There are and have been human societies who don't recognize the existence of a 'person' for periods up to one year after birth itself and many time periods in between.  While looking at a beating heart in an embryo is persuasive regarding the issue, I tend to believe 'viability'  is a better test.  Having personally had a child borne prior to 9 months of gestation tends to sway ones opinion, of course.  The pesky nature of personal anecdotal evidence does seem to creep in every now and then.