Navigation Links
Polygamy hurt 19th century Mormon wives' evolutionary fitness

BLOOMINGTON, Ind. -- Polygamy practiced by some 19th century Mormon men had the curious effect of suppressing the overall offspring numbers of Mormon women in plural marriages, say scientists from Indiana University Bloomington and three other institutions in the March 2011 issue of Evolution and Human Behavior.

Simply put, the more sister-wives a Mormon woman had, the fewer children she was likely to produce.

"Although it's great in terms of number of children for successful males to have harems, the data show that for every new woman added to a male's household, the number each wife produced goes down by one child or so," said IU Bloomington evolutionary biologist Michael Wade, whose theoretical work guided the study. "This regression is known as a 'Bateman gradient,' named after the geneticist who first observed a similar phenomenon in fruit flies."

The paper's coauthors were Jeffrey Moorad (Duke University, Indiana University Ph.D. 2005), Daniel Promislow (University of Georgia), and Ken Smith (University of Utah).

The researchers' survey of birth, marriage and death records from the Utah Population Database covers nearly 186,000 Utah adults and their 630,000 children who lived or died between 1830 and 1894. This period marked an important transition for the nascent Mormon Church, as polygamy began to be phased out in deference to U.S. laws banning the practice but also via internal pressure from the Mormons themselves.

The scientists' study confirmed their expectation that a moratorium on Mormon polygamy would have the effect of decreasing the intensity of sexual selection among males and ultimately bringing the strength of reproductive selection on men closer to that acting on women. With fewer polygamous marriages, more males had access to wives, which led to a decrease in the variation in Mormon males' mating and reproductive success. The scientists estimate that ending polygamy reduced the strength of sexual selection on males by 58 percent.

"This study was very exciting for us, in large part because you just don't get to see the demographic effects of dramatically changing a mating system within a single population -- in any organism," Wade said. "It's an added bonus that this change from polygamy to monogamy just happened to involve people who kept such thorough records of the marriages, births and deaths at that time."

Wade, who specializes in the evolutionary biology of mating systems, says much of his work has elucidated and expanded on the ideas of Angus Bateman. Bateman, a prolific theorist, was unable to empirically test all his theories about mating and mating fitness before he died in 1996. Last year Wade and Northern Arizona University biologist Stephen Shuster co-wrote a retrospective on a classic paper Bateman wrote for the journal Heredity in 1948. Wade and Shuster extolled Bateman's vision, in particular the way in which Bateman thought sexual selection should be quantified. Bateman's critics thought his reductions of biology were too simplistic, yet Wade says Bateman's simple formulas are often dead-on.

"Bateman's ideas still are very much alive, the present study included," Wade said. "It was also his idea that selection could be stronger on males than on females, that what can be an advantage to males can be a disadvantage to females of the same species. And the advantage isn't just in having more mates. You may simply produce more offspring, than the average, if you're a male successful in reproductive competition against other males."

Which isn't to say systems of polygamy in humans or elsewhere in nature are necessarily good for all the males involved. Indeed, Wade says, polygamy is a bad thing for most males of a species.

"When the ratio of sexes is about equal, for every male that has three mates, there must be two males that have none," Wade said. "If a male has even more mates, then the disparity among male 'reproductive' haves and have-nots can become quite great."

So if polygamy (or the female equivalent, polyandry) is disadvantageous to most of the sequestered sex and most of the mate-sequestering sex, why should such systems survive?

"The complete answer is still forthcoming," Wade said. "One thing we know now, based on rigorous studies in many species, particularly the fruit fly, is that selection can be so strong on males that it can drag the entire species off of a naturally selected viability optimum."

Wade points to a familiar example.

"Take the peacock," Wade said. "Its tail is magnificent for attracting females and bad for attracting predators. It is believed that in some situations there is a "predator hard cap" on the fitness of sexual characteristics. But there's also research suggesting even the predator hard cap can be overpowered if sexual selection on males is strong enough. That is, males trade high risks to their lives in order to gain large numbers of mates and thereby offspring."


Contact: David Bricker
Indiana University

Related medicine news :

1. Famed neurosurgeons century-old notes reveal modern style admission of medical error
2. Social class and changes in mortality from liver cirrhosis over the 20th Century
3. EcoFocus Study Identifies Opportunities for Companies to Target the New 21st Century Mom
4. Alzheimers Costs Could Explode by Mid-Century
5. Team outlines 21st century roadmap to make America the healthiest nation in the world
6. A century-old puzzle comes together: Scientists ID potential protein trigger in lung disease sarcoidosis
7. 21st Century Leadership: New Book Shows Why it's Different and How it Can Transform People and Organizations
8. American Human Development Project Releases 'A Century Apart,' Revealing Alarming Disparities in Well-Being Among U.S. Racial and Ethnic Groups
9. The Practical Visionary Offers Eight Keys to Surviving and Thriving in the 21st Century
10. Go Beyond Retro to Discover the World of 20th Century Fashion!
11. Director of top 10 nurse midwifery program inducted into the American College of Nurse Midwives
Post Your Comments:
Related Image:
Polygamy hurt 19th century Mormon wives' evolutionary fitness
(Date:11/27/2015)... (PRWEB) , ... November 28, 2015 , ... There is ... we outperform our billings from last year? , This question has not been an ... are coming to the retirement age and the younger workforce don’t share the same ...
(Date:11/27/2015)... ... November 27, 2015 , ... According to an article ... of Toronto and the University of British Columbia suggested that laws requiring bicyclists to ... article explains that part of the reason for the controversial conclusion is that, while ...
(Date:11/27/2015)... ... ... The rapid speed at which Americans are aging is ... needed, especially with Alzheimer’s, dementia and other cognitive conditions becoming more prevalent. Health ... of this equation: 80 percent of medical care occurs in the home, by ...
(Date:11/27/2015)... ... 27, 2015 , ... An inventor, from Hopkinsville, Ky., thought ... at home, so he invented the patent-pending ELECTRONIC M.D. , The ELECTRONIC M.D. ... doing so, it could help to prevent potential overdose situations. As a result, ...
(Date:11/27/2015)... Orange County, CA (PRWEB) , ... November 27, 2015 , ... ... holiday season , The company is offering customers 10% off of their purchase of ... purchase any treatment at full price. According to a company spokesperson. “Finding lice is ...
Breaking Medicine News(10 mins):
(Date:11/27/2015)... , Niederlande, November 27, 2015 ... fotodynamischer Bremachlorin-Therapie bei fortgeschrittenem Krebs.   --> ... Bremachlorin-Therapie bei fortgeschrittenem Krebs.   --> ... Bremachlorin-Therapie bei fortgeschrittenem Krebs.   Clinical ... --> Clinical Cancer Research vom ...
(Date:11/26/2015)... 26, 2015 Un nuevo enfoque ... para el cáncer avanzado.   --> ... fotodinámica de Bremachlorin para el cáncer avanzado.   ... inmunoterapia con la terapia fotodinámica de Bremachlorin para el ... . --> Clinical Cancer Research . ...
(Date:11/26/2015)... , Nov. 26, 2015 Research and Markets ... "Asia Pacific Cardiac Pacemaker Market Outlook to 2019 - Rise ... the Demand " report to their offering. ... --> Boston scientific and others. ... players including Medtronic, Biotronik, Boston scientific ...
Breaking Medicine Technology: