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🇰🇷 South Korea /Health & Science

Could sugar, not protein, have powered the evolution of the human brain?

From Hankyoreh · () Korean

Translated from Korean and summarized by DistantNews. Read the original for the full story.

At a glance

News Named sources Context piece
  • Researchers from the University of Sydney and the University of Glasgow argue that carbohydrate-rich foods may have supplied more of the energy needed for human brain evolution than protein-rich meat.
  • Their model estimates that early humans obtained more than half of their energy from carbohydrates, first through fruit and honey and later through cooked starches.
  • The researchers acknowledge that the findings rely on assumptions about ancient diets, and an outside anthropologist called the analysis valuable but built on uncertain foundations.

A new study challenges the familiar idea that meat and protein chiefly fueled the expansion of the human brain. It argues that sugars from fruit and honey, followed later by carbohydrates from cooked starch, may have supplied the energy that made larger brains possible.

The contrast is stark. Australopithecus, including the roughly 4-million-year-old ancestor known as Lucy, had a brain weighing about 300 grams. Homo sapiens, which appeared around 300,000 years ago, had a brain weighing about 1,500 grams. Although the brain accounts for only 2% of body mass, it uses about 20% of the body’s energy at rest. In children, the share can reach two-thirds.

It was as if a light bulb had switched on.

— Jennie Brand-MillerThe University of Sydney researcher described her reaction to earlier findings on fruit-eating primates.

Researchers from the University of Sydney and the University of Glasgow analyzed nutritional and metabolic models covering six stages of human evolution. They estimated that carbohydrates supplied more than half of total energy needs. At first, more than 65% came from natural sugars in fruit and honey. By the period associated with modern humans, fruit and honey contributed an estimated 20% to 35%, starch 25%, and protein less than 20%.

A very valuable analysis, but one built on uncertain foundations.

— Matt SponheimerThe University of Colorado Boulder anthropologist criticized the assumptions underlying the study.

The study builds on earlier research involving more than 140 primate species, which found that fruit-eating primates had brains averaging 25% larger than those of grass-eating primates and larger than those of omnivorous primates that ate meat. Lead author Jennie Brand-Miller said the finding prompted her to reconsider whether a meat-heavy diet could meet the glucose demands of pregnancy, breastfeeding and childhood.

The researchers propose that cooking, which began about 1 million years ago, made roots and grains easier to convert into glucose and supported another period of brain growth. They also link the evolutionary ability to process starch and sugar to modern health risks. Humans can have up to 20 copies of the amylase gene involved in starch digestion, compared with one in chimpanzees. Matt Sponheimer of the University of Colorado Boulder said the analysis was valuable but rested on uncertain assumptions, including the claim that Australopithecus ate a diet similar to chimpanzees. The researchers said fossil and other evidence, including teeth, dental decay, colour vision and isotope ratios, supports a major role for fruit and sugar in early human diets.

The role of diet in human evolution is inevitably speculative, but objective evidence suggests that early humans consumed large amounts of sugar through fruit-based diets.

— The researchersThe study authors acknowledged the limits of reconstructing ancient diets while defending their interpretation.
About this summary

Originally published by Hankyoreh in Korean. Translated, summarized, and contextualized automatically by DistantNews, with a note on how the source frames the story. Not individually reviewed before publishing. How this works.

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