Biologists recently found that feather colors and songs vary among some species within the South American genus Sporophila, also known as seedeater birds. But strangely, they did not find any genetic differences in the form of species-specific DNA markers. Do these variations fit any evolutionary pattern?

Does it matter whether the larvae of one fruit fly species have hairy backs while those of another are smooth? Well, for scientists who believe both species descended from the same ancestor population, it could perhaps be taken as an example of evolution in action. The genetic causes for these particular differences, however, clearly show that no Darwinian processes were involved.

More than 80 varieties of fish, amphibian, and reptile mothers are able to lay eggs that have not been fertilized and yet produce offspring. In a process called "parthenogenesis," these eggs hatch little clones of the mother, which in turn lay clone eggs themselves. Could this remarkable mode of unisexual reproduction have evolved?

What if there were not a fast or effective way to get rid of sewage waste? The world would be a pretty disgusting place.

If Charles Darwin could see today's best examples of evolution, would he be elated or depressed?