At NewAPPS there is a healthy discussion over the scholarly origins of the recent debate on the moral equivalence (and permissibility) of abortion and infanticide. Ever since writing a paper on Hobbes and Cathrine MacKinnon in a seminar taught by Martha Nussbaum (way back when), it has been my view that Hobbes has a story about common moral origin (and permissibility) of abortion and infanticide in the state of nature. (To be clear, I don't have a view on the way Hobbes anticipates and differs from Tooley!) Below two passages (one from De Cive, the other from Leviathan). I admit that neither passage speaks directly of abortion, although the first passage suggests it in various ways.
"Amazons, have in former times waged war against their adversaries, and disposed of their children at their own wils, and at this day in divers places, women are invested with the principall authority. Neither doe their husbands dispose of their children, but themselves; which in truth they do by the right of nature; forasmuch as they who have the supreme power, are not tyed at all (as hath bin shewed) to the civill lawes. Adde also that in the state of nature it cannot be known who is the Father but by the testimony of the Mother; the child therefore is his whose the Mother will have it, and therefore hers; Wherefore originall Dominion over children belongs to the Mother, and among men no lesse than other creatures: The birth followes the belly."
"For in the condition of mere nature, where there are no matrimonial laws, it cannot be known who is the father unless it be declared by the mother; and therefore the right of dominion over the child dependeth on her will, and is consequently hers. Again, seeing the infant is first in the power of the mother, so as she may either nourish or expose it; if she nourish it, it oweth its life to the mother, and is therefore obliged to obey her rather than any other; and by consequence the dominion over it is hers."
(Leviathan, ch XX).