It is much harder to empathise with a being as different in appearance as the early human embryo. These considerations are emotionally powerful, but have little rational appeal. Our rights as human beings do not depend on how we look, but on what we are. It would be quite unacceptable if, for example, newborn babies with disfigurements were treated as 'non-persons', on the grounds that they had less emotional appeal than other children. In the same way, it is unacceptable to say that the embryo is a subhuman being on the grounds of its challenging appearance.
Human beings are human organisms and go through different stages, just like other living things.
A caterpillar is the same insect as the butterfly into which it grows. In the same way, the embryo is the same human being as the foetus, the infant and the adult, even though his or her appearance goes through very different stages. The primitive streak, for example, does not come out of nowhere, but is carefully constructed by the embryo itself. Some claim that the embryo cannot have human status because it may naturally miscarry. However, many humans are at risk from natural causes, but still have human rights.