If Modern Humans Are So Smart, Why Are Our Brains Shrinking?

Here are some leading theories about the why the human brain has been getting smaller since the Stone Age.

Some believe the erosion of our gray matter means that modern humans are indeed getting dumber. [gray matter takes up enormous energy requirements]

The Homo sapiens with the biggest brains lived 20,000 to 30,000 years ago in Europe.

Recent studies of human fossils suggest the brain shrank more quickly than the body in near-modern times.

Just as I begin to absorb these varying interpretations, I am hit with the next surprise in our human evolutionary narrative: After a long, slow retrenchment, human brain size appears to be rising again.

*End clips from article, but it is has several neat theories and a lot more food for thought.

From that video I posted about ketosis you would learn that ketones are basically a multiplier for energy compared to glucose for the brain. Typical human uses the most ketones when they are babies to help develop their big brain. At least as far as white people go, we used to eat a diet far closer to ketosis than the modern diet. We had ice ages to deal with and long winters. It is very likely there was a lot of animal fat being eaten in that time compared to the modern diet.

Now brains are getting bigger finally and diets contain more meat than ever in modern times. Also people are starting to get off the grains more so. My hypothesis is big beautiful brains come from ketosis. You guys got anything?

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Posted by Not Cooper

Member since Jun 2015

5037 posts

Posted on 7/19/17 at 11:41 am to zatetic

There are such a wide variety of diet types out there. You can't just say "oh well the ketogenic diet is the new fad so that's why everyone's brains are getting bigger." It's likely something much simpler - we have a much higher caloric intake as adolescents than ever before, and the amount of physical labor is decreasing, which reduces in energy expenditure in the skeletal muscle and increases available caloric intake for the brain, so they get bigger.

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Posted by Bmath

Member since Aug 2010

18912 posts

Posted on 7/19/17 at 1:24 pm to zatetic

quote:
Now brains are getting bigger finally and diets contain more meat than ever in modern times. Also people are starting to get off the grains more so. My hypothesis is big beautiful brains come from ketosis. You guys got anything?

I would say that initially, large brains were important for squeezing more out of what little processing power early humans had.

While nutrition certainly played a role, I suspect that brain function became more efficient over time. This would explain why it shrank somewhat in size.

A good analogy would be computers, cell phones, and other electronics. They initially were really large machines. Now, my phone that fits in my pocket has more processing power than computers years ago that took up an entire room.

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Posted by zatetic

Member since Nov 2015

5677 posts

Posted on 7/19/17 at 1:30 pm to Not Cooper

quote:
You can't just say "oh well the ketogenic diet is the new fad so that's why everyone's brains are getting bigger."

I'm more so saying that people used to eat a ketogenic diet before switching with the agricultural revolution. It is well known that when people switched from hunter-gather to agricultural diet they literally became smaller than the previous generations.

https://phys.org/news/2011-06-farming-blame-size-brains.html

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