Modern humans may have evolved 200,000 years earlier than we thought

For early hominid hunters, there was no greater prize than an elephant. Kill just one of those, and a tribe could eat well for days. But when the elephants suddenly disappeared, something remarkable happened: Our hominid ancestors became more intelligent.

Homo erectus was particularly fond of eating elephants, and it isn't hard to see why. Elephants are slow moving, which makes them easy to kill, and their massive size provides a large number of people with bountiful food. As a bonus, elephant meat has just the right fat-to-protein ratio to sustain humans long-term, and unlike other animals that ratio remains consistent throughout the entire year. Like the bison for 19th century American settlers, they were the perfect meat.

And, like the bison, the elephant supply didn't last forever, though it did take more than a few decades to wipe out the population. Elephants were once common in the Middle East, which hundreds of thousands of years ago was the territory of Homo erectus. At one site recently excavated by archaeologists at Tel Aviv University, elephants accounted for 60% of all animal-derived calories. But by 400,000 years, elephants had completely disappeared from the region.

That date is intriguing, because it lines right up with the recent discovery in Israel's Qesem cave of a shockingly modern human tooth that dates back to 400,000 years ago. The researchers say the two events are likely linked — the loss of the elephants made the situation untenable for Homo erectus, and any hominids that wanted to survive there had to become better adapted to hunting and eating smaller, more agile prey.

These later, more modern hominids might have evolved from or simply replaced Homo erectus, but either way, the loss of elephants is key. This lines up with the disappearance of elephants from hominid archaeological sites in Africa. There, elephants lasted a bit longer, only disappearing from the human archaeological record 200,000 years ago - just when modern humans emerged in Africa. Although elephants of course survive today, we stopped hunting them long ago.

The behavior of early Homo sapiens is similar to that observed in the Israeli cave. There's evidence of more sophisticated blade technology and the sustained use of fire, as well as more complex behaviors like food sharing. The presence of elephants, it seems, had allowed our evolutionary ancestors to coast, so to speak, and without such a ridiculously easy food source, hominids both in Africa and the Middle East had to adapt very quickly to survive.

This new finding offers some corroboration for the still controversial discovery of that 400,000 year old tooth, though we still don't know what the full implications of that tooth might be. If the tooth belonged to an incredibly ancient member of Homo sapiens, it could rewrite our evolutionary history. Alternatively - and perhaps most likely, at least based on the current balance of evidence - it represents a previously unknown hominid species that since went extinct. Either way, it appears we all have elephants, or the lack thereof, to thank for our smarts.

Via PLoS ONE. Image by _Mrs_B on Flickr.