Custom Search

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:


Biologý's ‘Skeleton In The Closet’: The Broken Bones Of Origins Science

Robert Deyes writes:

Review Of Chapter 13 of Stephen Meyer's Signature in the Cell (Harper One, 2009), by Stephen Meyer, HarperOne Publishers.

I never would have suspected that the literary sensation Dr Seuss’ The Cat In The Hat Comes Back would be used to make a point about the devastating shortcomings of origin of life theories (1). But when I read one of the later chapters of Meyer’s Signature In The Cell which in one foul swoop discredited Hermann Muller’s fortuitous origins of DNA, Henry Quastler’s DNA self replication hypothesis and Manfred Eigen’s ideas on hypercycles I could not help but be fascinated by his use of this children’s classic in his exposition. Of course in their own unique ways each of these scientists became steadfastly convinced that they were onto something of great significance that would lead to fruitful avenues on the all important question of how life had begun. Muller drew inferences from his own work on viruses, in particular bacteriophages (‘bacteria eaters’), equating these simple organisms to “a gene that copies itself within the cell” (2). He envisioned these as being somehow analogous to primitive DNA floating around in the chemical-rich soup of the early earth (2). Quastler on the other hand suggested that polynucleotides could act as templates for replication through complementary base pairing (3). And Eigen chose to assume that ‘self-reproducing molecular systems’ involving RNA molecules and basic enzymes could somehow supply an early form of transcription and translation, later forming hypercycles that would have preceded the arrival of the earliest cells (4).

So how is the Cat in the Hat relevant? Crucial aspects of the above mechanistic propositions, writes Meyer, parallel the antics of our feline friend as he unwillingly redistributes the mess he has created in the house of his none-too-happy hosts. Origin of life scientists have similarly been trying for decades to “clean up the problem of explaining the origin of [biological] information” only to find that they have “simply transferred the problem elsewhere- either by presupposing some other unexplained sources of information or by overlooking the indispensable role of an intelligence” (1). And their modern day brethren, with the apparent sophistication of computer-housed evolutionary algorithms, have fared little better. Meyer’s unearthing of the reality behind Ev, for example, described by its author Thomas Schneider as “a simple computer program” that attempts to evolve the information content of DNA binding sites in a hypothetical genome, is a case in point (5). In Ev Schneider ‘specifies’ the sequence of these DNA binding sites and incorporates the code for the binding site ‘recognizer’ (protein) into the genome (5). The relative penalties for mis-binding or non-binding of the recognizer to sequences are pre-set into the program (5).

Read the rest (with references) here.

Labels: ,

Who links to me?