lecture 1 - evolution and the brain-annotated

7/28/2019 Lecture 1 - Evolution and the Brain-Annotated

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Evolution and the Nervous System


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Evolution

Evolution works by trial and error.

It has no goal, but it functions to keep life adapting

to a constantly-changing environment.

Organisms that are able to survive and pass on genesinfluence the development of future organisms.

Organisms that are killed off, and dont reproduce,

have their DNA eliminated from the gene pool. Whatever works is kept until it eventually fails.

Whatever doesnt work is gotten rid of.


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Evolution

Gene mutations occur randomly. One of the four base pairs is altered.

There are ~ 3.2 billion base pairs in the human genome.

There are ~ 25,000 genes in the human genome.

Nothing is perfect, and errors will happen.

These affect either the structure of essential proteins,

or the timing and expression of specific genes.

Many of these mutations will have a lethal effect. A large number will have a non-lethal, but negative effect.

Many will have no effect, or a negligible effect.

A small percentage will have a beneficial effect.


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Evolution

Evolution works with what its got, so this is another

factor making it an inherently conservative process.

Drastic changes in structure/function can occur, but these

are probably extremely rare events. A large number of genes is shared by large numbers of

species.

But evolution may shape the timing and the frequency of their

expression.


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We Belong to The Order Primates

The primates include the following: Prosimians such as lemurs and tarsiers

Small brains, reliance on scent, nocturnal

Anthropoids

New World Monkeys

Old World Monkeys

Hominids Great apes

Humans

Including Neanderthals and related extinct species


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Other Primate Species

Macaque

Chimpanzee

Gorilla

Orangutan


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Evolution

Survival of the fittest(probability of survival andcapacity to pass on genes)

Species are adapted to specific niches (polar bears,

Arctic plants, desert toads, extremophiles) Some live in a wide range of environments

(mosquitoes, humans)

Darwin: preservation of favourable individual

differences and variations, and the destruction ofthose which are injurious


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Four Conditions for Natural Selection

The individuals must be capable of reproducing.

The offspring must inherit characteristics oftheir parents.

There must be variation in individual traits(characters) among members of the population.

There is variation in the fitness of individual

organisms.


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Variability: Intelligence

By definition, half the population is below average. Height range: ~ 3 feet to ~ 8 feet tall

Weight range: ~ 40 pounds to ~ 1000 pounds

Normal distribution

Mean IQ: 100

84th percentile: 115

16th percentile: 85

98th percentile: 130 2nd percentile: 70


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More on Evolution

Most mutations either have no effect, or adeleterious one.

Some mutations provide a survival advantage in

current environment. Mutations may be problematic in other

environments, however (e.g., sickle cell).

Evolutionary adaptations arent necessarily efficient.

Spandrels may produce unintended traits that haveno apparent effect on survival.


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Human Tails


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Chimpanzees Have Cultures

Variation among geographically distinct groups

Gombe Stream (Tanzania) chimps use sticks to fishfor termites, other chimps do not.

Ivory Coast chimpanzees use stone hammers tobreak nuts, but in Gabon they do not.

Mother chimps have been observed teaching theiroffspring to use certain types of tools.

Chimpanzees use a variety of medicinal plants thatare effective for intestinal parasites, headaches, andschistosomiasis.


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Language and Nonhuman Primates

Washoe, taught ASL by the Gardners, taught her sonLoulis to sign.

Chimps can combine words to make new words.

Savage-Rumbaugh taught Austin & Sherman to solveproblems that required sign languagecommunication in planning (e.g., tool choice).

Koko can express her emotions, and could refer to

anger she experienced three days earlier. Koko engages in fantasy play in private.

Foutss chimps paint pictures, and title them.


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Overlap of Extinct Human Species


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Neanderthal

Slightly shorter than homo

sapiens

Longer arms, considerably

taller

Almost exclusively

carnivorous

Very little difference in

brain volume from homo

sapiens


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Homo Neanderthalensis


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Language and Neanderthals

Neanderthals and modern humans co-existed fortens of thousands of years.

Last Neanderthals appear to have died out near

Gibraltar around 28,000 years ago. The Neanderthal genome has been sequenced, and

some comparisons with modern humans made.

The FOXP2 gene, important for language, is very

similar in Neanderthals and modern humans

FOXP2 is conserved across a wide range of species


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Tactical Deception and Lying

Chimps with knowledge of a stash of bananaspretended not to know what was going on.

Luit and Nikkie in dominance struggle, and Luit hidhis anxious facial expression with his hand.

Yeroen, following a dominance struggle with Nikkie,would limp when Nikkie could see him, but nototherwise.

Koko lightly bit someone and when asked about it,replied no teeth. When told that was not true, shethen signed bad again Koko bad again.


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Reflective Self-Awareness

Gallups mirror self-recognition (1970)

Chimpanzees

Koko (gorilla), beginning at about age 3 1/2

Picking at teeth, grooming, making faces, dress-up

Interested in her tongue and things she cant see

Orangutans

Monkeys show no mirror self-recognition

Non-primate species include dolphins, whales, and

elephants


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Theory of Mind

The capacity to assess whats going on in another

animals mind.

Humans have it, but its subject to distortions, and

appears defective in autism. Chimpanzees appear to have it, and can use it to

guess at what other chimps can see from a totally

different visual perspective.


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Evolution of the Brain

Jellyfish have an undifferentiated, distributed network

of neurons that control movement.

Worms have the simplest central nervous system.

Their spinal cord, without the brain, is capable of suchbehavior as feeding, mating, and locomotion.

Vertebrates (animals with a spine) have more complex

nervous systems, and the brain plays a major role in

behavior.


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U of Wisconsin and Michigan State University; http://brainmuseum.org/index.html


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Summary

A wide range of abilities can be seen acrossevolution. Communication is found among many (ifnot most) animal species, but language seems to bepresent only in apes and humans, with speech and

complex language only in humans.

Natural variation is very important. Hence, somelearning disabilities may be normal variants (e.g.,dyslexia, ADHD).

What works is whatever gives animals a survivaladvantage.

lecture 1 - evolution and the brain-annotated

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