When does the fetus become a person?

What is it that makes  the zef -zygote, embryo, fetus - a person and thus worthy of equal right to life with the woman whose body it occupies?

Is it the fact that it possesses it's own unique DNA? Indentical twins have the same DNA yet no one has suggested that it is permisible to kill one or both of the twins.


Is it the possesion of a soul? If so, when does ensoulment occur?  The moment the sperm begins to penetrate the egg? After syngamy?  Or, around the 14th day when the chance of twinning has passed?

The Catholic Church teaches that ensoulment and therefore personhood,  begins at the moment of conception when the sperm penetrates the ovum   At a glance that sounds logical, unique DNA, two separate entities fusing into one. That view however, presents certain problems: If we are going to bestow personhood on a cluster of cells with no recognizable human features and no awareness or consciousness at all, we would need to look at the following situations:

Eg. For some time after fertilization, the embryo can split in two resulting in identical twins. If we think of the embryo as an individual - whom we will call Jane - endowed with a soul from the moment the sperm penetrated the egg, what happens to the individual when the embryo splits in two, is Jane one of the two, or does she disappear and replaced by Susan and Mary? If Jane disappears, does she go to heaven or limbo? If Jane is one of the two, which one is she? Does she retain the soul she received upon fertilization, or does she and her identical twin receive brand new souls? 

In cases when eggs are fertilized under the microscope in a laboratory, the embryo would receive it's soul the moment the scientist injects the sperm into the egg, that would mean that he/she is compelling God to dispatch a soul at that particular moment!  (If the scientist is capable of controlling fertilization and thus ensoulment that would imply that God's powers are not unique, since humans can do what he can do)   What we should ask is, where  in the embryo does the soul reside and why isn't the infusion of the soul observable when the egg is fertilized in the lab under the microscope? With a two celled organism and a powerful electron microscope that should not be too difficult!

Other religions have different beliefs about souls, for example Buddhists believe that souls are perpetually reincarnated until they attain Nirvana. So if a fertilized egg fails to implant the soul will go on to find another body. Their belief is just as valid or invalid as the pro life belief about ensoulment occuring at conception. The concept of an immortal, invisible soul belongs to the realm of beliefs, in the real world  we are dealing with  facts. In what part of the human body does the soul reside? And why isn't the departure of the soul visible at the moment of death?

Self consciousness is situated in our cerebral cortex. The cortex is the seat of awareness, all our emotions, thoughts, memories, wants and desires. It is this self awareness that makes up who we are. Without it we are just a body. Think about the vegetative patients with irreversible brain damage and no brain function  whose bodies are kept alive by machines such as ventilators and intravenous feeding tubes. They have no consciousness whatsoever, they cannot see, hear, think, remember or feel pain or pleasure, their cerebral cortex has turned to fluid. Yet, their bodies are kept supple and warm, their blood is circulating and the machine pumps air into their lungs. Where are their souls, are still somewhere in their body or have they departed?   


With cloning it  is possible to take one of my cells and clone it to create a new embryo that would be identical to me, like a twin. Does that new embryo receive a new soul the moment my cell is injected to the shell of an egg (whose nucleus has been removed in preparation for cloning) or does it share my soul? If it does share my soul that would mean one soul in two separate bodies.

Pro lifers are also opposed to the pill and IUD because of the possibility of action after fertilization. While  the IUD works by preventing the fertilized egg from attatching to the uterine lining, the pill works by preventing ovulation and consequently fertilization. Unlike abortion, the IUD does not kill embryos like a poison or a surgical instrument, but simply prevents them from implanting in the uterine lining. Even those who never use the pill or IUD  could still be unwittingly condemning many  embryos to death. A considerable number of fertilized eggs fail to implant and are flushed away with the next menstrual period. If  fertilized eggs are persons,  women should have a priest  perform a funeral service over their used santitary napkins, just in case there is a dead "baby/person"  in them. If a woman does not use any method at all, some of her fertilized eggs will perish naturally. If she uses the pill there would be no fertilized eggs dying because the pill prevents ovulation. Those who are concerned about the fate of fertilized eggs, "persons", the pill and sterilization would be a much more acceptable method than the Natural Family Planning or no method at all. Because couples are having sex on the fringes of the fertile period, they are more likely to conceive embryos that are incapable of surviving.

It is estimated that up to  40% of conceptions may not survive long enough even to disrupt menstruation, possibly embryos created from sperm that has been sitting for days within the woman's reproductive tract before ovulation, may be disadvantaged as they face a less-than-ideal uterine lining,  since the uterus is not as receptive outside of the most fertile period. If a woman doen't  use any method at all, a considerable number of fertilized eggs persons will meet their demise, particularly with older women. So, now that we know that NFP or no method results in the death of many "persons" it would be immoral and indeed criminal not to prevent that. Prevention can come in three forms, complete abstinence, use of unovulant pills or sterilization.

What makes us a person was summed up by Carl Sagan  when he wrote:

“If you deliberately kill a human being, it’s called murder. If you deliberately kill a chimpanzee – biologically, our closest relative, sharing 99.6 percent of our active genes – whatever else it is, it’s not murder. To date, murder uniquely applies to killing human beings. Therefore, the question of when personhood (or, if we like, ensoulment)arises is key to the abortion debate. When does the foetus become human? When do distinct and characteristic human qualities emerge?

We recognize that specifying a precise moment will overlook individual difference. Therefore if we must draw a line, it ought to be drawn conservatively – that is, on the early side. There are people who object to having to set some numerical limit, and we share their disquiet; but if there is to be a law on the two absolutist positions, it must specify, at least roughly, a time of transition to personhood.

Every one of us began from a dot. A fertilized egg is roughly the size of the period at the end of this sentence. The momentous meeting of sperm and egg generally occurs in one of the two fallopian tubes. One cell becomes two, two become four and so on - an exponentiation of base-2 arithmetic. By the tenth day the fertilized egg has become a kind of hollow sphere wandering off to another realm: the womb. It destroys tissue in its path. It sucks blood from capillaries. It bathes itself in maternal blood, from which it extracts oxygen and nutrients. It establishes itself as a kind of parasite on the walls of the uterus.

By the third week, around the time of the first missed menstrual period, the forming embryo is about two millimeters long and is developing various body parts. Only at this stage does it begin to be dependent on a rudimentary placenta. It looks a little like a segmented worm. (A number of right-wing and Christian fundamentalist publications have criticized this argument – on the grounds that it is based on an obsolete doctrine, called recapitulation. The comparisons of the human foetus with other animals is based on the appearance of the foetus. Its non-human form, and nothing about its evolutionary history, is the key to the argument of these pages.)"

"By the end of the fourth week, it’s about five millimeters (about a fifth on an inch) long. It’s recognisable now as a vertebrate, its tube-shaped heart is beginning to beat, something like the gill arches of a fish or an amphibian become conspicuous, and there is a pronounced tail. It looks rather like a newt or a tadpole. This is the end of the first month after conception.

By the fifth week, the gross divisions of the brain can be distinguished. What will later develop into eyes are apparent, and little buds appear – on their way to becoming arms and legs.

By the sixth week, the embryo is thirteen millimeters (about half an inch) long. The eyes are still on the side of the head, as in most animals, and the reptilian face has connected slits where the mouth and nose eventually will be.

By the end of the seventh week, the tail is almost gone, and sexual characteristics can be discerned (although both sexes look female). The face is mammalian but somewhat piglike."

Images of early embryos

"By the end of the eighth week, the face resembles that of a primate but is still not quite human. Most of the human body parts are present in their essentials. Some lower brain anatomy is well developed. The foetus shows some reflex response to delicate stimulation.

By the tenth week, the face has an unmistakably human cast. It is beginning to be possible to distinguish males from females. Nails and major bone structures are not apparent until the third month.

By the fourth month, you can tell the face of one foetus from that of another. Quickening is most commonly felt in the fifth month. The bronchioles of the lungs do not begin developing until approximately the sixth month, the alveoli still later.

So, if only a person can be murdered, when does the foetus attain personhood?

When its face becomes distinctly human, near the end of the first trimester?

When the foetus becomes responsive to stimuli – again, at the end of the first trimester?

When it becomes active enough to be felt as quickening, typically in the middle of the second trimester?

When the lungs have reached a stage of development sufficient that the fetus might, just conceivably, be able to breathe on its own in the outside air?

The trouble with these particular developmental milestones is not just that they’re arbitrary. More troubling is the fact that none of them involves uniquely human characteristics – apart from the superficial matter of facial appearance. All animals respond to stimuli and move of their own volition. Large number are able to breathe. But that doesn’t stop us from slaughtering them by the billions. Reflexes and motion and respiration are not what make us human.

Other animals have advantages over us – in speed, strength, endurance, climbing or burrowing skills, camouflage, sight, smell or hearing, mastery of the air or water. Our one great advantage, the secret of our success, is though – characteristically human thought. We are able to think things through, imagine events yet to occur, figure things out. That’s how we invented agriculture and civilization. Thought is our blessing and our curse, and it makes us who we are.

Thinking occurs, of course, in the brain – principally in the top layers of the convoluted ‘grey matter’ called the cerebral cortex. The roughly 100 billion neurons in the brain constitute the material basis of thought. The neurons are connected to each other, and their linkups play a major role in what we experience as thinking. But large-scale linking up of neurons doesn’t begin until the twenty-fourth to twenty-seventh week of pregnancy – the sixth month.

By placing harmless electrodes on a subject’s head, scientists can measure the electrical activity produced by the network of neurons inside the skull. Different kinds of mental activity show different kind of brain waves. But brain waves with regular patterns typical of adult human brains do not appear in the foetus until about the thirteenth week of pregnancy – near the beginning of the third trimester. Foetuses younger than this – however alive and active they may be – lack the necessary brain architecture. They cannot yet think.”

Excerpt from:
“BILLIONS AND BILLIONS”, (pages 176 to 180) by Carl Sagan, first published in 1997 by HEADLINE BOOK PUBLISHING, ISBN0-7472-5792-2