Full Idea
One might speak of 'Lockean real essences' of a natural kind, a set of properties that is basic in the explanation of the other properties of the kind, without commitment to the essence belonging to the kind in all possible worlds.
Gist of Idea
Locke's kind essences are explanatory, without being necessary to the kind
Source
Penelope Mackie (How Things Might Have Been [2006], 10.1)
Book Reference
Mackie,Penelope: 'How Things Might Have Been' [OUP 2006], p.172
A Reaction
I think this may be the most promising account. The essence of a tiger explains what tigers are like, but tigers may evolve into domestic pets. Questions of individuation and of explaining seem to be quite separate.