Mark Henderson
24feb07

THE survival techniques of West African chimpanzees have revealed that the first human weapons may have been developed by women.

The use of spears and axes to hunt and kill is commonly thought to have been pioneered among humanity's ancestors by males, but research has indicated weapons may have been a female invention that compensated for their lesser size and strength.
Anthropologists' observations of chimpanzees in Senegal have revealed they gnaw the ends of sticks to create rudimentary spears, which they use to hunt bushbabies, a small primate.

The findings are the first evidence of the systematic use of weapons in a species other than humans - and they are intriguing because all but one of the chimps using the spears were females or immature males.

This gender imbalance has led scientists to theorise that female chimps pioneered hunting with weapons as the only way in which they could compete with the physically stronger males to add animal protein to their diets. While males can hunt with their bare hands, females need weapons to help them.

"Females have to come up with creative ways at getting at a problem, whereas males have brawn," said Jill Pruetz, of Iowa State University, who led the research.

The findings support a hypothesis that women played an integral part in the development of weapons for hunting, and other kinds of tools.

"The observation that individuals hunting with tools include females and immature chimpanzees suggests that we should rethink traditional explanations for the evolution of such behaviour in our own lineage," Dr Pruetz said.

"Learning more about the behaviours of chimpanzees in such an environment can provide important clues about the challenges facing our earliest ancestors.

"This new information has important implications for the evolution of tool use and construction for hunting in the earliest hominids, especially given our observations that females and immature chimpanzees exhibited this behaviour more frequently than adult males."

Dr Pruetz said the discovery had been unexpected. "I talked to my project manager and he told me that he saw a female hunt with tools. When he looked through original data ... we realised he had other evidence and observations of them probably doing the same thing.

"While in Senegal, I saw about 13 different hunting bouts. So it really is habitual."

In the work, published in the journal Current Biology, scientists studied chimps in the Fongoli savannah, southeast Senegal.

They observed chimps using sharpened sticks to hunt bushbabies on 22 occasions, although only one was successful.

Chimps have long been known to use tools such as stones, to crack nuts, but this is the first evidence for the systematic use of tools as weapons.

In other regions, male chimps hunt red colobus monkeys and tend to share any meat with females, often in return for sex.

The Fongoli males, however, kept bushbaby meat for themselves, because it was scarce. This may have led the females and immature males to adopt weapons as a way of obtaining meat.

There is only one other observed instance of any animal using a tool to hunt - a female chimp that used a stick to rouse a squirrel from a branch.

Dr Pruetz said the findings suggested that chimps, the closest animal relatives of humans, were more similar to humans in behaviour than previously thought.