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Sunday, May 23, 2010

Polar bears and the skinny about real speciation

In “Polar bears and mammalian speciation”, British physicist David Tyler writes:

The polar bear (Ursus maritimus) exhibits numerous adaptations to cold environments, fur, foot pads, head shape, exclusively carnivorous diet, heightened sense of smell, etc. Their close relationship to the brown bear (Ursus arctos) has long been recognised. Fertile hybrids are well-documented in captivity and there are rare examples of hybrids in the wild - the most recent being in 2006. Interbreeding, however, has not outweighed other taxonomic criteria, although it has been a factor in moving the polar bear from the genus Thalarctos back to the genus Ursus. "With their distinctly different morphology, metabolism, and social and feeding behaviors, the polar and brown bears are classified as separate species." Interestingly, a cluster of brown bears (known as ABC bears) have been found with close genetic links to polar bears.

"Recent genetic studies have shown that polar bears evolved from within brown bears, and that a genetically unique clade of brown bear populations that live exclusively on the Admiralty, Baranof, and Chichagof (ABC) islands of southeastern Alaska's Alexander Archipelago are more closely related to polar bears than to other brown bears."

Speciation, then, has occurred, but when? how? and over what timescale? The opportunity to constrain the answers to these questions has come with the discovery of a jawbone with diagnostic polar bear traits from a site in Norway estimated to be 130-110 ky old. This makes it the most ancient sub-fossil yet to be recovered. Approximately 0.1 g of bone powder was used to generate a "complete, high-quality mt genome" using next-generation sequencing technology.

"The organization and length of the genome is comparable to that of extant bears, showing clear sequence similarity to both ABC bears and modern polar bears."

[ ... ]

This research raises important questions for advocates of Darwinism. The PE model has been interpreted by them as a broad brush perspective. Consequently, the fossil record is considered too coarse to pick out the gradual transformation they insist must have occurred (because gradualism is the 'only way' to build complexity and achieve adaptation). However, this polar bear study shows that the timescales for change are too short to permit a viable gradualist explanation. This research shows the PE framework (of abrupt appearance followed by stasis) is realistic. Evolutionary theory must address issues like this and Darwinists should cease their confident rhetoric about the sufficiency of the mechanisms of mutations and natural selection.

Furthermore, Darwinists should realise that mere evidences of speciation are not the same as evidences for their theory. Polar bears display sophisticated adaptations, and if they are not gradualist phenomena, how can they be explained?

If biological information is not acquired gradually, where does it come from? The ID perspective on this draws on numerous indicators of pre-existing information (for example, it is now widely recognised that much genetic information and associated regulative systems preceded the Cambrian Explosion). From this perspective, rapid speciation is possible because pre-existing information can be restructured and re-expressed in novel ways. The scientific challenge is to determine the mechanisms responsible for this type of information-rich speciation.

Go here for the rest.

Here’s a polar bear catching a seal:



Find out why there is an intelligent design controversy:

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