To an Embryologist, the first cell division of the conceptus is the first evidence of an individual human being expressing its unique life along a lifetime continuum. They are so certain of this individuality that they have devised all sorts of tests done on an embryo to discern whether the individual has Downs or anemia, or other disease. Were the tests not being done on a specific indivisual human being at their embryo age, the results of the tests could not be accepted as valid for the same individual forty weeks later.