The fact that both you and the amoeba use these universal molecules in your energy metabolism is as striking an example of the relatedness of life as… - Harold J. Morowitz

We recognize that to many people such a statement of cold biological fact misses something essential about the developing fetus. We recognize that there is a strong inclination to assign personhood or a soul to the single cell that results from fertilization on the grounds that it represents “potential life.” Our position is that this inclination, as strongly as it may be favored on religious or social grounds, has no basis in science because, as we point out in Chapter 1, personhood and soul are simply not scientific concepts.

This type of answer is profoundly unsatisfying, but it’s about all you can expect if you ask the wrong question.

Even with this abbreviated sketch of the process of fertilization, one thing is obvious. When biologists object to statements about life beginning at conception, they are not splitting hairs or being pedantic. There is no time in the sequence we’ve just described where new life is created. In fact, from the point of view of the biologist, at conception, two previously existing living things come together to form another living thing.