers. 2.) Vigilance model – bipedalism, by elevating the head, helped our ancestors locate potential food sources and dangers. This behavior is seen in other animals, squirrels and apes, but says more about upright posture than it does of actual locomotion. 3.) Heat dissipation model – the vertical orientation of the body in bipedalism helps cool the body by presenting a smaller target to the equatorial sun rays and placing more of the body above ground to catch cooling air currents. This model applies to hominids in the hot savannah but not so much in the shady forested areas. 4.) Energy efficiency model – bipedalism is an energy-efficient way of running and walking compared to quadrapedalism. Long periods of steady bipedal walking in search of food would seem to require less energy but the first hominids may not have walked quite like our more recent ancestors-they may have walked in a way more similar to chimps. So, it has been proposed that bipedalism may have had other advantages first and then further anatomical changes made it more energy efficient. 5.) Foraging/bipedal model – this model suggests that standing upright provided the benefit of reaching in bushes and trees, particular ones that were difficult to climb. 6.) Display model – bipedalism is thought by some to have emerged as a way to exhibit an upright display posture like that seen in chimps (and bonobos) during dominance confrontations. An upright display conveys meaning because it makes the individual seem larger and is directly related to mating success. 2 All of these models have some supporting evidence and it would not be absurd to assume that perhaps some or all of them worked together ...

1. 1
Lecture 7
Lecture Summary
In this lecture will continue the text’s discussion of bipedalism.
This lecture will also
provide some further information on the early hominids:
Ardipithecus, Australopithecus,
and Homo and their associated biocultural evolution.
Bipedalism
Perhaps the most crucial change in early hominid evolution was
the development of
bipedal locomotion – walking on two legs. We know from the
fossil record that other
important changes such as the expansion of the brain,
modification of the female pelvis to
allow bigger-brained babies to be born, and significant
reduction of the face, teeth, and
jaws, did not occur until about 2 million years after the
emergence of bipedalism. Be
familiar with the specific anatomical features associated with
bipedalism as described in
chapter 6 of your text.
Why did we evolve to become bipedal? There are at least 6
different models that have
been proposed to account for the evolution of bipedalism:
1.) Carrying model – bipedalism could have allowed our
ancestors to search for and

2. collect food in greater safety and with greater efficiency by
freeing the arms and
hands. Mothers could carry their children. They could carry
sticks and rocks to
throw at predators and scavengers.
2.) Vigilance model – bipedalism, by elevating the head, helped
our ancestors locate
potential food sources and dangers. This behavior is seen in
other animals,
squirrels and apes, but says more about upright posture than it
does of actual
locomotion.
3.) Heat dissipation model – the vertical orientation of the body
in bipedalism helps
cool the body by presenting a smaller target to the equatorial
sun rays and placing
more of the body above ground to catch cooling air currents.
This model applies
to hominids in the hot savannah but not so much in the shady
forested areas.
4.) Energy efficiency model – bipedalism is an energy-efficient
way of running and
walking compared to quadrapedalism. Long periods of steady
bipedal walking in
search of food would seem to require less energy but the first
hominids may not
have walked quite like our more recent ancestors-they may have
walked in a way
more similar to chimps. So, it has been proposed that
bipedalism may have had
other advantages first and then further anatomical changes made
it more energy
efficient.

3. 5.) Foraging/bipedal model – this model suggests that standing
upright provided the
benefit of reaching in bushes and trees, particular ones that
were difficult to
climb.
6.) Display model – bipedalism is thought by some to have
emerged as a way to
exhibit an upright display posture like that seen in chimps (and
bonobos) during
dominance confrontations. An upright display conveys meaning
because it makes
the individual seem larger and is directly related to mating
success.
2
All of these models have some supporting evidence and it would
not be absurd to assume
that perhaps some or all of them worked together to play a role
in the emergence of
bipedalism. However, those models that explain why hominids
would have more
reproductive success probably played the most important role -
as you recall that is the
measure of natural selection. Whatever the cause, bipedalism is
the trait that
distinguishes the hominids from other primates.
The First Hominids
Within the family Hominidae, anthropologists now generally

4. acknowledge at least 3
well-established genera: Ardipithecus, Australopithecus, and
Homo. Of course only the
last genus still exists; the others are long extinct.
Ardipithecus
Ardipithecus were the most ape-like hominids. Dating to 4.4
million years ago (mya),
Ardipithecus ramidus is considered a hominid because the hole
in the skull for the spinal
cord (foramen magnum) is positioned more forward than in
apes, indicating a more
bipedal locomotion. But the large canine teeth and other
features distinguish it from later
hominids. It seems that it is very close to the time when
hominids and apes split and may
be, as its name implies, the “root” hominid species. Another
relatively new species
emerged in 2004 called Ardipithecus kadabba. Found in the
same Ethiopian locale as
ramidus, kadabba dates to 5.8 to 5.2 mya. The toe bone is
angled in such a way as to
suggest habitual bipedalism at a very early date. The
interpretation of these fossils has
been controversial, however, and not everyone agrees that they
should be placed in the
Ardipithecus genus – some authorities think they are chimp
ancestors.
Australopithecus
There are two groups of australopithecines. One set of
Australopithecus is small-brained,
gracile (slender), with a mixed vegetable/fruit diet. Another set
of Australopithecus is
small-brained, robust, with a grassland vegetable diet. Some
authorities think that the

5. difference between the two groups is great enough to warrant a
separate genus called
Paranthropus (for the robust group). The authors of your text
are “lumpers” in this case
and don’t recognize a fourth genus of hominids so we will use
their taxonomy.
Australopithecus anamensis
The oldest, Australopithecus anamensis, dates to 4.2 to 3.9 mya.
Found only in northern
Kenya, they, too, exhibit ape-like features such as large canines
and parallel tooth rows
along with more human-like features such as thick molar
enamel. Their leg bones are
clearly those of a biped.
Australopithecus afarensis
Lucy (possibly our most famous human ancestor-named for the
Beatles song) was the
first specimen of Australopithecus afarensis discovered in 1974
and dating to 3.2 mya.
For more on Lucy’s story:
http://www.asu.edu/clas/iho/lucy.html
3
Afarensis more generally dates to 3.9–2.9 mya. Living off a
diet of fruits, nuts, seeds,
and tubers, the species is restricted to East Africa and is known
for being quite sexually
dimorphic. Their brain size is very similar to apes (380-500
cc), the face is projecting,

6. their canine teeth are smaller than apes but they have ape-like
features like parallel tooth
rows and relatively long arms. The curved finger and toe bones,
shortened pelvis, and
femur angled over the knee are some of the features that
demonstrate they were bipedal.
Laetoli footprint (left). Knee joint (right) from Hadar, Ethiopia
(where most of this
species is found including Lucy) showing a habit of walking.
A composite reconstruction of A. afarensis from Hadar,
Ethiopia (left) and jaw showing
ape-like features such as the u-shaped dental arcade (right).
Australopithecus africanus
Australopithicus africanus dates to 3-2.3 mya. These fossils are
mainly from South
Africa although some have been found in Kenya and Ethiopia.
Their body size and shape
4
and brain size (435-530 cc) is similar to afarensis but their
faces are less projecting
(prognathic) and they lack the ridge lying longitudinally along
the skull (sagittal ridge).
Their canine teeth are smaller and the tooth rows are more
rounded than parallel, i.e.
closer to humans than apes.

7. There is some evidence to suggest that these australopiths
(afarensis and africanus)
hunted small animals or scavenged carcasses of larger ones.
Carbon isotope analysis of
tooth enamel shows that they either ate tropical grasses or ate
animals that ate tropical
grasses, or both. Because the teeth do not show signs of wear
consistent with eating grass
researchers are more apt to believe they were eating meat. The
similarity of the two
species suggests a plausible interpretation that A. africanus is a
continuation of A.
afarensis showing some evolutionary changes (one hypothesis).
Australopithecus afarensis: “Taung baby” (left) and “Mrs. Ples”
(right) found in South
Africa.
Australopithecus garhi
The site of Bouri, in Ethiopia, dated to 2.5 mya has revealed
bones of hominids and
bones of antelopes, horses, and other animals with cutmarks
made by stone tools. The
hominid and animal sets of bones are found in different
locations within the site but
whoever the hominid was, they were butchering the animals for
meat and potentially
smashing the bones to get at the fat-rich marrow. The cranial
bones are similar to A.
afarensis (e.g. they have a prognathic jaw and similar brain
size) but they also share

8. features with early Homo (e.g. the relative length of legs are
arms)–leading researchers to
believe it was a new species, A. garhi. The evolutionary
relationship of garhi to other
hominids is still a matter of debate. Its discoverers feel it is
descended from A. afarensis
and is a direct ancestor of Homo.
Australopithecus aethiopicus
A. aethiopicus (sometimes called Paranthropus aethiopicus)
dates to 2.8-2.2 mya.
The original fossil, called the Black skull due to the stain from
minerals in the
soil, was found in Lake Turkana, Kenya. The Black Skull has
the smallest adult
5
brain, most prognathic face, and largest sagittal crest of any
well-established
hominid. In general, these fossils were considerably more
robust than the gracile
forms in those features involved with chewing. These large
cranial features point
to a diet of large amounts of vegetable matter emphasizing
seeds, nuts, hard fruits,
and tubers. This is confirmed with microscopic wear on the
teeth. Fossils of this
species have also been found in Ethiopia.

9. KNM WT 17000 or “Black skull” from Kenya with both derived
and primitive traits.
Australopithecus robustus
A. robustus was found in South Africa and dates between 1 and
2 mya. Like aethiopicus
it retains the body size of the gracile australopiths but there is a
slight increase in brain
capacity. The jaws are heavy, the back teeth are large, and there
is a sagittal crest-all
indicating a mixed, tough, vegetable diet. But the crania are not
as robust as aethiopicus.
A. robustus: SK 48 (left) and SK 46 (right)
Sagittal Crest
6
Australopithecus boisei
A. boisei was found in Tanzania, Kenya, and Ethiopia and
existed between 1.2-2.3 mya.
Boisei shows features that, along with aethiopicus, are
sometimes referred to as
“hyperrobust”. “Zinjanthropus”, found by the infamous
Leakeys, was the first specimen
of the species found. Dubbed “the nutcracker man”, this
specimen has extremely large
jaws and back teeth with a large sagittal crest.

10. A. boisei: “Zinj”.
Putting it all together
As stated in your text, the relationship among australopithecines
and their relationship to
Homo are still debated by anthropologists. Most would agree
that the robust forms
represent a separate evolutionary dead end branch and that at
least one of the more
gracile forms led to the genus Homo. Please refer to pg. 140 of
your text.
Homo
When the Leakeys discovered the robust australopithecine, Zinj,
they also found stone
tools at the same level as the fossils. They felt that Zinj was
too primitive to make these
tools in this time period called the Lower Paleolithic (or early
stone age). The tools,
called Oldowan (from Olduvai gorge where they were found)
are simple pebble tools:
water-worn cobbles 3-4 inches in diameter that have been
modified by knocking off
flakes from one or two sides to make a sharp edge. More recent
research suggests that
even at this time hominids may have been utilizing the flakes
(in addition to the cores) for
such tasks as cutting meat and plant material, scraping meat off
bone, and sawing wood
or bone. Microscopic analysis reveals polish along the edges of
the flakes that indicate
these kinds of use.

11. 7
Oldowan tools from the University of California Berkeley
Collection and University of
Indiana Collection/Lithic Casting Lab.
There has been some relatively new research suggesting that
australopiths may have
manufactured stone tools but the majority of evidence, and that
which is accepted by the
scientific community, is that the first hominid to manufacture
tools were members of
Homo habilis (“handy man”).
Homo habilis/Homo rudolfensis
Homo habilis shows an increase in brain size from the earlier
australopithicine genus.
The presence of stone tools indicates that these larger brains
were capable of a
complexity of thought not seen previously marking a beginning
of a new trend in
hominid evolution. Dating to 2.3-1.6 mya, H. habilis has been
found in Tanzania, Kenya,
Ethiopia, and perhaps southern Africa. Like australopiths, their
taxonomic affiliations are
not yet agreed upon. Fossils from east Turkana, Kenya are
different enough to be
considered a separate species, Homo rudolfensis. Rudolfensis
has a larger body and brain

12. size than habilis and lacks the continuous brow ridge existing
over the eyes. Others
believe that they are still a single species, habilis. The limb
proportions of both of these
early Homo species resemble A. africanus more than any other
australopith. This is why
africanus is usually argued to be the direct ancestor to our
genus.
Early Homo, it is hypothesized, lived in small cooperative
groups, possibly families,
foraging in mixed grassland/woodland areas for plant food and
carnivore kill. Their big
brains allowed them to better understand and manipulate their
environment, making
8
creative and technologically advanced stone tools that allowed
them to process the
carcasses they found and take them back to a safe place to
finish the job. It was likely a
harsh life, but they were successful. The adaptive abilities of
bipedalism, large brains,
social organization, and tool technology set the course for the
rest of hominid evolution.
Homo habilis (OH 24) and Homo rudolfensis (KNM ER 1470)
Homo erectus
In 1891 the first fossils of Homo erectus were discovered in
Java. At the time most

13. people thought that humans had first evolved in Asia, despite
Darwin’s suggestion that
Africa was the birthplace. When Eugene Dubois found a skull
cap and diseased femur
that he thought represented the “missing link” between apes and
humans, he called it
Pithecanthropus erectus, popularly known as Java man. Since
then numerous similar
fossils have been found in java and they are now recognized as
belonging to our genus
but a different species, Homo erectus. H. erectus in this region
is similar to H. erectus on
Asia and Africa except that their average brain size is often
larger.
Some of the more famous and numerous erectus fossils come
from Zhoukoudian, a cave
outside of Beijing, China dating between 460 and 230 kya. In
addition to the hominid
fossils, stone tools and animal bones have also been found.
New evidence suggests that
most of the H. erectus bones in the cave were the remains of
hyenas’ meals. Part of the
fame associated with Zhoukoudian lies in the fact that the
Peking Man went missing.
When the Japan invaded China in 1937, U.S. Marines
attempting to get the fossils out of
the country were captured by Japanese troops. The fossils have
been missing ever since
but this happened after measurements and casts of the bones had
been made.
It should be mentioned that the oldest fossils of this group
found in Kenya are considered
by some to be a separate species, Homo ergaster (work man). In
some ways these are

14. typical of Homo erectus from Asia: heavy brow ridges,
prognathic face, sloping forehead,
elongated profile, sagittal keel, and sharply angled occipital
bone with a pronounced bony
ridge (torus), and similar cranial capacity. In other ways they
differ: the bone is thinner
with smaller facial bones. These modern looking features are
what led to its placement in
9
the species H. ergaster. However, your text treats these fossils
the same, referring to
them as H. erectus.
From the neck up, Homo erectus/ergaster is quite distinct from
early Homo
(habilis/rudolfensis) in overall size, ruggedness, and
particularly brain size. The skull
still retains primitive features that distinguish it from modern
Homo sapiens.
Homo erectus skull cap (Sangirin 2) and Homo ergaster (KNM
ER 3733)
According to recent data, H. erectus reached China and
Southeast Asia by at least 1 mya
and perhaps as much as 1.8 mya. What prompted them to leave
the savannas they seemed
so well-adapted for? We don’t know for sure but some think it
is because of their

15. reproductive success. Their big brains allowed them to exploit
the savannas more so than
any of the earlier species of Homo. They had better and more
variable tools (discussed
below) and an increased ability to learn about their environment
and face the challenges
in it. They also likely had a more complex social organization.
With these adaptations,
H. erectus would have rapidly increased in population size.
With increase in population
size, however, comes competition for resources and pressure on
social groups. This may
have prompted H. erectus to move outside the familiar region to
seek out new resources
such as food, water, and shelter. Thus, they moved to China,
Indonesia, and perhaps
Europe, where they were eventually confronted with new
selective pressures of the
Pleistocene, in particular a drop in worldwide temperature.
What’s different about the H. erectus brain? Although it is
larger than early species of
Homo, it was not disproportionately larger than expected given
their larger body size.
Although the brains themselves are not preserved, a cast of the
brain (endocast) can be
made from the existing skull. Endocasts made from H. erectus
are similar in some ways
to Homo sapiens. Like modern humans, their brains were
asymmetric-because of the
specialization of the differing hemispheres (we see this also in
Old World monkeys and
chimps). Some research indicates that H. erectus possessed
linguistic skills and the
ability to manipulate symbols, along with hand-eye coordination
similar to ours. Not

16. everyone is convinced. But their brain seems to be associated
with several important
innovations: tool manufacture, controlled use of fire,
cooperative hunting, and language.
While we still see some of the simple pebble technology
associated with H. erectus, we
more often find a sophisticated toolmaking tradition called
Acheulean where the end
10
result is a hand axe. A hand axe is a symmetrical, edged,
pointed, bifacially flaked tool
that may have served many purposes-piercing animal flesh,
scraping hides, cutting wood,
digging roots. That the Acheulean tradition evolved from the
Oldowan, seems clear.
Oldowan choppers found in South Africa resemble crude hand
axes. Acheulean tools
arrive in Africa at about 1.4 mya, spread to Europe, and
continue to the Upper
Pleistocene. Though, hand axes are commonly found in Africa
and Europe, they are
absent from most H. erectus sites in Asia east of India. This
dividing line is so clear that
it has been called the Movius Line (named for the researcher
who first articulated it).
The fact that hand axes don’t exist east of the line, doesn’t
necessarily mean that these
hominids were less advanced. Perhaps there was a lack of
suitable stone or they relied on
other material; some have suggested that bamboo may have been
utilized for a similar

17. function as the hand axe. The line may also suggest that
hominids left Africa and arrived
in East Asia before the hand axe was first developed in Africa.
The Movius Line.
The ability to control fire is significant: providing heat and
light, protection from
predators, and the ability to cook food. Your text provides a
few examples of the earliest
use of fire but there are more possibilities, some dating to 1.6
mya in Kenya and China.
Similarly, your text points out only a couple of the sites that
reveal evidence of hunting.
Seasonal hunting camps where groups of individuals came
together to hunt, socialize, and
exchange information are potentially found in Spain, Kenya,
and Tanzania. The sites
have large concentrations of prehistoric animals that appear to
have been stampeded or
driven into a swamp, where they were then killed and butchered.
In some cases stone
tools are found in association with the animal bones. If the
interpretations are correct, we
can infer a high level of knowledge, cooperation, and
coordination among hominids
living several hundred thousand years ago.
Despite the fact that Homo erectus is now extinct, it was
certainly a success. Evolving
nearly 2 mya in Africa, possibly from an earlier species (Homo
ergaster) and spreading

18. as far as Java by 1.8 mya, reaching China and Europe by 500
kya, and lasting in Africa
11
and China until 250 kya, their adaptations clearly allowed them
to exploit a number of
different environments.
Weekly Readings Summary
Wilson 2007
This week wraps up the Wilson book with chapters 31-36. Here
he provides another
example of large groups in culture functioning as a collective
unit – nations. And he
reiterates, behavioral diversity can be studied like biological
diversity.
1
Lecture 3
Lecture Summary
Your text does not cover macroevolution until Chapter 5. If you
want you can skip ahead
and read the first few pages to help familiarize yourself with
what we’ll discuss here. I
want to go ahead and start talking about macroevolution now
within the context of our

19. discussion on evolution. I’m going to be tossing out a bit of
vocabulary here and all of it
is important (or I wouldn’t bother to include it). It’s important
to understand how
evolutionary biologists and paleoanthropologists bring order to
the varieties of groups of
living organisms. More specifically, we need to understand the
framework for looking at
the evolutionary relationships between them and placing them
into a family tree.
Macroevolution
We need a way to deal with the million of species that live
today and those that are no
longer living. We cope with this diversity by grouping
organisms together through a
classification system. Classification is the ordering of
organisms into categories such as
phyla, orders, and families to show evolutionary relationships -
taxonomy is the field that
specializes in the rules of classification. Very simply, animals
are organisms that move
about and ingest food (but do not photosynthesize as plants do).
Multicelled animals are
placed in a group called metazoa. Within the metazoa there are
more than twenty phyla.
One of these phyla are called chordata, animals with a nerve
cord, gill slits (at some stage
of development), and a stiff supporting cord along the back
called a notochord. Most
chordates today are Vertebrates, where the notochord has
become a vertebral column.
They also have a developed brain and paired sensory structures
for sight, smell, and
balance. Vertebrates are then divided into six classes-the one
we’re most concerned with

20. is mammals. Animals are classified first and most traditionally
by physical similarities.
This is often the starting point but for similarities to be useful
they must reflect
evolutionary descent. Structures that are shared by species on
the basis of descent from a
common ancestor are called homologies. We need to be careful
in making these
assessments, though, e.g. just because birds and butterflies both
have wings doesn’t mean
they have a common winged ancestor- birds and insects are very
different in more
fundamental ways. They developed wings independently, their
similarities are a product
of separate evolutionary responses to similar functional
demands. These kinds of
similarities are called analogies; they are based strictly on
common function and no
assumed evolutionary descent. The process leading to analogies
is called homoplasy
(homo meaning same and plasy meaning growth). The following
PBS web site has a fun
exercise to test your knowledge on homologies and analogies:
http://www.ucmp.berkeley.edu/help/timeform.html
There are two approaches or “schools of thought” by which
evolutionary biologists
interpret evolutionary relationships and produce classifications.
Both of these approaches
trace evolutionary relationships and construct classifications
that reflect these
relationships and both recognize that organisms must be
compared for specific features
and some of these features are more informative than others.
They also both focus
exclusively on homologies. But they differ in other ways:

21. 1.) Evolutionary systematics (also called gradistic taxonomy) –
this is the more
traditional approach and uses a phylogeny to illustrate the
evolutionary relationships. A
2
phylogeny or phylogenetic tree is a tree showing evolutionary
relationships as
determined by evolutionary systematics-it contains a time
component and implies
ancestor-descendent relationships.
2.) Cladistics – this approach is relatively new, emerging in the
last few decades and is
the predominate one among anthropologists. Cladistics more
explicitly and more
rigorously defines the kinds of homologies that yield the most
useful information. For
example terrestrial vertebrates share homologies in the number
and basic arrangement of
bones in the forelimb. This feature is useful for showing that
large evolutionary groups
(amphibians, reptiles, birds, and mammals) are all related
through a common ancestor, it
does not provide information useful for distinguishing one from
the other (e.g. a reptile
from a mammal). Such traits that are shared through common
ancestry are called
primitive or ancestral. (Careful of thinking of primitive as
negatively-it does not mean
to reflect evolutionary value but simply that the trait in two
organisms comes from a
common ancestor). The traits that cladistics focus on, those that
are more informative, are

22. ones that distinguish evolutionary lineages-called derived or
modified. Strict cladistics
shows relationships in a cladogram rather than phylogeny.
Cladograms do not indicate
time and make no attempt to discern ancestor-descendent
relationships in terms of time.
Also, both living and fossil forms are shown along the same
dimension.
In practice, most anthropologists and evolutionary biologists
expand cladistic analysis to
further hypothesize likely ancestor-descendent relationships
shown relative to a time
scale. In this way, both aspects of traditional evolutionary
systematics and cladistics are
combined to produce a more complete picture of evolutionary
history. In addition to
organizing life forms, time itself has been organized in the
geologic time scale (make
sure you eventually read the section on this in Chapter 5).
Organisms have been
profoundly influenced by geographic events during this time
scale such as continental
drift or the movement of the continents on sliding plates of the
earth’s surface.
For a quick glance at the geologic time scale click here:
http://www.ucmp.berkeley.edu/help/timeform.html
Note that we’re only concerned with the Cenozoic Era for the
majority of this course.
This brings us back to the mammals. The end of the Mesozoic
approximately 65 million
years ago marks the end of the dinosaurs and the opening of a
wide array of ecological
niches for the rapid expansion and diversification of mammals.
The relatively rapid
expansion and diversification of life forms into new ecological
niches is more generally

23. called adaptive radiation. This next division in time, the
Cenozoic, is thus called the
Age of Mammals. Mesozoic mammals were small, resembling
mice, but the Cenozoic
brought various types of mammals that, along with birds,
eventually replaced the reptiles
as the dominant terrestrial vertebrates. Why were the mammals
so successful? They had
larger and more complex brains than reptiles. In order for this
kind of brain to develop, a
longer period of growth is required. Dentition was also
different-having more variable
tooth types than reptiles. Finally, mammals have a constant
internal body temperature and
generate energy internally through metabolic activity. The three
major subgroups of
living mammals include egglaying, pouched, and placental. The
primates are of course
placental. But before we discuss early primate evolution (we’ll
save this for next week)
we need to say a little more about macroevolution.
3
The single most important factor underlying macroevolutionary
change is speciation –
the process by which new species are produced from earlier
ones. Species are a group of
reproductively isolated organisms- a characterization that
follows the biological species
concept developed by Ernst Mayr. According to this view, new
species are first produced
through some form of isolation, e.g. if a group is separated by

24. an ocean or
mountain range (geographical isolation). Over time these two
populations, because they
are unable to mate, will accumulate genetic differences. If the
population size is small we
can predict genetic drift to cause allele frequencies to change
(differently) in both
populations. The two populations will diverge through genetic
drift and natural selection
and eventually become separate species. Isolation can also
result from behavioral
differences (behavioral isolation), e.g. when behavioral
differences prohibit mating. Like
interpreting evolutionary relationships, there are two different
“schools of thought”
concerning the modes of evolutionary change- phyletic
gradualism and punctuated
equilibrium. The traditional view of evolution has emphasized
that change accumulates
gradually in evolving lineages – phyletic gradualism. In this
view, the entire fossil
record of an evolving group (if it could all be recovered) would
display a series of forms
with finely graded transitional differences between each
ancestor and its descendent. The
fact that such transitional forms (missing links) are rarely found
is attributed to the
incompleteness of the fossil record. Anagenesis refers to the
gradual, linear change that
occurs within a single line. For more than a century this idea
dominated evolutionary
biology but in the last few decades most biologists have called
this notion into serious
question. The evolutionary mechanisms operating on species
over the long run are often
not continuously gradual. In some cases, species persist for

25. thousands of generations
basically unchanged. Then suddenly (at least in evolutionary
terms) a spurt of speciation
occurs. This uneven, nongradual process of long stasis
interrupted by quick spurts is
called punctuated equilibrium. The idea was introduced by
Stephen J. Gould and Niles
Eldridge (not “Eldred” like it says in your book!) in the 1970s.
For the original paper
click here:
http://www.nileseldredge.com/pdf_files/Punctuated_Equilibri
a_Gould_Eldredge_1977.pdf
Advocates of punctuated equilibrium are disputing the tempo
(rate) and mode (manner)
of evolutionary change. Rather than gradual accumulation of
small changes in a single
lineage, another mechanism of evolution is necessary to push
the process along -
speciation. Punctuated equilibrium emphasizes cladogenesis –
the formation of branches
or clades. The paleontological record seems to support this idea
showing long periods of
stasis punctuated by rapid change (at an approximated 10,000 to
50,000 years). The
primate fossil record shows a bit of both gradualism and
punctuated equilibrium.
One more thing about species…you may be wondering…how do
anthropologists make
species determinations from fossils? How do we know if extinct
species were
interbreeding or not? The answer is we don’t. In modern
organisms we have no trouble
defining interbreeding groups of organisms-we just observe
them. But in the fossil record
we need to look at morphological similarities and refer to living
animals (their closest

26. living relatives). We need to determine if the variation we see is
biologically significant.
Either the variation is due to individual, age, or sex differences
or the variation represents
differences between reproductively isolated groups. Applying
strict Linnaean taxonomy
to such a situation presents an unavoidable dilemma. Making
decisions about
paleospecies can be somewhat arbitrary and this is true at the
genus level as well. It’s no
4
wonder there are “lumpers” (those that group like forms
together) and “splitters” (those
that focus on the differences to split individuals into groups) in
the field.
Weekly Reading Summary
Wilson 2007
In this week’s readings Wilson reminds us that we are 100%
products of evolution just
like any other animal and that evolution can, in fact, tell us a lot
about ourselves. Again,
one doesn’t need to be an expert to apply these concepts to
everyday life. He gives the
example of pregnancy sickness and homicide, which can both be
explained using
evolutionary principles. Evolutionary theory, he says, can be a
tool for change. Finally,
diversity doesn’t end at the species level. Individuals are also
diverse-this is where
personality comes into play.

27. Anth 330
Fall 2015
Summation paper
This is a summation document so there is no right or wrong
answer but I do want to see that you put some serious thought
into your response. The paper is worth 50 points that can
seriously help your final point total. I would recommend that
you answer the first part of the question now. Wait to answer
the second part of the question in week 10 near the end of the
lecture cycle. Turn in this paper at the final exam on Tuesday
December 8th. No electronic submissions.
I have found that a great many people know very little about
human evolution. There tends to be more fiction than fact out
there. Other than a few bits of historical fact and fiction
(mostly concerning Charles Darwin) many people have a poor
understanding of the historical development of the concept of
biological evolution and the Western World’s concept of time.
1. Briefly summarize your understanding of the concept of
human evolution and geological/archaeological time before you
took this course. I expect your answer to be at least 2 pages and
no more than three.
2. How have your concepts on these subjects changed having
taken this course? What are the two most interesting ideas that
you have gleaned from the readings or lecture material? I expect
your answer to be at least 2 pages and no more than three.
3. Has any information touched on in this class made you think
about taking any further course work in the subject area?