Scientists debate the riddle of monogamy

Updated: 2013-08-18 07:51

By Carl Zimmer(The New York Times)

  Print Mail Large Medium  Small

"Monogamy is a problem," said Dieter Lukas of the University of Cambridge.

In 9 percent of all mammal species, males and females will share a common territory for more than one breeding season, and in some cases bond for life. This is a problem - a scientific one - because male mammals could theoretically have more offspring by giving up on monogamy and mating with lots of females.

In a new study, Dr. Lukas and his colleague Tim Clutton-Brock suggest that monogamy evolves when females spread out, making it hard for a male to travel around and fend off competing males.

Kit Opie of University College London and his colleagues published a similar study on primates, which are especially monogamous - males and females bond in over a quarter of primate species. The London scientists came to a different conclusion: that the threat of infanticide leads males to stick with only one female, protecting her from other males.

What does this say about men and women?

Scientists debate the riddle of monogamy

"The human mating system is extremely flexible," Bernard Chapais of the University of Montreal wrote in a recent review in Evolutionary Anthropology. Only 17 percent of human cultures are strictly monogamous. The vast majority of human societies embrace a mix of marriage types, with some people practicing monogamy and others polygamy.

There are even some societies where a woman may marry several men. And some men and women have secret relationships that last for years while they're married to other people, a kind of dual monogamy. Same-sex marriages acknowledge commitments that in many cases existed long before they won legal recognition.

Each species faces its own special challenges - the climate where it lives, or the food it depends on, or the predators that stalk it - and certain conditions may favor monogamy despite its drawbacks. One source of clues to the origin of human mating lies in our closest relatives, chimpanzees and bonobos. They live in large groups where the females mate with lots of males when they're ovulating. Male chimpanzees will fight with each other for the chance to mate, and they've evolved to produce extra sperm to increase their chances that they get to father a female's young.

Our own ancestors split off from the ancestors of chimpanzees about seven million years ago. Fossils may offer us some clues to how our mating systems evolved after that parting of ways. The hormone levels that course through monogamous primates are different from those of other species, possibly because the males aren't in constant battle for females.

That difference in hormones influences how primates grow in some remarkable ways. For example, the ratio of their finger lengths is different.

In 2011, Emma Nelson of the University of Liverpool and her colleagues looked at the finger bones of ancient hominid fossils. From what they found, they concluded that hominids 4.4 million years ago mated with many females. By about 3.5 million years ago, however, the finger-length ratio indicated that hominids had shifted more toward monogamy.

Our lineage never evolved to be strictly monogamous. But even in polygamous relationships, individual men and women formed long-term bonds - a far cry from the arrangement in chimpanzees.

While the two new studies disagree about the force driving the evolution of monogamy, they do agree on something important. "Once monogamy has evolved, then male care is far more likely," Dr. Opie said.

Once a monogamous primate father starts to stick around, he has the opportunity to raise the odds that his offspring will survive. He can carry them, groom their fur and protect them from attacks.

In our own lineage, however, fathers went further. They had evolved the ability to hunt and scavenge meat, and they were supplying some of that food to their children. "They may have gone beyond what is normal for monogamous primates," said Dr. Opie.

The extra supply of protein and calories that human children started to receive is widely considered a watershed moment in our evolution. It could explain why we have brains far bigger than other mammals.

Brains are hungry organs, demanding 20 times more calories than a similar piece of muscle. Only with a steady supply of energy-rich meat, Dr. Opie suggests, were we able to evolve big brains - and all the mental capacities that come with it.

Because of monogamy, Dr. Opie said, "This could be how humans were able to push through a ceiling in terms of brain size."

The New York Times

(China Daily 08/18/2013 page11)

主站蜘蛛池模板: 免费看片aⅴ免费大片| 国产精品高清一区二区三区不卡| 五月婷婷丁香六月| 男女性潮高清免费网站| 国产在线国偷精品免费看| 亚洲加勒比在线| 精品国产乱码久久久久久1区2区| 国产日韩一区二区三区在线观看| A级国产乱理伦片| 我与白丝同桌的故事h文| 亚洲xxxxx| 热99re久久国超精品首页| 国产xvideos在线观看| 亚洲国产91在线| 在线视频你懂的国产福利| 中文字幕の友人北条麻妃| 日韩在线视频导航| 亚洲成av人片在线观看无码| 精品一区二区三区免费毛片爱| 国产精品特级露脸AV毛片| 一级做性色a爰片久久毛片| 日本高清护士xxxxx| 亚洲另类欧美综合久久图片区| 男女性潮高清免费网站| 国产99久久久国产精品~~牛| 99国内精品久久久久久久| 成年视频在线播放| 久久精品国产亚洲av麻豆| 欧美性猛交xxxx乱大交丰满| 人妻大战黑人白浆狂泄| 精品欧美小视频在线观看| 国产亚洲欧美一区二区三区| 欧美性另类高清极品| 很黄很黄的网站免费的| 久久婷婷五月综合尤物色国产| 欧美大香a蕉免费| 亚洲综合区小说区激情区| 香蕉免费看一区二区三区| 国产精品真实对白精彩久久| mm131美女爱做视频在线看| 成人区人妻精品一区二区不卡视频|