WWU’s Michael Medler Presents Hypothesis on Lava, Fire and Human Evolution at Annual AGU Conference in San Francisco

According to the fossil record, two to three million years ago, humankind’s ancestors lived in East Africa; their brain size was that of a chimpanzee, and these precursors to homo sapiens, called australopithicus, were far more akin to today’s apes than to modern humans.

Then something happened about 2.5 million years ago that changed everything.

Our ancestors began to evolve, quickly. Their mouths, teeth, and digestive tracts began to change, and, most importantly, their brains began to grow bigger. Hypotheses on what jump-started this evolutionary leap are legion, but one recent theory is that this change in human morphology could only have been possible through the huge caloric jump available in eating cooked instead of raw food, and cooked food requires fire. So how did australopithicines with brains half the size of modern humans readily acquire fire to cook with?

According to research and a hypothesis of Western Washington University associate professor of Environmental Science Michael Medler, presented at the American Geophysical Union’s annual conference in San Francisco last month, the key to this entire equation might be the massive, long-term lava flows in East Africa at the time.

“The Rift Valley in East Africa 2 million years ago was an area of constant lava flow and volcanism. Many places may have looked like the Big Island of Hawaii or Yellowstone today,” he said. “In places, the lava would have been very approachable, and there would have been thermal features such as hot springs or hot sands associated with it that could also have been used by our ancestors.”

A constant heat source that wouldn’t have to require users to have the skills needed to start a fire but allowed for the cooking of food would have unlocked a huge reservoir of calories in the diets of the australopithicines – for example, consider how much more nutritionally valuable cooked corn is as opposed to raw corn. According to Medler’s hypothesis, the same amount of the same kind of food would have given these lava users much more nutritional value then their relatives elsewhere that didn’t have access to the thermal energy of the lava flows.

“I call these ‘islands in the pyrosphere,’ because these pockets of early humanity were given different sets of resources and evolved very differently than their cousins,” Medler said. “We have seen how islands produce unique traits among isolated species, such as Darwin’s finches on the Galapagos. I believe it is the same with these small islands of fire.”

Medler and his students are working to show the overlap between sites in the fossil record where these early hominins – the taxanomic term for humanity and all its ancestors ­– lived at times that coincided with lava flows in the Great Rift Valley in modern day Ethiopia, Sudan, Kenya and Uganda. Assisting Medler is WWU undergrad Kate Harrison (Arnold, California) and one of his former graduate students, cartographer Paul Whelan (Yakima), who now works for the Washington Department of Fish and Wildlife’s Wildlife Science Division in Spokane.

“The cooked-food hypothesis is a huge piece of the puzzle in terms of how our ancestors made that evolutionary jump, and my part of the equation is to simply explain how and where that cooked food was available due to volcanism and the front edges of these slow-moving lava flows,” he said.

Medler said he will submit his research for publication this spring and is working on a book that will explore the entire notion of fire and human evolution.

For more information on Medler’s research, contact him at (360) 650-3173 or Michael.medler@wwu.edu.