From “Why cooking counts” (Eurekalert, 7-Nov-2011), we learn more about the thesis:
In a first-of-its kind study, Harvard researchers have shown that cooked meat provides more energy than raw meat, a finding that suggests humans are biologically adapted to take advantage of the benefits of cooking, and that cooking played a key role in driving the evolution of man from an ape-like creature into one more closely resembling modern humans.
Though early humans were eating meat as early as 2.5 million years ago, without the ability to control fire, any meat in their diet was raw, and probably pounded using primitive stone tools. Approximately 1.9 million years ago, however, a sudden change occurred. The bodies of early humans grew larger. Their brains increased in size and complexity. Adaptations for long-distance running appeared.
Though earlier theories suggested the changes were the product of increased meat in their diet, Carmody’s research points to another possible hypothesis – that cooking provided early humans with more energy, allowing for such energetically-costly evolutionary changes.
Of course, there is a huge assumption here: That cooking drove the changes, as opposed to being itself one of them – which is more likely.
See also: Were people cooking two million years ago?