Hacker News Reader

Comment by lordnacho | Hacker News Reader

Why is there evolutionary pressure for the brain to shrink? We seem to have enough calories to feed our brains, and we're not beholden to some master species that needs to economize.

View on HN

Because we no longer need to run away from predators and process information at the same rate we'd need to in a more wild enviornment. The survival pressures of our ancestral environment are no longer relevant. We've essentially destroyed and driven to extinction every other predator on the planet and now the only selective pressure is adaptation to the human created environment which is much nicer and simpler than the wilderness we came from. Simpler and safer environments make simpler brains and that's my best guess at why our brains are shrinking but I'm just an armchair scientist so it's better to ask the experts. The only remaining selective pressure is basically human predators, a.k.a. sociopaths.

> and process information at the same rate we'd need to in a more wild enviornment

If anything that rate of processing has gone up, not down.

And most of it has been offloaded to computers (big data, deep learning, etc). I don't think we're going to have "mentats" any time soon.

You have this backwards. We are dealing with orders of magnitude more information than we did in ancient times, and we are required to remember a good chunk of it and to be able to recall and use it at a moments notice.

Computers are a big factor in generating all of that information, even if they help process some of it the net effect is a huge surplus.

I don't think I have it backwards. I don't remember anything or know much about the world in general terms. I just know and remember enough key phrases for google to give me the answers when I need them which requires very little cognitive effort on my part. [1]

1: https://www.psychologytoday.com/intl/blog/the-athletes-way/2...

Computers are less than 100 years old, the idea that their existence has lead to brains shrinking is preposterous.

That wasn't the argument. You seem to be saying that the increasing volume of digital information will require new cognitive adaptations and I'm saying that's not the case because I don't need to be as smart to appear smart on a digital medium, I can just rely on external cognitive aids like google.

> You seem to be saying

I'm not.

Then we don't really have anything to discuss.

> We are dealing with orders of magnitude more information than we did in ancient times, and we are required to remember a good chunk of it and to be able to recall and use it at a moments notice.

Surely you mean required, meaning you could end up embarassing yourself in front of your coworkers if you aren't able to recall that particular bit of information.

It's very different from REQUIRED, meaning that if you take a left turn instead of a right turn while running away from a predator you end up in a canyon... or the predator eats you because you have no way to escape...or both.

Yes but let's say, pre-writing people needed to remember 100% of all information they needed to use - which writing people can offload to tablets and parchments.

Pre-agriculture people had it worse, they needed to remember 100% of all pertinent informations by the hunting band, which had a max amount of 50-100 people. All the predictive abilities for preys in their lands, natural disasters, medicines, rituals, etc.

It's logical that adoption of technology and farming led to lesser pressure for memory recall, at least for the median human.

The brain itself is the evolutionary pressure. It is often repeated that the brain takes ~20% of our body's energy despite being ~2% of our body's mass. If there is no need to have a brain so large (due to a lack of predators) it is beneficial to shrink it.

It's beneficial to lower the brain's calorie intake it if it results in higher reproductive fitness. But like GP said, we have plenty of calories, more than we've had compared to the entire history of humanity. So it doesn't naturally follow that lower calorie brains are higher fitness in 2021.

"Although our brains were getting bigger progressively, around 70,000 years ago they plateaued, and have been shrinking ever since."

From the article. 2021 is very recent.

The article also discusses energy usage a little under the section "Fuel".

There are no guarantees civilization won't collapse. The traits that were essential for our survival in the stone age aren't things we want to abandon. I'm a big fan of redundancy.

Beneficial how? Reduction in calories? We tend to have diseases of excess calories in the developed world now. If anything, the greater brain metabolism may actually help by burning some of those excess calories off…

https://news.ycombinator.com/item?id=29033971

“Use it or lose it” applies in evolution, because of energy usage, but also because of complexity. More features means more things to go wrong, more options for cancers, etc.

> Why is there evolutionary pressure for the brain to shrink?

Less energy demand, I guess.

Reply on news.ycombinator.com