It's still up for debate when the kid starts feeling pain and becoming aware and that sort of thing(which is where that research comes in I guess!) for the most part the first trimester is expected to be a period where the above doesn't happen currently, but then in chatting with the aforementioned people we eventually got around to... what is and isn't a child? Where do you draw the line? Is masturbating the same thing as an abortion? How about people who never have sex but have the potential to, is that equally wasteful? I think for me the line is as soon as the fetus starts forming so I don't really consider abortion a viable option, I'm definitely not a man of strong morals but I just don't think I could justify it to myself.
Well, here are my thoughts on why I solidly draw the line at conception.
1. I have never heard of, or seen, a sperm turn into a human by itself. Similarly, I've never seen an ovum turn into a human by itself. If anyone got some contradictory information... then I'll refine my argument.
2. From any adult human, you can do the following. Was he a human 1 minute before? etc. etc. until he was back inside the mother's womb. This is "critical point #1". Is a baby a human before it is born? IMO, yes, it is. I can argue this point later, but for now, I'm going to assume that everyone agrees with me on this one. A baby, seconds before it is born, is a human. Why? There are plenty of sucessful premature births and the baby does survive.
3. From inside the womb, we can then reverse the process. The stages of a fetus are multiple shades of gray. Yes, we can split them up into trimesters similar to how we can split shades of hot colors into red, orange, and yellow. But really, it all flows together. Seconds before "seconds before birth", the child still is human. Seconds before seconds before... (repeat as necessary till you have the zygote), the thing is still human. Unless someone wishes to clearly draw a line elsewhere. But "trimesters" are really just as blurry as any other line drawn biologically. (even super-precise words like "species" have things that fall under the grey line, such as ring species)
*reads over argument*. Damn, it sounds circular. Oh well, I'm going to post it anyway >_> I'll deal with it in the morning.
Anyway, my point is, conception is the only moment where I can clearly divide between "human" and "non-human". Humans have all 46 chromosomes, haploid cells (such as sperm and ovums) have only 23 chromosomes.
Minor variations of the chromosome number, such as in down's syndrome or whatnot, still keep the human human.