I suggest you inform yourself about the gestation process. I used to think the same way, but when we had my daughter I was surprised how early everything happened. First, embryonic age is measured from the date of the last missed period. So even people who find out early are already several weeks along. By six weeks, before many women even realize they are pregnant, the embryo has a heartbeat. By 13 weeks, most of the basic functionality is already there. By 24 weeks, or the time the baby is a pound and and a half, the fetus isn't a glob, but a fully recognizable, if fragile, human. Much of the development after that is external: hair, subcutaneous fat, etc. I don't know what you consider a coherent thought, but at our 24 week ultrasound our baby already responded as we tried to push her into a position to check her gender. I don't think infants who are born full term are more intellectually sophisticated in some fundamental way.

Yes, this has implications for abortion. I support abortion rights, but the "its just a ball of cells" is a rationale that isn't convincing after week 6-9. And lines drawn on intellectual abilities don't justify in a principled way why it isn't okay to abort full term babies. Lines based on viability are susceptible to the progress of medical technology. The typical 24-26 week line we use is fairly arbitrary in all three regards.