Science, Creation & EvolutionSudden appearance of phyla in the Cambrian explosionGreen, on the variability of pacing for evolution: New families of insects in a few hundred years. New orders of birds in a few hundred thousand years. So it's not surprising that new phyla show up in millions of years. If the niches are open, as they were in the Cambrian, rapid evolution, of the sort we see in the case of Hawaii and New Zealand is quite expected. Actually, reptiles didn't evolve from worms. We do, however, have abundant evidence for the evolution of mammals from reptiles. Since this is really about the way that the Cambrian explosion is understood by science, perhaps we can start another thread on the way mammals evolved from reptiles? You mean mentioning that all those other organisms didn't really appear until long, long after the Cambrian? Just an example of how limited the Cambrian explosion actually was. Almost all the organisms we are familiar with, did not exist for hundreds of millions of years afterwards. It seems pertainent. On the other hand, we have all those signs of soft-bodied animals before the Cambrian. Furthermore, we know that the arthropods who left tracks before the Cambrian were soft-bodied, since the first trilobites we find are soft-bodied, and only obtain scleretized shells later,after which the relatively few forms suddenly "explode" into a wide diversity of trilobites. Here's a nice site, showing that the phylum arthropoda did not first appear in the Cambrian, but had Precambrian antecedents. http://www.trilobites.info/trends.htm The Cambrian, it appears, was not a time when the first phyla appeared, but rather a time when a wide diversity of life evolved from simpler members of these phyla, which existed before the Cambrian. As the site above shows, scientists no longer say 5 million years, since there are earlier members of these phyla. "The fossil record of molluscs extends back 500 million years and indicates that molluscs first appeared during the Precambrian period. " Molluska http://www.personal.psu.edu/users/m/w/mwj121/ There have also been sea pens and jellyfish fossils dating from the Precambrian, so we can cross coelentrates off the list. http://www.science.uwaterloo.ca/earth/waton/F975.html There's more, but the Precambrian is not my speciality. I imagine I can cross a few more off, if I take a look. The Cambrian was a time of great radiation of forms from a few pre-existing ones. But rapid evolution has happened since, and will no doubt happen again. |
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