What is generally true of any given species is not necessarily true of each and every individual member of that species at every point of each individual's life. Human beings as a species can be said to have two legs and arms, 10 toes and 10 fingers. This applies to 99+% of Homo sapiens. But there's a small number of some human beings who for one reason or another are outside the norm for our species. However, that does not mean they are no longer members of the species Homo sapiens. It does not mean they are not human any more, or never were.

As I've said elsewhere, you need to study up on classification and categorization. And on the difference between descriptive and prescriptive definitions.

I think you would greatly benefit by learning about the lives of people with severe disabilities. Starting with reading Dalton Trumbo's Johnny Got His Gun, all the people born with missing limbs due to the Thalidomide tragedy, and watching the Daniel Day- Lewis film My Left Foot, based on the real life story of Christy Brown.

You could easily have an accident tomorrow that causes you to lose a limb or an eye, or get sick and have to have your appendix or spleen removed. You really think you would then no longer be human?

Have you really never met a single person in your whole life who due to accidents, combat, blasts or surgery necessary coz of illness, dental wear & tear and/or aging doesn't have every single body part that the majority of humans have and which constitute the norm for our species? You don't know anyone who's had their tonsils or gallbladder out, or is missing teeth? You know no completely bald men? That's really hard to believe.