“NBC News, CBS News, BBC, CBC online, CBC News Now, The Guardian, The Los Angeles Times, The Telegraph, The Daily Mail, Fox News, U.S. News and World Report, Global News, The Scientist, New York Daily News, Salon.com, MSN UK, MSN New Zealand, Discovery News, Cosmopolitan, The Globe and Mail, The National Post, The Toronto Star, The Vancouver Province, The Hamilton Spectator and many others reported on research by Rama Singh, Jonathan Stone and Richard Morton (all from Biology), proposing a new theory to explain the evolution of menopause, one that suggests it arose as the result of men preferring younger women over thousands of years.” – See more at: http://bit.ly/19YBZju
-Daily News (McMaster University, Jun 19, 2013)
Scientific literacy in contemporary societies is determined by scientific culture, public interest, and communication. Public passion for knowledge, new findings, and novel discoveries catalyzes media activities. While scientists increasingly have become interested in publicizing science and publishing popular books, media have played important roles in translating science from the field or laboratory to the public domain. Thus, scientists, media, and the public flanked by industry, business, and government define the consortium of producers, consumers, and sponsors of discovery.
Effective communication constitutes an important component in the scientific enterprise and sometimes good communication fails because scientists, media, and the public perform their roles inadequately. We recently published a paper on the origin of menopause (1), which received unexpected worldwide publicity. At the time of writing this review (one week after publication), the paper has received over 10000 hits. Media portrayals were hyperbolic and public misunderstanding rampant, so we were invited to write this review to ensure that our role, as scientists, was fulfilled. We also speculate on why menopause is an important research topic from a female health perspective.
A Novel Hypothesis for the Origin of Menopause
Menopause poses a challenge to evolutionary theory. As with other anthropophilic traits (e.g., communication, consciousness), menopause might be observed in other organisms, but it is found in its most-pronounced condition in humans. Classic Darwinian natural selection operates to effect intergenerational change in traits that affect individual survival and reproduction. For humans, this amounts to averting death, a unique event in an individual’s life, and striving for sex, which hopefully comes a little more frequently. Menopause seemingly imparts a negative impact on these two fitness measures. Neo-Darwinian processes such as mutation and biased mating also seem impotent as explanatory principles. These impotencies, however, were revealed as only apparent in our paper: a simple hypothesis combined with a computational model demonstrated that mutation accumulation enabled by a change in reproductive behaviour is sufficient to establish diminished fertility with continued survival in one sex.
Formally, the hypothesis states that a switch to mating involving males and exclusively young females is sufficient to evolve menopause. The change in mating relaxes selection on older women; thereafter, any mutations that decrease female fertility at advanced ages become effectively neutral and can accumulate over time; eventually, menopause is established. Longevity is maintained by selection operating on men, eliminating mutations that decrease survival and male fertility at advanced ages (ironically, the paper was published online immediately preceding Father’s Day weekend in most of the countries in which it is celebrated).
Media Reception
Communication and advertisement differ in degrees, in accuracy and expected gains (e.g., recognition, financial) terms. Paper titles used to suggest only a general research field (e.g., genetics, development, physiology, evolution, ecology), and one learned specific details about a study only by reading the abstract or summary. This was followed by a tradition in which titles comprised two levels, a main heading, to indicate a general research field, followed by a subheading, to provide details about a study. The fashion currently is to advertise the main finding directly in the title, itself. This is a most-effective way to attract attention, faced with ever-increasing competition in publication space.
Whereas we conservatively titled our paper (“Mate choice and the origin of menopause”), we were intrigued sufficiently with the idea that a change in mating could produce menopause that we succumbed to temptation and issued as our press release a dramatic interpretation: “Researchers determine that menopause is caused by – wait for it – men.” We had no idea that this would be portrayed as if contemporary men were responsible for menopause – naïvité.
Portrayal & Coverage – While the statement, itself, presented accurately our notion for a plausible ultimate cause, media portrayal, especially in traditional (e.g., news agencies and radio and television broadcasts) and social media outlets was exaggerated. Some traditional outlets exercised creative license, turning-out tantalizing titles to titillate client attention (e.g., “‘Cradle snatchers’ cause menopause, says biologist”), accompanying pieces with images depicting older celebrity males with their much younger wives and even younger children. The story went viral. We refer to the epidemic-meme spread in this case as the ‘Larry King effect’ (e.g., one outlet used as its subtitle “Prof Rama Singh warns that Michael Douglas and Rod Stewart wannabes have stacked the Darwinian deck of cards against older women remaining fertile;” another included a King family image). Other, more-traditional outlets adopted a more-conservative approach (e.g., “Men ‘to blame for the menopause’”). Given that such ‘spins’ were turned-out without an evolutionary context for interpretation, any meaningful scientific message was bound to be misinterpreted. Once this spin had been spun, outlets picking-up wire service stories perpetuated the hype, and coverage became pandemic. We remark that we, too, played a role in perpetrating the Larry King effect; the short title that appears on alternate pages in our paper, “Putting the Men in Menopause,” can be interpreted as only slightly less misleading, equally in jeopardy to be misrepresented by the public. The research was the top health story on Google News from the Friday through the Sunday immediately following publication. We were inundated with requests for interviews on radio and television and via email and Skype. Most reporters demonstrated understanding the research in their summaries. But evolution is a subtle game…
Solicited Comments – We were impressed and surprised by comments that were solicited from researchers. Some, evolutionary biologists, were familiar with the topic and challenged the main idea that mating behavior could produce menopause (or at least its spin, as they would have had insufficient time to have perused the paper), offering specific, competing, alternative explanations like the reproduction-cost, reproduction-conflict, mother, and grandmother hypotheses, often in combinations. Others, clinical researchers, were more familiar with topics that relate to the hypothesis only as Larry King effects and (also without having had time to have read the paper) described the research using terms like balderdash, unable to appreciate that a change in reproductive behavior, like a male preference for younger females, could manifest its effects physiologically. At least one reporter dismissed the research outright on the basis that computation provides a completely impotent approach for understanding evolution – identifying unknown viruses, as in the SARS epidemic (as just one example) aside.
Public Reception
Email and Social Media – Some public comments were more-extreme than were the media portrayals! One reader sent an email message directly to one author, casting us all as feminists, presumably intended in a negative, derogatory manner, and castigating us for blaming men for menopause (other, more-personal accusations will be treasured privately by the authors). Interestingly, the same reference was offered in a positive, complimentary manner via social media, like facebook. Another asked how sexually active a women has to be to avoid menopause. One sent an email message declaring that the research constituted nothing more than wasted funding (softened later, respectfully, by a follow-up email message, presumably after the author had had an opportunity to read the paper, apologizing for the “ignorant tone” of the previous email message). Another sent an email message suggesting that the research amounted to nothing more than an attempt at ‘headline grabbing.’
Online Comments – Among public reaction in comments to online articles, some were informed, just enough to temper more-extreme comments – perhaps popular books are being read! The most-popular explanation for menopause – the one referred to with greatest frequency in comments following online articles – is the grandmother hypothesis, according to which older females increase their inclusive fitness by helping to raise grandchildren rather than producing and raising their own. The next-most-popular explanation – referred to with the next-greatest frequency – is the extended longevity hypothesis, according to which older females experience decreased fertility because individuals live longer in modern human populations than in ancient ones.
Remarks and Speculation
The ignorance about evolution, especially the time periods over and mechanics by which natural selection can operate to effect change, is widespread. In addition to our interactions with media and the public, we were contacted personally by people from a variety of backgrounds and vocations. All had their own ideas for why menopause originated. None among them – none – considered time on a macroscopic scale or mutations as having anything to do with menopause. This is shocking, especially when most comments were offered by people with university education.
We raise three points for concern: (1) lacking knowledge about evolution to deal with health and other life-history issues; (2) medical professionals considering human bodies as objects without any regard to their being produced by evolution; and (3) gender and health and how gender relationships transform into an inter-dependent, major, life history factor – impacting the health of one gender through the other.
Health is a primary concern for many ‘modern’ societies, probably the most important concern after food for more-traditional societies. Public awareness on progress in molecular biology and genetics and concerns about antibiotic resistance and genetically-modified, pesticide-contaminated, and hormone-infused food has attracted public attention. These issues relate to fear from mutation (e.g., cancer and other diseases). But people exercise very little interest in understanding how organisms respond to environmental challenges and, generally, most students, biologists included, avoid taking a course in evolution at university.
Premedical students in Canada in the recent past could enter medical school without ever having taken a course in genetics. That situation has changed, but practicing doctors pay little attention to evolutionary principles in practicing health science. Anecdotally, a reporter mentioned to one author that a gynecologist friend considered the hypothesis as nonsense, that menopause occurs because women deplete their egg supply (the follicular depletion hypothesis, which data seem to falsify). Confusing effects with causes is a major problem in health disciplines.
Menopause is a major health issue for women. Presently, little more can be done than treating symptoms. However, as a result of changing demographics and later reproduction, menopause is becoming a serious concern to women between 30 and 40 years age. They have a very narrow time period for reproduction. If menopause could be delayed by medical intervention, that time period could be expanded. Menopause is starting to become a priority health concern. For women, menopause may be a matter of life and death; for families and society, it also is a matter of reproductive and population health.
Lacking understanding about evolution was the single most important factor limiting our ability to communicate with the public as well as health professionals. We will suffer – personally in individual health and as a society in environmental health – if we fail to impart education about evolution and how it can inform us on how to deal with health issues.
Reference
(1) Morton RA, Stone JR, Singh RS (2013) Mate Choice and the Origin of Menopause. PLoS Comput Biol 9(6): e1003092. doi:10.1371/journal.pcbi.1003092
Jonathan Stone and Rama Singh are professors of biology at McMaster University
“First, for the sake of computation, they assumed that females have infinite capacity for both fertility and survival.”
This assumption could only have been made by someone who has little appreciation for the toll pregnancy, lactation, and our ridiculously long period of childhood take on the human female. Menopause isn’t something bad that the wonders of science must do away with. It is an adaptation that prolongs female life past the age where direct reproduction would be dangerous. Pregnancy carries a non-trivial risk of death due to complications as we age.
If you want to know why women go through menopause, look at the energy costs associated with bearing and raising a human child. We are born as helpless fetuses that cannot even sit up much less walk or move around freely, as most mammals can. We require enormous parental investment in order to survive during the first decade of life, and don’t reach sexual maturity until well into our teens—unlike most mammals who mature within a few years.
This cost-benefit tradeoff favors the abrupt shift from direct fitness (having your own offspring) to indirect fitness (investing in your relatives’ offspring, particularly your own grandchildren). In other words, when you reach age 50, your genes benefit more if you invest your effort in assisting the reproduction of genetic relatives rather than risking yet another pregnancy or dying before your child reaches maturity.
But none of this would make sense to men who see reproduction only from a male viewpoint, and who reflexively believe that everything male must be better than anything female. So they suspect that somehow women got cheated out of the opportunity to remain fertile throughout our lifespans, and devise a simulation based on prejudice and naivete to prove that men’s choices determined female biology.
Models pretty much always begin with absurd simplifying assumptions. More realistic assumptions are then added to the basic model to see how they affect the outcome. This avoids making models unnecessarily complicated (you don’t add complications that don’t explain anything), and it aids in explaining a complex model to others.
The fact that this model proposes male mate choice as the origin of menopause is no evidence that it was devised out of prejudice and naivete (regarding naivete, the authors are clearly familiar with the hypotheses in Denise’s comment, which they list by name in this article). There is also a hypothesis that pair-bonding in humans originated from female mate choice. One might, with equal justification, say that this proposal exists only to “prove” that women’s choices determined male mating behavior.
Thanks for the lecture on how modeling is done, but having done modeling work myself (albeit in a different field), I really didn’t need it.
There are simplifying assumptions, there are unjustified assumptions, and then there are assumptions that defy evidence and logic. The assumption upon which this model is based falls into one or both of the latter categories.
I assume you are familiar with the fact that female choice looms large in evolutionary biology, and has an enormous impact on evolution of species. In fact, that is what a good deal of sexual selection is about. There are characteristics about human pair-bonding that are best explained in terms of female choice, such as the fact that our ovulation is not displayed but concealed. This throws a monkey wrench into a male mating strategy that focuses on mating only with estrus females in order to maximize reproductive success. It is difficult to do that if you can’t tell who’s ovulating. Also telling is the fact that human females are sexually receptive throughout their menstrual cycles, unlike many mammals. So any model or theory that begins with an assumption that female choice played a role in human evolution is probably on safe ground—as opposed to being motivated by a desire to “prove” that women’s choices matter.
This theory assumes males can choose partners based on age. Human age is not very cryptic. If human males showed a sexual preference for young human females, why wouldn’t that weaken selection against an age-related decline in fertility in women?
Don’t get me wrong. I find your explanation for menopause more compelling (although this isn’t my field of expertise, either). What confuses me is your belief that their theory is motivated by prejudice and naivete.
The naivete and prejudice that lurks under the surface of this research stems from vastly underestimating the amount of energy that is involved in human female reproduction and human parental investment.
I will say it again: Humans are born completely helpless and have protracted childhoods. Our brains do not mature until we are in our 20’s. The resource demands placed on parents by human infants and young children are enormous. So I find myself wondering why any theory would even consider discounting these facts by making assumptions such as “females have an infinite capacity for fertility and survival”.
Even in today’s first world countries, the issue of childcare demands on working women is a source of ongoing controversy and workplace revision. But given that, even in first world countries, men spend comparatively little time on child rearing than do women, it is not surprising that they spawn theories that so discount these demands. To put it colloquially, the underlying assumption is that child rearing is no more demanding than babysitting, so why bother to take it into account when the real issue is what men find attractive?
The idea that menopause is an adaptation to male mating preferences rather than an adaptation driven by the demands placed on human females by the energy costs of pregnancy, lactation, and child rearing simply pushes the bounds of credulity.
I understand now. I doubt the authors are totally ignorant of the costs of having children, but it’s true that the model ignores them (as well as female mate choice). They excluded everything other than male mate choice that could produce the same result. They wanted to know if male mate choice COULD produce the evolution of menopause, but they’re a long way from showing that it was even a minor factor in the actual evolution of menopause. Given the factors you’ve listed, I don’t think it was.
I guess I should also mention that when I heard Kristin Hawkes give a talk on the grandmother hypothesis at UC-Davis, one of the anthropologists in the audience made this comment: When she asked the women in the aboriginal group she studied “When do you stop having children”, the most common answer was when your eldest daughter has her first child. The time and energy commitment demanded by infants meant that grandmother’s input was needed to ensure the infant (and mother) survived.
Interesting. I hadn’t thought of the grandmother hypothesis being consciously implemented, but your story shows that it can be. I wonder of part of the difficulty in figuring out human evolution is that we ignore the power of humans to make fitness decisions consciously. What may be the optimum fitness strategy in most animals may be sub-optimal in humans, depending on how their society responds.
Good point. Some are already known. For example, in many societies, if a man dies, his wife’s brother is obligated to care for her children. The most common explanation is that of paternal uncertainty. The wife’s brother is certain that he shares genes with his nieces and nephews, the husband’s brother not so much.