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29 Cards in this Set
- Front
- Back
- 3rd side (hint)
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What are the lines of evidence with respect to brain evolution?
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Direct--paleoneurology
Indirect--comparative anatomy of living species and archaeological record of hominins ...use ENDOCASTS! |
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What is the rationale underlying the comparative approach to studying human brain evolution?
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If we can identify an aspect of the human brain absent in other primates (esp. chimps--our closest living relatives), then we can infer the trait developed after our divergence ~6 mya
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Human brains are how much larger than chimp brains?
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~ 3x (300-400 --> 1300-1400cc)
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What is allometry? What does it tell us?
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The study of how one part of an animal grows either in relation to the whole animal or one other part
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Describes rules of growth, reveals evidence for adaptation by natural selection (through departures from allometry)
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In living vertebrates, brain weight scales to what power of body weight? What type of allometry does this represent?
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2/3 or .75 (??lol), negative allometry
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Which types of vertebrates appear at higher elevation/intercept when compared to fish/reptiles? Which taxonomy reveals the highest overall?
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birds and mammals...and PRIMATES!
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What are some aspects of brain-body allometry that fossils have revealed?
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-No encephalization in reptiles
-archaic mammals 4x more encephalized than reptiles -Nocturnal animals--improved olfactory and auditory systems |
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Why are modern mammals 4x more encephalized than archaic mammals?
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Extinction of dinosaurs--> radiation into daytime niches-->development of diurnal vision
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What is the encephalization quotient? How is the EQ calculated?
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Proposed measure of intelligence that highlights how much "extra" brain tissue a species possesses
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Actual brain size divided by expected brain size for an average living animal of the same size (avg mammalian EQ = 1, avg anthropoid EQ =~2)
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What were the most encephalized species throughout the Miocene epoch?
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Cetaceans (whales/dolphins), hominin brain evolution has been recent and rapid (tripled in last 3 million yrs)
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What is microcephaly? What is special about the ASPM gene?
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A neurodevelopmental disorder (results in small head) that results from mutation of the ASPM gene that regulates neurogenesis
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Has been under strong positive selection in human evolution
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What does Ka/Ks represent?
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The pace at which a gene has evolved compared to what is expected in the absence of selection
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What are residuals? What factors can be used to explain them?
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Variation in relative brain size
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-Ecological variables--diet
-Life history variables--lifespan -Social variables--group size |
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Why do frugivores have larger residuals than folivores?
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1) greater variability in food supply demands greater memory capacity 2) smaller guts because of higher quality diet, so they can afford larger brains
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How would life span be a factor in the development of larger brains in primates?
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Large brains needed for memory for emergency sources of food during periodic crises involving food shortages
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Developmentally, how do human brains become large?
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The fetal brain growth trajectory extends into post-natal life
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What is the rhinal sulcus?
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Defines the border between paleocortex and neocortex
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What are key aspects of the evolution of the primate brain?
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Expansion of neocortex, reduction of olfactory bulb and paleocortex, appearance of Sylvian Fissure, expansion of visual cortex--all more pronounced in anthropoid primates than prosimians
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What is the key difference in primate vs. non-primate PRF connections?
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Primate PFC has strong connections with temporal and parietal association cortices--non-primate connections are with limbic areas
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Both human and Neanderthal brains triple how much after birth? Do they grow in the same way?
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3x
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No, neanderthals retlack the globularization phase
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What are the two types of theories regarding hominin encephalization?
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Releasers: factors which allowed brain size to increase by removing some constraint
Movers: factors which drove brain size increases |
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In the expensive tissue hypothesis, how can humans afford such a small gut?
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Shift to a higher quality, more easily digestible diet (meat) in H. erectus/ergaster
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What is the social intelligence hypothesis (Byrne and Whiten)?
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Large brains have been selected for because they help animals deal more effectively with the complexity of social INTX
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What is the difference between the mammal and primate approach to social status? How could this have resulted in larger brains?
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In mammals, social status depends on the size/strength of an animal. In primates, social status depends on alliances (which are more complex social INTX)
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Primates work with others to achieve outcomes that benefit themselves, but others have interests of their own that do not completely overlap
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What is the evidence for the social brain hypothesis?
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Relative neocortex size is correlated with group size among anthropoid primates
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What is the cultural intelligence hypothesis (Tomasello)?
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Humans use social learning/imitation more effectively which has led to a larger brain
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What are the two main outcomes of mammalian brain evolution?
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Expansion of neocortex (6 layered cortex) and the appearance of the corpus callosum (connects neocortex in the two cerebral hemispheres)
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What are the main aspects of primate brain evolution?
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Expansion of visual cortex/reduction of olfactory cortex & olfactory bulb and development of PFC connections with posterior association cortices
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What is the major characteristic of human brain evolution (compared to ape brains)?
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Expansion of association cortex relative to primary sensory and motor cortices
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