How Darwin predicted the genetic link

Just over a century and a half ago, Charles Darwin finally published On the Origin of Species, explaining how all life had been shaped by natural selection. Before he explained this blind mechanism though, he softened up his readers by showing how we humans had shaped some species through artificial selection.

Darwins_pigeons

A selection of fancy pigeon breeds that Darwin studied

His audience of educated Victorian gentlemen would have been more or less familiar with breeding cabbages, cows and dogs for various characteristics, but Darwin also explained the breeding of fancy pigeons.

John Ross - historian of Darwin's pigeons - with an English pouter

John Ross – historian of Darwin’s
pigeons – with an English pouter. Photograph courtesy of John Ross.

It seems fanciful to us, but scholars used to believe that different breeds of sheep or cattle had each been domesticated from a separate wild variety, instead of from just one. Darwin decided to study one species in detail to explore this notion, and hit upon fancy pigeons. According to John Ross [pictured] –  an historian of Darwin’s pigeons (www.darwinspigeons.com) and a pigeon fancier himself – it was all down to a chance sighting on a trip to London:

In early 1855, Charles and his family spent several weeks in London in what was to become one of the coldest winters in living memory, parts of the Thames froze at Richmond at low tide. Maybe on one of his regular walks, he noticed common pigeons foraging for oats from spilt horse feed.  Later at home by the fire reading the Illustrated London News, where fancy pigeons featured on the front page, perhaps an idea came to Charles to prove that all fancy pigeons are descended from the common pigeon known as Columba livia or rock dove. He finally made up his mind when Yarrell the well known ornithologist persuaded him to try. So in March 1855 Charles Darwin was to become a pigeon fancier and set up a breeding loft at his home in the village of Downe, Kent.

Darwin did his homework. He read the published works on fancy pigeons. He had the local carpenter build a pigeon loft in the grounds of his house in Kent and he sought out a reputable pigeon dealer in London to secure himself a couple of pouters and fantails. He expanded his stock later to other breeds and threw himself into the study joining the Columberian Society, attending poultry shows and corresponding with many experts on the subject. As he himself put it:

I have associated with several eminent fanciers, and have been permitted to join two of the London pigeon clubs. (1859, 20-21).

Darwin went on to say:

Altogether at least a score of pigeons might be chosen, which is shown to an ornithologist, and he were told they were wild birds, would certainly, I think, be ranked by him as well-defined species… Great as the differences are between the breeds of pigeons, I am fully convinced that the common opinion of naturalists is correct, namely, that all have descended from the rock-pigeon (Columbia livia) (1859, 22-23).

He explained why these outwardly very different birds could not have been domesticated from several different species that had since gone extinct. This would, for one thing, be highly unlikely. None of the existing Columbidae species had any of the extreme characteristics in the fancy breeds anyway. So small differences between individual birds had clearly been selected for, generation after generation, to breed two varieties as dissimilar as the frillback and the carrier.

Recently, a team from the University of Utah working with scientists at BGI-ShenZhen in China and the University of Copenhagen in Denmark, sequenced a complete reference genome from a Danish tumbler, and then the genomes of 36 other breeds and two feral birds. They found that all these breeds did indeed descend from the rock dove, which was domesticated once in the Middle East. This provided hard data to back up Darwin’s argument made over a century ago, with no knowledge of genetics.

 

Muffled Tumbler

A Muffled Tumbler. Photograph courtesy of John Ross.

This hi-tech genetic work referencing the father of modern biology in many ways shows how the questions originally thrown up by Darwin’s breakthrough are still being answered. But it also shows how things have changed. Instead of working alone, the team behind the pigeon genome sequencing is 18 strong (at least that’s the number of authors on the original piece in Science, and span three countries. But, then, Darwin didn’t quite work alone, having contact with “several eminent fanciers”, after all.

Emma Newall, Education Consultant with the Charles Darwin Trust with a background in genetics is thrilled with this work.

I think it is so exciting that Darwin’s idea that “endless forms” are derived from a common ancestor continues to be supported by new methods of investigation. DNA based science continues to back up and illuminate Darwin’s theories. Darwin’s work continues to inspire scientists and in science education will inspire the next generation too.

Let’s hope that the modern team weren’t as squeamish as Darwin, who hated having to kill the pigeons he was breeding for his studies, as he describes to his cousin William Fox in a letter dated 22nd July 1855:

I am getting quite “a chamber of horrors”… I have done the black deed & murdered an angelic little Fan-tail & Pouter at 10 days old.

Then again, you don’t have to kill a pigeon in order to sequence its genome. The bones and some of the skins of the pigeons Darwin dispatched are now kept at the Natural History Museum in Tring. Joanne Cooper, a curator at the museum who has worked on Darwin’s pigeon collection, is happy the pigeons are being recognised as more important to Darwin’s work than the famous Galapagos finches:

I’m pleased that their profile has gone up considerably. Some of them are now permanently on display as one of the museum’s (and therefore the nation’s) greatest natural history treasures.

Finally, this story adds further weight to the counter-argument against the idea that evolutionary biology is not a predictive science. From predicting that the Star of Bethlehem orchid, with its characteristic long spur, could only be pollinated by a moth with a proboscis of matching length to predicting that the ancestor of all humans would be found in Africa, Darwin has now had another prediction vindicated. John Ross imagines that Darwin would have been very interested in the findings from Salt Lake City:

I am sure Charles Darwin would have been checking his daily postal delivery for news from Utah with the confirmation of his theory. Well done to Michael Shapiro and his team for having the vision to continue in the footsteps of Charles Darwin with his research into the far from humble pigeon.

Acknowledgements

Thanks to John Ross, Emma Newall and Joanne Cooper for their take on the results of this study. Thanks to John Ross for kindly supplying the images.

References

Kim Biddulph

Kim is a humanities graduate who realised, after working in museums for ten years, that she should have studied science. She has converted to biology, mainly through the medium of spiders. Like most people, Kim was scared of spiders, but after having a child has decided not to be and to learn all about them instead. Kim has also had the great honour of working on the education programme for local schools at Darwin's family home, Down House in Kent.

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