See it from a biological way. You are born when your parents' gametes meet and fuse during fertilization, forming a zygote. Then, it goes through cleavage, morula, blastula, gastrulation, neuralation, and yeah, so on. Then, everything just grows from there, until you reach adulthood with an adult body. You're still a human being, but just use gametes for reproduction. The other way doesn't make sense to me. You wouldn't go up to a person and be like "Are you a human being or a gamete." People will look at you weird.