Causes of Bipedalism: Food Carrying

Outline

This was another early theory of bipedalism. It assumed that the bringing of food (hunted meat, probably by men) was the trigger. In more recent times it has been given a new lease of life as a way of gathering vegetation too although recent studies of chimpanzees in the field has shown them capable of carrying food on three legs.

Largely discredited today.

Authors

Attributed to Etkin (1953) but many have added their voice to it since.

Location

The assumption is that this occurred in Africa. At the time the savannah was the place everyone assumed was the centre of human evolution.

Selection Pressure

As with the hunting idea, the ability to carry food to one's group would undoubtedly help them to survive but again it is not clear that doing this bipedally as opposed to quadrupedally would favour an individual much and help them to reach sexual maturity.

Intermediate Steps

Once again it is not clear that this theory would explain how the form of locomotion would have arisen. 

Both Sexes?

The assumption for the theory is quite male-biased although recently a female-based child carrying theory has also been offered.

Explains Australopith Anomalies

It is doubtful whether the Australopith morphology would lend itself to hunting. It does not appear to be energetically efficient enough to be useful for high speeds or long distances. (Ruff, McHenry & Thackery 1999)

Why not Pan? Observed in Pan?

Chimps have been observed carrying things bipedally adding to the arguments against it. If chimps carry things bipedally sometimes, why didn't they become fully bipedal too?

Links with other Theories

This theory is very compatable with most of the other theories.

Popularity

A very old and therefore popular theory. Listed in 6 out of 8 of my sample textbooks.

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