A new study suggests that primates’ ability to see in three colors may not have evolved as a result of daytime living, as has long been thought.

The findings, published in the journal Proceedings of the Royal Society B, are based on a genetic examination of tarsiers, the nocturnal, saucer-eyed primates that long ago branched off from monkeys, apes and humans.

By analyzing the genes that encode photopigments in the eyes of modern tarsiers, the researchers concluded that the last ancestor that all tarsiers had in common had highly acute three-color vision, much like that of modern-day primates.

Such vision would normally indicate a daytime lifestyle. But fossils show that the tarsier ancestor was also nocturnal, strongly suggesting that the ability to see in three colors somehow predated the shift to daytime living.