Whay do all male animals have nipples?
2007-06-16 02:00:40 · 2 answers · asked by Mezmarelda 6 in Science & Mathematics ➔ Biology
Because all embryos start out as female. By the time sex is differentiated, the nipples have already started to form.
2007-06-16 02:04:31 · answer #1 · answered by Joan H 6 · 5⤊ 0⤋
All female cells contain X-X chromosomes and all male cells contain X-Y chromosomes. This difference causes a shift in the balance between female and male hormones in the fetus (but both are present throughout life). This hormonal difference results in very similar beginning fetuses to develop male or female primary sexual traits. Puberty completes the development (when there is a final hormonal upheaval) and includes development of secondary sexual traits (curves and facial hair, etc.).
2007-06-16 10:03:09 · answer #2 · answered by Kes 7 · 2⤊ 0⤋