Transcript Ch03x
Animal Behavior and Evolution (Dunbar Ch 2) • Biologists often commented on behavior and adaptation –Physical traits –Altruism (Group selection) Natural Selection • Focuses on individual survival • According to Darwin, noble behavior is a death sentence (for the genes) Core Premises of natural Selection • The Principle of Variation: All individuals in a species show variation • The Principle of Inheritance: Variation is heritable and offspring resemble parents more than other members of the species • The Principle of Adaptation: Competition will favor some and disadvantage others. Favored individuals will reproduce (and their genes will survive). Survival defines fitness. Adaptations • Traits (physical or behavioral) can be identified as adaptations if they can be linked to survival and/or reproductive success. • The concept of group selection has slowly faded from modern evolutionary theory. (We’ve covered this…) Niche Construction Theory John Olding-Smee • Niches are not passively occupied, they are modified. – Spider Webs – Bird nests – Beaver dams – Ant tunnels – Wasp/caterpillars Niche Construction Theory • The organism can put selective pressure on the environment – What if the dam reshapes the river, driving it to a plain (shallower) or what if competition leads some beavers downstream (deeper). Offspring will inherit new environments with new selective pressures. – Organisms can change the environment and the environment can, in turn, present new selective pressures. Niche Construction in Humans • Stone tools led to the pursuit of game which led to changes in digestion and the ability to defend livestock which changed eating habits and digestion again. Environment Olding-Smee Darwin Organism Niche Construction Theory • Organisms shape the forces that shape them – Most probably don’t realize that they are doing it • Culture is Niche Construction as it applies to humans – We, of course, make some (most) changes with no idea of how it will shape us and our offspring – We make many changes fully expecting them to shape us and our offspring Shaping Minds • A human raised in isolation – if it survives will be unrecognizable to other humans • How well would a human do in an “unconstructed niche” Human Niche Construction • Did our desire to change our niches (through both modification and migration) accelerate selective changes? • Is that why we’re special? The Human (cognitive) Revolution • We are special, but why… • When did we adopt “human” traits? – Language – Toolmaking and coordinated hunting – Cooking – Artistic expression Homo Paranthropus Australopithecus A. afarensis 3.9-2.9 m.y.a • • • • • East Africa Bipedal Tools? Brain ~ 400cm2 SRGAP2 – 2 in humans – Cortex growth – Synapses P. robustus 1.9-1.4 m.y.a • Paranthropus (beside human) • South Africa • Bipedal, no fire, no language, maybe tools? • Doomed by limited diet? H. habilis 2.8-1.5 m.y.a • “Handy man” • Olduvai Gorge, Tanzania – Brain ~ 650cm2 – Toolmaking (inherited?, but certainly perfected) – Organized disposal of waste (social) 650 cm2 400 cm2 The Oldowan Tool Set (2.6-1.7 m.y.a) H. ergaster 1.9-1.4 m.y.a • East Africa and beyond! 1000 cm2 650 cm2 400 cm2 – – – – – – – H. erectus into Asia (70kya) Brain ~ 1000cm2 Sophisticated Toolmaking Controlled fire Cooking and socializing? Language? Care for injured? Acheulian Tools (2.6-1.7 m.y.a) • What is the significance of tools? – Mental representation of an ideal – Planning, Sharing – Remarkable Stability of the erectus branch – Evidence of progress from H. habilis, but then little change – Were they stuck in an evolutionary dead-end? H. heidelbergensis 700-200kya • East Africa, Europe, Asia 1200 cm2 – Brain ~ 1200cm2 1000 cm2 650 cm2 400 cm2 – Buried dead – Ochre paint – Language? H. neandertalensis 300-60kya 1600 cm2 • Europe, Asia 1200 cm2 – Brain ~ 1600cm2 1000 cm2 650 cm2 400 cm2 – Buried dead – Ochre paint – Language? H. sapiens 200kya- 1600 cm2 1200 cm2 1000 cm2 650 cm2 400 cm2 • Common origin in Southern Africa – Brain ~ 1400cm2 • Brain size cannot explain everything! • Genetic bottleneck 150,000-200,00ya The Revolution • Blombos Cave, South Africa The Revolution • Blombos Cave, South Africa Artefacts from 100,000 ya Artefacts from 100,000 ya Chauvet Cave, France 30,000 ya The significance of Metaphor • Creating things that represent other things – Does abstract drawing emerge with abstract thinking? – Do visual metaphors emerge with auditory metaphors (is evidence of art evidence of language)? Homo genus • • • • Brain growth is progressive Tool use emerges progressively Migration spans Africa, Europe, Asia We do things that were never done before, but there is no evidence (within the history of our species) to suggest a single, great leap forward. • When addressing the adaptive origin of a trait, we cannot point to a single time in our species’ past. The Revolution • The modern human mind can be recognized in artefacts that are 100,000 years old • Before that time, there is no evidence of a cognitive “big bang” • Our “minds” have been cobbled together over years.