Option D3 IB Biology

1. Option D: Evolution
D3 Human evolution
WE DID NOT EVOLVE FROM MONKEYS!
(And no decent scientist says we did). Instead, we share a common
ancestor.

2. What you need to be able to do
and understand:
 D.3.1 Outline the method for
dating rocks and fossils using
radioisotopes, with reference to
14C and 40K.
 D.3.2 Define half-life.
 D.3.3 Deduce the approximate
age of materials based on a
simple decay curve for a
radioisotope.
 D.3.4 Describe the major
anatomical features that define
humans as primates.
 D.3.5 Outline the trends
illustrated by the fossils of
Ardipithecus
ramidus, Australopithecus
 D.3.6 State that, at various
stages in hominid
evolution, several species
may have coexisted.
 D.3.7 Discuss the
incompleteness of the fossil
record and the resulting
uncertainties about human
evolution.
 D.3.8 Discuss the
correlation between the
change in diet and increase
in brain size during hominid
evolution.
 D.3.9 Distinguish between
genetic and cultural
evolution.
 D.3.10 Discuss the relative
importance of genetic and

3. How old is old?
The universe is full of naturally occurring radioactive
elements. Radioactive isotopes are inherently
unstable; over time, radioactive ―parent atoms‖
decay into stable ―daughter atoms.‖
When molten rock cools (igneous rocks), radioactive atoms (isotopes) are
trapped inside. Afterwards, they decay at a predictable rate. By measuring the
quantity of unstable isotopes left in a rock and comparing it to the quantity of
stable daughter isotopes in the rock, we can estimate the amount of time that
has passed since that rock formed.
Fossils are generally found in sedimentary rock—not
igneous rock. Sedimentary rocks can be dated using
radioactive carbon-14, but because carbon decays
relatively quickly (half-life of 5730 yrs), this only works for
rocks younger than about 50 thousand years.
So in order to date most older fossils, scientists look for
layers of igneous rock or volcanic ash above and below
the fossil. We date igneous rock using elements that are
slow to decay, such as uranium and potassium (half-life of
1.3 billion years). By dating these surrounding layers, they
can figure out the youngest and oldest that the fossil
might be; this is known as ―bracketing‖ the age of the

4. Dating with carbon-14
(14C)
Half-life is the period of time it takes for a substance
undergoing decay to decrease by half.
Watch this short clip on carbon
dating
C-14 is used to date organic materials.C-14 is formed as the
result of the bombardment of Earth by cosmic rays, mostly
protons. When the protons crash into atoms high in the
atmosphere they create a ton of things, including neutrons.
Neutrons that strike the nuclei of nitrogen atoms cause the
following reaction:1
0n + 14
7N 14
6C + 1
1p
This reaction happens at a relatively steady rate. The
carbon atoms then combine with oxygen to produce
carbon dioxide. About 1 molecule in each trillion contains
C-14 instead of C-12. C-14 decays radioactively with a
half-life of 5730 yrs. As long as a plant (or animal)
lives, its organic material contains the same fraction of C-
14 as does the atmosphere. When the organism dies, it
no longer exchanges C with the atmosphere and the
decaying C-14 is not replaced. So the fraction of C-14 to
C-12 can be used to determine the time of death of the
organism.
Carbon dating is only accurate to about 60,000 years-
farther than this we have to use other radioactive
isotopes…

5. Dating with potassium-40 (40K) Watch this short clip on radiometric
dating- using uranium as an example
Potassium-argon dating uses the radioactive
isotope potassium-40. Potassium-40 naturally
decays to argon gas. These two elements
(among others) are contained in volcanic rock.
When the rock is molten, it releases gases
such as argon into the atmosphere. As it cools
and hardens, the volcanic rock traps the gases
inside small crystals. The potassium-40
continues to decay into argon gas, but the gas
cannot escape the rock. Geologists can melt
the rock and measure how much time has
passed since the rock was molten.
The half-life of potassium-40 is 1.3 billion
years. Because it takes at least 200,000
years for enough argon gas to build up to
allow accurate measurement, the
potassium-argon technique is used to
date older objects.

6. A review of all the different types of
dating methods
Data analysis activity
Go to the VLE and download the
word document called ―Working
with decay curves‖- this will be
graded. You will learn how to
analyze half-lives and determine
the age of a sample using a
simple decay curve like this one:

7. Why are we primates?
Primates include:
humans, apes, monkeys, tarsiers, lemurs
and lorises.
What are the common characteristics for all
primates?
•grasping limbs, with long fingers and a
separated opposable thumb
•mobile arms, with shoulder joints allowing
movement in three planes and the bones of
the shoulder girdle allowing weight to be
transferred via the arms
•stereoscopic vision, with forward facing
eyes on a flattened face, giving overlapping
fields of view
There are around 230 or so living species of primate, a
number which represents only a tiny fraction of all the
primate species which have once existed on our planet.

8. A common ancestor for all
primates
Read this article on a recently discovered
fossil named ―Ida‖:
http://www.sciencedaily.com/releases/2009
/05/090519104643.htm
The fossil is a transitional species – it shows characteristics from the very
primitive non-human evolutionary line (prosimians, such as lemurs), but is more
related to the human evolutionary line (anthropoids, such as monkeys, apes
and humans). At 95% complete, the fossil provides the most complete
understanding of the paleobiology of any Eocene primate so far discovered.

9. What are hominids?
The Hominidae are great apes and humans. They form a taxonomic family, including
four existing genera: chimpanzees, gorillas, humans, and orangutans. Hominidae is a
family within the order Primata which is defined by bipedal locomotion.
One trend in hominid evolution includes
increasing adaptation to
bipedalism, especially forward
movement of the foramen magnum.
Watch this clip on why
chimps, gorillas, and orangutans have
48 chromosomes and humans have 46.

10. Understanding standing up
http://www.becominghuman.org/node/building-bodies
Anthropologists and evolutionary biologists agree that upright posture and the
subsequent ability to walk on two legs was a crucial major adaptation associated
with the divergence of the human lineage from a common ancestor with the
African apes. Efficient upright walking required numerous changes in the anatomy
of the limbs and pelvis and we are the result of the variations and selection
pressures that forged this new ability. The ability to walk on two legs was later
followed by other human evolutionary trends that lead to tool manufacture and the
enlargement of the brain.
Can you separate the bones
between a chimpanzee and a
human?
Can you see the small
differences that enabled
humans to walk upright while
chimpanzees have a form of
walking called a ―knuckle walk‖
See this recent article
on national
geographic about a
foot fossil

11. tree
This evolutionary tree depicts
lines of possible descent for
hominids. In other words, it
proposes relationships among
species over time. All trees are
hypotheses, and are based on
comparison of living
species, fossils, and genetic
data.
Dashed lines show how
related species diverged from
each other through a common
ancestor.
Faded lines indicate very
unclear origin or descent.
Branch points are called
nodes. Nodes indicate a
species that once lived, and
was the common ancestor of
two or more descendants.
Horizontal lines indicate time.
Orange vertical bars indicate
From:
http://www.amnh.org/education/resources/rfl/web/hh
oguide/tree.html

12. Why are there faded lines on the hominid family tree?
Because the hominid fossil record is incomplete, it is unclear how the various
hominid species are related.
Why is the fossil record incomplete?
The fossil record for hominids is incomplete because it is difficult for remains of
animals living in arid or semi-arid habitats to fossilize. Fossils only form when buried
under sediment before decomposition occurs. Another reason is that animal bodies
are usually eaten by detritivores, decomposed by bacteria, or broken down
chemically. For example, organic acids react with alkali (bases) in bones and teeth
therefore, few fossils found of savanna-dwelling hominids.
If remains do become fossilized, most remain buried in sediment or may never be
found. Hominid fossils that have been found may or may not be representative of
hominid history- anthropologists are unsure of their history so more questions may
arise. Hominid fossils that have been found are usually partial, and the remainder of
the organism must be inferred. These inferences may or may not be correct. As only
hard parts of individuals fossilize this leaves many questions concerning the rest of
the individual’s phenotype (physical characteristics).
A) The complete evolutionary history would show
gradual transitions between these forms. (B) A
relatively complete fossil record preserves only one of
the speciation events, but still shows evidence of
gradual change. (C) A typically incomplete fossil
record shows only scattered forms through time. (D)
Reconstruction of the evolutionary history based on
co-occurence and similarity of forms incorrectly shows
Species 2 as having evolved from the extinct
species, and seriously underestimates the time of

13. We are going to
focus on:
•Ardipithecus
ramidus
•Australopithecus
afarensis
•Australopithecus
africanus
•Homo habilis
•Homo erectus
•Homo
neanderthalensis
•Homo sapiens
As you can see a
number of
Australopithecus and
Homo species
probably coexisted

14. •Australopithecu
s sp. purple/gray
squares
•Homo habilis-
dark blue
squares
•Homo erectus-
light blue
squares
•Homo
neanderthalensis
- yellow/orange
squares
•Homo sapiens-
red squares
Where
have we
found
these
fossils?

15. Ardipithecus ramidus: 5.8 mya - 4.4
mya
Go to: http://www.glencoe.com/sec/science/cgi-
bin/splitwindow.cgi?top=http://www.glencoe.com/sec
/science/top2.html&link=http://www.talkorigins.org/fa
qs/homs/specimen.html for more information on
hominid fossils
Its age is about 4.4 million years. Ar. ramidus is
considerably more primitive than the
australopithecines. The skull and brain size are
very small, comparable to a chimpanzee. The
teeth fossils show that ramidus was
omnivorous, unlike chimps which are adapted to a
diet of mostly fruit, and australopithecines which
were adapted to heavy chewing on abrasive
foods. Ar. ramidus also has greatly reduced
canine teeth in the males, compared to apes. This
is important because in apes canine teeth are
important weapons against other males in the
social group, so the diminished canines probably
indicate a significant change in the social
dynamics of ramidus.
The leg and pelvis bones show only imperfect
adaptation to bipedalism, compared to
australopithecines.

16. Australopithecus afarensis: 3.9 mya - 3
myaA. afarensis which lived from 3.9 to 3.0 million years ago, is
one of the first species to appear after the split between
emerging hominids and ancestor chimpanzees. It seems to
descend directly from Australopithecus anamensis, a
species of large ape that lived from 4.2 to 3.9 million years
ago.
Not surprisingly, there are several points of resemblance
between the afarensis and chimpanzee skulls: a
wide, apelike face with a low forehead, bony browridges, flat
nose, protruding upper jaw, and a massive lower jaw with
large back teeth. (The pointed canine teeth, missing from
the afarensis fossil, were smaller than those in modern
apes.) Both have a brain volume of around 480cc. The
shape of the jaw is intermediate between the rectangular
shape of apes and the parabolic shape of humans.
The larger australopithecine body included changes to the
spine, pelvis and leg joints that make walking an effective
form of locomotion. Though still capable of climbing and
resting in trees, a habitual bipedal posture freed the hands
to manipulate, carry and throw objects. Though the finger
and toe bones are curved and proportionally longer than in
humans, afarensis hands were similar to humans in most
―Lucy
‖

17. Australopithecus africanus: 3 mya - 2
mya About 3 million years ago, Australopithecus
afarensis gave rise to two distinct evolutionary lines:
one leading into the first humans, and the other into
the robust australopithecines. Though its place is still
unclear, A. africanus is most likely the key
transitional species toward the emergence of the
human line.
It's really in the skull that africanus is noticeably
different from afarensis: in the more vertical slope of
the face, the narrower cheekbones and reduced
browridges, and the more rounded shape of the
cranium. Brain endocasts show significant increases
in the frontal and parietal lobes in comparison to
chimpanzee brains; the africanus brain clearly
prefigures that of humans. The teeth are also more
similar to human teeth than to those of modern apes;
the canine teeth are smaller than those in
afarensis, and the shape of the jaw is now fully
parabolic, again like humans. These features
"Taung
Child‖

18. Homo habilis: 2.4 mya - 1.5
mya Discovered by the Leakeys in the early 1960's at
Olduvai Gorge in Tanzania. H. habilis lived from
about 2.4 to 1.5 million years ago, and is the earliest
known species to show novel differences from the
chimpanzee and australopithid skulls. The face is
still primitive and projecting, but the jaw is pulled
under the brain, with smaller molars (though still
much larger than in modern humans), and the skull
is thinner, with a distinctive rounded shape, vertical
sides and a small forehead above the brows. The
first humans have arrived on the scene.
In habilis, increased brain power coincided with the
first known use of manufactured stone or quartz
tools (hence the choice of name, which means
"handy man‖).
Despite its distinctively human cranium and its
chronological position near the origin of the human
line, habilis had a fairly apelike physical form: its
arms were almost as long as its legs. It is therefore

19. Homo erectus:
1.8 mya –
300,000 yrs ago H. erectus represents a long line of fossils found in
eastern Africa, the Middle East and southern and
southeastern Asia from about 1.7 million to 200,000
years ago.
Erectus shows a gradual lightening of the ergaster
features, though many similarities in the skulls
(pronounced browridges and an elongated brain
case) persist. Indeed, some of the erectus
modifications are adaptations for heavy chewing
power, and in that sense reflect a radiation into the
ecological niches and diets dominated in Africa by
the australopithecines.
Brain capacity increased gradually throughout the
erectus line, from a range of 800cc to 1060cc at the
time erectus first appeared to a range of 1060cc to
1300cc around the time it went extinct.
Despite its long survival and continually increasing
brain size -- and cultural advances that included
geographic dispersion throughout southern Asia, the
domestication of fire, refinement to Acheulean
―Peking Man‖
―Java Man‖ ―Chellean Man‖
―Turkana Boy‖

20. Homo
Neanderthal
ensis:
230,000 -
30,000 yrs
ago
H. neanderthalensis, which lived from about 250,000 to
30,000 years ago, is the last species to diverge from the
human line prior to the emergence of modern humans, and
the last species of hominid to have gone extinct.
Neandertals lived mostly in cold climates, and their body
proportions are similar to those of modern cold-adapted
peoples: short and stocky with solid limbs.
Neandertals had a slightly larger brain capacity than
modern humans (1450cc on average, but as large as
1800cc or more), with a developed material culture and
some form of spoken language. A large number of tools
and weapons have been found from Neandertal sites, all
from the Mousterian tool industry. Neandertals were
formidable hunters, and are the first people who may have
buried their dead, with the oldest known burial site dated to
around 100,000 years ago.
Like erectus, Neandertals had a protruding jaw, weak chin
and receding forehead. The nose and brow also protruded
and was probably an adaptation to cold climates. The brain
case is longer and lower than that of modern humans, with
a marked bulge at the back of the skull. Bones are thick
and heavy and show signs of powerful muscle
attachments.
The extinction of Neandertals coincides in most geographic regions with the arrival
of modern humans and the most recent Ice Age. There is no reason to conclude
that Cro Magnon man intentionally eradicated the Neandertals. Neandertals
already led a difficult, scarring existence. Add to this the final glaciation of their
northern ranges, the increased competition with Homo sapiens for large game, and
perhaps too the new diseases that the southern immigrants brought with them.

21. Homo sapiens: 195,000 yrs ago -
present
Our ancestors seem to have appeared out of
some regional subpopulation of Homo
heidelbergensis over 130,000 years ago, most
likely in the Kenya-Tanzania area of Africa.
In sapiens the face is markedly shrunken in
relation to the brain, which attains an adult size
of 1040cc to 1595cc. The forehead rises
sharply, browridges are very small or
absent, and the chin is prominent.
The skeleton is very gracile; bones are lighter
and smoother, without any loss in body size.
Compared to the Neandertal skull, modern
humans (shown in a Cro-Magnon exemplar)
look almost infantile. The cranium seems
vulnerably round and delicate.
Discovered by workmen in 1868
at Cro-Magnon, in the village of
Les Eyzies in France. The
estimated age of the site is
30,000 years. The Cro-
Magnons lived in Europe
between 35,000 and 10,000
years ago.
―Cro-Magnon Man‖
For more information go to:
http://www.handprint.com/LS/ANC/evol.html

22. http://www.pbs.org/wgbh/nova/evolution/whos
-who-human-evolution.html
Using this online interactive tool can you identify any
trends and patterns in Hominid evolution?
Trends and patterns in hominid evolution:

23. Trends and patterns in hominid evolution:
When looking at hominid evolution some
trends and patterns can see seen:
•increasing adaptation to
bipedalism, especially forward movement
of foramen magnum
•increasing brain size in relation to body
size
•hominids originated in Africa and spread
to other continents
Ardipithecus fossils found in Ethiopia
Australopithecus and Homo habilis
fossils found in Southern and
Eastern Africa
Homo erectus fossils found in
Eastern Africa and in Asia
Homo neanderthalensis fossils found
in Europe
Homo sapiens fossils found in all
continents except Antarctic
•decreasing relative size of:
face, jaw, teeth, especially canines;
increasing relative size of brain
Cranial capacities plotted against time.
Key to symbols;
triangles, (Australopithecus africanus);
squares, australopithecines from South
and East African (Paranthropus);
circles, Homo (filled, individual
specimens; open, group averages)
Read more: Brain Size Evolution - Constraints on
Brain Size, Selection for Neurological
Adaptations, Measuring the Size of Hominid
Endocasts, Figure 1
http://science.jrank.org/pages/48331/Brain-Size-
Evolution.html#ixzz17V2mrAlb

24. Note that as many as 4 or 5 species of early hominids were living at the same time.
Observe also that, in at least a half-dozen instances, a parental species continued to
exist for a lengthy period of time after a daughter species evolved. The arrangement
shown here is not accepted by all paleoanthropologists. For instance, there are some
who would merge H. erectus and H. heidelbergensis, considering them as one
species. Also, there are those who maintain the H. neanderthalensis is a subspecies
of H. sapiens while many others disagree. From: http://darwiniana.org/hominid.htm

25. Early hominids (Australopithecus) brain sizes were similar in size to those
of apes today. They had powerful jaws and teeth which indicated a mainly
vegetarian diet.
About 2.5 million years ago Africa became much cooler and
drier, savannah grassland replaced forest which may have prompted
evolution of Homo. This change in environment may have caused the
development of increasingly sophisticated tools for a change to hunting
and killing large animals instead of a vegetarian diet.
The increasing meat in diet corresponds to the start of increase in hominid
brain size in early hominids. Brain growth slows after birth but Homo has
rapid brain growth after birth as well.
How could this happen?
1. Eating meat increases supply of protein, fat and energy, making
larger brain growth possible.
2. Hunting and killing prey on savannas is more difficult than
Could a change in diet bring larger
brains? Read this article on diet and brain size in early
hominids: http://scitizen.com/evolution/diet-brain-
evolution-another-item-on-the-menu_a-27-
1088.html

26. Two TED talks on hominid evolution:

27. http://www.hhmi.org/biointeractive/evolution/Sci
entific_Process/01.html
To sum it all up!

28. Nature Vs. Nurture?
Which do you think plays the bigger role in human
evolution?
Diseases show a continuum.
Some, such as Down's
Syndrome, are completely genetic
in origin, while others, such as
scurvy, are completely
environmental. But most diseases
— ulcers, for example — are
somewhere in the middle: people
with different genes will react

29. Genetic Evolution-
“NATURE”
Cultural Evolution-
“NUTURE”
 inherited vertically between
generations
 physically inherited as genes
coded within DNA
 change is random, through
mutation
 natural selection determines
likelihood of inheritance
 occurs slowly as gene pools
alter gradually
 inherited
vertically, horizontally, or
between any group, across any
time or distance
 inherited physically or non-
physically, independent of DNA
 change can be random or
directed by intelligence
 selection determines likelihood
of inheritance
 can occur at any rate, typically
much more rapidly than genetic
evolution, and even
instantaneously
Read this article from Wired
Science:
http://current.com/1um864c

30. Genetic Evolution-
“NATURE”
Cultural Evolution-
“NUTURE”
 genes produce the
abilities to learn
language
 genes produce the
abilities to learn about
natural history
 genes produce the
abilities to learn complex
social information
 culture produces specific
languages
 culture produces specific
natural history
information
 culture produces specific
complex social
information
There is no nature without nurture, and no nurture
without nature
Is the product of selection for
genes producing large brains
which are capable of
learning.
Is the specific learning
done by groups of people
sharing similarly selected
large brains.

31. Why are cultural AND genetic evolution important?
Cultural evolution has played an increasingly greater role in the lives of
humans over time, especially over the past few thousand years, during which
human characteristics have changed hugely.
Genetic change happens too slowly to produce the huge changes in human
culture. Some cultural changes have, such as medical advances, reduced
natural selection pressures between phenotypes.
The last word…
http://www.pbs.org/wgbh/evolution/human
s/humankind/index.html

32. Read this article for a good chuckle on
what we have inherited
http://www.smithsonianmag.com/science-
nature/The-Top-Ten-Daily-Consequences-
of-Having-Evolved.html including a reason
for hiccups and goosebumps!