Taint of the quagga

Slate has an interesting slide-show by Jon Lackman about efforts to resurrect the quagga. The quagga was either a species or subspecies of Plains zebra, living in South Africa until the mid-19th century, when it was hunted to extinction. Here's the only known photograph:

The Quagga

The slideshow discusses the history and the present attempts to breed a quagga-like zebra back into being.

In 1971, taxidermist Reinhold Rau realized that the quagga's genes had not been forever lost. Zebras had occasionally interbred with quagga over the millenniums, and some of the descendants of these pairings still roamed South Africa. Rau surmised that he could retrace evolution's trail by mating the most quagga-looking zebras he could find and then mating certain of the offspring. In each generation, quagga genes will be further concentrated -- so that eventually, Rau believes, two zebras will produce a real quagga.

The slideshow has a picture of one of the more recent foals, named Henry, which really is quagga-like in its coloration. Of course, there is more to a species than its pelage, and since we know very little about any possible quagga-specific behaviors, there is no way to select for them in living zebras.

Then the slideshow includes this interesting tidbit:

A popular 19th-century theory held that men and animals inherit traits not just from their parents but also from their mother's first partner. This supposed phenomenon was called "the taint of the quagga" because it was said to have been discovered in the animal. The taint was alluded to by journalists of the era and in the writings of Goethe, Strindberg, Ibsen, and Zola. It reinforced the taboo of miscegenation and encouraged men to keep their women under lock and key.

Google brings this passage from chapter 11 of Darwin's "The variation of animals and plants under domestication":

Turning now to the animal kingdom. If we could imagine the same flower to yield seeds during successive years, then it would not be very surprising that a flower of which the ovarium had been modified by foreign pollen should next year produce, when self-fertilised, offspring modified by the previous male influence. Closely analogous cases have actually occurred with animals. In the case often quoted from Lord Morton, a nearly purely-bred Arabian chestnut mare bore a hybrid to a quagga; she was subsequently sent to Sir Gore Ouseley, and produced two colts by a black Arabian horse. These colts were partially dun-coloured, and were striped on the legs more plainly than the real hybrid, or even than the quagga. One of the two colts had its neck and some other parts of its body plainly marked with stripes. Stripes on the body, not to mention those on the legs, are extremely rare, -- I speak after having long attended to the subject, -- with horses of all kinds in Europe, and are almost unknown in the case of Arabians. But what makes the case still more striking is that in these colts the hair of the mane resembled that of the quagga, being short, stiff, and upright. Hence there can be no doubt that the quagga affected the character of the offspring subsequently begot by the black Arabian horse. Mr. Jenner Weir informs me of a strictly parallel case: his neighbour Mr. Lethbridge, of Blackheath, has a horse, bred by Lord Mostyn, which had previously borne a foal by a quagga. This horse is dun with a dark stripe down the back, faint stripes on the forehead between the eyes, plain stripes on the inner side of the fore-legs and rather more faint ones on the hind-legs, with no shoulder-stripe. The mane grows much lower on the forehead than in the horse, but not so low as in the quagga or zebra. The hoofs are proportionally longer than in the horse, -- so much so that the farrier who first shod this animal, and knew nothing of its origin, said, "Had I not seen I was shoeing a horse, I should have thought I was shoeing a donkey."

Karl Pearson, in his Life of Francis Galton, runs across a letter from Galton to Darwin mentioning the "Quagga taint", and adds this:

The Quagga case, as indeed all instances up-to-date, of so-called telegony can now be dismissed from consideration. They depend essentially on (i) observation of variation within the pure breed not being sufficiently wide, or (ii) the assertions of kennel-men and others endeavouring to screen their responsibility for unplanned matings (Pearson 159).

The Galton letter is part of a series reporting his experiments in transfusing blood into rabbits to see whether "foreign gemmules" in the blood might influence the rabbits' offspring. They are fascinating to read, considering the difficulty of determining whether traits sported in the offspring are variations common within a given breed or not. Galton's (and others') immediate purpose, of course, was to look for the locus of inheritance, and he was looking for evidence of a blood effect.

May 12, 1870: My Dear Darwin, Good rabbit news! One of the latest litters has a white forefoot. It was born April 23rd, but as we did not disturb the young, the forefood was not observed till to-day. The little things had huddled together showing only their backs and heads, and the foot was never suspected. The mother was injected from a grey and white and the father from a black and white. This, recollect is from a transfusion of only 1/8th part of alien blood in each parent; now, after many unsucccessful experiments, I have greatly improved the method of operation and am beginning on the other jugulars of my stock. Yesterday I operated on 2 who are doing well to-day, and who now have 1/3rd alien blood in their veins. On Saturday I hope for still greater success, and shall go on...until I get at least one-half alien blood. The experiment is not fair to Pangenesis until I do (quoted in Pearson 160).

Today, these kinds of experiments -- uncovering latent phenotypic variation by intensively breeding in a particular genetic background -- illustrate canalization and other epistatic effects. They are just as useful in uncovering these complex mechanisms today as they once were in obfuscating germline inheritance for Galton and so many others.

References:

Pearson K. 1924. The Life, Letters and Labours of Francis Galton. Volume 2. Cambridge University Press, Cambridge UK. Online at galton.org