Lord Morton's mare

Lord Morton’s Mare was once an often noticed example in the history of evolutionary theory.

In 1820 George Douglas, 16th Earl of Morton, F.R.S., reported to the President of the Royal Society that being desirous of domesticating the quagga, [A quagga was a relative of the zebra, now extinct.] he had bred an Arabian chestnut mare with a quagga stallion, and that subsequently Lord Morton bred the same mare with a white stallion and found that the offspring had strange stripes in the legs, like the quagga. The Royal Society published Lord Morton's letter in its "Philosophical Transactions", 1821. ["A Communication of a singular Fact in Natural History. By the Right Honourable the Earl of Morton, F.R.S. In a Letter addressed to the President" "Philosophical Transactions of the Royal Society" 1821:20.] In the same issue "Particulars of a Fact, nearly similar to that related by Lord Morton, communicated to the President, in a letter from Daniel Giles, Esq." reported that in a litter of a black and white sow, by a "boar of the wild breed, the chestnut colour of the boar strongly prevailed" in the piglets, even to the third subsequent litter.

These circumstantial reports seemed to confirm the ancient idea of telegony in heritability: Charles Darwin cited the example in "Variation of Animals and Plants Under Domestication" (1868). The concept of telegony, that the seed of a male could continue to affect the offspring of a female, whether animal or human, had been inherited from Aristotle and remained a legitimate theory until experiments in the 1890s confirmed Mendelian inheritance. Biologists now explain the phenomenon of Lord Morton's mare using dominant and recessive alleles.

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