When does life begin? Like I said before, there are several schools of thought on this subject, but I find it quite easy to see which makes the most sense, scientifically.
Life begins at conception-this is when the DNA from the father and the mother mesh into one new set of DNA, one that is totally unique to the new life. Moments after conception, this DNA is fully intact. From this point on, growth occurs, but no other changes happen on the DNA level. Just after conception the following criteria to establish biological life are present:
reaction to stimuli and
Related to life beginning at conception, here is a link discussing the fact that the baby is autonomous of the mother from the very beginning.
Life begins at implantation-this misunderstanding, I feel, is perpetrated by our current medical system. Since the 1960s, In order to continue to market products like abortifacient birth control methods, pregnancyhas been redefined as starting at implantation. This means that any method used to keep a baby from attaching to the womb/nourishment (like the IUD and any hormonal birth control methods) can be allowed (with the new definition). It's a definition of convenience, but it's not based in truth.
In truth, the zygote's cells have been multiplying away while it travels down the fallopian tube. Once it reaches its destination, the uterus, it plugs in for nourishment. The act of implantation doesn't jolt it alive or make any other changes, its just allows for nourishment to be given to the growing, fertilized egg and it sends signals to the woman's body to stop menstruation. In my limited search today of informative links, I can't even find this point, so I'm wondering if it's been left behind as our technology has progressed...
Life begins when the embryo looks human-does this even justify an answer? Looks human? How scientific is that? A charred tree doesn't look like wood, yet in science class we all learned that fire brings a chemical change to the wood. It was still wood and is still wood, it's just burned wood. Looks mean nothing-what does the DNA say?
Life begins at viability-this is a subjective argument. Viability depends on our technology, which is always changing. We can't base something as important as when life begins on our ability to maintain that life outside the womb. Viability continues to inch up earlier and earlier, so does that mean that 20 years ago life began at a later stage than it does now, just because we couldn't sustain that life outside of the womb in 1988? No. Life has always begun at the same time, it doesn't depend on us.
Life begins at birth-this again is subjective because birth can occur at so many different gestational ages. Just because someone wants to justify abortion doesn't mean they can decide to stamp personhood on only those who are born. Tell a mother the child in her womb, whom she can already see has a personality, isn't yet a person. No scientific changes occur at birth that would make a child suddenly become a person.
Life begins after birth-Peter Singer believes personhood arrives sometime after birth-weeks afterwards. This is also philosophical argument, not scientific and therefore can not be taken seriously. If science backed it up, yes, it'd be worth discussion, but science clearly points to the other end of the spectrum (conception).
I've tried to not spiritualize this discussion, because while I fully believe in the truths of the Bible, not everyone does. However, science and scripture will not contradict each other, so we can depend on true science. Here is an excellent site that explains succinctly when life begins without using any religious reasoning. If you don't check out any other links on this post, check out this one.
And for the visual learners, here's a beautiful youtube video of fetal development. It's been said that if wombs were made of glass, there'd be no abortion. Consider this the glass womb.