https://www.youtube.com/watch?v=HgqbCq_sxmoWhy did humans and chimpanzees diverge so sharply on the primate family tree?

Because of our diets, say German anthropologists.

In a study published yesterday in Public Library of Science ONE, a team of Max Planck Institute researchers compared gene expression in three groups of mice – one given a cafeteria-style human diet, another given the fruits and veggies consumed by chimps in zoos, and the last given McDonald's takeout.

The chimpanzee diet produced thousands of changes in gene expression, especially in the mice's livers. The same genes have been observed to differ between humans and chimps, who are otherwise nearly 99 percent identical at the DNA level.

If human and chimp diets triggered such changes in mice, figured the researchers, maybe a few million years of eating well are the reason why people aren't still sucking termites off sticks.

"Some have proposed that it was our high-energy, high-protein and cooked diet that enabled us to fuel our big brains during our evolution," said study co-author Mehmet Somel.

It's an interesting proposition – but how much can we really infer about primates by giving our food to mice? I posed the question to

Somel.

"Mice and rats have been used to study dietary effects before, but when starting the experiment, we weren't sure whether the effects of different diets in mice would be of any relevance to human and chimpanzee differences," he said.

"However, we couldn't have conducted the same experiment on humans and chimpanzees. Consuming each other's diet could be detrimental to both species, and then, it is not really possible to measure brain or liver gene expression from live tissue. So the mouse experiment was worth a try. And in the end, we did get a positive result in liver. This was one of the most interesting points in itself: that mice can be used to analyse human and chimpanzee differences."

Note: As an aside, Somel noted that the McDonald's diet correlated with a slight downtick in brain gene expression – too small to be statistically significant, but tantalizing in light of other findings suggesting that diets high in saturated fats and refined sugars are

neurologically damaging.

Human and Chimpanzee Gene Expression Differences Replicated in Mice Fed Different Diets [PLoS ONE]

Image: What would you rather have – another picture of lab mice, or video of competitive eating superstar Takeru Kobayashi taking on a bear? That's what I thought.

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