• Question: what are our nipples for because women use them for breast feeding but what use are they for men

    Asked by ashley to Alastair, Emma, Hywel, Keith, Vicki on 16 Jun 2010 in Categories: .
    • Photo: Hywel Vaughan

      Hywel Vaughan answered on 16 Jun 2010:

      That’s an interesting question ashley!
      From my understanding, when we are first conceived, the foetus has no specific gender. At this point we have nipples because the flood of hormones that decides whether we are male or female have not arrived yet. After this happens, the female form develops quicker than the male, which means that the female brain has longer to develop in the womb than the male.
      This is one theory as to why girls tend to be smarter than boys up until puberty!
      One slightly scary fact though is that men can actually produce milk (i.e lactate) as they have all the structure needed to produce milk.

    • Photo: Alastair Sloan

      Alastair Sloan answered on 16 Jun 2010:

      Excellent question Ashley.

      Darwin’s idea of natural selection means that men really should not have nipples as we don’t require them (you rightly say that women use them for breastfeeding).

      The reason men still have them is that when an embryo first develops it is female – all embryos are female to start with so have similar body parts when they are developing. So, when developing all embryos have nipples present. A few weeks into development It is the effect of sex genes, start to make the final decision on of the embryo remains female or becomes male. The male Y gene and hormone testosterone in (males) start to work and make changes to the embryo to make it more male and cause development of the testicles and penis, but because the nipples were there before all this influence of the Y genes, they stay. That’s why men have nipples

    • Photo: Keith Brain

      Keith Brain answered on 16 Jun 2010:

      Men don’t need nipples, but then again, we don’t our appendix either. Nipples are still there in men probably because evolution hasn’t yet worked out a way for turning off nipple development in men but not in women. Hence, the nipple in men can be described as “rudimentary”. Of course, there is a minor role for nipples in men, related to sexual stimulation, but I don’t think it’s particularly important …

      Interestingly, its quite common (5-10% of people) for multiple “accessory”, or extra, nipples to form (just the nipple – not the dark area of skin, or areolus, around it). They tend to form along two lines, running on the left and right sides, from under the armpit, through the nipple, and down towards the groin (somewhere about the midpoint of the inguinal ligament if you want to get really technical). This is another subtle hint of evolution in action – this is the nipple line for most (?all) mammals – you can see the full set in pigs, we kept a set close to the head, cows and sheep have a set close to the groin. So, next time you’re in the shower, and no-one is looking, check out your nipple lines … you might be in for a surprise!

    • Photo: Vicki Stevenson

      Vicki Stevenson answered on 16 Jun 2010:

      We all (male and female) start off the same, and it’s not until about 14 weeks after conception that gender specific development starts. The nipples are just one of those things that are determined before this point. So if you know someone who is pregant and they’re getting a 12 week scan, there’s no point asking if it’s a girl or a boy – even the baby doesn’t know at that point! You’re all going to have to wait for a later scan.

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