The most basic answer to the question "why do men have nipples" is that in the womb, male and female fetuses have the same form for the first few weeks following conception. After the fourth week, the fetus begins to produce either male or female hormones. There is a generic human template which is then modified by hormones. Nipples are a feature of the template—they are a genderless feature. That feature is then modified by the female hormones to include lactation. The male hormones block the development of the structures and ducts necessary for lactation.
Why do men have nipples?
Male and female nipples do have some similarities. Both have lots of sensitive nerve endings which contribute to sexual pleasure in both genders. Both are aesthetically pleasing. Solomon poetically compares his wife's breasts to two fawns, grazing among the lilies—the nipples would be compared to fawns' noses (Song of Solomon 4:5). His bride, says that her husband's body is "polished ivory, bedecked with sapphires" (Song of Solomon 5:14) the nipples in this case being compared to jewels in an ivory sculpture. This is an interesting comparison of the difference between female and male beauty; the one is beautiful for being soft and alluring, and the other is beautiful for being well-formed and solid. This again shows how the nipple is a generic feature which is modified by male or female hormones first in the womb and then again at puberty.
King David said, "I praise you, for I am fearfully and wonderfully made. Wonderful are your works; my soul knows it very well" (Psalm 139:14). It is easy to see God's creative power and genius in the design of the human body.
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