Rise and fall of male hormones
Peter T. Ellison
Ellison is a professor of evolutionary biology at Harvard
Q. A study published last week found that a man’s levels of the hormone testosterone generally fall when he has children. Beyond the blow this may deliver to a man’s ego, what does this kind of research tell us?
A. There are direct health implications from this, and it tells us something about human evolution and the way our bodies have been designed to function.
Q. What are the health implications?
A. This study and others like it have established the fact that men have reproductive states, just like women do. We’re used to thinking of women as having reproductive states: pregnancy, lactation, menstrual cycling or not. We also know that the amount of time a woman spends nursing children or not menstruating lowers her risk of breast cancer. The more time a man spends in low testosterone states over his life may [turn out to] influence his risk of diseases like prostate cancer or osteoporosis later in life.
Q. What are those different male reproductive states?
A. One of them might be called ‘mating mode’ in which a man’s testosterone levels are high and his physiology is geared toward seeking mates. And another might be called ‘parenting mode,’ when his testosterone levels are lower and his physiology is geared toward being a better caretaker and provider and not being distracted by mate-seeking.
Q. Does this research also have implications for our understanding of parenting?
A. Humans have evolved to have mates that last for more than just one copulation or one season and to participate together in raising a family. I think we can realize that being a father is part of what evolution has equipped a male to do.
Q. Is this surprising - that men evolved to be fathers?
A. It shouldn’t be surprising, although much of the popular literature and even a good deal of the scientific literature stresses the differences between the sexes - the Mars and Venus dichotomy - and men as being perpetually mate-seeking and women as being the nurturing ones. This softens that dichotomy significantly.
Q. Does this kind of research have any personal implications for your life?
A. I’m waiting to find out whether there’s a grandfather effect.
Q. Do testosterone levels fall with age, too?
A. Men’s testosterone levels decline with age and we often think of that as [deterioration], but they reach their peak in their early 20s and decline from then on. I think that’s too early to be senescence. I think that’s design. And part of the design is we are expected to taper off our mating effort as we age, and perhaps to be available for more of a nurturing and supportive role.
Q. Testosterone is usually associated with virility, but what else does it do?
A. A good way to think about testosterone in men is that it is the major modulator of what we would call ‘reproductive effort.’ It supports sperm production, libido and sex drive, accumulation and maintenance of muscle mass, and it will affect behavior in more subtle ways that sometimes come out as aggression or temper or assertiveness.
Q. What happens when levels of testosterone get too high, say when men take steroids that include testosterone?
A. I can’t help but notice that the day this study came out, [former
This interview has been edited and condensed. Karen Weintraub can be reached at Karen@KarenWeintraub.com.