The Watchmaker: my fav argument

[The Architect Of Fate]

I think your example is a bit off. Darkness doesn't make blindness more adaptable. Whether its day or night―you can't see.

Darkness allows for a host of unique adaptions and niches

---

But darkness makes it useful because they can develop other features that beings who can see don't have, like I said: "because they can use that energy and part of the brain for something else that will make it thrive".

For instance, this is what Darwin wrote about moles:

The eyes of moles and of some burrowing rodents are rudimentary in size, and in some cases are quite covered by skin and fur. This state of the eyes is probably due to gradual reduction from disuse, but aided perhaps by natural selection. ...

As frequent inflammation of the eyes must be injurious to any animal, and as eyes are certainly not necessary to animals having subterranean habits, a reduction in their size, with the adhesion of the eyelids and growth of fur over them, might in such case be an advantage; and if so, natural selection would aid the effects of disuse. 

Moles, in particular, have a number of special adaptions in their olfactory system and their ability to sense vibrations in the soil.