Do We Know When Human Life Begins?

The Observer—Official Newspaper of the Catholic Diocese of Rockford
Publication date: December 3, 2004

Life Lines
By Patricia Pitkus Bainbridge
Director, Respect Life Office

“T.R.” writes in response to last month’s column three objections that “seem to lend weight to the idea that ‘human life cannot begin at conception.’” He writes, “ How can, at conception, a ‘separate, distinct human being’ be created when anytime between fertilization and implantation . . . twinning can occur, raising the question, ‘which twin got the human life at conception?’”

T.R. refers to the case of identical twinning, which occurs when a single embryo splits into two within 15 days of fertilization. With monozygotic (identical) twinning it does not matter if the split takes place at day two or fourteen. Each twin has the full complement of genetic material identifying her or him as fully human. If their division is incomplete, they will be conjoined. Regardless of where they are joined, each twin is a separate, distinct human being.

Robert P. George, Ph.D., writes, “Consider the parallel case of division of a flatworm. Parts of a flatworm have the potential to become a whole flatworm when isolated from the present whole of which they are part. Yet no one would suggest that prior to the division of a flatworm to produce two whole flatworms the original flatworm was not a unitary individual. Likewise, at the early stages of human embryonic development, before specialization by the cells has progressed very far, the cells or groups of cells can become whole organisms if they are divided and have an appropriate environment after the division. But that fact does not in the least indicate that prior to such an extrinsic division the embryo is other than a unitary, self-integrating, actively developing human organism. It certainly does not show that the embryo is a mere clump of cells.”

In other words, the human organism present at fertilization is complete with a set of genetic information to direct its own development; if it happens to divide, there may be more than one distinct human organism whose life began at fertilization and continued through the moment of twinning and beyond. Identical twins share the moment of conception and then divide.

T.R.’s second concern is about fertilization in a petri dish. He writes, “it can never grow into a human being unless first implanted . . .” What he doesn’t realize is that we do not grow into human beings. All of us became human beings at fertilization. Some of us die minutes after fertilization; others die 80 years later. All began life as unique, single-celled humans. All were human beings at different stages of development. None of us can continue to grow unless we are in an environment conducive to growth at our particular stage of development, whether in the womb or in our homes.

The third query posed by T.R. is that it is an “impossible stretch of the imagination to consider that a purposeful human life exists [in a single zygote that never implants].” It is a stretch of the imagination only if we recognize human life by the way one “looks.” We all were the size of a grain of sugar when we came into existence. We all looked like a shrimp at four weeks of development. None of us look like we did five minutes after we were born. Yet, we are all humans who looked the way we were supposed to look at specific times in our development. Our size, our age, our capabilities or the way we look does not determine our humanity.

Dianne N. Irving, Ph.D, writes, “The question as to when a human being begins is strictly a scientific question, and should be answered by human embryologists—not by philosophers, bioethicists, theologians, politicians, x-ray technicians, movie stars, or obstetricians and gynecologists.”

A brief perusal of standard human embryology textbooks finds “fertilization marks the beginning of the life of the new individual human being.” There is no question. The intellectually honest know that human life begins at fertilization.



Copyright, 2004