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1 CE
Aquatic Ape
Hardy 1960
Human ancestors were aquatic: bipedalism evolved in water
Counter argument:
Evidence suggest hominins 5-6 Ma were terrestrial and adapted to life in trees -
2
Free the Hands A
Washburn 1960
1st suggested by Darwin
For carrying weapons and tools
Use of tools mean no need for canines as tools to process food
Counter argument:
Early hominins not hunters most likely the prey -
3
Free the Hands B
Zihlman and Tanner 1979
For carrying food, water, and infants
Fit for hunter-gatherer society
Allowed early hominins to extend foraging range -
4
Energy Efficiency
Rodman 1980
Bipedalism is an adaptation for traveling between food trees, more energy efficient, chimps less efficient than humans in locomotion
Counter argument:
energy efficiency comparable to chimp knuckle walking -
5
Provision the Family (Reproductive efficiency)
Lovejoy 1981
Bipedalism facilitated monogamy:
Slow reproductive rate of early hominins
Males ensured paternity, Females ensured male support
Bipedalism increased reproductive efficiency, allowed better provisioning: males carried food, females received food, resulted in greater reproductive success.
Counter argument:
Monogamy likely not conditions, evidence of sexual dimorphism suggest polygamy -
6
Better Thermal Regulation
Wheeler 1984
Bipedalism is an adaptation to hot and dry environments: less solar radiation, less heat from ground, more wind -
7
Postural Adaptations
A. Feeding upright from bushes
B. Feeding upright from seeds and nuts
C. Looking over tall grass: predation, communication
D. Feeding and moving upright in trees, evidence from orangutans
Counter arguments:
Why don't other animals become bipedal?
Orangutans less closely related to apes
Ancestral habitats likely semi open