"Even though they're closely related genetically and live close to each other geographically, still there are big differences in the average number of copies in these populations," Dominy said. "So we felt like geography and relatedness are not driving these differences. It's got to be diet."
For Dominy and his coauthors, the finding goes beyond the mouth. In pondering human origins, Dominy said, anthropologists have long been stumped by the sudden, nearly simultaneous increases in our brain size, body size, and geographic range, while other apes changed little. Early humans simply must have found some source of better nutrition to make it all possible, they reasoned.
"That's the big mystery of paleoanthropology," Dominy said. "What changed" Why did our earliest human ancestors deviate from the pattern we see in living apes to evolve this incredibly large brain, which is very energetically expensive to maintain, and to become a much more efficient bipedal organism""
For years, the answer was thought to be the growing importance of meat in the diet, as early humans learned to hunt. But, Dominy pointed out, "Even when you look at modern human hunter-gatherers, meat is a relatively small fraction of their diet. They cooperate with language, use nets; they have poisoned arrows, even, and still it's not that easy to hunt meat. To think that, two to four million years ago, a small-brained, awkwardly bipedal animal could efficiently acquire meat, even by scavenging, just doesn't make a whole lot of sense."
Some anthropologists have begun to suspect the new source of food consisted of starches, stored by plants in the form of underground tubers and bulbs--wild versions of modern-day foods like carrots, potatoes, and onions. Once early humans learned
|Contact: Tim Stephens|
University of California - Santa Cruz