The human brain grew as a result of the extinction of large animals: new paper

Our large brains are good for prediction and problem solving in complex environments... capabilities needed to be a generalist rather than a specialist.

Changing food sources may be part of the picture, but it seems more likely that it'd be a need to utilize more varied and unpredictable food sources, not just a different staple, that'd require these capabilities.

It also seems inevitable that there'd have been multiple selection pressures all acting on whatever evolving capabilities we had. Maybe changing food sources upset the status quo, and favored some initial spurt in brain growth, but that in turn would eventually have lead to new social/communication capabilities (and what else?) that would have themselves then acted as differentiators for selection.

The story of the selection pressures acting along our evolutionary history is going to be multifacted and messy, ergo any simple explanation is at best incomplete or wrong. Why didn't all animals preying on these larger animals develop large brains? Where are the sabre-tooth developers among us?

Intelligence is meta-adaptation - adaptation that allows you to adapt to environment changes on the fly (without wasting many generations for mutation and selection).

So, the evolutionary pressure must have been something that required adaptation within one generation - for hundreds of generations.

If the need for adaptation was a single big event - brains wouldn't have the time to evolve - it would be easier to adapt directly. You don't need human-level intelligence to hunt big prey nor small prey.

The changes must have been frequent enough to be worth wasting calories on bigger and bigger brains and supporting them through the time when there were no changes to adapt to.

So I don't think overhunting was it. Every predator species deals with overhunting.

This is more or less what Yuval Noah Harari lays out in the first section of his book 'Sapiens': 1 - homo sapiens have a cognitive revolution 70k years ago which makes them able to think and communicate in more sophisticated ways. 2 - homo sapiens spread all around the world and wipe out ~all the large animals (including other human species..). His evidence from various places (Australia, America, various islands) of humans arriving then the large animals disappearing is pretty convincing.

You are on the target. Fish contain high levels of the fatty acid DHA. DHA is the main limiting factor on the growth of the brain, and needed exogenously (AA needed too, but can be converted internally). Humans cannot easily get access to DHA from things like grass. That’s why large herbivores grow in bodymass, but their brain size (encephalizatiom quotient) stays low. Dolphins, who eat primarily fish, have a much more similar brain to us, and one of the highest encephalization quotients...

Due to changes in geography in Africa, proto-humans found themselves along the shorelines with ample supples of fish for the first time. They ate more DHA, which lead to the growth in brain cells (brains are built of these fatty acids). This extra brain power, through the process known as exaptation (the lesser known evolutionary concept to survival of the fittest), is what is theorized to have then opened the door the human creativity, symbols, language, etc.

Basically, our bigger brains were caused by an increase in the previously limiting nutrient, which was then put to to use for advanced traits, not the other way around as this article purports....

That is a TL;DR as don’t have time to write it all out, but have written and presented on this topic...

https://www.wiley.com/en-us/Human+Brain+Evolution%3A+The+Inf...

Edit: this abstract below has a good summary, and book above is great compilation of papers on the topic.

“The circumstances of human brain evolution are of central importance to accounting for human origins, yet are still poorly understood. Human evolution is usually portrayed as having occurred in a hot, dry climate in East Africa where the earliest human ancestors became bipedal and evolved tool-making skills and language while struggling to survive in a wooded or savannah environment. At least three points need to be recognised when constructing concepts of human brain evolution : (1) The human brain cannot develop normally without a reliable supply of several nutrients, notably docosahexaenoic acid, iodine and iron. (2) At term, the human fetus has about 13 % of body weight as fat, a key form of energy insurance supporting brain development that is not found in other primates. (3) The genome of humans and chimpanzees is https://pubmed.ncbi.nlm.nih.gov/16828044/

I think all the brain matter can be composed by the body itself, indcluding DHA or DHEA. It is just easier to get big quantities from exogenous sources. The world champion of chess, Carlsen, comes from Norway where they produce the most salmon in the world. You can buy salmon everywhere, relatively cheap comparing to other places.

However i am a vegan for 4 years, and i think my brain never worked better. Everything that comes from animal sources, can be substituted by plants, or from endogenous production of the body.

How about our brain got evolved because of our vocal chords? I didn't see anyone considering that hypothesis. I can personally can imitate many animals, birds or whatever. My ancestors, ancient Greeks said that music is the ultimate art. How about we are making music for millions of years, and our brain processing that information, got so much ahead of all the other organisms?