Nine Books on the Nature of Things

It is also naturally possible for humans to be born from animals, and this has natural causes; yet it cannot occur without impiety and heresy. For if a man mates with an animal, and that animal, as a female, receives the man’s sperm into its womb with appetite and desire, conceives and retains it, the sperm necessarily putrefies, and through the body’s continuous heat a human, rather than an animal, is born from it. The fruit that arises always corresponds to the seed sown; if this did not happen it would be contrary to the light of nature and to philosophy. The plant that grows therefore corresponds to its seed. An onion grows again from onion seed, not a rose, a nut or a lettuce. Spelt grows from spelt, barley from barley and oats from oats. It is the same with every other fruit which has seed and is sown, and so forth.