Why do men have nipples and dense facial hair, while women dont? any scientific evolutionary evidenc

Nipples on men are like appendixes (appendices). Probably just some evolutionary trash that hasn't gotten lost. Developmentally, the little proto-nipples form before the fetus boys and fetus girls have differentiated at all anyway.

Maybe when women started to not go outside of the cave as much, they needed facial hair less. Maybe men found women's faces sexually stimulating, hence encouraging the evolution of smooth-faced women.

Why do men have nipples and dense facial hair, while women dont? any scientific evolutionary evidence!?

Well, there are two distinct questions.

We are sexually dimorphic animals, thus, of course, there are some differences between our sexes. Sexual differentiation starts during mother's pregnancy, and become evident in puberty, when levels of sexual hormones are rising.

Generally, evolutionary explanation for sexual dimorphism is very simple - sexual selection. There are innumerable studies about this interesting topic. When sexual partner is anyhow choiced, there is a scene for sexual selection.

Men nipples are another exciting story. In fact, they are deluxe living proof of evolution. Men and women have nearly same genetic program and both sexes have instructions for making nipples. Men nipples are useless but not dangerous or biologically expensive. Therefore, there is no heavy evolutionary pressure to remove them. It is only defect of evolution, with no deep reasons. But this is the very point. Evolution is blind and patchs together living organisms.

Why do men have nipples and dense facial hair, while women dont? any scientific evolutionary evidence!?

Well, both are evidence of a feature controlled by the Y chromosome. In the case of nipples, this indicates a feature (breasts) that is present in the genes of males and females, but suppressed during adolescence by the presence of the Y chromosome. And in the case of facial hair, this is something triggered by the Y chromosome during adolescence.

In the case of nipples on men, this is further evidence that embryos go through a phase where gender is not yet determined. All mammal embryos (male and female) get nipples during this early stage, and it is only later in development (adolescence) that these are differentiated.

Another way to look at it is that both of these features provide some evidence against intelligent design (or deliberate creation). Any time there is some feature without a function, this poses a problem for intelligent design. This is stronger in the case of nipples on men ... as an intelligent design of males would have left these features off, as they do not help in the design of function of being male, or being human. This is less clear for facial hair, as one could postulate a function for facial hair (and other secondary sexual characteristics) that is consistent with the design of function of being male ... namely as a signal in adolescence of sexual maturity. But facial hair still poses a problem because it is evident that these have no other function besides signalling ... as females and children are able to survive quite well without facial hair. And the fact that men can shave off facial hair without loss of being recognizable as sexually mature males, shows that the signalling function is minimal if any. So facial hair really has no significant function at all ... it is better explained as a side-effect of other functions in the Y-chromosome that *do* have function.