[AnimalMuppet]

> Humans don’t really use stereopsis beyond the reach of their arms (which makes sense if you think about it).

But of course we do. It's how we throw rocks and hit what we aim at. It's how we catch things. It's how we walk around anywhere that has obstacles. We use it beyond the reach of our arms really frequently.

[oh_sigh]

I can still throw a rock fairly accurately with one eye closed. I can catch pretty much perfectly with one eye closed. I can walk around without hitting anything with one eye closed.

[Sohcahtoa82]

The point was that you don't need stereopsis to do that.

Basically, could you do it with one eye closed? Without stereopsis, tasks involving close-up things are harder, but farther away things are not.

[AnimalMuppet]

Depends. If I'm hunting with a bow or a throwing stick, I'd bet stereopsis is pretty important. Do I need it? Maybe not, but I'll be more accurate with it.

If I'm running through the woods, trying to escape from a bear, stereopsis is pretty useful, because dodging trees while at a dead run is life or death.

I don't do either of those, but some of my ancestors probably did. But I play sports. I may be able to catch a ball with one eye. Getting myself to where the ball is going? I couldn't do that as well with only one eye.

So: Do I need stereopsis? No. Did the human race? Yes, it was a competitive advantage to have.

[tbabb]

> I play sports. I may be able to catch a ball with one eye

I would love to see a sports game where one team can use both eyes, and the other team only has one eye uncovered. I imagine it'd be downright funny.