KWED
Scratching head, scratching knee
Imagine 1000 random humans from around the world. All genetically Homo sapiens. God creates them all at once. Boom! Problem solved.100 original pairs: 100 original kinds. Hence, 100 different humankinds. Not all are brothers and sisters. Hence, we need 100 Jesus crucifixions to save all 100 humankinds. But God is having only one Jesus. Hence, there is only one humankind.
For a "logic genius", you seem to struggle with pretty basic concepts.