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When does human personhood begin?

Secularly-based beliefs that person-
hood occurs during pregnancy

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Why do they believe that a zygote is not a human person?

Most pro-lifers believe that personhood is attained during the fertilization process. Others believe that a zygote -- a just-fertilized ovum -- is a potential person, but not a human person: they reject some of the arguments put forth by pro-lifers. Some of their reasons for rejecting the personhood of a zygote are:

bullet Atheists, Buddhists, Humanists, many religious liberals, and others generally reject the possibility of God injecting a soul into the zygote at conception. The concept of the soul is plays a major role in many religions, and is one of the reasons -- often unstated -- why pro-lifers believe that a zygote is a human person.

The soul is a largely religious concept whose existence has never been proved scientifically. It cannot be located, weighed, seen, smelled, felt, measured, or otherwise detected by any known instrument or human sense.
bullet Most reject the belief that the presence of a unique DNA code converts the egg into a human person. They note that a skin scraping of a child or adult contains a very large number of living, single cells; each has the same unique human DNA code as does the human from which it came.  Scottish scientists removed a cell from the mammary tissue of a sheep, injected it into a sheep ovum whose DNA has been removed, and produce "Dolly," a cloned sheep who is genetically identical to her "parent." This same procedure has been replicated for many other mammals. A sample from a human skin scraping, or from a swab of the inside of a person's mouth, or a hair follicle contains the same type of human DNA information as does a zygote. They presumably should both be given the same status. Skeptics might argue that since we don't consider a hair follicle, etc. to be a human person, we should not look upon zygotes as persons either.
bullet Some pro-choicers note that a zygote has no limbs; no head; no brain; no ability to see, hear, smell, taste or touch; no internal organs, no self-consciousness, no ability to think, reason, sense its environment, etc. Even at the age of one month, a human embryo cannot be distinguished from the embryo of a cat or dog. They might argue that four things make us human persons: awareness of the environment, the ability to think, a moral sense, and physical appearance. The zygote exhibits none of these. It is closer to a doll than a human person.

When to they believe human personhood begins?:

They differ widely:

bullet A few hours after conception when the ovum splits into two cells. Some regard human personhood as being defined by the first act of cell splitting.
bullet About two weeks after conception, when a yellow streak develops in the embryo. This will later become the neural tube which will be protected by the backbone. It develops into the brain and central nervous system. Once this develops, it is impossible for the embryo to split into a pair of identical twins. The concept of personhood implies a single entity; twins develop into two persons. After two weeks from conception, the embryo can no longer split and grow to become two persons. Some consider it a person at this stage.
bullet 3 weeks from conception when the embryo is about 2 mm long and has started to develop visible external body parts. It is no longer a blob of tissue.
bullet At about 4 weeks, when its heart starts to beat.
bullet 6 weeks from conception, when primitive brain waves can be first sensed.
bullet 2 months, when the fetus has lost its neck structures which resemble gill slits, and its tail. Its face resembles that of a primate. 
bullet 3 months the fetus begins to "look like" a baby. The recent development of high resolution 3-D ultrasound equipment provides incredibly detailed pictures of the fetus at this stage. These photographs are convincing many people that the fetus is a human person at this stage because it looks like one -- even though none of its higher brain functions are functioning. 1

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bullet 16 weeks: Fetal movement, often called quickening, is usually detectable by this point in pregnancy. It is apparently an involuntary movement of arms and legs. At this stage in gestation, the brain is not developed to the point where the fetus is conscious.
bullet 4 months when the fetus' face has developed to the point where one can tell one fetus from another.
bullet About 24 weeks, when the fetus becomes viable, (i.e. able to live outside the womb) with current technology. When medical ethicist Bonnie Steinbock was interviewed by Newsweek and asked the question "So when does life begin?," she answered:
"If we're talking about life in the biological sense, eggs are alive, sperm are alive. Cancer tumors are alive. For me, what matters is this: When does it have the moral status of a human being? When does it have some kind of awareness of its surroundings? When it can feel pain, for example, because that's one of the most brute kinds of awareness there could be. And that happens, interestingly enough, just around the time of viability. It certainly doesn't happen with an embryo." 2
bullet At 26 weeks or later, when the fetal brain's higher functions become operational. Scientists have: " measured brain-wave patterns like those during dreaming at 8 months gestation." 3 Carl Sagan discusses this point in his final book. He suggests that the one factor that is uniquely human is our ability to think. Thus we become persons when the cerebral cortex is in place and "large-scale linking up of neurons" begins. This does not start until the 24th to 27th week of pregnancy -- the sixth month.
bullet Some believe that a personhood happens when a soul enters the body at some stage of gestation or -- as in the case of some Aboriginals -- after birth has taken place.

There appears to be no hope that a future consensus can be reached on when personhood is attained.


  1. Newsweek published six ultrasound images of a fetus at seven, nine, 13, 16, 23 and 35 weeks gestation. See:
  2. Debra Rosenberg, "' When Can It Feel Pain?' For this philosopher, 'viability' makes the moral difference," Newsweek, 2003-JUN-9, at:
  3. "Do You Hear What I Hear?", Newsweek, Special Issue, Summer 1991.

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Copyright 1995 to 2009 by Ontario Consultants on Religious Tolerance
Latest update: 2009-SEP-06
Author: B.A. Robinson

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