File under: Evolution is always two steps ahead of you.
I was wondering why it is that domestic cats have slit-shaped pupils, whereas none of the big cats (tigers, lions, leopards) have them. Turns out that scientists have only relatively recently started figuring that out. It probably has to do with chromatic aberration. The adaptations that give cats excellent night vision would actually impair their vision in brighter conditions if they had to contract a round pupil. (See the diagram in this article.)
Slit pupils are apparently also seen in a variety of other animals that are partly nocturnal and partly diurnal, and that have relatively small eyes.
Science is awesome.
And yes, this is totally the way I waste time at the end of the day. Doesn't everyone get obsessed with random knowledge?