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Neurological Basis of Behavior (PSY - 610)

Lesson 06

EVOLUTIONARY AND GENETIC BASIS OF BEHAVIOUR

Objective:

To understand

· The Brain behavior relationships from the perspectives of biological systems.

· The concepts of theory of evolution and its developmental process.

· Evolution of the homosapien and to understand brain development and behavior changes.

Evolution:

As we have seen in the last lesson, the concepts of evolution were also evolving, Darwin has built on

what was already being thought about, but what makes his theory unique is what we are going to talk

about today

Theory of Evolution:

Darwin was the first one who actually gave the mechanism of how or why the process of evolution

takes place. The first premise being that there are limited resources and all living organisms compete for

the limited resources available. Therefore a struggle for existence is essentially a struggle for resources

and a struggle for survival.

Who wins the battle? Clearly the species which has even slightest advantage, (long neck for giraffes if

food higher up in the trees), will have the best chances for survival, and can continue to propagate under

hostile and competitive conditions. The best adapters are therefore the best reproducers and the best

reproducers are the ones best fit for survival.

Decent With Modification

Variation in genetic population provides a rough template for natural selection to work on (the variation

can also occur via mutation: change in chromosomal order or genetic code). Modification of genetic

variation takes place through natural selection.

What is Natural selection?

Natural selection affects all living organisms, in keeping a species strong and fit for existence under the

conditions in which it is living. NATURE SELECTS! Natural selection pressure s can work only in the

presence of genetic variability

Adaptations made in one generation, if beneficial would be carried on to the next generation there is

constant process of adaptation. If species do not adapt they do not survive (dogs which do not learn to

watch for cars on the road, diewhich means the end of their genes). Primates developed extensions to

help in survival/hunting (young chimps use hollow sticks for ants), as they could not compete with the

stronger hunters and predators.

Genetic Variation: What is Genetic variation or phylogenetic inertia, these can be defined as basic

inherited properties in which there is a variation and can be changed and the extent they can. All

organisms have combinations of characteristics; however each has a unique combination. These

combinations can change.

Changes in the genetic combination can occur through a) combinations of different gene pools i.e.

interracial marriage or marriage of completely unrelated individuals b) mutations; these are changes in

the gene material through radiation or a genetic accident (or now genetic manipulation). These changes

would lead to a new and unusual combination of genes.

Neurological Basis of Behavior (PSY - 610)

Survival of the fittest: qualities which enable survival and further propagation in a hostile environment.

We are not talking of being healthy or physically strong but having qualities with which animals can

propagate successfully and offspring survive to continue to contribute to gene pool. The gene pool for

the next generation is better as weaker genes do not survive to contribute to gene pool. The fittest genes

live on, propagate and make up the upcoming successive generations.

What if we have a species doing very well, this would increase the number of surviving animals. This

would again lead to competition for food thereby struggle for existence would continue

Evolutionary adaptation and speciation: these are also evolutionary processes/ changes which a

species goes through to enhance its survival.

Evolutionary adaptation: there are two kinds of adaptations which can take place during the process of

evolution, 1) Centripetal: which means the organism would remain in the same state, for millions of

years as there are no environmental pressures to change. There is stability, and no change is beneficial

for survival. The animal does not change e.g. silver fish is the same for millions of years. 2) Centrifugal:

when there is a non stable environment with very rapid changes taking places, therefore rapid change in

the species occurs to survive. It is during centrifugal change that mutations occur in large numbers and

very rapidly as the selection pressures are intense.

Speciation: when the same species spread to different geographical locations, they evolve differently

into different species. The same birds in the sea would develop qualities of sea- birds, those which go up

into the hills would develop characteristics needed for survival in the hills.

Isolation: whenever a species was geographically isolated and there was no competition, theses would

evolve into different species depending on the locations (divide territory for mutual benefit).The animals

in Australia, and Galapagos are good examples

Adaptive radiation: adaptive process where the same species develops different characteristics. In

Australia the marsupials radiated into different species such as tasmanian cat, koala (trees), duckbill

(water), kangaroo (land) spreading and foraging across grass, tree, water, hill, land),

Evolution: Mammalian, Primate To Homosapien

The first major phase in evolution is speculated to be when fishes move on to land, they evolved

into amphibians dinosaurs. The dinosaurs ruled earth in various forms they were huge, physically

but had very small brains. At about the end of reptilian era a very small mammalian species

evolved: a) it had a fur coating for thermoregulation b) had strong olfaction (brain grew-due to

olfaction?) c) better hearing (had to compete with large animals so had to forage in the dark)-bones

in jaws moved to side to form ear bones, d) Vision gradually highly evolved for higher primates

Mammalian evolution began with the monotremata these were egg layers like reptiles but were fur

bearing and nursed their young (this led to attachment benefit for survival teaching young to

survive. young to stay with mother till they are out of vulnerable stage).

Advantages: instead of having 10 eggs and have none survive (open to predators), have one (major

investment which develops slowly and lives to propagate). POPULATION GROWTH SLOW BUT

STEADY

This also brought about change in the maternal role. : The young suckles and stays with mother,

Purpose of such a development, a) nurturance provided directly so that there is fitness, b) learning

directly form an adult: Learns to run when mother does, to eat what she does, c) is protected from

all bigger and more dangerous animals by the adult ( mother: maternal aggression is well

documented). Thus, early development became and important period where attachment and

bonding began. This is a sensitive period where the young is tied to the mother through pheromonal

Neurological Basis of Behavior (PSY - 610)

signals. The highest form of attachment bonding with mother developed in primates

Human Evolution

Hominids evolved into at least 7 different species their names specify the location their remains

were discovered in: Australopithecus ( about 2 -3 million 500 cc brain ), Java ( Indonesia), Peking

( China), Olduvai man ( in the Olduvia Gorge in Africa), Pithecanthropus, Homo Erectus,( brain

size about 900 cc) Neanderthal (brain 1400cc) ( Germany), Cro-magnon

Pithecanthropus: the earliest man-ape who was cage living, used stone tools. There is evidence in

the cages of use of FIRE (therefore fire had been discovered). There is also evidence of

cannibalism, especial favourite appears to be the brains (cracked cranium is evidence for such

activity). There appears to be family and some social groups.

Neanderthal: remains found in the Neander Valley in Germany. The evidence indicates that the

Neanderthal was present around 1, 00,000 to 50,000 years. In appearance they were small and

heavy set, brutal looking, slightly larger brain size but very efficient brain compared to earlier

species. This was the beginning of a man shaped like an ape. There is increased tool use with

specialized tools for cutting, piercing, shaping. This ape-man migrated by traveling across as

indicated by the finds of remains which are spread over Europe, Africa, and Near East.

Reference

Pinel, John P.J. (2003) Biopsychology (5th edition) Allyn and Bacon Singapore

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