New study finds evolution of brain and tooth size were not linked in humans

January 2, 2017
3-D reconstruction of a modern human cranium showing the teeth and endocranial cast. Credit: George Washington University

A new study from the George Washington University's Center for the Advanced Study of Human Paleobiology (CASHP) 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 finding suggests that our brains and teeth did not evolve in lock step and were likely influenced by different ecological and behavioral factors.

This research challenges the classically accepted view that reduction of in hominins is linked with having a larger . The reasoning is that larger brains allowed hominins to start making and that the use of these tools reduced the need to have such large chewing teeth. But recent studies by other authors found that hominins had larger brains before chewing teeth became smaller, and they made and used stone tools when brains were still quite small, which challenges this relationship.

The new 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 , 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.

To conduct the research, Dr. Gómez-Robles and her colleagues analyzed eight different hominin species. The researchers 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, university professor of human origins at GW and a co-author of the paper. "The co- of brains and teeth was on a fast-track to dogma status, but we caught it in the nick of time."

The research published Jan. 2 in the Proceedings of the National Academy of Sciences.

Explore further: Tooth wear patterns suggest Paranthropus early hominins had softer diets than expected

More information: Brain enlargement and dental reduction were not linked in hominin evolution, PNAS, www.pnas.org/cgi/doi/10.1073/pnas.1608798114

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blovel
1 / 5 (3) Jan 03, 2017
A new study of brain size and belief in evolution IS linked in humans. The smaller the brain, the greater the belief in evolution, according to this landmark study. The exquisite profusion of reality filters drape the smooth exterior of these brains, 'photographing' the lack of logic and derivative thought processes. The ability to conjecture tiny, disparate and unrelated pieces of bone from piles of dirt into sophisticated delusions of ancient ancestors prove that there are high order modalities of skills, highly related to smashing pieces of jigsaw puzzle into place with a sledge hammer and then scotch-taping over the edges and calling it a perfect fit. The study meta-analyzes thousands of publications that support the highly cantilevered pseudo-science presently called 'evolution'.
danfwalker
not rated yet Jan 09, 2017
@blovel to quote Winston Churchilll: "it has been said that democracy is the worst form of Government except all those other forms that have been tried from time to time."

Evolution is the worst theory of the origin of life, except all those other theories that have been tried from time to time.

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