Chimps and a number of other animals, including non-primates, have been observed using tools. Chimps use tools in a wide variety of contexts, however, up until now they had only been observed using tools to process plant matter or insects. For example, chimps use twigs to fish termites out of holes, rocks to smash nuts to get at the nutritious pith inside, and partially chewed leaves to sponge up water to drink from tree cavities. Recently, Iowa State University anthropology professor Jill Pruetz observed chimps using sticks to fish bushbabies out of tree holes.
This spear hunting was observed in the Fongoli population of West African chimps in SE Senegal. Chimps in other parts of Africa cooperatively hunt and eat red colobus monkeys, a species absent in SE Senegal. They have never been observed using tools to do this.
Ian Gilby, who has studied chimp meat eating, has anecdotally observed chimps using sticks to fish birds, another prey item, out of tree cavities.
Pruetz proposes the tool use she observed, which only occurred once successfully, qualifies as tool use for hunting because sticks were modified systematically and used consistently in an effort to catch bushbabies. One of the spear-making steps involves biting the stick tip to a point. Chimps were observed using the spear in a stabbing motion inside tree cavities 22 times. They also sniffed and licked the spear points after withdrawing them.
"In the single instance in which a chimpanzee was observed to extract a bushbaby, it was unknown whether the prey was alive or dead after the use of the tool, but it made no attempts to escape, nor did it utter any vocalization. In that case, the chimpanzee ultimately broke off the terminal end of the hollow branch by moving several meters up the large (>10 cm diameter) branch and jumping on the branch until it broke off. She then climbed down, reached into the cavity, and pulled out the bushbaby," reports Pruetz in the in-press Current Biology article, "Savanna Chimpanzees, Pan troglodytes verus, Hunt with Tools."
The observation that chimps use biodegradable tools to hunt meat suggests that early human ancestors probably used tools far earlier than previously thought. Though I am skeptical about exactly how much foresight this spear hunting demonstrates, such observations can provide valuable insight into the lives of early hominids.
You can read a brief about the study here.