Brains, brawn, and human nature

The food you ate today for breakfast has been transformed. Your body has used some of it to generate energy and some to build new tissues. Your body controls your metabolism in a marvelously sophisticated way, channeling resources to each organ to keep it functioning. In my new “Matter” column for the New York Times, I look at how our metabolism evolved. It turns out that our brains and our muscles have an odd kind of metabolism compared to other mammals. Did we lose muscular strength to fuel a big brain? Or did we switch our muscles to a different kind of metabolism, which let our brains burn brighter? The answer’s not clear yet, but the research is pretty cool. Check it out.

2 thoughts on “Brains, brawn, and human nature

  1. It’s too good to resist…
    I Corinthians 15:39a All flesh is not the same flesh: but there is one kind of flesh of men, another flesh of beasts…

  2. Today’s report is part of a growing body of work pointing in the same direction. For example, if you’ll pardon my tooting my own horn a little:

    O. Fedrigo et al., 2011, “A potential role for glucose transporters in the evolution of human brain size”, Brain, Behavior and Evolution 78:315-326.

    Abstract: Differences in cognitive abilities and the relatively large brain are among the most striking differences between humans and their closest primate relatives. The energy trade-off hypothesis predicts that a major shift in energy allocation among tissues occurred during human origins in order to support the remarkable expansion of a metabolically expensive brain. However, the molecular basis of this adaptive scenario is unknown. Two glucose transporters (SLC2A1 and SLC2A4) are promising candidates and present intriguing mutations in humans, resulting, respectively, in microcephaly and disruptions in whole-body glucose homeostasis. We compared SLC2A1 and SLC2A4 expression between humans, chimpanzees and macaques, and found compensatory and biologically significant expression changes on the human lineage within cerebral cortex and skeletal muscle, consistent with mediating an energy trade-off. We also show that these two genes are likely to have undergone adaptation and participated in the development and maintenance of a larger brain in the human lineage by modulating brain and skeletal muscle energy allocation. We found that these two genes show human-specific signatures of positive selection on known regulatory elements within their 5′-untranslated region, suggesting an adaptation of their regulation during human origins. This study represents the first case where adaptive, functional and genetic lines of evidence implicate specific genes in the evolution of human brain size.

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