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Humans have 23 chromosomes in their sex cells.
At birth, the differences between humans are genetic. Cultural and experiential differences come later.
Jane Barr Stump has written:
'What's the difference?' -- subject(s): Miscellanea, Sex differences, Sex differences (Psychology), Sex role
They have sex
Christel Dormagen has written:
'Mond und Sonne' -- subject(s): Sex differences, Sex role, Social aspects, Social aspects of Sex differences