Ok, you win. The mutation of bacteria has been observed, and that is considered speciation.
Big whoop.
Technically, that is.
Of couse, you won't get a disagreement with the Ayatollah, that bacteria mutate. That is not what a discussion on evolution of species is about. If you want to include bacteria as species, then you are just being underhanded.
Now mass extinctions, happen for a reason.
But the mass extinction itself, is just that. It is the effect of a cause. If the cause is that the Earth became destroyed, then how would evolution be sped up?
Perhaps if you would quit speaking like a child, you could communicate properly.
The latest research on what you are talking about is pretty interesting. Have you seen "Night of the Living Dead"? A meteor causes the dead to become animated and to start eating human flesh. Well, this article, a meteor impact causes a mass extinction, and the surviving species become meat eaters.
But of course, these events were not observed.
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Did an Impact Trigger the Dinosaurs' Rise?
Richard A. Kerr
Large impacts would seem to be bad for dinosaurs. After all, a huge asteroid or comet ended the 135-million-year reign of the dinosaurs when it hit Earth 65 million years ago. But on page 1305, a group of researchers suggests that an impact also triggered the final rise of dinosaurs to dominance 200 million years ago. Proving that an impact is a two-edged sword will depend on demonstrating that a large body hit Earth at the very geologic instant that the dinosaurs' reptilian competitors abruptly died away and meat-eating dinosaurs came into their own.
By following fossil footprints, geologist Paul Olsen of Lamont-Doherty Earth Observatory in Palisades, New York, and his colleagues show for the first time that the final ascent of the dinosaurs was indeed abrupt, at least in eastern North America. And they now have a geochemical hint--although not yet proof--of an impact at the geologic instant that dinosaurs established their supremacy. "There was something interesting going on" 200 million years ago, says Olsen.
Linking evolution to impacts is a tough job. When researchers made the first impact-extinction connection in the 1980s, most of their colleagues were skeptical. But the case for an impact's wiping out the dinosaurs and numerous other creatures strengthened steadily following the discovery of high levels of iridium--an element rare on Earth but abundant in asteroids--in rock laid down at the boundary between the Cretaceous and Tertiary periods (K-T), when the dinosaurs disappeared and mammals began their rise. The iridium showed up around the globe sandwiched between Cretaceous rock and Tertiary rock, often accompanied by mineral bits bearing scars from the shock of impact. And these traces of impact always fell at the moment of extinction, a time pinned down with increasing precision as paleontologists built more detailed fossil records.
Many paleontologists began to think that before long, every mass extinction would have its impact. No such luck. Not a single other extinction has been firmly linked to an impact, although there have been hints. In the early 1990s, palynologist Sarah Fowell of the University of Alaska, Fairbanks, and Olsen found a rock layer rich in the spores of ferns--plants that rush in when the landscape is devastated--in southeastern Pennsylvania. These fern fossils appear in rocks formed at the Triassic-Jurassic (T-J) boundary 200 million years ago. (A similar fern spike marks the K-T boundary in western North America.) And geologist David Bice of Carleton College in Northfield, Minnesota, found what he suggested were impact-shocked quartz grains near a marine T-J boundary in Italy (Science, 11 January 1991, p. 161).
But the Pennsylvania fern spike and the unimpressive Italian shocked quartz never won anyone over, so Olsen and colleagues checked the fern spike for iridium and hit pay dirt. As they report in their paper, three sites in Pennsylvania show elevated iridium across the same 40 centimeters of rock containing the pollen spike. Peak iridium comes at the base of a 5-centimeter coal layer sitting on top of a layer of claystone, much as K-T rock looks in western North America. But at a maximum of 285 parts per trillion, the T-J iridium is not far above a background of 50 parts per trillion and is only one-third the size of the lowest concentrations found at the K-T. That small an amount of iridium might have been concentrated by natural geochemical processes or perhaps even carried in from volcanic eruptions; one of the largest outpourings of lava in Earth's history began nearby no more than 20,000 years after the boundary and has itself been suggested as a trigger for the T-J events (Science, 18 August 2000, p. 1130).
What was happening to the dinosaurs during the iridium-dusted fern spike? To find out, Olsen and his colleagues--especially amateur paleontologists Michael Szajna and Brian Hartline of Reading, Pennsylvania--collected footprints left in the mud of the string of lakes that ran through the middle of what was then the supercontinent Pangea. Lumping together more than 10,000 tracks found in former lake basins from Virginia to Nova Scotia, they found that "the nondinosaurs were getting wiped out" across the boundary, says Olsen; dinosaurs jumped from 20% to more than 50% of taxa. At the same time, meat-eating dinosaurs ballooned to twice their previous mass, to judge by the size of their tracks--much as mammals grew larger after the K-T.
In the Newark basin lake sediments in New York and Pennsylvania, the group found that tracks of Triassic reptiles that had been around for 20 million years disappeared within 20,000 years of the spore-iridium event. Then the first distinctive tracks of dinosaurs that would dominate the Jurassic appeared within 10,000 years after the event. Given the high statistical unlikelihood of ever finding the last Triassic track or the first Jurassic track, that places all four events--the disappearance of Triassic reptiles, the ascendancy of the dinosaurs, an apparent disaster among plants, and a hint of an impact--in the same geologic instant.
Paleontologists like what Olsen and his colleagues did with their huge footprint database. "They've definitely pinned [the evolutionary transition] right on the boundary," says paleontologist Michael Benton of the University of Bristol, U.K., thanks to their use of clocklike climate cycles recorded in the lake basins. Impact specialists are less impressed. The iridium by itself is unimposing, says cosmochemist David Kring of the University of Arizona in Tucson. Finding clear-cut shocked quartz would be convincing, he notes, but analyses for other, iridiumlike elements could show that the iridium is truly extraterrestrial. Then the dinosaurs could feel ambivalent about visitors from outer space.
sciencemag.org |
