What your Waist-to-Hip Ratio Says About Your Health

A few weeks ago I had my annual checkup with my doctor. The drill was the same it's always been, except this time her nurse took a measurement on my waist.

Immediately I saw the connection to the research I am familiar with on the WHR (waist-to-hip ratio). WHR is a favorite topic of evolutionary psychologists.

It all started with an Indian researcher named Devendra Singh who demonstrated that men express the most sexual attraction to women with an hourglass figure - and not just any old hourglass figure. Men, in samples drawn from around the world, including non-Western and non-Industrialized cultures, agreed that women who have a waist-to-hip ratio of .70 are the most sexy.

Right about now, you might be wondering how to measure your WHR. Measure the narrowest part of your waist and the widest part of your hips. Divide your waist measurement by your hip measurement - that gives you your WHR.

A .70 WHR is roughly equal to a 25 inch waist and 36 inch hips. Regardless of weight or BMI (body mass index), those proportions are considered the most attractive to men all over the world.

Why? Men find sexiest those women who are likely to be fertile and nubile, i.e. able to get pregnant. Women with smaller waists and wider hips:

* aren't obviously pregnant
* tend to be younger
* have more circulating estrogen

- all of which are associated with higher fertility. Ancestral men who preferentially mated with women who showed signs of fertility left more offspring than men who were indifferent to such signals. Those are the men alive today.

And, ancestral women with those signals produced more offspring.

Women tend to be pear shaped, as opposed to the more apple shape of men. Why are the sexes shaped differently? The answer is probably obvious, because women's wider hips are "good for childbearing," but the evolutionary mechanism isn't obvious.

You've probably heard of natural selection, but what about sexual selection? Sexual selection is another way that organisms change over time.

Rather than changing in response to different climate conditions or the presence of predators as with natural selection, under sexual selection, change occurs due to competition for mates. Women become more pear shaped over time because that's what men find appealing, and women with sexier bodies can get better, more "fit" mates.

Although Singh's and other similar research has been fairly criticized on the grounds of flawed measurement instruments (at right), subsequent research using more valid techniques has achieved the same results.

The key piece in all of this is that question of whether women with .70 WHRs are really more fertile. As it turns out, women with smaller WHRs get pregnant more readily, according to a study of female fertility clinic patients.

Of course, I'm scratching my head at all this wondering why, if I have the ideal WHR and BMI and hormone levels, why can I not get pregnant then? It's the curse of endometriosis, a condition made worse by frequent menstruation, that probably never existed in ancestral times because women got pregnant soon after they started menstruating and then nursed, weaned the baby, and became pregnant again over and over.

Estimates are that ancestral women only menstruated about 30-40 times in their entire life. Can you imagine that? The average women living now menstruates hundreds of times in her life. And that, my friends, is an evolutionary novelty.

Medical doctors have caught on to the trend of WHRs - except they're interested in what it signals about your overall health - not just your reproductive health. Smaller waists and wider hips are associated with better coronary and vascular health. It's that connection with estrogen. Estrogen is "heart healthy." Must be, because my cholesterol numbers came in the mail today and mine are as healthy as they get.

My HDL "good cholesterol" is 83 out of 89 (higher is better), and my LDL "bad cholesterol" is 66. It's supposed to be under 130. And I eat cheese all the time - and milk. It's genetics, I tell you. It's genetics. Diet makes it worse, no doubt. I'm not going to start eating mac and cheese at every meal.

Evolutionary Psych Meets the Opera

Tonight I went to the theatre and saw live opera. The production was littered left and right with themes that could be interpreted through an evolutionary lens. I came in late to the production and left early, so I am bound to have missed a few things.

In a nutshell, two women have fiancés who go off to war. The ladies are dreadfully distraught with the abandonment. A guy makes a bet that he can get these ladies to have affairs while their men are away. Although he is confident the ladies will prove to be unfaithful because that's what he knows women do, he nevertheless enlists the help of their maidservant who will get paid if she helps set the ladies up with two men he has chosen - rich, handsome, healthy foreigners.

From an EP perspective, why would these ladies be unfaithful? They might be tempted to cheat for a variety of reasons.

In this context, hooking up with a new guy can be an insurance policy against the death of the fiancée. Let's assume these women were already "knocked up" by their fiancés. If the father died in the war, who would provide for the offspring? Back up man. Why would he provide? Providing for the child shows he is a good father. He might be able to translate that into having his own offspring with her.

Or, he could do what some primate males do when a child is born who "is not of his blood" - kill it. Infanticide is one male reproductive strategy. By killing her child and otherwise acting domineering, he might intimidate her into staying with him and having his children. Primate females have evolved strategies for dealing with infanticidal males, but none of these do much good if the woman is dependent on that man.

Even if she didn't get knocked up, or wasn't already preggers, she could benefit in other tangible ways from having a short-term affair.

But what if these women don't need a provider? Let's say these ladies are from wealthy families or are otherwise able to provide for themselves and potential dependents.

They might be tempted to cheat if these suitors are handsome and physically fit. They might have "good genes" that could be passed on to her offspring - genes that would make her children more desirable as mates themselves. Poor women would be tempted by this too. But in this scenario, the rich women could have a fun little affair and ditch the guys when the fiancés come back from the war without worrying about the loss of a provider.

They might even become pregnant with a more handsome man's baby. And if they can convince the fiancée the baby is his, well bingo for the woman - she will have successfully cuckolded the fiancé and settled down with a war hero. She risks an awful lot if she is caught in the ruse though. War hero may desert her and the baby. No big deal - if the woman is financially independent, she doesn't need him to stick around and support her and her dependent. Good riddance.

He may try to kill her for cheating. Nothing less would be expected of a man who just returned from participating in state-sponsored murder. Even men who aren't fresh off the front lines can be violent and physically aggressive when consumed by sexual jealousy. If she is a wealthy heiress, she probably has "back up" in case he turns homicidal.

As you can see, poorer women risk more by being unfaithful. They also potentially benefit more. Wealthy women have less to gain and less to lose by being unfaithful.

There is much more to the opera storyline than a simple tale about infidelity during war. There is also much more that can be said about reasons for female infidelity. As I walked away from the production after the first act closed, I lamented not being able to discuss the themes from an EP perspective with my students. That would have been fun. They would eat that stuff up. I miss my Thursday night "mating seminars." They were the liveliest discussions ever.

My new avatar

Interview with Marc Hauser

American Scientist interviewed cogntive primatologist Marc Hauser by e-mail about his new theory of "moral grammer."

"Can you describe what you mean by a moral grammar?"

[Hauser]: "The core idea is derived from the work in generative grammar that [MIT linguist Noam] Chomsky initiated in the 1950s and that the political philosopher John Rawls brought to life in a short section of his major treatise A Theory of Justice in 1971. In brief, I argue that we are endowed with a moral faculty that delivers judgments of right and wrong based on unconsciously operative and inaccessible principles of action. The theory posits a universal moral grammar, built into the brains of all humans. The grammar is..."

Read more.

The Gift of Language

One of the benefits of sticking around college (and specifically sitting in on a colleague's class) even though I'm not teaching this semester, is that I still get to have engaging conversations with bright students. These conversations truly are gifts. Oh man, it also reminds me of what I miss out on by not teaching. Well, I'll be back into it soon enough! That's what I remind myself in moments of doubt.

This morning's conversation evolved from a simple comment at the end of class about how the video shown in another class of Washoe, a sign language trained chimp, was not as impressive as the one I showed in class last year. Here I had to negotiate the murky territory of being this student's prof last year, sitting in a class as a 'student' with him, and hearing comments about my colleague and how he should have used some other (better) video.

First, I asked the student to defend his statement that the video I had shown was in fact more impressive. I simply responded, "Oh yeah? What part?" To which he gave a typical student response, "Oh uh, mmmm, the whole thing." He convinvingly displayed his enthusiasm for the video nonverbally.

We then proceeded to have a wonderful conversation that brought up some core issues in the evolution of thought on language evolution. I was even able to impart a bit of information that he found utterly fascinating. It was all so very rewarding, and just what I needed. I'm finally beginning to understand what Henry Gleitman meant when he told me "Research is your bread; Teaching is the cake."

I shared with this student that for me, what excited me the most was the scene where Sue (Savage-Rumbaugh) cooks alongside Kanzi in a kitchen. He follows her spoken directions to rinse off a knife, turn on the burner, and other actions involved in preparing a meal with such seemlessness that it appears he must for certain understand language. I added - "BUT my scientific mind remians critical off this. They could have gone through these motions so many times and is so well rehearsed that all Sue does is add labels to his actions."

I don't really believe this, because I have seen the results of many double blind tests that show definitively that Kanzi understands spoken language, can produce language with lexigrams, and shows evidence of understanding syntax. He can tell the difference between "Pour the water into the Coke" and "Pour the Coke into the water" for example. But I wnated the student to think critically about the possibility that Kanzi has been conditioned to do what he does. Incidentally, the topic for the intro psych class was classical conditioning so we had a perfect prime for our discussion.

"Couldn't we say then that human language is learned conditioned associations?" He asked.

"Oh yes, indeed! You've just hit on one of the great debates of psychology," I said. "B.F. Skinner proposed that very idea in his book Verbal Behavior."

So then is it all learning? he ponders aloud. "Well that is the age-old debate," I add.

At this point we transitioned into a conversation about how one system of communication (human language, chimp gestures, dog signals, squirrels squeaks, etc) is not inherently superior to another and that really they all exist because they solved some problem or conferred advantages. I asked him to consider what language does for us that chimps miss out on - the ability to share information, talk about what's not present, and plan ahead. This gives us a tremendous advantage and may explain why humans took the evolutionary trajectory they did rather than go the direction chimps did.

Here the student asked a terrific question: "But why did we develop language and not chimps when it's so beneficial?" He adds, "And why does Kanzi have what he has; what does that say about bonobos?"

So I told him that Steven Pinker writes about this and his theory of language evolution in his book The Language Instinct. Pinker proposes that Language is the product of a freak genetic mutational accident. I even called it a gift.

At this point my student, who is now trying to wrap his head around the idea, asks or comments on something that prompts me to say:

"Ah! But yes there is - the FOXP2 gene."

I told him about how deficiencies in this area of genetic code are associated with deficiencies in language that mimic Broca's aphasia, a condition remarkable for the utter lack of patients' ability to produce syntactically correct sentences. They produce pure gibberish.

"Woah! Really?" he exclaims. "So we really are biochemical machines." He must have been picturing Descartes. "I already was already heading there but now I'm onboard" (or something like that) he mutters as he walks off in direction of science building...

Students like him make my day.

If you'd like to read some of my other thoughts on language, click here.

Welcome Statement

ScienceWoman provided me a perfect description of my blog:
"Field Notes From An Evolutionary Psychologist is written by Holly. She's got some great posts on aspects of evolutionary psychology, which I know nothing about but am finding totally fascinating. Plus she manages to find the science and the beauty in her everday life, with posts on seed gathering, bats and much more. Plus, she's an academic struggling to finish her PhD. Plus, she's a great writer. How much more do I need to say. Go. read. now."

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