Bone marks: tools vs. teeth.

Bone marks: Tools vs. teeth

A new method of analyzing tiny pits and grooves on broken animal bones, developed by anthropologists at Rutgers University in New Brunswick, N.J., promises to help clarify questions about the proposed hunting and scavenging strategies used by human ancestors nearly 2 million years ago.

Robert J. Blumenschine and Marie M. Selvaggio used a piece of sandstone to break limb bones taken from the carcasses of African gazelle, impala and wildebeest. They broke the bones so they could remove marrow with a stick, a technique Blumenschine suggests early human ancestors used to scavenge the remains at carnivore kill sites (SN: 3/9/85, p.155).

The resulting pits and grooves or "percussion marks" on the bones, usually found near the notches created by the impact of stone, look much like carnivore tooth marks at first glance, the researchers report in the June 24 NATURE. But when the broken bones are viewed under a scanning electron microscope, patches of distinctive parallel lines are found in and around percussion pits and grooves; a different line pattern is observed near hyena tooth marks on marrow bones, explain Blumenschine and Selvaggio. Minute percussion marks also differ from stone-tool cut-marks and scraping marks, thought to be signs of meat defleshing.

Percussion marks are likely to turn up among animal bones found at human ancestor sites in East Africa, predict the researchers, since the prehistoric inhabitants had access to stone similar to that used in their experiment. In previous investigations, they maintain, researchers probably have underestimated or overlooked the breaking of bones by early humans to obtain marrow. Percussion mark analysis also can test claims for a human presence in the New World up to 100,000 years ago based on tools allegedly shaped from bone (SN: 3/14/87, p.172).