Elephants have long been known to be part of the Homo erectus（直立人） diet. But the significance of this specific food source, in relation to both the survival of Homo erectus and the evolution of modern humans, has never been understood -- until now. When Tel Aviv University researchers Dr. Ran Barkai, Miki Ben-Dor, and Prof. Avi Gopher of TAU's Department of Archaeology and Ancient Near Eastern Studies examined the published data describing animal bones associated with Homo erectus at the Acheulian site of Gesher Benot Ya'aqov in Israel, they found that elephant bones made up only two to three percent the total. But these low numbers are misleading, they say. While the six-ton animal may have only been represented by a tiny percentage of bones at the site, it actually provided as much as 60 percent of animal-sourced calories.

The elephant, a huge package of food that is easy to hunt, disappeared from the Middle East 400,000 years ago -- an event that must have imposed considerable nutritional stress on Homo erectus. Working with Prof. Israel Hershkovitz of TAU's Sackler Faculty of Medicine, the researchers connected this evidence about diet with other cultural and anatomical（解剖的） clues and concluded that the new hominids（人种） recently discovered at Qesem Cave in Israel -- who had to be more agile（敏捷的） and knowledgeable to satisfy their dietary needs with smaller and faster prey -- took over the Middle Eastern landscape and eventually replaced Homo erectus.

The findings, which have been reported in the journal PLoS One, suggest that the disappearance of elephants 400,000 years ago was the reason that modern humans first appeared in the Middle East. In Africa, elephants disappeared from archaeological sites and Homo sapiens（智人） emerged much later -- only 200,000 years ago.