the whole classification of metal development is based the averages derived from the study of it and you said averages don't matter because some fetuses develop faster than others so certainly people will all have different rates of mental development won't they?
And it's not the issue of life the issue is when does the fertilized ovum become a person. All human cells are human life but not all human cells are persons.
And because most opposite sex couples can procreate, procreation could not be used to exclude same sex couples from the right to marry, because the fact that some opposite sex couples cannot procreate made the same sex couple “similarly situated”, to the opposite sex couples that could not.
To exclude the same sex couples was discriminatory regardless of the average of the total.