So, for example, Thomas explains the natural law of marriage as
serving two natural ends--parental care and spousal love--that
can be explained by comparing human beings with other animals
that show parental care by both parents. For many animals, he
observes, the mother alone is sufficient to care for her
offspring. But for some animals, such as some species of birds,
the mother needs the help of the father or others in caring for
offspring, and this is especially true where the offspring are
dependent on adult care for a long time during which they need
not only nourishment but also social learning if they are to
flourish as adults. This is true for human beings, Aquinas
argues, who are naturally inclined to be cooperative breeders,
which is the natural foundation for human marriage and familial
bonding. If this is true, then we might expect that modern
biological research can show the evolved neurophysiological
basis for such natural inclinations to parental care. Indeed,
there is now extensive evidence th