Nipples - Men
This one has puzzled me for a long time, and I thought maybe you would have an answer:
Why do men have nipples?
The Aish Rabbi Replies:
Nipples represent the ability to nurture. Women can obviously experience this from both a physical and spiritual perspective. As modern research has shown, mother's milk provides the best possible nutrition for a baby. But the same applies to the spiritual nourishment an infant absorbs from its mother. For example, a tender, caring mother will impart those deep feelings to the child. Thus, the physical act of breast-feeding passes crucial spiritual influences to an infant. (see Talmud - Avodah Zarah 10b)
Since a man does not breast-feed, his ability to nourish is limited to a purely spiritual level. The physical existence of nipples, however, remind him that although he lacks the means to nurture a child physically, he must still take a primary role in the child's spiritual nourishment. This is alluded to in the verse, "From my flesh, I will see God." (Job 19:26)
Throughout Torah literature, we see the breast frequently used as a symbol of spiritual nourishment. In his deeply symbolic work, "Song of Songs," King Solomon writes: "I am a wall and my breasts are like towers" (verse 8:10). The reference here is to Torah scholars: Just as the breast provides physical sustenance, so too Torah scholars provide spiritual sustenance to the world. (Talmud - Pesachim 87a, Rashi)
Furthermore, breasts symbolize the idea that each person must draw sustenance on his own level and must not seek a lifestyle that is inappropriate to his current abilities. For this reason, breasts are termed "Shadayim," which contains the word "Dai - enough!" The message is that there is no need to look beyond one's own source of bounty to fulfill one's needs; there is ample spirituality available for everyone. (see Rabbi Chaim Kramer - "Anatomy of the Soul")
On a more medical note, while only females have mammary glands, we all start out in a similar way in utero. The embryo follows a female template until about six weeks, when the male sex chromosome kicks in. By that time, the nipples have already formed.
By the way, there's one more reason for men's nipples. The Midrash (Genesis Rabba 30) describes the case of a man whose wife died shortly after giving birth. God then made a miracle and granted him the ability to breastfeed the baby. A miracle!