Our brains and teeth did not evolve together and were likely influenced by different ecological and behavioural factors, a new study has found which challenges the belief that reduction of tooth size is linked to larger brains.
Researchers at the George Washington University's Centre for the Advanced Study of Human Paleobiology (CASHP) in the US 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.
The study evaluates this issue by measuring and comparing the rates at which teeth and brains have evolved along the different branches of the human evolutionary tree.
"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 Gomez-Robles from CASHP.
To conduct the research, researchers analysed eight different hominin species.
They identified fast-evolving species by comparing differences between groups with those obtained when simulating evolution at a constant rate across all lineages and they found clear differences between tooth evolution and brain evolution.
If the classical view proposing co-evolution between brains and teeth is correct, they expected to see a close correspondence between species evolving at a fast rate for both traits.
The differences they observed indicate that diverse and unrelated factors influenced the evolution of teeth and brains.
"Once something becomes conventional wisdom, in no time at all it becomes dogma," said Bernard Wood, professor at the university.
"The co-evolution of brains and teeth was on a fast-track to dogma status, but we caught it in the nick of time," Wood said.
The study was published in the journal Proceedings of the National Academy of Sciences.
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