You may remember that on my posting of 31 May (The Control of Life) I included “But one theory, albeit controversial, may have strength. In the very early days, it is argued, the conceptus does not yet constitute an individual. At that stage it can still develop into two individuals, who would be identical twins. If so, the moral issues concerning methods of preventing womb implantation would be different.” And we had some discussion to try to understand this further.
Interestingly a new study which is relevant to this question, has just been published. Until now, it was believed that the male and female genes blended at fertilization – producing the whole genome of the conceptus. But now it is understood that this does not appear to be the case: the male and female genes do not blend until after the first cell division – some 24 hours later.
If this discovery is confirmed it is clear that we are not talking about an individual human being until this stage. Here is one secular issue, noted in the study.
“Furthermore, the knowledge from this paper might impact legislation. In some countries, the law states that human life begins — and is thus protected — when the maternal and paternal nuclei fuse after fertilisation. If it turns out that the dual spindle process works the same in humans, this definition is not fully accurate, as the union in one nucleus happens slightly later, after the first cell division”.
There are theological consequences too. The Church argues that we are talking about a human being, with its consequential rights, ab initio (Evangelium Vitae, para 60), nevertheless we may think that our moral duties to a conceptus which is not yet an independent human being vary from those which apply to one who is.
You can find the report at