DNA Divergence is in How You Count

It’s a common misconception that chimp DNA differs from Homo sapiens sapiens genes by only a single percent, but this number is apocryphal. In actuality, the degree of similarity of human and chimp genetic code depends mostly on how you count. Since all complex organisms from Earth possess great swaths of junk DNA inherited from a distant common ancestor, there tends to be startling similarity between many organisms. Sure, humans are like chimps—but they’re also like flatworms and fruit...

 Evolution of the Eye

A possible sequence of such changes begins with simple eyespots made of light-sensitive pigment, as seen in flatworms. The skin then folds in, forming a cup that protects the eyespot and allows it to better localize the light source. Limpets have eyes like this. In the chambered nautilus, we see a further narrowing of the cup’s opening to produce an improved image, and in ragworms the cup is capped by a protective transparent cover to protect the opening. In abalones, part of the fluid in t...