Humans aren't the only ones who hunt with weapons -- a troop of chimps in the wild have been observed crafting sharp spears to stab their prey.
The technique, described in the latest issue of the journal Royal Society Open Science, could have originated with the common ancestor of humans and chimps, suggesting that the earliest humans hunted in a similar manner.
The chimps spent time making the deadliest, most effective spears.
"The tools (spears) are made from living tree branches that are detached and then modified by removing all the side branches and leaves, as well as the flimsy terminal end of the branch," lead author Jill Pruetz told Discovery News.
"Some individuals further trim the tip of the tool with their teeth," added Pruetz, who is a professor in the Department of Anthropology at Iowa State University. "They average about 75 centimeters (around 30 inches) in length."
Pruetz and her team watched chimpanzees from a site called Fongoli in southeastern Senegal, West Africa, making spears in this manner.