The date range is based on CD’s interest in gathering information about the ancient history of domesticated birds and animals. See nn. 2 and 3, below.

The memorandum has not been found. Horner knew Karl Richard Lepsius, ordinary professor at Berlin University, through their mutual interest in Egyptology. Horner visited Lepsius in Berlin on several occasions and toured the Museum of Antiquities, of which Lepsius was keeper. In addition, Joanna Baillie Horner and Leonora Horner translated and published Lepsius’s Letters from Egypt (1853).

CD probably refers to Lepsius’s great illustrated work on the monuments of ancient Egypt (Lepsius 1849–58). This work was entered in CD’s list of books to be read (Correspondence vol. 4, Appendix IV, *128: 165). From other entries in the list, it appears that CD recorded the work early in 1856 when he was reading widely in the history of domesticated animals; another entry dated January 1856 indicates that he read a review of a different work by Lepsius (Lepsius 1842) in the Athenæum (ibid., Appendix IV, 128: 14). In Variation 1: 17, CD referred to Lepsius 1849–58 in relation to dogs.

CD cited information that may have been drawn from Lepsius’s memorandum in Origin, p. 27. The passage reads: ‘[Pigeons] have been domesticated for thousands of years in several quarters of the world; the earliest known record of pigeons is in the fifth Ægyptian dynasty, about 3000 B.C., as was pointed out to me by Professor Lepsius’. The same information was given in Variation 1: 204–5, where CD cited Lepsius 1849–58, Abt. II, Bl. 70.

There is a list of books from the Bible correlated with periods of human history on the verso of the letter, possibly in Horner’s hand. In his study of recent geological deposits, Horner attempted to date the strata through correlating them with human historical records.