Today of all days I remembered this old question.
I first came across it in the 1970s but it seems to have been first asked more than 200 years before, and perhaps humorously. This is my attempt at a reconstruction.
A Gentleman doth Enquire recently: whether it is Probable that: at any time which should be nominated: In the City of London there must bee,Two Persons, who have exactly the same numerosity of Haires on their Heads (supposing the Capital had sufficient Barbers to perform this Census &&).
I answer: For Certain. Since the Roy. Soc. of London have determined by what is called field-work, that the the count of Haires on any person's never doth, even if they be be-wigged, extend beyond ca. 250 Thousand.
Thus having thought to the vast Numbers of London-dwellers (which doth over-top 1 mill.) since the latter number be greater than the first, a co-incidence cannot be avoided.