week 4 readings Flashcards
what were the (3) key developments in human evolution?
what necessitated this change?
Changing features can ___ to the increased complexity of behavior and cognition.
Key developments in human evolution were upright walk, tool usage, and brain size.
Environmental changes.
ratchet up.
is the relationship between genotype and phenotype always 1-1
what are (4) types of effects and examples of them.
no.
Direct link: gene has one distinct
biological effect.
Pleiotropy: where a gene has multiple
effects! (i.e., tameness and the
domestication syndrome)
Polygenetic: many genes contribute to
the same single effect (i.e., humans
think IQ is a latent variable-not directly
observable-construct; variation comes,
according to fishers’ principle, when
there are multiple genes contributing to
the same phylogenetic behavioural
expression).
Polygenetic and pleiotropy genes can
coccur and things can get pretty
complicated very quickly (via random
assortment).
The four laws of behaviour genetics
§ All human behavioural traits are
heritable (to some degree)
§ The effect of being raised in the same
family is smaller than the effect of genes
(genes > environment; in personality for
example)
§ A substantial portion of the variation in
complex human behavioural traits is not
accounted for by the effects of genes or
family (malleability to the environment;
or choice)
§ The missing gene problem: A typical
human behavioural trait is associated
with very many genetic variants, each of
which accounts for a very small
percentage of the behavioural variability
(a behavioural trait is associated with
many genes; polygenic).
The Tree of Life is…
Darwins phylogeny tree of life were scribbles as how he thought species were related. There are too many branches are not filled in. He was not operating from genetics view and more off of phenotypical similarities between species which is not the best method, but the best at that time.
three fields of study, three methods, and four questions you can answer looking at human evolution:
Fields of study:
1. Nonhuman primate evolutionary biology
2. Archaic Hominin adaptation &
introgression
3. Local adaptation in modern humans
Techniques:
- Omics
- Cell Culture
- Ancestral protein reconstructionQuestions:
- Morphology
- Diet
- Health
- Natural Complexity
Using mitochondrial DNA (passed on 1-1 to phenotypes) the powerhouse of the cell. Add it to Darwin’s tree of life and make it more accurate.
What is the timeline?
(A) Aye-Ayes, Lemurs and Loris
81-61 million
(B) Tarsir
77-64 million
(C) Anthropoids
(D) Proboscis Monkey
34-29 million
(E) Gibbons:
24-21 million
(F) Orangutan
18-16 million
(G) Gorillas
12-10 million
(H) Chimpanzee
7.6 million
(I) Sahelanthropus tchadensis
6-7 million
(J) Australopithecus (afrensis, africanus,
robustus)
4-2 million
(K) Homo habilis
2.3-2.58 million
(L) Homo Erectus
1.75 million
(M) Homo Sapiens
First wave, 250-300 thousand years
Second wave, 50-100 thousand yearsSahelanthropus tchadensis
Toumaï; “hope of life“
• Split off from our common ancestor 6-7
million years ago (approx. same time of
split from chimps)
• Is the first hominini
• Has the cranial capacity about the
same as a chimp.
• Found in the upper miocence of chad
in central Africa.
• Walked upright (not like humans;
foramen magnum position on the
spinal column to the head indicates
that they walked upright to align their
head for vision required for upright
walking some of the time)
• Smaller canines (different diet which
was plant based with more molars to
grind plant matter)
(3) Australopithecus
• Saddest of the human ancestors. There
are multiple types but the get lumped
together into one category.
• It is hard to extract DNA from the
fossils we have of them to compare
species together. We tend to rely on
morphology with only a single molar to
use.
• Three types: afrensis, africanus,
robustus.
a. Lucy In The Sky With Diamonds
• Lucy was discovered by Donald
Johansson in Hadar, Ethiopia in 1974 .
• There is debate in where she should be
classified.
• Indication of upright walking (walked
upright all of the time; her arms are
shorter and she can not knuckle walk
anymore; she is short).
• Why did she die? Fell from a tree or
strarved. Lucy belongs to the species
Australopithecus afarensis, and lived
3.2 million years ago. She stood around
1.1 metres (3.5 feet) tall and she walked
upright on two legs, although she
probably had a less graceful gait than
us, since she walked with her legs bent.
• This discovery confirmed that
bipedalism evolved very early in our
evolutionary history.
b. A few years later a set of footprints
were discovered in hardened ash in
Tanzania.
• These footprints date to 3-4 million
years ago and were probably also made
by Australopithecines.
• The creature that made these footprints
undoubtedly walked upright further
confirming that our ancestors were
bipedal several million years ago.
• More recently discovered fossils dating
back 5-6 million years also show signs of
being bipedal.
• The shift to bipedalism was a highly
significant event in our history as it freed
the hands to use tools.
Homo habilis
o Your Hands are Free…
Now you can use more elaborate tools!
The earliest stone tools are from 2.3-
2.58 million years ago.
These are associated with Homo habilis
fossils.
Fossils, footprints, and tools (high
variability in tool use) help us
understand our human evolution.
It is not just fossil bones and footprints
that can tell us about our evolutionary
history – scientists also look for
evidence of the things our ancestors
used and ate in order to understand
how we evolved.
The first stone tools appear in the fossil
record 2.3-2.5 million years ago. These
are associated with Homo habilis
fossils.
Tools are classified arbitrarily post hoc.
Tool shape and marks on animal bones
near fossils; rebuild them now and test
them out to figure out what
motion/action they were used for and
for what purpose.
A significantly greater number of tool
edges bear traces of plant processing
(53.1%; majority used for plants; plant
diet) than animal processing (15.6%;
rarely used on meat).
• Is the next ancestor in the homio linegage
and is the first “true true” human
• Handy human (first stone tool maker and
user)
• Olduwan tools (particularly these stone
tools)
• Also likely routinely used targeted
gestures and speech
(structure/grammar/syntax i.e., an
understanding of word orders; and
content/vocabulary; both are needed).
• Homo habilis was more recognisably
human than the Australopithecines – he
had a smaller jaw, larger brain and ate
meat. Eating meat may have driven
development of larger brains.
(2) Why do humans have such large brains?
Can you identify some problems?
Instead we should look at ___
(A) Food Patches
o Change in brain size coincided with
global cooling (environmental factors;
rescission of rainforests, spread of the
savanna, cooling of the air and change in
food source location; patches in
grassland with high nutrient content and
then nothing; in forests food sources are
less patchy).
(B) Group Size
o Hominini group sizes increased due to
cooling and food distribution factors.
o Foraging with food patch environment is
better with larger group sizes that can
help locate and forage food sources.
o Larger body size (most), diet (medium),
and group size (small effect) influence
brain development.
o Speculation time: Carl Bruggeman rule-
in colder climates individuals are larger
for optimal energy retention (the reverse
is true for hotter climates). Asaph Allen
says the size of the appendages is
inversely related to the temperature
(higher temperature means larger ears;
smaller appendages are easier to keep
warm in cool climates to avoid frost bite).
o How quick can environment influence
populations in migratory birds (1980s-
2010; effects of climate change) they
found that body size decreases over this
period when the climate warmed and
wing size as well! (it can happed very
fast)
Can you identify some problems?
• Group size might not be the best
measure of social complexity
(stratified/interactions common or not
common?)
• The importance of technical intelligence
(how much does brain size translate into
usable intelligence like tool use)
• Whole brain size vs neocortex (some
people argue only the neocortex not the
whole brain matters)
• Evolutionary trajectories may differ
(between species in phylogenetic tree
and environments may shape their
needs differently)
• Special diets & food preparation (e.g.,
use of fire; meat, predigestion)
It’s about the patterns
• The patterns of food source in their
environment!
• The optimal foraging strategies states
that where food is patchy (high density in
sparse patches; it pays off to go out
foraging in bands that are loosely
connected; social complexity to manage
within these groups to not fight each
other if not enough food for everyone
and continue till everyone has food).
• Changes in environment (patches)
requires a different way of life which
requires adaptations to cope with this.
• Changes in environments leads to
changes in our living environment which
is associated with changes in social
structures which resuscitates brain
growth.
• For example, habitat quality (impacts
foraging strategy and range which
increases interpersonal contact with
other groups, day journey, diet),
predication risk (group size and social
cohesion; sexual selection, hierarchy,
conflict, migration etc.)
___ is necessary for group sizes to increase.
This is an example of how ___ leads to ___.
More interpersonal contact with inter and intra personal peers placed selective pressure on the need to develop….
Larger brain size lead to….
Being able to manage social hierarchies (cooperation!) is a crucial necessity that evolved in ancestorial environments (patches; changes in environment) to be able to move into large groups.
small environmental factors can ratchet up to big physiological changes
More interpersonal contact with inter and intra personal peers.
• This places selective pressures on the
development of theory of mind (to be
able to understand others, move as a
cohesive group). Foraging behaviour in
machines study; mathematically
machines work better
loosely/independently but humans work
better as a cohesive group
(choice/agency; above mathematics;
through culture pass on better foraging
strategies; rachet effect).
Brains:
(A) Life Histories
• Our large brain necessitate changes in our
life histories.
• Offspring require a lot more parental
investment in care till they can live on their
own (i.e., brain; more adaptive in the future;
makes birth harder though-more c-sections).
(B) Thermoregulations
• Brains get hot
• How do environmental factors produce
physiological changes to cope with larger
brain sizes.
• Walking upright, reduces surface area of the
skin exposed to sunlight, reduces the
energy required to cool the body and can
now be focused on cooling the brain.
• Fat layer, easier to regulate than fur.
• Cooling of the planet allowed for larger
brains because it is more thermally efficient
(less energy to cool).
Lecture 2:
Key points:
• Over the developmental history in homo
lineages, we see increases in cognitive
capacity
• Adaptations to cope with changing
environments increased the necessity
for social structures and communication
• Human development is not a line, but
rather a tangled tree
who was the first “true true” human?
Homo habilis
How do we know Homo Habilus used organized speech?
• How do we know that they probably
used organized speech?
• Using experimental archology studies’
we can see that teaching others on how
to make tools requires the use of
targeted language. To effectively
communicate the process to make the
“better” tool, it’s a hard process to make
a usable tool. Flaking is a very hard
stone tool making process.
• Method: compared different modes of
instruction. They showed them the final
product and asked them to make it.
They compared this to an instructor
which used movement without words to
get them to understand it, pointed,
verbal instructions.
• Results: verbal instruction and pointing
were the best communication methods
to teach others how to make the best
stone tool (= targeted speech and
gestures) more quality flakes. Verbally
instructed members retained better
transmission chain, where quality of
flakes were more consistent as the
number of people along the chain it was
passed down to (relative to the other
methods the effects of instruction lasted
longer).
• Coincided with ear anatomy changes
with the increase in tool use.
• High quality stone tool teachers need to
be consistently passing on information
to other to keep up the quality! Refining
the skill as new information comes out.
Homo erectus (The upright human)
• He looks the most like human but the
eyebrow ridges are still very distinctive
from homo sapiens
• They are good at loco-motion (they
needed to be better at it, they’re bigger
to cope with cold, but their larger size
required substitutionally more energy to
expend; therefore need to be able to
extract more energy from the
environment; they need adaptations to
the environment to do this; they have
longer legs to allow them to travel more
efficiently; the larger you are the less
energy intensive travel is, the more you
can travel, the more energy you can
extract from the environment; how did
they carry all of their food? They had
short arms that were structured in a way
which allowed them to carry their
foraged good from patch to patch).
• Fire was mastered, controlled use, they
used it consistently to cook their food
which aids in predigesting to have break
it down to digestion requires less
energy expenditure.
• They show evidence of material culture,
cave paintings, beliefs that world is a
womb due to hypoxia, shells that were
intentionally pierced to show they were
worn and marked and worn as
ornaments is a sign of culture.
• Olduwan tools was not a category of
highly specialized tools, why, because
not all stones are good for tool use, they
travelled 20-35 miles to get good
enough stones to make tool use, this
would have been heavy and high
energy expenditure to do this, for this to
be worth it they would have needed to
be used as multi-functional tools.
• Locomotion!
Size of Hominini’s
Got bigger over time
e.g., Austropalithicus 44.6
Homo erectus 63
males bigger than female!
