The ethical problems posed by abortion and embryo cloning boil down to agreeing or disagreeing to consider embryos as human beings; or to having a clear idea of how the human condition of an embryo occurs.
From a scientific standpoint, what determines that a being is human, and different from all other beings, can only be its genetic makeup. And this stays exactly the same from the first embryo stage until the individual dies. At no time during its development may it be genetically established that it was one thing before and it is a different thing from now on.
Then, if that ends up as a human being, this means it was so from the beginning. And what if one is not 100% convinced? If one cannot scientifically prove that that thing is not a human being, the ethical approach is to behave like a hunter, who, in order to be able to shoot at something moving behind the thicket, must be absolutely sure that that thing is not a person. In case of doubt, one must not shoot. Thus, logic tells me one must not destroy embryos.