Review of “Should You Fear the Pizzly Bear?“
As someone who likes everything well-organized, evolutionary categorization is starting to give me a headache. At first I liked the phylogenetic tree, with its carefully branching lines leading from one species to the next. But the more I learn, and, in fact, the more scientists and researchers learn about the specific contents of an organism’s genome, the more factors must be considered to determine lineages. Inevitably, the water gets murky.
In “Should You Fear the Pizzly Bear?,” published in The New York Times on August 14, 2014, writer Moises Velasquez-Manoff explores more than evolutionary change, he reminds readers that nature, like all good practical jokers, tosses in a wildcard now and then with hybridization.
Have you heard of a coywolf or pizzly bear? How about a mule? A female horse that mates with a male donkey may produce offspring, but the resulting mule will most likely be sterile. As Velasquez-Manoff explains, our understanding of this situation has often led us to believe that most hybrid animals are not viable. However, armed with ever increasing knowledge about RNA and DNA, scientists are learning that hybrids may have helped shape the course of evolution in some significant ways.
According to Velasquez-Manoff, coyotes, wolves and domestic dogs have interbred to varying degrees, lending beneficial traits to their offspring that help them endure human-implemented selection pressures, similar to what is happening with grizzly and polar bears, due in large part to necessary climate change-related habitat adjustments.
That is just the beginning of how hybridization is mixing up our well-defined species categorization system. We generally look at it as a bad thing, when invasive species put selective pressure on other animals, cause interbreeding and eventually the loss of a previously established species. However, it’s beginning to look like that’s a big part of what has been happening all along.
Read Should You Fear the Pizzly Bear in The New York Times for even more interesting details. And check out this story in the Denver Post about a mule who actually bore a viable foal – something we once thought impossible.