What makes human typical human Flashcards Preview

Genetics > What makes human typical human > Flashcards

Flashcards in What makes human typical human Deck (47)
Loading flashcards...


as an organism increases in size, the dimensions of its parts do not increase proptionally


What are the costs of a large brain?

- it is metabolically expensive -> BUT there is no correlation bw brain size across mammals and metabolic rate

-> larger brian will only envolve if payoffs are even greater


metabolic rate

amount of energy used by an animal per unit of time


expensive tissue hypothesis

metabolic requirment of large brains are offset by corresponding reduction of the gut

-> human gut is significantely smaller than predicted by patterns in other species -> need for high quality diet


lifting energetic constraint

1 change in diet to fruit
2 meat eating
3 cooking food
4 cooperated breeding
5 alloparental care


evidence for change in diet

( Howler and Spider Monkey)

howler ( leaf eater) x spider monkey (fruit eater)

-> monkeys of the same size differ in degree of brain development

-> fruit eating spider monkey has a much better developed and larger brain


What are payoffs that make animals want a bigger brain?

1 Ecological hypothesis
2 social / machiavellian hypothesis
3 cultural intelligence hypothesis


Ecological intelligence Hypothesis

Selective pressure due to change in diet
-> need to monitor the availability of dispersed food supply
-> extractive foraging
-> requirement of mental map in order to find food
-> knowlege when food is ripe


extractive foraging

removal of food items from an embedded matrix


Does lifting constraint or selective pressure lead to larger brains?

higher diet quality leads to an (1) increased energy availabiltiy (2) more complex foraging behaviors and (3) more rapid assimiliation -> smaller gut -> increased energy availability

all these factors end up in larger brain
-> see graph in lecture 3


skills that are distinctly to human

there is something special about social domain ( physical domain monkeys and children are quite similiar )


social hypothesis

= large brains have envolved via intense social interactions and competition

1 Social Hypothesis (Dunbar)
individuals living in a stable social group face cognitive demands that individuals living alone dont

large brains of primates reflects the computational demands of the complex social systems that characterize the order
(-> pairbonded species have larger brains)
-> linear correlation between group size and neocortex


Machiavellian Hypothesis

what differentiates primates from other species is complexity in social life -> requieres domiance rank means who is dominant, is standing above you -> leads to need of face recognition


Cultural Intelligence Hypothesis

argues that humans unique cognitive skills is mainly due to species specific set of social cognitive skills for participating and exchangning knowledge in cultural groups


merging ecological and and social drivers

Ecological factors drive growth brain
Cooperation shapes brain (limited because it is often associated with cheating)
Culture may be crucial to rapid increase in skill learning needed for brain growth

-> three aspects are not in conflict with each other


dominance hierarchies

some individuals consistently able to displace others from the resource -> rank depends on strength , size age etc


stable hierarchy vs unstable hierarchy

stable hierarchy : low ranks have worse health and increased stress

unstable hierarchy : vice versa


social brain hypothesis

idea that maintaing social relationships requires devoted brain mechanisms -> social species tendence to have larger brains -> evidence is found in primates


Which features do humans and primates share?

1 grasping by using their hands and feet
2 highly dependent on vision
3tend to hav forward facing eyes
4binocular vision and colour vision
5 larger brains for their body size


What are new world monkeys?




long term bonds and social groups consist of monogamous pair plus one or more dependent offspirng

Brachiation :mode of hand, arm and shoulder anatomy -> involves swinging from branch to branch using only arms


Orang Utans

fruit eaters and arboreal ( living in trees)
Polygyny with much larger males than females



lives on ground ; knuckle walking
highly sexual dimorphic -> polygynous group structure ( single dominant maleand multiple female )



knuckle walk, arboreal, omnivorous ( allesfresser) and occasionally hunt
fluid multiple male
multiple female social groups with a promiscious ( häufig wechselnde sex partner) mating structure


The ape phylogeny

Humans belong to the great apes -> not equally related to but close to chimpanzees (99 % DNA resemblance)



Phylogeny, the history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of org



intermediate form of chimpanzees and humans



4-1 million years ago
-> skulls are chimpanzee like
-> back then there were new savannahs and lots of the apes died bc they were more adapted to the forest

-> scenario for evoloution of BIPEDEL LOCOMOTION
disadvantage : time spent in trees
advantage: moving on the ground -> more energy efficient at slow speeds and upright absorbs less heat bc smaller surface to sun


Origin of the genus Homo

2.5 million years ago
-> brain size moves away from chimpanzee to human
- migration from africa to southeast asia
- appereance of stone tools


The archaics

0.8 million years ago
- larger brains and bodies and more complex stone tools