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Scientists May Have Finally Figured Out Darwin’s Love: Pigeon Beaks
By Ell Ko, 22 Sep 2021
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Image via Sydney Stringham
Although Charles Darwin lived more than a century ago, biologists are still carrying out research that stemmed from his incessant love for domestic pigeons; specifically, their beaks.
Darwin felt that pigeons’ beaks reflected the secrets of evolution: they weren’t confined by the need to survive in the wild, which then results in natural selection. Some of them showed signs of extreme evolution in the shortness of their beaks, which could result in parents struggling to feed their young—the opposite of what natural selection is meant to do.
For centuries, interbreeding pigeons demonstrated that the length of their beaks was most probably down to a few heritable factors, but it was never revealed just which ones exactly. But now, researchers from the University of Utah have managed to come to a conclusion.
The culprit, as it turns out, is a mutation in the ROR2 gene. Two pigeons were bred, a Racing Homer with a medium beak and an Old German Owl with a short one. As predicted, their initial brood of children turned out to have intermediate-length beaks.
Then when the children were bred with each other, the grandchildren showed beaks ranging in all sizes from big to little. Through studying their DNA sequences, the team realized that the grandchildren with small beaks shared the same piece of chromosome as the original Old German Owl.
Additionally, it was on the sex chromosome. This is in line with old-time genetic experiments, which got the team excited, says Michael Shapiro, senior author of the paper published in the journal Current Biology.
Further investigation revealed that all the birds with small beaks had the same DNA sequence in an area of the genome that contains the ROR2 gene.
While this leads to a reduced beak size in various breeds of domestic pigeons, it also is behind a disorder called the Robinow syndrome, which affects humans. Interestingly, some of the most “striking characteristics” of the syndrome are facial features, explains Elena Boer, lead author of the paper.
These include “a broad, prominent forehead and a short, wide nose and mouth, and are reminiscent of the short-beak phenotype in pigeons,” Boer states. But it makes sense, she continues, especially from a developmental standpoint, “because we know that the ROR2 signaling pathway plays an important role in vertebrate craniofacial development.”
“One of Darwin’s big arguments was that natural selection and artificial selection are variations of the same process,” Shapiro recalls. “Pigeon beak sizes were instrumental in figuring out how that works.”
[via University of Utah / SciTechDaily, image via Sydney Stringham]
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