Friday, February 19, 2010

Testosterone does not what you think it does

During the past couple of days I enjoyed this video series of a fascinating, yet funny lecture on primate sexuality by Robert Sapolsky.

Technically, Sapolsky is an neuroendocrinologist (i.e. studying the link between brain activity and hormones), but he is even better known for his primatological work since he wrote a popular (and highly recommened) book of his life among baboons.

Interestingly enough (given the context of this blog), he studied the hormonal difference between alpha males and subordinates.

There is plenty of interesting stuff in this lecture (I will deliberately not go into his emphasis on the human specialty of mixing aggression and sexual arousal - just listen to it yourself), but one in particular sticks out: when it comes to testosterone, common opinion might have it all backwards.

As an example - let's assume the cartoonish extreme of two kinds of men:
One type of men is only interested in short term mating (think: one night stands), thus avoiding commitment and child rearing activities. Let's call them Lovers.
The other kind has a preference for long term relationships and family life. Let's call them Providers.
Which of these groups do you think has higher levels of testosterone?

Interestingly, the answer is not that simple. In monogamous species, it actually is the latter who is flushed in testosterone. This is not true for promiscuous mammals. But according to Sapolsky no one knows as of now where humans belong in that spectrum.

This is fascinating. There are studies that prove that married men have lower levels of serum testosterone than bachelors. If one assumes that the bachelors of equal age are single by choice and able to enjoy their freedom, the idea fits the assumption that humans are just like the promiscuous species, with the most promiscuous individuals having high testosterone.

Yet, the same study also demonstrated that "married men who are considered aloof spouses and provide minimal parenting", in particular men with more than one wife had even lower levels of testosterone. To be fair, while there is consensus that committed men have lower testosterone, there are other studies that completely contradict the harem result


But given its consistency, the fact that committed men have lower testosterone is worth further consideration.


One explanation is that they are the "natural betas" (or low status specialists as Johnstone would call them). This would sit well with the picture that biologists got from promiscuous species. 

In this theoretical framework, low testosterone males might give up on sexual variety in order to increase their paternity certainty - by watching over the female, thus keeping her from copulating with others the possibility of sperm competition can be decreased. Scientists call this phenomenon "mate-guarding" and it has been demonstrated to occur in primates when "males are unable to monopolize multiple females at one time" (i.e they are not alpha males). 

Sapolsky also hints at the fact that unlike other primates, women do not show any obvious signs of peak fertility ("hidden ovulation"). 

This mechanism disables the targeted mate-guarding observed among apes: 
Chimpanzee beta males stay with their females for a few days and part again once the obvious signs of ovulation have passed
In contrast, romantic relationships among humans seem to last about four years on average. Some people believe that it is not a coincidence that this corresponds to the time it takes to rear a baby to autonomy (Sapolsky calls it the "inter-birth interval"). 

[Note, however, that there is some interesting new evidence suggests that there is no such thing as hidden ovulation for us humans.]

There is good evidence that humans are rather polygamous. To quote Sapolsky:
"What you wind up seeing in about 90% of human societies the dominant mode is a monogamous marriage [system], despite fact that a lot of these are polygamous societies ... What the genetic studies suggest is that anywhere from %- 40% of kids in Westernized societies are not the offspring of the man who believes he is there father. Those numbers are fairly consistent" 

Sapolsky refers to the "social monogamy" that characterizes humans despite the hard scientific evidence to the contrary (the "genetic [trace of] polygamy"). 

Citing from David Barash and his wife's(!) book "The Myth of Monogamy", he goes on:
"Social monogamy is the whole societal sing and dance about how monogamy exists and how great it is and that it is one of the things that our society loves, and at the same time there is lots and lots of cases where there is no genetic monogamy. ... The conflict between those two is the driving force between at least three quarters of movie plots out there."



But, there is another important factor that correlates with a man's testosterone (which affects the finding that married men have less T). Sapolsky quotes some studies which found that:
Men with a more active sex life have higher levels of serum testosterone.
 [Although it has to be noted that these results are not entirely conclusive; see this and this for example].


Again, this might seems to nicely fit the idea that there are some high testosterone alpha guys out there who bang chicks left and right while the low testosterone betas stick to the mate guarding strategy. After all, we all know the jokes how marriage (and especially kids) kill a man's sex life. But, of course in reality things are not that simple. The comparisons do not really make sense. One cannot divide men into Lovers and Providers based on their marital status alone. To quote from the roissysphere: "In aggregate, of course, married men get more sex than unmarried men do. But that's because the latter category is dragged down by men who are unattractive or uninterested in women."


The interesting story that Sapolsky is getting at, however, is that when it comes to what testosterone does to men the causality may be reversed.


He recounts a story about a paper in Nature written by an anonymous author. This is astonishing as a paper in Nature literally makes a man's career in science. Doing all the work without claiming any credits shows quite an admirable motivation (to be fair, Sapolsky admits that the identity of the author is well known within the field).


The reason why the author preferred to stay anonymous is intriguing: 

"The anonymous scientist had been living and working for weeks at a time on a remote island; no women were on hand to distract him ... He soon noticed an intriguing phenomenon: his beard was growing less rapidly than normal." He knew that the rate of beard growth depended on serum testosterone. So he decided to weigh the remains of his daily shaves and compared the difference over days. 

And what he found was that his beard would start growing more rapidly as he expected to come home to his lover, and declined after the deed was done. In other words, sex (or the prospect of it) triggers testosterone and not the other way round.
"Males have high levels of testosterone because they are having lots of sex!"


Sapolsky cites more studies making similar points, and even predicts what has has been confirmed by a recent study that was all over the news: 
High testosterone does not lead to increased violence. Increased violence leads to higher testosterone.


Whether or not Sapolsky is right (note my caveats and concerns), the lectures are great to watch. I think it was him who once started an after dinner talk with a slide showing a cartoon depicting a missionary inside a big boiling pot of water, surrounded by what seems to be wild cannibals. The caption went:
"Guys, you have to believe me - I am actually a great after dinner speaker!"

9 comments:

  1. I always knew there was something seriously wrong with the traditional idea that high testosterone creates confident, aggressive males, from personal experience as well as historical anecdote.

    Supposedly testosterone is high in hairy men who grow beards at a young age, yet I have had several friends with lots of body hair who grew bears well before myself, yet are fearful, timid, and the farthest cry possible from the confident, aggressive male, and I`ve known many blond, fair skinned, hairless men who were fearless and aggressive.

    So the link between testosterone and aggression and confidence simply cannot be as clear and simple as supposed.

    Supposedly light hair and pale skin and a hairless body are markers for low testosterone and swarthy complexion and lots of hair are markers for high testosterone, yet historically the hairless pale skinned people of Northern Europe provided us with examples of some of the most fierce, aggressive, and confident peoples throughout history - Vikings, anyone? - not to mention the history of Europe as a whole.

    So the whole thing doesn`t make sense - it`s more complicated than people think

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  2. Yes, as any body builder knows testosterone is only part of the story when it gets to androgenic effects. Key players are DHT and the conversion rate to estrogen, as well as how much of your testosterone is actually bioavailable. And I haven't even started to talk about the receptor side.

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  3. "low status specialists" - best terminology ever.

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  4. Wonderful read! Researched well on the effects of testosterone.

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  5. If you had some way of rating posts I would for sure give you a high rating my friend!
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    ReplyDelete
  6. Nice post! Can anyone give me an idea where I can purchase an effective health supplements for my husband to increase his testosterone levels? Is it really advisable to use health supplements?


    testosterone booster

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  7. maggie.danhakl@healthline.comJune 6, 2014 at 7:54 PM

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    ReplyDelete
  8. As a male who's been single since 2013 and who has an undeniably high level of "serum" tedtosterone I feel compelled to ask you how the fuck you warped your mind into believing providers/ married men of monogamy have higher T. Bro, I got my T even higher witn my latest girl simply because I didn't really want her but had sex with her nearly 6 days a week for nearly 6 months. You can't imagine. Why are you so ridiculous?

    ReplyDelete