Scientists discovered something remarkable in a recent study—evolution can’t be reversed. In tracing the supposed evolution of a common protein, they introduced mutations to move the protein “backward” to each of its hypothetical transitional stages and discovered that each one wouldn’t work. What does that mean to the theory of evolution?

A media frenzy about life on Mars broke out back in 1996 when researchers announced they had found what they interpreted to be fossilized bacteria on a rock from the red planet. Photos of a little, worm-shaped structure were liberally posted, and the subject was discussed for weeks.

Researchers have described remarkably well-preserved tissue discovered inside a salamander fossil. The fully intact muscle tissues also had blood-filled vessels, and they had not been mineralized like most fossils.

David Queller and Joan Strassmann, evolutionary biologists at Rice University, recently proposed a new way to describe what makes an organism a unified whole. They defined an organism as an entity made up of parts that cooperate well for an overall purpose, and do so with minimal conflict. But how do parts like these get together, and where does purposeful behavior come from?

“Darwin’s finches” are a variety of small black birds that were observed and collected by British naturalist Charles Darwin during his famous voyage on the H.M.S. Beagle in the early 1800s. Years later, Darwin argued that subtle variations in their beak sizes supported his concept that all organisms share a common ancestor (a theory known as macroevolution).