Mate Choice and the Origin of Menopause

Mate Choice and the Origin of Menopause

Abstract

Human menopause is an unsolved evolutionary puzzle, and relationships among the factors that produced it remain understood poorly. Classic theory, involving a one-sex (female) model of human demography, suggests that genes imparting deleterious effects on post-reproductive survival will accumulate. Thus, a ‘death barrier’ should emerge beyond the maximum age for female reproduction. Under this scenario, few women would experience menopause (decreased fertility with continued survival) because few would survive much longer than they reproduced. However, no death barrier is observed in human populations. Subsequent theoretical research has shown that two-sex models, including male fertility at older ages, avoid the death barrier. Here we use a stochastic, two-sex computational model implemented by computer simulation to show how male mating preference for younger females could lead to the accumulation of mutations deleterious to female fertility and thus produce a menopausal period. Our model requires neither the initial assumption of a decline in older female fertility nor the effects of inclusive fitness through which older, non-reproducing women assist in the reproductive efforts of younger women. Our model helps to explain why such effects, observed in many societies, may be insufficient factors in elucidating the origin of menopause.

Author Summary

The origin and evolution of menopause is understood poorly and explanations remain contentious. Virtually ignored among explanations is the effect that mate choice can exert on an evolving population. We designed and used a computational model and computer simulation to show that male mating preference for younger females in humans could have led to the accumulation of mutations deleterious to female fertility and thereby produced menopause. Our model demonstrates for the first time that neither an assumption of pre-existing diminished fertility in older women nor a requirement of benefits derived from older, non-reproducing women assisting younger women in rearing children is necessary to explain the origin of menopause.



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Study blames men for menopause

Study blames men for menopause

    POSTED: 15 Jun 2013 7:44 AM
   
Men and their preference for younger female mates may have led to the phenomenon of menopause in women, according to a controversial study by Canadian researchers published this week.

WASHINGTON: Men and their preference for younger female mates may have led to the phenomenon of menopause in women, according to a controversial study by Canadian researchers published this week.

"If women were reproducing all along, and there were no preference against older women, women would be reproducing like men are for their whole lives," said evolutionary geneticist Rama Singh, a professor at McMaster University.

Singh said the conventional "grandmother theory," which holds that older women grow infertile so that they can assist the survival of their kin by helping to raise their children's offspring, did not make sense to him.

Instead of age leading to infertility, Singh theorised that the dwindling pool of male mates for older women - because many older men seek to mate with younger women - led to a lack of reproduction that gave rise to menopause.

His work, backed up by computer models, suggests that a male mating preference for younger females could have led to the accumulation of genetic mutations that would harm female fertility and bring on menopause.

The study was published on Thursday in the open-access, peer-reviewed journal PLOS Computational Biology.

But while the assertion raised many eyebrows, not all experts are convinced by Singh, who questioned why menopause appears to be mainly a human phenomenon.

"I cannot agree with the theory put forth," said Steven Goldstein, professor of obstetrics and gynaecology at New York University School of Medicine.

"There are other primates who do experience menopause, although life expectancy after menopause is extremely limited," said Goldstein, who was not involved in the research.

"The same was true of humans until roughly the 1850s. In 1850 the average age of menopause was 46 and life expectancy was 50, which more closely parallels that of chimpanzees or gorillas.

Rather, a more accurate explanation would be that scientific advances like water purification and antibiotics have led to much longer lives among humans, he said.

"The cessation of reproductive capabilities in higher primates has always come shortly before the life span ends. It is only the advances of modern society that have women living so very long," he told AFP.

- AFP/fl

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《爱情保卫战》拜金女重钱不重情

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Thoughts

奔小康 means to strive for a comfortable life.

Yes, I want to strive for a comfortable life.

How can I do it?


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Marriage Is Good for Physical and Mental Health, Study Finds

Marriage Is Good for Physical and Mental Health, Study Finds

ScienceDaily (Jan. 28, 2011) — The 'smug marrieds' may have good reason to feel pleased with themselves as experts now confirm that long-term committed relationships are good for mental and physical health and this benefit increases over time.

In an editorial published by student BMJ, David and John Gallacher from Cardiff University say that on average married people live longer. They say that women in committed relationships have better mental health, while men in committed relationships have better physical health, and they conclude that "on balance it probably is worth making the effort."

Men's physical health probably improves because of their partner's positive influence on their lifestyle and "the mental bonus for women may be due to a greater emphasis on the importance of the relationship," they write.

But the journey of true love does not always run smoothly, maintain the authors, pointing to evidence that relationships in adolescence are associated with increased adolescent depressive symptoms.

And not all relationships are good for you, they add, referring to evidence that single people have better mental health than those in strained relationships.

They also confirm that breaking up is hard to do, saying "exiting a relationship is distressing" and divorce can have a devastating impact on individuals. Having numerous partners is also linked with a risk of earlier death.

They conclude that while relationship failures can harm health this is not a reason to avoid them. A good relationship will improve both physical and mental health and perhaps the thing to do is to try to avoid a bad relationship rather than not getting into a relationship at all.

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Singapore may face brain drain of accountants

Singapore may face brain drain of accountants
By Jonathan Peeris | Posted: 08 November 2010 2009 hrs

	Photos 1 of 1 An accountant at work

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SINGAPORE : As demand for accountants intensifies in line with robust economic growth in the region, some practitioners are concerned that better salaries abroad will lure sorely needed talent out of Singapore.

Practitioners brought up the issue at the Singapore Accountancy Convention last week.

According to Robert Walters 2010 Global Salary Survey, the average basic salary of a senior tax accountant in Singapore with six years of experience is around S$110,000 a year.

This compares poorly with Hong Kong where the same experience would fetch the accountant S$132,000.

If the same person were to move to Sydney, he could be looking at annual remuneration of S$162,000.

The pay difference exists partly because the hourly contract rate charged by accounting firms in these countries is higher than in Singapore.

Practitioners said the pay gap could prompt local accountancy graduates to look for better opportunities overseas.

"The concern there is that if you don't get it right, then what's going to happen is there will be a hollowing out of accountants; they will prefer to work overseas rather than work in Singapore and that will be a major concern," said Chaly Mah, chairman of Deloitte & Touche Singapore.

Such a brain drain could also affect Singapore's ability to be a global accounting hub.

"How are we able to attract talents into Singapore if we are not able to pay the rate for the accountants that a market like China, Hong Kong, Indonesia can afford to pay," questioned Ernest Kan, president of the Institute of Certified Public Accountants of Singapore (ICPAS).

Following the recommendations of the Committee to Develop the Accountancy Sector (CDAS), the industry here is currently undergoing a facelift. 

Practitioners hope that better service standards will mean better rates in the future. 

- CNA /ls

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NTU Graduating Class Of 2009

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1-in-3 Singapore professionals "happy" to take up contract work

1-in-3 Singapore professionals "happy" to take up contract work
By Hoe Yeen Nie, Channel NewsAsia | Posted: 22 April 2009 1946 hrs

SINGAPORE: A survey has shown that one in three professional workers in Singapore are happy to take on contract work, but this figure still falls short of the global average of one in two.

The web poll by recruitment consultant Robert Walters saw 4,288 respondents from 17 countries.

700 respondents were from Singapore; of which half said they would consider contract work only if permanent positions were not available. 17 per cent said they would not consider contract work at all.

Across the Asia Pacific, those from Australia and New Zealand were most open to the idea, with six in 10 responding favourably.

42 per cent of professionals in Hong Kong said they would be happy to take on contract work; an equal proportion would consider it if there were no permanent openings; while 16 per cent said no to contract work.

Robert Walters said the numbers reflected more realistic attitudes in the economic downturn.

- CNA/yt

Does this reflect changing of attitudes in the current situation? What do you think?

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'Afraid of graduating'

'Afraid of graduating'
Some who had nailed cushy bank jobs even before graduation get regret letters

By Estelle Low

Heard this? You are fired even before you are hired.

For final-year economics student J. Lim, this was not funny - she was 'retrenched' even before she started work.

The National University of Singapore (NUS) student was overjoyed when, in September last year, an American bank wrote to say she would be hired as an investment banking officer when she graduates in July this year.

Ms Lim, 23, even made plans to use her first pay cheque for a holiday in Europe. But in December, another letter arrived. 'The letter stated that the bank was freezing its headcount and thus had to withdraw its job offer,' she said.

The Sunday Times learnt that at least three other yet-to-graduate university students share her plight. The cushy bank jobs they thought they had nailed after their internships did not materialise.

After reading this piece of article, the situation is quite not so rosy now.

What are your views?


-http://www.straitstimes.com/Breaking%2BNews/Singapore/Story/STIStory_338660.html

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