One of the abortion debates is between those, like Mary Anne Warren, who think that personhood requires a "developed" capacity for distinctively personal functioning (including all or many of features like: self-awareness, general communication, freedom, problem-solving, etc.), or at least that such a developed capacity is needed for the prohibition on killing to apply, and those who think an undeveloped capacity is sufficient, either for personhood or the prohibition on killing or both. Of course, normal fetuses have an undeveloped capacity for distinctively personal functioning.
Here is a line of thought. Imagine an alien species that suffers through a boiling hot season every ten earth years ("The Boiling"). Most species on that planet die off at that time, leaving some hardy spores or seeds. But one species, the cysters, evolved intelligence and an ability to gather experience over a period of time longer than ten earth years. A biological cycle triggered by increased temperatures records one's memories and character traits in a hardy storage module that can survive The Boiling, and the body entirely sheds its brain and other soft tissues, becoming a kind of cyst. When The Boiling passes, the brain and other soft tissues regrow based on the genetic code, in the same way that they grew in the first place, and memories and traits from the storage module are written back into the regrown brain.
We would expect the cysters to have strong prohibitions against destroying normal fellow cysters once they have gone into the cyst stage (say, with a time bomb). And it is intuitively very plausible that these prohibitions would be correct: killing normal cysters in the cyst stage is wrong. Furthermore, it is plausible that a cyster in the cyst stage is still a person, though I am not insisting on this.
But notice that in cyst stage, the cysters do not have a developed capacity for distinctively personal activity. They have no brains! Granted, they have a module that holds memories and character traits. But they no more have developed capacities for distinctively personal activity than an embryonic gecko has a developed capacity for eating insects. The embryonic gecko presumably has genetic information sufficient to produce a vertebrate brain that will guide its eating of insects. All the information is there, just as in the cyster's memory module. But the presence of the information is insufficient for a developed capacity.
Moreover, imagine that Sam is a cyster who has acquired a capacity for distinctively personal activity an hour earlier, and has since had an hour of experiences. Moreover, suppose Sam does not remember anything prior to the acquiring of that capacity and Sam's character's non-genetic development only started when Sam acquired that capacity. And now the signs of The Boiling show up, and Sam goes to cyst. Clearly it's wrong to kill Sam. But it would be weird to think that the hour of experience makes the crucial difference here.
So it is false that the prohibition on killing requires developed capacities for distinctively personal functioning. And it is likely also false that such capacities are required for personhood.