percentage with D than D has with B; but the historical fact is that E
For example, we might have a situation in which proto-language A splits
into B and C. C in turn splits into D and E. E then undergoes a period
of close contact with a completely unrelated language, Z, as a result
of of which it borrows a lot of new vocabulary. Now E has a lower cognate
percentage with D than D has with B; but the historical fact is that E
is more closely related to D than D is to B.