Eye-Opening Sex; March 2008; Scientific American Magazine; by Charles Q. Choi; 1 Page(s)

Anatomical features that took millennia to evolve can revert in a single generation. Specifically, sex between blind cavefish, if done right, can lead to progeny that can see.

The blind, albino, cave-dwelling form of the Mexican tetra (Astyanax mexicanus) evolved from ancestors living near the waters surface whose eyesight withered after they descended into complete darkness roughly one million years ago. These cavefish, which thrive in the freshwater caves of northeastern Mexico, can reach about 12 centimeters in length, and skin grows over their useless eyes.