It is being said that it is “scientific fact” that there is a human being at the point of conception - I have yet to find this “fact” in any of my medical books - in some of my Catholic books, yes, but medical books, no. Which non Catholic based medical book do you find it said that when the sperm and egg meet that a human being is present - if it’s in one of my medical books, I have yet to find it and they are 2008 publication.
from Princeton:
The following references illustrate the fact that a new human embryo, the starting point for a human life, comes into existence with the formation of the one-celled zygote:
princeton.edu/~prolife/articles/embryoquotes2.html
From
Pregnantpause.org
pregnantpause.org/develop/when.htm
and from development Biology:
8e.devbio.com/article.php?id=162
Genetic View:
The genetic view takes the position that the creation of a genetically unique individual is the moment at which life begins. This event is often described as taking place at fertilization, thus fertilization marks the beginning of human life. During this developmental event, the genes originating from two sources combine to form a single individual with a different and unique set of genes. One of the most popular arguments for fertilization as the beginning of human life is that at fertilization a new combination of genetic material is created for the first time; thus, the zygote is an individual, unique from all others.
Although the opinion that life begins at fertilization is the most popular view among the public, many scientists no longer support this position, as an increasing number of scientific discoveries seem to contradict it. One such discovery in the last twenty years is that research has shown that there is no “moment of fertilization” at all. Scientists now choose to view fertilization as a process that occurs over a period of 12-24 hours. After sperm are released they must remain in the female reproductive tract for seven hours before they are capable of fertilizing the egg. Approximately ten hours are required for the sperm to travel up to the fallopian tube where they find the egg. The meeting of the egg and the sperm itself is not even an instantaneous process, but rather a complex biochemical interaction through which the sperm ultimately reaches the inner portion of the egg. Following fertilization, the chromosomes contained within the sperm and the chromosomes of the egg meet to form a diploid organism, now called a zygote, over a period of 24 hours. (Shannon and Wolter 1990). Thus, even if one were to argue that life begins at fertilization, fertilization is not a moment, but rather a continuous process lasting 12-24 hours, with an additional 24 hours required to complete the formation of a diploid individual.
The most popular argument against the idea that life begins at the moment of fertilization has been dubbed the “twinning argument.” The main point of this argument is that although a zygote is genetically unique from its parents from the moment a diploid organism is formed; it is possible for that zygote to split into two or more zygotes up until 14 or 15 days after fertilization. Even though the chances of twinning are not very great, as long as there is the potential for it to occur the zygote has not completed the process of individuation and is not an ontological individual.
Proponents of this view often propose the following hypothetical situation: Suppose that an egg is fertilized. At that moment a new life begins; the zygote gains a “soul,” in the Catholic line of thought, or “personhood” in a secular line of thought. Then suppose that the zygote splits to form twins. Does the soul of the zygote split as well? No, this is impossible. Yet no one would argue that twins share the same “soul” or the same “personhood.” Thus, supporters of this view maintain that the quality of “soul” or “personhood” must be conferred after there is no longer any potential for twinning. (Shannon and Wolter 1990)
The argument that human life begins at the moment that chromosomes of the sperm meet the chromosomes of the egg to form a genetically unique individual is also endangered by the twinning argument because genetic uniqueness is not a requirement for an individual human life. “Genetic uniqueness” can be shared by multiple individuals, particularly indentical twins. Thus, this argument continues, the moment at which a unique individual human forms is the not the moment when its genetic code is determined, but rather the moment when the zygote can no longer split into multiple individuals.
In addition to twinning, there are other complexities that further confound the idea of the moment of conception. Just as it is possible for a zygote to form two or more individuals before it is implanted in the uterus, it is also possible for it to not continue to develop at all, but rather just become a part of the placenta. (Shannon and Wolter 1990). It is estimated that more than 50% of fertilized eggs abort spontaneously and never become children (Gilbert 2002). Or, if the zygote splits into multiple zygotes, it is also possible for these to recombine before implantation. All of these possibilities are examples of the ways in which the individuation of the zygote is incomplete until it has been implanted in the uterus.