@Ghislaine >day old baby can easily be taken care of...

Not the point, the point is dependence of the baby on another.

Even if I were to grant you your point, you will also have to explain to me how this point of yours is not completely facile and actually has some level of significance.

>sperm and egg (I'm shortening these for convenience)...

AFAIK, the chances of one sperm fertilizing an egg is actually very low in the first place. So it is already not guaranteed that an individual sperm will actually reach an egg.

Also, a sperm is a sperm. It can't really be compared to an embryo because a sperm compared to a full human embryo is like, missing half the DNA or something. A sperm by itself will also still remain a sperm unlike a human embryo even if it is fed with food and given time.