It has been argued that dinosaurs did not die out, but just evolved wings and flew away. At a certain level, this reasoning is sound.... Birds, as a group, did descend from dinosaurs and ... all 8,600 species of birds living today carry some inheritance from their reptilian ancestors.

It has been argued that dinosaurs did not die out, but just evolved wings and flew away. At a certain level, this reasoning is sound.... Birds, as a group, did descend from dinosaurs and ... all 8,600 species of birds living today carry some inheritance from their reptilian ancestors.

The once rather old-fashioned science of paleontology finds itself in a maelstrom of excitement and controversy. Astrophysicists, atmospheric scientists, geochemists, geophysicists, and statisticians are all contributing to the extinction problem. And the general public is taking part through television talk shows, magazine cover stories, newspaper editorials, and even the occasional mention in gossip columns.

Perhaps the only thing that saves science from invalid conventional wisdom that becomes effectively permanent is the presence of mavericks in every generation - people who keep challenging convention and thinking up new ideas for the sheer hell of it or from an innate contrariness.

Now let me step back from the problem and very generally discuss natural selection and what we know about it. I think it is safe to say that we know for sure that natural selection, as a process, does work. There is a mountain of experimental and observational evidence, much of it predating genetics, which shows that natural selection as a biological process works.

A large number of well-trained scientists outside of evolutionary biology and paleontology have unfortunately gotten the idea that the fossil record is far more Darwinian than it is. This probably comes from the oversimplification inevitable in secondary sources: low-level textbooks semipopular articles, and so on. Also, there is probably some wishful thinking involved. In the years after Darwin, his advocates hoped to find predictable progressions. In general. these have not been found-yet the optimism has died hard and some pure fantasy has crept into textbooks.

In the beginning, there were bacteria.... [A] nearly universal assumption is that all subsequent life descended from the original life form through a continuous chain of ancestor-descendant pairs. This assumption looks good because all living organisms share biochemical traits. It is conceivable, of course, that life originated more than once on the early earth but that all except one life form died out early, leaving a single lineage as the ancestor of life as we know it. If this did happen, it was the first important species extinction.