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Speciation: Do interspecies hybrids help drive evolution?

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This article is remarkable for its honest look at the mess the “biological species concept,” rammed into high schoolers’ heads since forever, has become.

Sarah Hartwell/Polar-Brown Bear adult hybrid/Sarah Hartwell, Rothschild Museum

From Jordana Cepelewicz at Quanta:

In 2006, a hunter shot what he thought was a polar bear in the Northwest Territories of Canada. Closer examination, however, revealed brown patches on its white fur, uncharacteristically long claws and a slightly hunched back. The creature was in fact a hybrid, its mother a polar bear, its father a grizzly. Although this cross was known to be possible — the two species had mated in captivity before — this was the first documented case found in the wild. Since then, it has become clear that this was not an isolated incident. More.

The fact that the two closely related types of bear mated at the edges of their territories is actually old news but some environmentalists, fearful of the effects of global warming, think that such hybrids should be killed lest they endanger the genetically isolated polar bear population.

Michael Arnold, an evolutionary biologist at the University of Georgia, defends the “grolar” bear, some call them:

“If this mixing is a common natural event,” he warned, “then killing hybrids to prevent them from mixing with the ‘pure’ parent genomes is not a management technique we should do lightly.” In fact, it may be that the genetic variation introduced by this kind of hybridization could save the polar bears, whose survival in the face of rising temperatures and melting ice may hinge on their ability to adapt to a rockier, less frozen habitat. Taking in some genes from grizzly bears is highly likely to be adaptive for polar bears, Arnold said, even though the results “won’t look exactly like a polar bear.”

It’s nice to hear a voice for common sense among the many voices for the a-crock-alypse-of-the-minit. How do people think animals survive ice ages, warming periods, and many other changes? Hybridization is probably common at the edges of territories and hybrids may win out. In territorial species like bears, it’s possible that the main reason that, for example, polar bears are not often found in more southerly grizzly bear territory is the presence of the grizzlies…

The big cats, of course, gave the game away:

In a paper published last month in Science Advances, a team of researchers from institutions spanning seven countries examined the genomes of the five members of the Panthera genus, often called the “big cats”: lions, leopards, tigers, jaguars and snow leopards. The scientists sequenced the genomes of the jaguar and leopard for the first time and compared them with the already existing genomes for the other three species, finding more than 13,000 genes that were shared across all five.

This article is remarkable for its honest look at the mess the “biological species concept” has become:

Other types of organisms, from fish and birds to wolves and sheep, experience their share of introgression, too. “The boundaries between species are now known to be less rigid than previously thought,” said Peter Grant, an evolutionary biologist at Princeton University who, along with his fellow Princeton biologist (and wife) Rosemary Grant, has been studying the evolution of Galápagos finches for decades. “Phylogenetic reconstructions depict treelike patterns as if there is a clear barrier between species that arises instantaneously and is never breached. This may be misleading.”


Of course, as noted here, as a mechanism, hybridization may have developed a taint due to implausible hypotheses such as the supposed pig-chimp hybrid that, according to one theory, produced humans. It would help if we kept things plausible.

Usage note: Grashelis said a hybrid bear is unofficially called a grolar bear if the sire is a grizzly bear and a pizzly bear if the sire is a polar bear.

See also: Nothing says “Darwin snob” like indifference to the mess that the entire concept of speciation is in


Life continues to ignore what evolution experts say

Note: The field is full of myths and hoaxes, where animals are concerned. This vid provides attested examples of animal interspecies hybrids, including big cats:

So, which is the intermediate and which is the waste product? That which lives and that which dies, respectively? Doesn't nature sort this out for itself? Do we include or exclude ourselves as "nature"? Can humanity, invoking Charlie's wisdom, fix this "problem" it created? Which species has the bigger mouth? Perhaps they shall become whales after all; a perfect adaptation to an arctic thaw. LocalMinimum

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