Did you imagine that adding meat to the diet and adopting some simple food processes could lead to a cataclysmic change in human evolution millions of years ago? Well, that is what Harvard researchers surmise. The enhancement in ancient food habits with the help of stone tools gradually reduced the size of the human jaw, teeth and gums and created an upheaval in human evolution.
The researchers said that teeth are not intended to tear raw meat into smaller pieces that could be swallowed. After all, predators have teeth meant to slice through elastic muscles and tissues, whereas human teeth act more like mortar-and-pestle systems and crush, rather than slice, food.
Still, according to paleoanthropologist Daniel Lieberman, fossils indicate that ancestors' teeth were similar to modern humans', yet forefathers were consuming meat regularly even two to three million years ago.
Through a number of tests in the lab, the research team explored how sharp rocks could cut, slice and pound meat and vegetables. They discovered that the processes led to "2.5 million fewer chews per year."
First author Katie Zink, a lecturer who undertook the experiments at Harvard University, explained it further. "What we showed is that by processing food, especially meat, before eating it, humans not only decrease the effort needed to chew it but also chew it much more effectively," she said. "With the advent of our genus, we start to see this suite of changes that continue on throughout time. In general, we see a decline in tooth size and jaw size."
The experiments were called "creative but sometimes, frankly, a little stomach-churning."
"Not only did she have people come into the lab, chew the raw meat and other foods, and spit them out, but then she had to analyze the stuff," Lieberman said.
The results showed that humans found it tough to eat raw meat with low-crested teeth. "When you give people raw goat, they chew and chew and chew, and most of the goat is still one big clump - it's like chewing gum," Lieberman said. "But once you start processing it mechanically, even just slicing it, the effects on chewing performance are dramatic."
"Human teeth don't have the kind of shearing ability that, say, dogs' teeth have, and that is necessary to break down meat," he added. "With human chewing it just stays in a clump, and studies have shown how that makes digestion far less efficient."
The experiments suggested that humans could not have eaten meat without putting it through processing. Lieberman agreed that even if they had not begun to eat meat at a particular time, they had found some techniques that could make the food more digestible.
"The evolution of the ability to chew food into smaller particles gave mammals a big boost of extra energy because smaller particles have a higher surface area to volume ratio, allowing digestive enzymes to then break food down more efficiently," Lieberman said.
The meat eaters had smaller teeth than their vegetarian forefathers, along with weaker chewing muscles and bite force.
Hence, spending less time in chewing and masticating food, humans developed bigger brains and better thinking ability.
The study was published in the March 9 edition of Nature.
