My initial response to this is that it is a bit of a wrong assumption. Big isn't necessarily better. Better is better! And it seems to me that efficiency is better than size. If our brain were twice as small but four times more efficient, it strikes me that that would truly be better for us. But what do I know! That's just a guess on my part. - Dallas
Our Brains Are Shrinking. Are We Getting Dumber?
When it comes to brain size, bigger doesn't always mean better. As humans continue to evolve, scientists say our brains are actually getting smaller.
The downsizing of human brains is an evolutionary fact that took science writer Kathleen McAuliffe by surprise.
"I said, 'What? I thought it was getting bigger!'" she tells NPR's Jacki Lyden. That was the story up to 20,000 years ago, she learned. Then, the brains of our ancestors reversed course and started getting smaller — and they've been shrinking ever since.
Cro-Magnon man, who lived in Europe 20,000 to 30,000 years ago, had the biggest brains of any human species. In comparison, today's human brain is about 10 percent smaller. It's a chunk of brain matter "roughly equivalent to a tennis ball in size," McAuliffe says.
The experts aren't sure about the implications of this evolutionary trend. Some think it might be a dumbing-down process. One cognitive scientist, David Geary, argues that as human society grows increasingly complex, individuals don't need to be as intelligent in order to survive and reproduce.
But not all researchers are so pessimistic. Brian Hare, an anthropologist at the Duke University Institute for Brain Sciences, thinks the decrease in brain size is actually an evolutionary advantage.
Read the rest or listen to the story on NPR.
3. Our brains use too much energy and people with smaller brains have more children.
Oh, yes, I forgot to mention that. I think that in a resting state, the brain uses 20% of our cardiac output. That's a lot. Smaller brains would take less caloric energy, I suppose. And I guess efficiency has somethign to do with that, too.
It's not just size that matters, but how it's used. (Ahem. No thread tangents, please.)
Big physical brains have big physical costs at various stages of development, birth, life, and species evolution. Whenever nature can pack just as much power into a smaller brain, she does, but it takes thousands to millions of years of trial and error.
Instead, humans advanced evolutionwise with advanced language and communication skills, metaphorical and symbolic thinking, and social/cultural evolution. (E.g. an ant is dumb, but a huge colony has significant intelligence.) As the power of "software" enhancements (enabled by built-in neuro-plasticity and enhnaced by social/cultural intelligence) rose in orders of magnitude, "hardware" (genetic selection and optimization) took more of a back seat. Even Conan The Barbarian would have huge, unfair advantage over the smartest, bigger brained caveman.
Thousands of years of cultural advancement now usurps millions of years of nature. Even decades of science and technology now usurp centuries of tradition (including religion!). Much of our intelligence is now artificial, in the sense that it's man-made. I'm not saying that artificial is inferior, but am just pointing out how our modern definition of intelligence should account for nature vs nurture, and big vs cultured. (In fact, human-made, artificial intelligence is now leaping higher, into Artificial Evolution, Phase 2.)
Like, geez, I didn't mean to kill the discussion. Hmm, perhaps it can continue in...