Lecture 7- Brain size and intelligence

Question 1

What is the amount of similarity in gene-coding DNA in us and the great apes?

Answer 1

-

Question 2

What are some life-history similarities in the great apes?

Answer 2

-All great apes usually give birth to single offspring and invest heavily in their young

Question 3

What are the obvious and fundamental differences in our life history compared to other great apes?

Answer 3

1. Bipedalism 2. Reduced upper limbs and increased manual dexterity (ability to throw very accurately, tool use, playing instruments etc.) 3. Flattened face profile (partly because of the bigger brain) 4. Diet 5. Strong social behaviour 6. Unusual kinship, parenting and grandparenting 7. Unusual life histories 8. Unusual sexual characteristics 9. Other unusual physical features 10. Larger population size 11. Our extraordinary brain and mental capacity

Question 4

How is our diet different to chimps?

Answer 4

-Chimps: Predominantly omnivorous but some meat -Humans: Highly omnivorous but with high meat content Considerable processing of food (cooking, pickling, fermenting)

Question 5

What are some examples of strong social behaviour in humans?

Answer 5

-friendships, complex play, laws and their enforcement, morals and ethics, long-lasting friendships, war -long-lasting friendships -war in chimps as well= access of territory is the reason, purpose of increase fitness -in humans war doesn’t fulfill the same role

Question 6

What are some of the unusual kinship aspects of human life?

Answer 6

-male parental car and grandparents looking after subsequent generation (cross-generational care)

Question 7

What are some of our unusual life histories?

Answer 7

-menopause, pubertal growth spur and extended childhood -living after reproductive age= also in dolphins and whales -puberty= big growth -much longer childhood than other apes

Question 8

What are some of our unusual sexual characteristics?

Answer 8

-Concealed ovulation -Tendency to monogamy (in comparison with other primates) -humans do not show ovulation= but females change behaviour and smell when ovulation (but much more concealed) -enlarged breasts throughout life -and loads of strange sexual behaviour…

Question 9

What are some of our unusual physical features?

Answer 9

-Massive reduction in body hair -Wide variation in hair and skin colour -Large whites of the eyes (sclera) -humans use sclera= -humans use eyes much more than apes, we interpret the movement of eyes and use it a lot -the chimps would follow head movements= do not respond to eye movements= humans much more attentive to it -whites of eyes= a sign of health

Question 10

What is our population size compared with the other great ape populations?

Answer 10

-Orangutans = 48,500 -Gorillas = 110,000 -Chimpanzees = 150,000 -Humans > 7,000,000,000 (7.2 billion in 2015)

Question 11

What is generally true of mammal brains?

Answer 11

Generally, larger mammals have larger brains, but this doesn’t necessarily equate to intelligence

Question 12

Do humans have the largest relative brain size of any mammal?

Answer 12

• yes
• take into account how big the animal is relative to brain
• homo sapiens has a larger brain than expected

Question 13

How did the human brain increase in size through time?

Answer 13

when did the brain start getting bigger

• grey= australopithecus
• white= our own genus= homo not bipedality, not tool use, it is when we shift what we eat we see the changes in teeth etc and then we see increase in brain size!

Question 14

Is diet linked to brain size?

Answer 14

• Evidence from bats & primates that fruit-eating species are “brainier”
• Associated with difficulty in finding and extracting fruit? -Need for colour vision (to detect ripe fruit against background)?
• Leonard et al. (2003), examined brain size and diet quality in 41 primate species
• Diet quality assessed by looking at % of plants, fruits and animals in diet
• Higher score given to animal > fruits > plants -as the diet gets more complex the brain gets larger but human brain still larger than predicted via this method

Question 15

How does diet enable us to develop larger brains?

Answer 15

-the brain is incredibly metabolically expensive -Therefore, higher quality diets enable us to feed our hungry brains

Question 16

What are the metabolic requirements of the brain in humans?

Answer 16

• Brain tissue is the most energetically expensive tissue ( ≈ 16x more energy consuming than muscle) • Human brain = 2% of body mass (20-25% of our energetic demands) • Other primates = 8-10% of energetic demands

Question 17

Are humans metabolically demanding animals (on the whole)?

Answer 17

-NO! Humans aren’t metabolically demanding compared to other primates, in fact, humans are metabolically almost perfectly average for primates

Question 18

Do we compensate for our large brains by reducing the demands of other tissues?

Answer 18

-took primates and looked at the weights of gut/heart/brain etc. -then where would you expect the human to lie on how much energy expected for each -so liver, kidney, heart = as expected -the gut is 1/3 smaller than expected for our body size -relatively small guts for our body size -Primate gut size is strongly negatively correlated with brain size

Question 19

What is the relationship between brain size/ diet / gut size?

Answer 19

• if have high energy food= and more energy efficient assimilation= can reduce the gut and still have enough energy for the brain
• these processes feed into each other

Question 20

Why have we evolved the big brain?

Answer 20

-one idea is the social brain hypothesis -Living in large groups imposes large cognitive demands -Better ability to process social information - Better ability to anticipate others’ behaviour - Better ability to manipulate others

Question 21

What part of the brain is important in the human brain (evolution-wise)?

Answer 21

-neocortex -The neocortex is the most important for explaining large brain size in humans and other primates -it’s not the whole brain that gets bigger, it is the neocortex that is most important in sociability

Question 22

What is the relationship of the neocortex size and group size in primates?

Answer 22

-the larger the neocortex the bigger the group size

Question 23

What is the diagram of the social brain hypothesis?

Answer 23

-

Question 24

What is social intelligence?

Answer 24

• Is it ability to learn from social interactions? • Reader and Laland (2002) examined published records of social learning in primates

Question 25

What is the relationship between social learning, brain size and group size?

Answer 25

-as you have larger brain= linked with social intelligence -Social learning is not related to social group size

Question 26

Does a larger brain size equate to a higher intelligence?

Answer 26

-No link has ever been found between measures of intelligence (e.g. IQ) and brain size in humans

Question 27

Who had the biggest brain from the Homo family?

Answer 27

-the Neanderthals

Question 28

So what is intelligence then?

Answer 28

-Problem solving?: This is not a unique human trait, apes copy but people expect to be taught -we copy from those who are our superiors Innovation?: Again, not a unique human trait,eg. crows and nuts= dropping them into the traffic, instead of just dropping the nut -retrieve the nut thanks to dropping it on a pedestrian crossing so they do not get run over -is it language and culture that makes us different?

Question 29

Questions from the lecture:

Answer 29

• How do we define intelligence in humans? What evolutionary forces may have shaped the large brain size of humans? • How have comparative studies of primates helped us to understand the evolution of human intelligence? • What is social intelligence? In what ways is it possible to measure it in humans and other animals?