Human evolution; the brain differs from all others (Introduction)

by David Turell , Thursday, August 22, 2019, 01:03 (1918 days ago) @ David Turell

A newly studied 20 myo monkey brain reveals clues as to brain evolution:

https://cosmosmagazine.com/palaeontology/lifting-the-lid-on-primate-brains?utm_source=C...

"A fossilised primate skull the size of a chicken egg has yielded insights into how primate brains – including our own – evolved.

"The 20-million-year-old near-complete skull is a rare specimen. It belongs to Chilecebus carrascoensis, a primate that scampered around the Chilean Andes during the Miocene.

"The species is a member of the New World monkeys, or platyrrhines, a group found in Central and South America which today includes marmosets, capuchins and spider monkeys.

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"Weighing in at around eight grams, Chilecebus had a brain roughly the size of a marmoset’s.
However, unlike a marmoset’s brain, which has quite a smooth surface, Chilecebus’s brain had seven pairs of grooves – sulci – on its surface.

"The presence of sulci is usually associated with larger, more cognitively advanced brains. The Chilecebus brain suggests size and brain folds don’t go hand in hand.

"Other anatomical features also seem to evolve independently.

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"The findings support the idea that the primate brain evolves in a complex “mosaic” fashion, with different functional regions evolving independently of others.

"New World monkeys split from the other main group of primates, the catarrhines, more than 40 million years ago. This group includes the Old World monkeys of Asia and Africa – baboons and mandrils and the like – and apes, to which our own lineage belongs.

"In both groups, brain size has increased over time – a situation of convergent evolution.
But the comparison also reveals just how weird human brains are.

“'Only within the human lineage are the brains exceptionally enlarged,” says Ni. Human brains enlarged three times more than would be predicted based on the evolutionary trajectory of other lineages". (my bold)

Comment: Note my bold. Our brain evolved in a different trajectory.