From Newsgroup: talk.origins
https://www.science.org/doi/10.1126/science.aed8437
https://phys.org/news/2026-08-sugars-fuel-evolution-human-brain.html#goog_rewarded
Glucose is the main metabolite producing energy in neurons. Since gluconeogenesis (glucose from amino acids) isn't the main means of
producing glucose, these researchers think that fruit, honey, and plant
starch were the main support for evolving large brains and not meat.
The problem is that you need meat to grow big brains. Human milk has
twice the amount of omega 3 fatty acid than cows milk and a lot of that
omega 3 comes from consumption of animals. Grass fed cattle have 200 mg
of omega 3 fatty acids per 100 g and fish have at least 5 times that
amount. To produce the long chain omega 3 fatty acids in their eggs
hens have to be fed algae or fish oil. If they are fed plant based unsaturated fat, they put mostly short chain fatty acids into the egg.
Chimps likely get the omega 3 that they need from invertebrates that
they eat, and they likely do not need as much as humans do.
What likely is the case is that large brains needed more food to evolve.
Monkeys evolved as fruitivores and did have more starch and sugar in
their diet than their insectivore ancestors and did evolve larger brains
to body weight than those insectivore ancestors. They obviously can
feed a larger brain with their lifestyle.
Humans ancestors needed to be able to grow their brains larger and feed
them. Larger brains allowed these ancestors to gather the food that
they needed to evolve larger brains. When I took anthropology in the
mid 1970's they did not know why Homo erectus needed to create the large
hand axes (we are still guessing). Flakes took less stone and probably
did fleshing and skinning more efficiently. The main proposal then was
that they were used to dig up roots and tubers. They required a lot of
stone to make them, so they needed to have some important purpose. Some people were claiming that they could be used as cores to make working
flakes. Modern humans are not known for making hand axes. Neanderthal
and Homo erectus did make them. Some of them were so large and ornate
that my guess is that the large ones were status symbols. Instead of
hand axes modern human hunter gatherers used digging stick made of wood,
bone or antlers, but they also made flat stones to dig with. The flat
stones were not made like hand axes that were made from a larger stone core.
Plant starch could have been a major food source for hunter gatherers.
Hunter gatherers maintained a diet that supported larger brains than did
the advent of agriculture and the reliance on mainly storable grain and
tubers when our average brain size decreased. Agriculture was not a
good diet for big brains.
This likely means that hunting and the ability to exploit more plant
foods likely fueled the evolution of bigger brains to help our ancestors gather more of the foods that were needed to grow and maintain larger
brains.
Ron Okimoto
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