Guest essay by Eric Worrall

The discovery of a rare wild Grolar bear, a fertile Grizzly / Polar bear hybrid, is being treated as a terrifying sign of global warming in the Arctic.

Grolar bears: Climate change could be behind grizzly-polar bear hybrid, scientists say An unusual bear shot by a hunter days ago in Nunavut, a territory in northern Canada, is thought by experts to be a “grolar” or “pizzly” bear. But some scientists say the two bear species are breeding more often because climate change is causing them to cross paths. Chris Servheen, a bear biologist and Adjunct Associate Research Professor at the University of Montana, said sightings of this hybrid bear species have been very rare in the past. “But they seem to be more common now,” he said. Mr Servheen said not very much was known about the grolar and pizzly bears, as little contact had yet to be made between them and humans.

Read more: http://www.abc.net.au/news/2016-05-19/grolar-pizzly-bears-climate-change-creating-hybrids/7428354

My question: why aren’t greens celebrating this find, as evidence that Polar bears are capable of rapidly changing their phenotype, in response to radical changes to the polar climate?

Hybridisation is a common form of adaption in the natural world, which allows the rapid spread of important survival traits amongst diverse populations. Modern humans carry the genetic fingerprint of frequent hybridisation, including evidence of likely cross breeding with Neanderthals. Some scientists even claim hybridisation was not only important, but essential to the rise of modern humans.

The Hybrid Origin of “Modern” Humans Recent genomic research has shown that hybridization between substantially diverged lineages is the rule, not the exception, in human evolution. However, the importance of hybridization in shaping the genotype and phenotype of Homo sapiens remains debated. Here we argue that current evidence for hybridization in human evolution suggests not only that it was important, but that it was an essential creative force in the emergence of our variable, adaptable species. We then extend this argument to a reappraisal of the archaeological record, proposing that the exchange of cultural information between divergent groups may have facilitated the emergence of cultural innovation. We discuss the implications of this Divergence and Hybridization Model for considering the taxonomy of our lineage.

Read more: http://link.springer.com/article/10.1007%2Fs11692-015-9348-1

Evidence of occasional fertile hybridisation of Polar Bears is simply evidence that Polar Bears are more adaptable than environmentalists generally accept. If the arctic ever warms to such an extent, purebred Polar Bears are no longer ecologically viable, they would simply be replaced with hybrids, or even near purebred Grizzlies. And when Arctic conditions cooled again, creating strong selection pressure for lighter fur, “Polar Bears” would quickly re-emerge from the diverse ursine gene pool.

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