Screenshot from p 214 of Digby's book TWO TREATISES. It reads: And an other particular that I saw when I was att Argiers, maketh to this purpose, which was, of a woman that hauing two thumbes vpon the left hand; foure daugthers that she had, did all resemble her in the same accident, and so did a litle child, a girle of her eldest daugthers; but none of her sonnes. Whiles I was there I had a particular curiosity to see them all: and though it be not easily permitted vnto Christians to speake familiarly with Mahometan women; yet the condition I was in there, and the ciuility of the Bassha, gaue me the opportunity of full view and discourse with them: and the old woman told me, that her mother and Grandmother had beene in the same manner. But for them, it resteth vpon her creditt: the others I saw my self.
Same evidence can mean different things at different times. In 1644 Sir Kenelm Digby tells of a woman in Algiers with two thumbs on one hand. All her female ancestors and descendants had the same condition, but not her sons. He draws no conclusion about heredity. A century later, Maupertuis would.
