Years ago during debates on the issue of abortion, the pro-abortion side would attack by saying the pro-life side was anti-science and simply religious fanatics. They claimed the moral high ground based on their understanding that science was on their side. They mockingly stated the pro-lifers needed to enter the 21st century, throw away their religious arguments and face the facts; the unborn was simply a conglomeration of cells and science confirmed human life begins at birth. In their minds abortion was a scientifically justified procedure. To go against science and say the unborn deserved life was simply an affront to the rights of women.
Today in debates on the issue of abortion the table has been turned. Science is no longer a friend for the pro-abortion advocates. We now find skilled pro-life debaters like Scott Klusendorf using science to support the unborn is fully human deserving of rights and protection. In fact some pro-abortion debaters have criticized the pro-life side for their over dependence on science in their arguments. The reason for this dramatic change is the fact that modern science is on the side of the pro-life advocate.
I begin with citing leading embryology books that confirm this. For example, Keith L. Moore & T.V.N. Persaud write, “A zygote is the beginning of a new human being. Human development begins at fertilization, the process during which a male gamete or sperm … unites with a female gamete or oocyte … to form a single cell called a zygote. This highly specialized, totipotent cell marks the beginning of each of us as a unique individual.” Here the text clearly states that upon conception the unborn is a unique human being.
Moving to the textbook Human Embryology and Teratology we read: “Although life is a continuous process, fertilization is a critical landmark because, under ordinary circumstances, a new, genetically distinct human organism is thereby formed….The embryo now exists as a genetic unity.” Again additional evidence the unborn is a distinct, living, whole human being.
Prior to his abortion advocacy, former Planned Parenthood President Dr. Alan Guttmacher was perplexed that anyone, much less a medical doctor, would question the humanityof the unborn. “This all seems so simple and evident that it is difficult to picture a time when it wasn't part of the common knowledge,” he wrote in his book Life in the Making.
Many more embryonic books could be cited as evidence. I found a web site that quotes and displays many books that serve as medical testimony for identifying the unborn is fully human. The site is called ABORT73 and the key page can be found at Medical Testimony.
When answering the question “what is it” the evidence is clear; the science of embryology establishes from the earliest stages of development, the unborn are distinct, living, and whole human beings. And yes they have yet to grow and mature, but they are whole human beings nonetheless.
 See also, T.W. Sadler, Langman’s Embryology, 5th ed. (Philadelphia: W.B. Saunders, 1993) p. 3; Ronand O’Rahilly & Pabiola Muller, Human Embryology and Teratology, 2nd ed. (New York: Wiley-Liss, 1996) pp. 8, 29.
 Keith L. Moore and T.V.N. Persaud, The Developing Human: Clinically Oriented Embryology (Philadelphia: W.B. Saunders Company, 1998) p.2.
 O’Rahilly, Ronand and Muller, Pabiola, Human Embryology and Teratology, 2nd ed. (New York: Wiley-Liss, 1996) pp. 8, 29. This text book describes “pre-embryo” as a discarded and inaccurate term (p. 12)
 A. Guttmacher, Life in the Making: The Story of Human Procreation (New York: Viking Press, 1933) p. 3.