When does a fetus become a human? Pro-life advocates claim that personhood begins when the sperm and egg join to form a zygote. The zygote is genetically unique and complete and will be the grandparent of every other cell this person will ever have. The fact that the zygote is the first entity to have all 46 chromosomes of a future person seems, at first, to be good evidence of personhood. But consider the counter-examples,
there are many entities which are genetically complete which contain all 46 human chromosomes which we nonetheless do not recognize as persons: ancient fossils, blood samples, hair cuttings, fingernail clippings, even skin cultures grown in burn centers. This is proof that genetic completeness, in and of itself, does not constitute personhood.
The pro-lifer would then object, entirely correctly in fact, that none of the above examples have the potential to grow into a person. But left alone, the zygote will naturally become a person. Please note that this is a switch of argument: the pro-life advocate is no longer claiming that genetic completeness is a sign of personhood, but that the potential to become a person is a sign of personhood. But what about egg and sperm cells, they all have a potential to become what we define as human life. Therefore, if we outlaw abortions, do we outlaw male masturbation that results in the murder of hundreds of sperm cells that have potential to become humans? The answer is logically no. People may say that there is no answer to the abortion argument, but I believe there is. Only when we truly understand when human life begins can we even discuss the idea of abortion.
To be able to define when a fetus becomes human, we must first define what it merely means to be human. Even more specific, we must fundamentally examine why the majority of people in the world believe one human does not have the right to murder another human. The reason we dont allow people to murder each other must be because of some quality human beings possess, a quality we especially prize, that few or no other organisms on Earth have. It cannot be the ability to feel pain or deep emotions, because that surely extends to many of the animals we gratuitously slaughter.
This special human quality, I believe, can only be our intelligence which is superior to all other life forms. If so, the particular sanctity of human life can be identified with the development and functioning of the neocortex. Like all mammals and primates, humans possess a highly developed neocortex. In humans, the neocortex is responsible for conscious thought and language which distinguishes us from all other animals. When discussing the development of the neocortex as a measure for when abortion is moral, we cannot require its full development because that does not occur until many years after birth. But perhaps, we might set the transition to humanity at the time when neocortical activity begins. There has been very little research in this field to date, but such investigation could play a major role in an acceptable compromise in the abortion debate. Undoubtedly, there would be a variation from fetus to fetus as to the time of initiation on the first neocortical EEG signals, and a legal definition of the beginning of characteristically human life should be based conservatively toward the youngest fetus that exhibits such activity. This would shut the mouths of pro lifers and choicers, because it would allow for abortions to be moral and legal in the early stages of pregnancy and immoral and illegal during the rest of the pregnancy.

Hmm I dont think so. I grew up in Ireland at a time when abortion was debated ad-nauseum, and must have heard every argument pro and contra under the sun. I have also been informing myself about the pro life cause for the last few years and I have never heard the argument about the 46 chromosomes. If it was so common, I am surprised I have not come across it.

The pro-lifers (I am one) generally base their argument on the right to life of the unborn child, and the damage abortion causes the mothers. Sperm cells and Ovum separate from each other are not of interest. Ah but when joined together in the womans body they form a human baby if not interfeered with.

When does life begin? Ask any pro-lifer and they will say at fertilisation. Thats when the cells start to divide and grow. It is undoubtedly alive, and undoubtedly human.

I dont think extensive research on neocortical EEG signals would bring the pro lifers and the pro choicers one whit more together than what they are now. Abortion will never be moral. The fertilised egg cannot be compared with hair and nail clippings, it is far far more. For this reason you will not see pro lifers praying the rosary outside the local hairdressers, but outside the abortion mills!

What makes us different from the animals is that we humans are made in the image and likeness of God. (yep here she goes bringing religion into it) We have a body which can be examined in the lab, and a soul which can be examined in deep prayer.

So this pseudo intellectual argument and 'solution' really wont work. Sorry.