So organoid studies would suggest:
In a study of “mini-brains” (brain organoids), the size of a pea, grown in a dish and incapable of further development, researchers have discovered a “key genetic switch” that makes human brains grow three times larger than primate brains…
But what have we learned? Is larger brains really what makes us human? Then what about the people who function normally with a very reduced brain? Remember, they are functioning normally in a world where humans typically have very large brains. And, before medical imaging, no one knew that these people had hardly any brain.News, “Do larger brains make us human? Is that all?” at Mind Matters News
Takehome: Some researchers believe that our diet led to a larger brain but they differ as to which food was the ultimate brain booster. Are we missing something here?
You may also wish to read:
Lemurs with brains 1/200 the size of chimps’ pass same IQ test. Such findings only accentuate the vast gap in intelligence between humans and lemurs, chimpanzees, or ravens today. Efforts to account for this gap in evolutionary terms have not been particularly successful.
Your mind vs. your brain: Ten things to know