Modern man found to be generally monogamous, moderately polygamous

Mar 02, 2010
Homo sapiens would usually have been monogamous

(PhysOrg.com) -- Did women and men contribute equally to the lineage of contemporary populations? Did our ancestors, Homo sapiens, lean more toward polygamy or monogamy? To answer these questions, Dr. Damian Labuda, an investigator at the Sainte-Justine University Hospital Research Center and a professor at the Department of Pediatrics of the Université de Montréal, headed a team that analyzed genomic data from three population samples of African, Asian and European origin. The study's findings are published in the most recent issue of the American Journal of Human Genetics.

Genetic Population History

In a strictly monogamous , one would expect to have an equal number of breeding females and males and, therefore, a breeding sex ratio of one female to one male. In a population where males tend to have more than one female mate, more females than males contribute to reproduction; for this reason the breeding ratio exceeds one. The authors of this study estimate that the breeding ratio varies between 1.1 and 1.4 according to population: 1.1 in Asia, 1.3 in Europe and 1.4 in Africa.

Modern man or Homo sapiens would, therefore, usually have been monogamous while exhibiting tendencies toward polygamy over the course of evolutionary history. These findings are consistent with studies in evolutionary psychology and anthropology that depict contemporary human populations.

An innovative method of analysis

To estimate the breeding sex ratio based on genomic data, the authors developed a novel method to capitalize on how females carry two X chromosomes, whereas males carry only one. Consequently, during the recombination process, X chromosomes can only exchange their genetic information with females.

An excess of breeding women causes an excess of recombination signals in terms of quantifiable X chromosomes. This new method is more reliable than the previous approaches that quantified the breeding ratio using another method. It may be applied to any species for which data on genomic diversity are available.

"Our results allow better understanding of the genetic population structure and demonstrate once more the importance of population genomics in genetic epidemiology. Being able to analyze the female-male ratio in the history of humans provides new insights into the evolution of our species, which, in turn, leads to better understanding of ourselves through the knowledge of our past," says Dr. Labuda.

Explore further: Study shows how epigenetic memory is passed across generations

More information: The article, "Female to male breeding ratio in modern humans - an analysis based on historical recombinations," published in the American Journal of Human Genetics, was authored by Damian Labuda, Jean-François Lefebvre, Philippe Nadeau and Marie-Hélčne Roy-Gagnon, Sainte-Justine University Hospital Research Center and the Université of Montréal. eproof.dartmouthjournals.com/p… jhg0577_r_sdjte1.pdf

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User comments : 12

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marjon
1 / 5 (1) Mar 02, 2010
Polygamists have rights, too.
JayK
1 / 5 (3) Mar 02, 2010
What does that have to do with the article, troll?
bottomlesssoul
not rated yet Mar 02, 2010
I wonder what the influence of monogamy / polygamy is for genetic transfer through a species, does it speed it up? slow it down? no effect?
KB6
not rated yet Mar 03, 2010
I think that monogamy would slow it down a lot. All the time that monogamous males spend devoted to pregnant females is time they could be spending spreading their genes around to a bunch of other females.
TheBigYin
Mar 03, 2010
This comment has been removed by a moderator.
Yellowdart
not rated yet Mar 03, 2010
Wasnt there an article last week based on the opposite? That men were mostly "polygamous"...
gwargh
4 / 5 (2) Mar 03, 2010
I think that monogamy would slow it down a lot. All the time that monogamous males spend devoted to pregnant females is time they could be spending spreading their genes around to a bunch of other females.

...Who, at an equally male/female population would probably already be pregnant. Since pregnancy in humans is 9 months, monogamy actually increases survivability of children. Polygamy only helps one individual spread his genes around more, it does not increase overall gene variability in the population. Monogamy means many different genes are being conserved, so it is more effective at increasing gene variation.
JayK
1 / 5 (2) Mar 03, 2010
I'd have to see a citation that monogamy increases the survivability of children versus polygamy, qwargh. That doesn't quite sound correct.

Looking at your statement from a moral superiority angle, I'd definitely wonder if that wasn't an opinion influenced by religious moral boundaries.

http://links.jsto...0.CO;2-L

That citation notes that the split in primates is about 50-50 monogamous/polygamous with parental care.
KB6
5 / 5 (1) Mar 03, 2010
gwargh, I wasn't considering the conservation of genetic diversity; I was considering the most effective strategy for spreading the genes of an individual throughout a population. At least that's how I interpreted bottomlesssoul's original question about "genetic transfer through a species...". But it is true that sheer reproductive rate is not the measure of evolutionary success; it's how many of your offspring survive. Otherwise evolution would be a straight line to reproduction as frequently and as profligately as possible for all organisms.
TheBigYin: Unfortunately, I can assure you that life at my house is not nearly as genetically diverse or evolutionarily dynamic as my comment may have led you to believe. ;)
Skeptic_Heretic
not rated yet Mar 04, 2010
I'd have to see a citation that monogamy increases the survivability of children versus polygamy, qwargh. That doesn't quite sound correct.

I'd definitely wonder if that wasn't an opinion influenced by religious moral boundaries.

I don't think it's influenced by morals or religion. With fewer offspring you spend more resources on each ensuring higher chances of your genes' survival.

The real measure would be in which method has greater success? Having many children to increase your genetic line's chances or having fewer children and providing more for them.

Seeing as human gestation is a large percentage of a female human's fertile years when compared to other species one would think that females are more tuned to monogamy. Whilst species with shorter gestation to fertility ratios tend to reproduce at a higher rate.

Within your example, among primates,what are the demographics of the social groups for each in regards to sex? Harem cultures promote polygamy.
bottomlesssoul
not rated yet Mar 07, 2010
@KB6 I was considering survival of the species, not survival of an individual. Firstly polygamy does not imply reduced resources for offspring. I know many more monogamous men who have abandoned their offspring then I know of polygamous men abandoning children. Of course true polygamy is rarer. But I don't immediately see it as obvious. In fact the woman has more to loose if her mate selection abandons rearing so she has a great deal to say in the decision making.

I wonder if there isn't some ideal mixing ratio where lower than this, the gene pool complexity decreases and higher than this it becomes too socially complex to manage, the groups break up and the offspring die.

The goal being maximum mixing of genes with maximum survival of offspring.
bottomlesssoul
not rated yet Mar 07, 2010
@Skeptic_Heretic
Harem cultures promote polygamy.
Harem is Arabic for private place. It was the home with in the home of royalty, the palace which was a busy place. It's actually not a cultural phenomena of Arabs but rather a cultural phenomena of royal life around the world.

Oh, and Arab culture also promotes polygamy but only if the father can support all the wives and children. But that's just a coincidence with your claim. :-)
KB6
not rated yet Mar 07, 2010
@bottomlesssoul

I wonder if there isn't some ideal mixing ratio where lower than this, the gene pool complexity decreases and higher than this it becomes too socially complex to manage, the groups break up and the offspring die.


That may be what the study found. The benefits and drawbacks of both polygamy and monogamy tend to reach an equilibrium. Look at the way humans, as a group, *behave* today. You see primarily monogamy, but with a certain smaller percentage of polygamy. All the study found was that things haven't changed that much through most of human history. It's like population genetics dictates and culture follows, at least in regard to mating habits.