According to Science Daily report, the new study found that whereas brain size evolved at different rates for different species, especially during the evolution of Homo, the genus that includes humans, chewing teeth tended to evolve at more similar rates, and that they were likely influenced by different ecological and behavioral factors.
Based on the study published at National Academy of Sciences, brain size evolution with reduced tooth size rates in eight hominin species: two australopiths (A. africanus and A. afarensis, roughly 1.9-2.9 million years old), two members of Paranthropus (P. robustus and P. boisei, 900,000-1.2 million years old) and four examples from our own genus Homo (H. habilis, H. erectus, H. neanderthalensis, from the last 1.7 million years, and modern humans) have been compared.
Although conventional wisdom has pointed to co-evolution of the big human brain, little human teeth traits, the study showed the rate of brain size evolution varied from one species to the next with occasional bouts of rapid development.
"The findings of the study indicate that simple causal relationships between the evolution of brain size, tool use and tooth size are unlikely to hold true when considering the complex scenarios of hominin evolution and the extended time periods during which evolutionary change has occurred," said Aida Gómez-Robles, lead author of the paper and a postdoctoral scientist at GW's CASHP.
The team concluded that different environmental and behavioral influences were at work in human brain and teeth evolution rates, though speculating on what those influences might have been went beyond the scope of their research.