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Peppered Hares — An Emerging Evolutionary Icon


Here is an emerging icon of evolution: the snowshoe hare. This animal is similar to the jackrabbit, except that it turns white in winter, giving it camouflage against the snow. In milder climates, though, turning white would be a disadvantage, so its relatives remain brown in winter. One notices a similarity to the story of peppered moths, but the authors of a recent study compare it to Darwin’s finches. Maybe we’ll get two icons hybridizing into one!

No Support for Directional Evolution

The report by Jones et al. in Science, “Adaptive introgression underlies polymorphic seasonal camouflage in snowshoe hares,” makes this comparison to Darwin’s finches:

Recurrent introgression of coat color variants could facilitate evolutionary responses to environmental change within populations as well as the long-term maintenance of adaptive variation among species, similar to adaptive polymorphisms of beak morphology across the radiation of Darwin’s finches. [Emphasis added.]

They refer to a couple of earlier papers by Peter and Rosemary Grant (2016, 2017, both open access). Neither paper, however, supports directional evolution, since the finch species can interbreed. The species can exchange genetic traits by “introgressive hybridization,” and so can adapt to the food supply by using pre-existing genetic information that regulates beak size. The best they can say is that their data is “consistent” with Darwinian evolution, and that eventually interbreeding might cease. In the 2017 paper in Genome Research, the Grants use metaphor and promissory notes to envision Darwinian speciation occurring someday.

Our data are consistent with an evolutionary scenario where genomic islands of divergence have evolved throughout the radiation of the Darwin’s finches, most often in regions with low recombination and often due to genetic adaptation, as exemplified by the beak loci. Introgression may occur through inter-island movements and interbreeding. As divergence proceeds further, introgression gradually diminishes as the islands are now “protected” by selective exclusion of foreign gene regions corresponding to the islands, and dXY rises above background level. Later still, interbreeding ceases, or all but ceases, and the number of islands decreases as divergence of the background increases and the islands no longer stand out: metaphorically, the sea rises and the islands disappear.

In other words, the Grants have not demonstrated reproductive isolation or speciation, but only imagined that it might occur in the future. We already know from the extensive critique of these icons by Jonathan Wells in Icons of Evolution and Zombie Science that there’s not much to sneeze at in either icon: Darwin’s finches or peppered moths. Darwinian biologists need a much stronger example of positive evolution to make their case. In short, they need random mutations leading to a persistent improvement that sets a species apart as more fit than its competitors. Mere shuffling of existing genetic traits is not enough.

In the case of snowshoe hares, the researchers compared genomes of a winter-white hare from Montana, a winter-brown hare from Washington, and a black-tailed jackrabbit from Nevada. Snowshoe hares display a gradation of color that tracks with snow cover. “Direct estimates of hare survival have shown that mismatch between coat color and snow cover increases predation,” a 2016 study claims, so having the right color is an advantage to the hare. 

An Existing Gene

But did this benefit arise through unguided Darwinian processes? No; they only found differences in the expression of an existing gene. They could not tie it to a de novo mutation. Instead, they believe it was a case of introgression from hybridization from the jackrabbit. Traits were shared, in other words: they did not arise by mutation and selection. News from the University of Montana says:

Hybridization between species has played a key role in the development of many domestic plants and animals, and recent research suggests that it is also surprisingly common in nature. In snowshoe hares, hybridization with black-tailed jackrabbits provided critical coat color variation needed to adapt to coastal areas where winter snow is ephemeral or absent.

Notable is the absence of any of the classic Darwin words: mutation, selection, or speciation. It claims that hares “have evolved” the ability to match coat to background color, and that the trait has been “shaped by evolution,” and yet the cause is decidedly non-Darwinian: 

“This result is exciting because it shows that critical adaptive shifts in seasonal camouflage can evolve through changes in the regulation of a single gene,” Jones said.

The genetic discovery came with a surprising twist.

“When we looked at the same gene in other closely related species,” Jones said, “we found that the brown version of the gene in snowshoe hares was recently acquired from interbreeding with black-tail jackrabbits, another North American species that remains brown in the winter.”

The paper itself also lacks any reference to positive selection in the hares. Instead, the authors’ only reference to positive selection is for Darwin’s finches. But that, as work by the Grants showed, was another non-Darwinian case of genetic sharing by introgression and hybridization. These authors misrepresent the situation, mentioning the advantage to large-beaked finches during the drought in 2004-2005, but not the return to normal in the next wet period. Wells calls this “Sisyphean evolution,” a kind of cyclic change that goes nowhere.  

Sisyphean Evolution

With this background, let’s ask some questions about the work by Jones et al. on snowshoe hares.

  1. Did they find a random mutation? No, they found existing variants. 
  2. Did they find new genetic information? No, just differences in the amount of regulation of an existing gene.
  3. Did they find positive selection? Not for this case; they only mentioned it for Darwin’s finches, but misrepresented the situation.
  4. Did they find speciation? Arguably not, because jackrabbits and snowshoe hares can hybridize and produce fertile offspring. According to the biological species concept, that makes them varieties, not separate species.
  5. Did they find irreversible, directional change? No, they admit that climate change “may further intensify directional selection for winter-brown camouflage,” which would simply change the ratio of existing varieties. That would mimic the peppered moth icon.
  6. Did they rule out intelligent design? No, because ID would predict that species will be engineered to adapt to the environment.

In Zombie Science, Jonathan Wells tells about the shenanigans Darwinians pulled with finches and peppered moths. For instance, Michael Majerus showed sampling bias in his counts of peppered moths, and assumed that those he released that he couldn’t find had been eaten by birds (pp. 64-66), when they might have just flown to some other place. From this dubious work, he claimed that peppered moths remain “proof of evolution” and concluded that humans had invented God, a “helping hand from on high” when the grand materialistic story of Darwinism had rendered a designer superfluous.

No one suspects the Montana team of gluing white hares to brown rocks. But neither should you be surprised if some Darwinists try to make the conclusions outrun the data.

Photo credit: Snowshoe hares, via National Park Service.