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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.
DAVID M. RAUP, Extinction: Bad Genes or Bad Luck?
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.
DAVID M. RAUP, The Nemesis Affair
There are millions of different species of animals and plants on earth--possibly as many as forty million. But somewhere between five and fifty BILLION species have existed at one time or another. Thus, only about one in a thousand species is still alive--a truly lousy survival record: 99.9 percent failure!
DAVID M. RAUP, Extinction: Bad Genes or Bad Luck?
Well, we are now about 120 years after Darwin and the knowledge of the fossil record has been greatly expanded. We now have a quarter of a million fossil species but the situation hasn't changed much. The record of evolution is still surprisingly jerky and, ironically, we have even fewer examples of evolutionary transitions than we had in Darwin's time. By this I mean that some of the classic cases of darwinian change in the fossil record, such as the evolution of the horse in North America, have had to be discarded or modified as a result of more detailed information -- what appeared to be a nice simple progression when relatively few data were available now appear to be much more complex and much less gradualistic. So Darwin's problem has not been alleviated in the last 120 years and we still have a record which does show change but one that can hardly be looked upon as the most reasonable consequence of natural selection.
DAVID M. RAUP, "Conflicts between Darwin and Paleontology", Field Museum of Natural History Bulletin, Jan. 1979
We generally think of humanoid intelligence as being the most significant aspect of our species, and this is probably true. But high intelligence could have evolved at almost any time in the Phanerozoic and in almost any biological group--in reptiles, in fish, in insects, and even in trilobites. To suggest that insects could have developed intelligence like ours sounds a bit extreme; after all, they have small brains and are obviously dumb. But I know of no neurological or other reason why intelligence could not have evolved in insects, accompanied by changes in anatomy and embryology to accommodate it. By the same token, intelligence need not have evolved at all.
DAVID M. RAUP, Extinction: Bad Genes or Bad Luck?
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.
DAVID M. RAUP, Extinction: Bad Genes or Bad Luck?
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