[dymk]

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.

[rackjack]

"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".

[Fricken]

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.