The first part of the quote was a mistake and was addressed to someone else I apologize. Secondly yes science is clear. Leading embryology books 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.” Prior to his abortion advocacy, former Planned Parenthood President Dr. Alan Guttmacher was perplexed that anyone, much less a medical doctor, would question this. “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. Again the development of the brain is your standard in which you claim is necessary to be human. And what to you is the true difference between a human life and human being? What follows by your reasoning is that those who do not have your standard of sentience is not worth protection. So if sentience is your standard than the mentally ill or disabled who may not be able to feel or perceive something subjectively may not have the same right to life. The phrase “just a clump of cells” is meaningless – at what point does a human being cease to be a “clump of cells”? We are all “clumps of cells” - just larger than we were when we were in our mothers' wombs! The fetus is a genetically distinct human person – even as a single cell, that fetus is alive and is a person with the complete genetic information of the adult. The only thing that is required to allow that fetus to grow into an adult human is time and nutrition.
If a fetus is not a person, when does it become a person? And what is added to the fetus to make it into a person? What else could the offspring off two humans be but a human person?
The argument that because a child is incapable of certain things – living without its mother, or reason – is also ludicrous. There are many people who are rightly and correctly called “persons” who can't do these things; infants, the handicapped, the very old, the injured. Is a person who is mentally retarded not a person because he cannot reason and interact? Newly born infants cannot survive without their parents – in fact, much older infants cannot survive without their parents. Does this mean they are not people too?
All of these arguments attempt to establish a definition of “person” which is at odds with the traditional view (namely, a person is made in the image and likeness of God) and which does not make consistent logical sense. All of these arguments simply seek to justify the selfish murder of children for no reason other than convenience by attempting to deny personhood to those who have it.
Another form of this argument is the view that late term abortions are not permissible but early ones are. This is a flawed argument simply because where is the line drawn? On what basis is the distinction made? What is the difference between (for example) a twelve-week and a twenty-week fetus which means one can be destroyed and murdered and the other cannot? There is no distinction except age – an entirely arbitrary choice. Is it right to murder someone who is 59 but not 60, for example?