3 lecture 9 Flashcards
During what time period did humans begin to walk upright and make simple tools
as well as brain size increased slightly
6–2 million years ago
what species was lucy
Australopithecus afarensis
when did lucy exists
3.85-2.95 million years ago
how long did Australopithecus afarensis last
Existed for around 900,000 years
how was Australopithecus afarensis like apes
Grew rapidly after birth and reached adulthood earlier than modern humans
Long, strong arms, curved fingers adapted for tree-climbing Apelike face proportions
Small brain
how was Australopithecus afarensis like humans
Small canine teeth Bipedal (walked upright)
what is Bipedalism
walking on two limbs instead of four
apes can do so occasionally, but are they are posturally more suited for
using four limbs
–for humans to do this required changes in the hips, lower back and pelvis
how did Proportions of arms/legs change
long arms are adaptive for climbing and swinging through trees
While A. afarensis was bipedal, changes in the proportion of arms/legs/torso wouldn’t occur until later
when did Brain and body size increase
From 2 million–800,000 years ago
what else happened From 2 million–800,000 years ago
During this time period early humans spread around the globe, encountering many new environments on different continents.
Greater use of tools and fire (though not yet controlled use)
These challenges, along with an increase in body size, led to an increase in brain size
when did Homo erectus exist
1.89 million to 143,000 years ago
what species was the first to live outside africa
Homo erectus
what are the traits of homo erectus
Oldest known early humans with human-like body proportions –longer legs, shorter arms relative to the torso –indicates adaptations for ground dwelling and loss of adaptations for tree-climbing
Expanded brain case relative to the size of the face
May have been one of the earliest humans to show reduced hair or fur
what species is our closest extinct human relative
Homo neanderthalensis
when did Homo neanderthalensis exist
200,000-28,000 years ago
what were the traits of homo neanderthalensis
Lived in the cold
–shorter and stockier than us, thought to be an adaptation to the cold
Made and used a diverse set of sophisticated tools
Skilled hunters, also ate plants Controlled fire
Lived in shelters
Wore clothing
Buried their dead
–marked graves with flowers or offerings
is it possible to study neanderthal DNA
yes, neanderthal genome project
when did homo sapiens happen
200,000 years ago to present
what are the traits of homo sapiens
Lighter skeletal build compared to earlier humans
Less heavily developed jaws, with smaller teeth
Less (if any) heavy brow ridges and prognathism of other early humans.
Skull reorganization – a thin-walled, high vaulted skull with a flat and near vertical forehead.
Very large brains
Based on current fossil data, how many “bursts” or big increases in brain size have occurred
2
when did the first “burst” happen
The first occurred with the split between the australopithecines and the homonids –Around the emergence of Homo erectus
when did the second “burst” happen
The second was around the time of the emergence of the first Homo sapiens
what is brain size related to
Brain size is generally related to body size
–We see this relationship across species
Bigger animals have bigger brains
So what could lead to those big shifts or bursts in brain size that we see
In general, H. erectus was significantly larger and had a larger brain than ancestral hominids
These things appear to go together
Large size makes them better equipped to get food
–chase carnivores off of carcasses
–hunt animals by running them to heat exhaustion
–dig deeply for tubers which are more energy rich than grasses
A better diet was critical to produce a large, metabolically expensive brain
are brains energy-consuming
Brains are energetically expensive, you need a way to give them energy
what did humans do to provide the right amount of energy
Early humans, like apes, ate mostly fruit, plants, insects
Transition to eating meat was important for growing and maintaining a larger brain
This meant there needed to be a way to hunt that food
–we see the appearance and development of stone tools
what is cooking important for
getting more calories out of the food
who pushes the idea that the expansion in the size of homo erectus’ skull was due to the additional energy released from cooking meat
Harvard primatologist Richard Wrangham
what is The strongest evidence of habitual cooking including
stone hearths
–clay cooking vessels –bones encircling patches of dark ground or ash
Evidence of “controlled” fire and cooking here
Appear around 1.4 million to 790,000 years ago
did cooking lead to the split between Homo and australopithecines
probably not
(though the hunt is still on for finding earlier evidence of controlled fire use)
However, cooking could have contributed to the increase in brain size after the split from australopithecines
what does all this mean?
Homo erectus was a little larger and had a larger brain
Large size makes them better equipped to –chase carnivores off of carcasses
–hunt animals by running them to heat exhaustion –dig deeply for tubers which are more energy rich than grasses
A better diet probably allowed them to evolve smaller teeth and smaller intestines (because they no longer have to get calories from nutrient poor grasses)
Could devote that energy to producing a large, metabolically expensive brain
Having a bigger brain helped them to invent new tricks for improving the diet (e.g. cooking, new tools for hunting, getting more nutritious food like eggs or shellfish)
So what do you need to have a big brain
1) Brains are energetically expensive, you need a way to give them energy
2) Need to actually grow that big brain
why is Need to actually grow that big brain important
This is important because when do you grow a brain? Can do so in utero, BUT this can complicate childbirth
what happened in order to make the shift from quadrupedal to bipedal walking
To move from quadrapedal to bipedal walking, the orientation of the pelvis, lower back and hips changed
Instead of holding the body at an angle from the hips to the head, the reorientation resulted in the torso and all of the organs resting vertically on top of the hips and pelvis
This reorganization was significant not just for walking but also for what
child birth
what does upright walking result in
Results in a vertical shortening of the pelvis Limits how wide the pelvis can be
At the same time, brain size and therefore skull size is increasing
–how can both of these things happen?
This is known as the “obstetric dilemma”
what is “obstetric dilemma”
how do you fit a large head through a small, short pelvis and birth canal?
what is the solution to Obstetric Dilemma
Sutures and Fontanelles
explain the solution to Obstetric Dilemma
The ancestor to humans, chimps, and bonobos already had the start of a solution to this
There skull of great apes is not one solid piece of bone, but a number of large pieces of bone connected by more flexible tissue
These connections between the large bones are called SUTURES
The soft spots are called FONTANELLES
Before birth, the sutures and fontanelles are soft, which allows the skull and brain to be molded and squeezed a little as the head passes through the birth canal
Then, after birth, these sutures solidify or fuse, resulting in a continuous, solid skull –But WHEN after birth this happens is important
what is hypothesized between larger brains and diets
We hypothesize that there would have been strong, coordinated natural selection for larger brains and adaptations that lead to better dietary quality
Predict there would be selection for any mutation that took advantage of the flexibility of the skull and extended the time for brain growth after birth
–Better diet and cooking likely also influenced increase in brain size (and brain size influenced diet and cooking)
We then see a plateau in brain size between 1.5 and 0.5 million years ago. WHY?
One hypothesis is that eventually the benefits of improving diet
no longer offset the costs of increasing brain size
So then what could have lead to the next burst in brain size?
One possibility is that this was due to intraspecies interactions
what is intraspecies interactions
Basically, as population sizes started to increase
There was more competition for resources within a species Food, mates, good places to live, etc
And relatedly,
More cooperation and alliances between individuals
Social interactions became more complex and this required a bigger brain
Does brain size really matter?
kind of
A larger brain can hold more cells, larger cells, and more connections between cells
Cells are larger when they hold more DNA
The human genome is pretty big, so it requires larger cells
Having more cells and connections allows for more complex behavior
Of course, while we assume that these changes in size are associated with changes in organization, we can’t tell that from fossils
are bigger brains good for language
yes
Did big brains produce complex social environments? Or did they result from those social interactions?
it is hard to determine because it is almost like the “what came first, the chicken or the egg” question
but current theories look like this;
Increased hunting/tool use –> increased brain size –> increased sociality/language
but the last two are not set in their order because we have to rely on just fossils
what species is vocal learning found in
Found in very few species –humans
- -cetaceans (dolphins, whales) –hummingbirds, parrots –elephants
- -bats
what does vocal learning require
Requires sensory input
–young animals need to hear examples of the sound –if the don’t they will produce abnormal sounds
and Requires practice
–young animals have to try to make the sound many times before they get it right –they have to be able to hear themselves while they do it
–if they can’t hear, they will produce abnormal sounds
what brain area is important of vocal learning
The brain areas (like the basal ganglia) that are important for this sort of learning are similar across species
And similar to brain areas that you need for learning other “motor” tasks
e.g. how to throw a ball, how to run or swim or kick, etc
How better can we define language? And is it a specifically human trait?
Referential signaling Displacement Syntax
Productivity
what is Referential Signaling
Signals can contain information
Chickadees can use referential signaling
They can indicate the size as well as how dangerous a predator is by changing the number of ‘D’ notes in their calls
what other animal uses referential signaling
Vervet Monkeys
how do Vervet Monkeys use referential signaling
Live in close-knit social groups or tribes
Have different sounds for different types of predators
Have different sounds for different types of predators
Snakes
–when someone makes the snake call, everyone looks down, and stands up bipedally
Hawks
–when someone makes the hawk call, everyone looks up and runs for the nearest bush
Leopards
–when someone makes the leopard call, everyone checks the trees and ground, runs out onto branches that can’t support the leopard’s weight
You can get the vervets to respond by playing back the calls
–so it’s not that everyone sees the predator and therefore knows what to do the information is in the call itself
Young vervets don’t know where to look at first
Adults don’t trust young vervets (often get their “vocabulary” confused)
–will wait for another adult to call
Young vervets have to learn from adults WHEN to make the calls and WHAT the calls reference or mean
is referential signalling language
Not really
why isn’t referential signalling language
With language, we can talk about things that happen at a different time
–the future, the past
This is known as DISPLACEMENT
Vervet alarm calls are only used to sound the alarm
–calls not produced when predator is absent, i.e. they don’t chat about the
predator after the fact
–whenever they hear the call, they respond by looking for the predator or hiding
Where else might we find language
bees
how do bees content for language-users
Bees perform a “waggle dance” to indicate where a good food source is (the rest of the video is here http://youtu.be/bFDGPgXtK-U)
Through this dance, they can communicate where they came across a good food source as well as how good the food was
So their communication has DISPLACEMENT, but is it a language
what is Syntax
There are rules or principles governing the structure or sequence of communication signals
Once you know the rules, you can change the content
–i.e. once you know the rules for making a sentence in English, you can make all kinds of sentences with different words and meanings, following the same structure
how do bees use Syntax
The waggle dance has a clear structure or syntax
–parts of the dance can be modified to indicate different information (distance, direction) –perhaps not as flexible as our language, but it does have a modifiable sequential structure
what is Productivity
we can make new signals out of existing signals
– means that language isn’t finite but can increase to incorporate new things
Without this ability, we would have much more difficulty talking about all kinds of things today (everything from airplanes to the internet)
how do bees use productivity
they don’t
Bees
Bees perform a “waggle dance” to indicate where a good food source is
Productivity
– we can make new signals out of existing signals
– means that language isn’t finite but can increase to incorporate new things
Without this ability, we would have much more difficulty talking about all kinds of things today (everything from airplanes to the internet)
The
language involves or allows for what
displacement
syntax
productivity
define Displacement:
the ability to talk about something temporally or spatially distant
define Syntax:
a detailed structure or sequence that has rules and allows
define Productivity:
the creation of new signals
Our examples so far indicate that no other species possesses language But, could other species evolve language
Sure!
On the one hand, the sequence of environmental factors, mutations, etc that lead to human language seem unique and rare
But at the same time, there are many examples of really complex things evolving more than once
This is known as CONVERGENT EVOLUTION
what are HOMOLOGOUS traits
are those that arise from a common ancestor
what are ANALAGOUS traits
are those that are similar in function or structure, but not because they come from shared ancestry
Things that are analagous are said to evolve independently, that is, without a shared ancestor
give an example of convergent evolution
common example that we talk about is wings Birds, bats and insects all have wings
but they all evolved them independently
common example that we talk about is wings Birds, bats and insects all have wings
but they all evolved them independently
We can see how different they are when we look closely at the structure
In addition, we can determine whether something is convergent by looking at the phylogeny
what is Parsimony
is how you get a pattern of trait expression with the fewest changes
In order to develop an eye, vertebrates require a gene called what
PAX6
what is PAX6
PAX6 is a control gene
It regulates the expression of other genes in a cascade during development
In particular, PAX6 determines where an eye will develop
–if you put it on the leg of an embryo, the embryo will develop an eye there
mutations in the PAX6 gene result in what
individuals with small (or no) eyes
wherever PAX6 gets turned on or expressed, the embryo will…
eventually develop an eye
What’s interesting is that even though eyes are examples of convergent evolution (they did not arise from a common ancestor)
what does this mean
Every time a species goes to make or evolve an eye, it uses that PAX6 gene
What does the evolution of eyes have to do with language
In 2001, the gene FOXP2 was implicated in a speech and language disorder affecting half of the members of a particular family
It was hailed as the “language” gene and the hunt was on to find out more about it
1) Just in humans?
No. it turns out that FOXP2, like PAX6, is an ancient control gene, found in a wide array of species
–But, maybe FOXP2 works like PAX6 and could allow the convergent evolution of language in other species?
In songbirds, FOXP2 deficits result in poor song learning, and the production of aberrant, garbled songs
This implies it might be important for vocal learning
if not just humans,, then what
What does the evolution of eyes have to do with language?
In 2001, the gene FOXP2 was implicated in a speech and language disorder affecting half of the members of a particular family
It was hailed as the “language” gene and the hunt was on to find out more about it
1) Not just in humans
2) Important for vocal learning?
Knocking it out in mice affected pup alarm calls (which are vocalizations). But, it also resulted in poor motor learning and motor ability
In bats, it may be important for echolocation, which requires a lot of sensory-motor integration but isn’t a learned vocalization
is the evolution of eye Important for vocal learning
May be important for motor learning
But doesn’t appear to be a “language” gene
Could other species evolve language
Sure!
On the one hand, the sequence of environmental factors, mutations, etc that lead to human language seem unique and rare, but there are lots of complex traits and behaviors out there, some of them are convergent
But, from current data, it doesn’t seem to have happened yet
give a summary of all that has been discussed
Over the past 5 million years, humans diverged from a more ape-like ancestor
Multiple different human species have existed, each displaying differences in posture, brain size, and behavior
We discussed what would be necessary for those changes in brain size and behavior, as well as what those changes would be useful for
Then we talked about one of the traits that we consider uniquely human, language, and how it compares to communication systems in other species
–convergent evolution
–referential signalling, vocal learning, etc.
