How so? They estimated, in their analysis, how long we should spend feeding every day, based on our body sizes throughout evolutionary history. Sure, it might seem at first glance like cooking would add more time than directly eating but their results say we would need to spend almost half of our time in the 'feeding' process given our current sizes - cooking basically made food easier to chew and digest and as a result we got more caloric benefit and a smaller digestive tract.
Result: Instead of 48 percent, we spend less than 5 percent of our time feeding now and so did earlier man. So, they contend, cooking was not simply a social or cultural invention to make food taste better, it was a vital part of human adaptation. With less time spent in the feeding process, more time could be spent on other things, like hunting to grow bigger societies and other pursuits which began the path to our modern brain.
How did they determine the date? Softer molars in teeth over time. They confirmed research showing that the changes in molars were evident in Homo erectus and H. neanderthalensis - the change in teeth was happening much faster than should have happened compared to other body changes. That means cooking predated them (H. erectus was 1.9 million years ago) and had been passed down from an ancestor.
Prof. Richard Wrangham, Ruth Moore Professor of Biological Anthropology, has championed the idea that cooking was not merely a way to prepare better-tasting food, but was an important development in human evolution. He led the new research in PNAS. File photo by Rose Lincoln/Harvard Staff Photographer
It wasn't all great, sociologists will be happy to note - co-author Dr. Zarin Machanda, Human Evolutionary Biology Associate Concentration Advisor&Lecturer at Harvard, says with cooking freeing up males' time for hunting and evolving, females were stuck with the cooking and gathering, so they were oppressed even 2 million years ago.
Citation: Chris Organa, Charles L. Nunn, Zarin Machanda, and Richard W. Wrangham, 'Phylogenetic rate shifts in feeding time during the evolution of Homo', published online before print August 22, 2011, doi: 10.1073/pnas.1107806108