If you had unlimited fuel and money forever, which car would you choose? Probably something very powerful with a big engine.

But if there were a fuel shortage forever, you would probably choose something with a small, efficient engine.

The same logic was used by our bodies during evolution. When resources were scarce, we evolved to have as little muscle as possible to survive and be efficient.

But now is a time of abundance. And it's probably a good idea to pack on as much muscle and power as naturally possible.