Until quite recently, tool use was considered to be a uniquely human behavior. Early anthropologists taught that the use of tools was limited to Homo sapiens and used the presence of tools as an indicator of the presence of humans. Even after tool use by earlier Homo species was demonstrated, anthropologists still insisted that tool use made the species human.

More recently, scientists have observed many different animals using tools. Sea otters use rocks as anvils to break open shellfish. Galapagos finches mold twigs to probe holes in trees to obtain insect larvae. Egyptian vultures use rocks to crack open ostrich eggs. The burrowing wasp, Ammophila, uses a small pebble to hammer down the soil over its nest of eggs. And green herons use bait to attract small fish.

Since nonhuman animals were clearly observed to be using tools, anthropologists reconsidered their earlier position and decided...