Chapter 2: Evolution, Genetics and Experience
From Dichotomies to Relations and Interactions
There is a tendency to think in simple dichotomies when explaining behavior.
o Is it physiological or psychological?
o Is it inherited or is it learned?
Both questions are common, yet misguided
- We think in dichotomies to opposing tings, black and white type of thinking,
which shouldn’t be the way of thinking about stuff.
- Important when we start talking about nature vs nurture to shape how an animal
behaves, its always going to be an INTERACTION between the two
- Yore psych state depends on your physiological state and vice versa
1) Physiological or Psychological?
- This dualistic way of thinking rose in the 17 century in Western culture
following the Dark Ages, in response to conflict between science and the roman
- Way of thinking changed during the Renaissance and scientists started to study
things directly by observing them modern science
- Conflict was resolved by René Descartes argued that the universe consists of
o Physical matter (science)
o Human mind (soul, self, or spirit) (church)
- Cartesian dualism was viewed the mind and brain as separate entities
- The link between the two gets blurred but that dualistic way of thinking has
survived until modern times.
2) Is it Inherited, or is it Learned?
The ―nature-nurture‖ issue
Watson, a behaviorist, believed that all behavior was the product of learning
o We behave the way we do because we learned to do that (nurture way of
thinking); I behave that way because I see people doing that. Monkey sees
Ethology, the study of animal behavior in the wild, focuses on instinctive (nature)
o Then you have ethologists show that animals behave this way because
they’re hard wired – genetics (nature)
*** Now still butting heads. But majority in science and psych, realize that it is an
INTERACTION how they work in concert. Problems of Traditional Dichotomies:
Problem 1: Brain damage has an impact on psychological functioning.
Oliver Sacks’ case study of a man with asomatognosia: mental representation of
his body is some how fractured, no longer seeing and feeling that his left leg is
o Deficiency in awareness of parts of one’s own body
o Due to damage to the right parietal lobe
- In the case, after he woke up form this, he feels a leg but it’s not actually his so
tries to throw it out but then he falls out of bed because it’s his leg.
- To show its not dualism
Physiological- or-Psychological thinking
Problem 2: Chimps show psychological (i.e., ―human‖) abilities. For example: Gallup’s
research on chimp self-awareness
Researchers looking at animal’s behaviour, trying to break though the dualistic.
For animals to see if they can identify themselves
Expose chimp to a mirror, and never seen a mirror at first they start playing games
with their reflection
After a coupe f days they realize its them in the mirror
And start doing weird behaviors, using mirror to self groom, and look at the full
body making funny faces in the mirror
To test it truly they took these chimps and anesthetized them and put dye with no
odor in it and cant be wiped off and place it on parts of the chimps body that they
cant see directly and they realize that it was themselves.
**Chimps spontaneously groom themselves in mirror
**Chimps examine and touch red mark on their own face seen in mirror
- Because of the beliefs of that time, it was thought that the mind (hopes, dreams,
self awareness) is the property of humans only. Only humans have those things.
- Small number of animals have traits that were previously thought to be human
property. EXAMPLE when Lewis is having a bad dream, cry and bark
Many factors have an impact on behavior other than genetics (nature) or learning
―Nurture‖ now encompasses learning and environment
While it is generally accepted that behavior is a product of nature and nurture,
many still ask how much is determined by each, but genetic and experiential
factors do not merely combine in an additive fashion
- We know that nature shaped behaviors to some extent - We know that we can learn under certain circumstance
- Some things that we express shape our environment.
- ALL AN INTERACTION
- The music instrument metaphor** we wouldn’t ask how much musicians and
instrument contribute to music.
Figure 2.3 in textbooks
- All behavior is the product of interactions among:
1) The organisms’ genetic characteristic, which is a product of its evolution
2) Its experience
3) Its perception of the current situation
While Darwin was not the first to propose that species evolve, he was the first to
compile supporting evidence (and to suggest how evolution works)
For a little while, several ppl suggest that animals change subtly over generations.
But had no evidence to prove it, but Darwin was the first one to prove it and had
The father of evolution
He argued that evolution occurs through natural selection
o If an animal is to behave a certain way he’s more likely to survive and
live to a certain age to off spring and if they produce an animal that is less
likely fit for the environment they will be selected out of the population
o Because of the pressure environment, like access to food. Some animals
survive some don’t.
o Fitness: an organism’s ability to survive and contribute its genes to the
Scientific Theory: an explanation that provides the best current account of a
phenomenon based on the available evidence
Darwin presented 3 kinds of evidence
1) Fossil evidence of evolution
2) Structural similarities among living species suggesting common ancestors
3) Impact of selective breeding
- Direct observation of evolution in progress: Grant (1991)
- Finches of the Galapagos islands changed dramatically after a single
sethon of drought
- 18 month drought on the islands, left only large, difficult to eat seeds and
increased the beak size in one of the Finch species
- If I find bones closer to surface or the youngest and the deeper are the oldest.
- He looks at the fossils, and show if you go back in time you see similar animal
structure and by looking at it you see the subtle change of structure between
similar animals. - Over the course of millions yrs. these species are changing due to environmental
- We can do those ourselves – artificially.
- People have been doing it for maybe 10 0000 yrs. ish. But we’ve been animal
husbandry, agriculture, we want corn and you roll bag 4958409 yrs. corns did not
look like that they were small and gross.
- Selective breeding
- Over the excess of generation they are pushing the normal distribution
until they get the perfect breed of corn
- You think 9485094386 yrs. ago, there were box terriers?
- Fossil records whether were taking about change
moving from earlier primates getting to humans, you
can change in posture and pelvic shape and brain cavity
- And you can go really far and show the change
in the wings of a bat arm, they have similar born present
as a human arm but in different proportions.
- Elephants have finger nails
Evolution of Behavior
- Some behaviors play an obvious role in evolution.
- Example: ability to find food, avoid predators, defend young increases an
animal’s ability to pass on its genes.
- Just as physical features contribute to fitness, so do behaviors
o The males establish hierarchy of social dominance through combative
encounters with other males
o The dominant male wins over all other males of the group and the number
2 wins over all males except dominant male and so on. o Once established, hostilities diminish because low ranking males learn to
avoid and submit to the dominant.
o Dominant males copulate more and thus more effective in passing on their
characteristics to future generations
o McCann ’81 studied the effect of social dominance of the copulation rate
in 10 bull elephant seals that cohabited the same breeding breech
o Results showed that the dominant male did 37% of the copulation,
whereas the lowest ranked accounted for only 1%
- Some dominant females are more likely to produce more and healthier off spring
- Goodall ’97 found that high-ranking female chimps produced more offspring that
were more likely to survive to sexual maturity.
- More likely to maintain access to productive food foraging areas.
- The males approach the female and signal his interest.
- Thought to promote the evolution of new species
- Species: a group of organisms that is reproductively isolates from others. A
member of the species can produce offspring only by mating with members of the
- A new species starts to branch off from existing species when some barrier
discourages breeding between the species itself.
o You have a species of birds, its coming to mating season and the birds
will attracts mates and then maybe anything that deal with the genetic
behavior that maybe other birds with mimic how the other male bird
o You have some males and females aren’t attracted to each other.
o But with the success of generations and things start to drift, the females
that aren’t attracted to those shall shift to other attraction- beak shape
o You end up with, when you had one single species, the changes of
genetics becomes enough even if you try to mate the two, to a point where
two of the same cant fertilize to one and now you have two different types
o Species of small rodent, was the same from one lives on the opposite sides
of the canyon but once upon a time they were the same
Course of Human Evolution
Evolution of Vertebrates
- Begins being a complex multi cellular organisms
- Then, develops chordate and vertebrate for protection
- Vertebrates are chordates with spinal bones
- The first vertebrates were primitive bony fish. (7 types)
- (3) Fish, amphibians, birds and mammals
- Fossil found many anatomical features were found only in land animals shows
linkage between fish and land vertebrates prediction by the evolution theory Evolution of Amphibians
- Bony fishes leave the water briefly
- Advantages include fresh water and new food sources
- The verbrates start to become fish, then bony fish want more bone structure,
eventually these fish develop the ability to move about outside of water, to use
there pectoral fins to walk up on a muddy slope a beach, once one can do that it
will make them more likely to survive
- More access to food, and run away from predators. And then eventually
Recent finding of missing links0 pectoral fin getting bon wrist structure
- With these animals, water is a big thing they have depending on what species
were looking at. Their fins allow water to come in and they develop lungs and
scales to leave water for longer. Then we end up with reptiles
- Their skin has changed so much that now it’s not a permeable structure that now
does not lose a lot of water through skin.
- Need water for off spring
Evolution of Reptiles
- Lay shell-covered eggs; covered by dry scales
- Can live far from water
- Now we have watery environment with the eggs, now with mammals we have
water inside the female
- Before the watery of the egg somewhere in the water, now they have the egg
comforted in water in the females
Evolution of Mammals
- Develop mammary glands to nurture young
- Eventually no longer lay eggs: raise young in mother’s body
- Humans emerge from the order primates
- Difficult to categorize because there is no single characteristic that is possessed by
- Chimps are the closes living relatives of humans. Almost 99% of genes are
identical in the two species
Emergence of Human Kind
- Humans belong to family hominids, genus Homo
- First homo species emerged from Australopithecus 2 million years ago
o Homo sapiens emerged 200,000 years ago
- Primates early- monkey like
- We get more and more species developing as were working through evolution
here, we have a lot of those species dying off
- Thinking of evolution don’t think of it as a telephone pole, its like a real dense
bush we co existed with many of the branches but they died off. - Were the last of one of those branches
- All the creatures that we have eon the planet is about 1% of the ones that lived.
Thinking about Human Evolution
Evolution does not proceed in a single line
Humans have only been around for a brief period of time
Rapid evolutionary changes do occur
Fewer than 1% of all known species are still in existence
Evolution does not necessarily result in perfect design
Not all existing behaviors or structures are adaptive
Spandrels—incidental nonadaptive by-products (such as the human belly button
We talked about the idea of survival of the fittest.
The idea that you evolved to be this perfect creature- no that’s not right
It means you fit for survival of that time
The dinosaurs were used to be the biggest baddest of the planet. – They’ve been
around for so long. They’re perfect. One event happens. They’re all gone
Were not perfect designs—
o We have these things- about that is going one
o Spandrels- accident by products, why do we have a belly button? Why do
we have an appendics? Why do men have nipples?
Not all existing adaptive characteristics evolved to perform their current function
o Exaptations – evolved to do one thing, but now do something else
o Bird wings: came from dinosaurs front leg for eating walking and some
developed feather, maybe for warmth and if they do a rapid movement, to
fly away from predators, evolved for locomotion
o But now used for flight
Similarities among species do not necessarily mean that the species have common
o Just because species have the same things going on doesn’t’t mean theres
a common origin
Homologous structures – similar structures due to a common evolutionary origin
Analogous structures – similar structures without a common origin
Convergent evolution – the evolution of similar solutions to the sa