Monogamy is not natural — hardly any species practice it, except for birds. Social monogamy wherein two creatures mate and work together to meet their needs is especially uncommon among nonavian warm-bloods; only about 5% of the 4,000 mammal species are monogamous. Since mating with one female at a time lowers a male’s chances of producing as many offspring as possible, what good, evolutionarily speaking, can come of monogamy? Why would mammals be monogamous?
One reason, according to a report in the Proceedings of the National Academy of Sciences (PNAS), suggests that males stayed with one female to ensure their young were not killed by another male, but survived to reproduce to carry on their genetic lineage. Based on breeding and parenting behaviors of 230 primate species over several generations, the researchers determined that males balanced the need to spread their gene pool against the need to protect their young from being killed. The attacking males needed to kill the young so they could breed with its mother, who would delay conception of another offspring if she were nursing. So the father hung around to protect his genetic line and help raise the young so the mother could reproduce again sooner. “This is the first time that theories for evolution of monogamy have been systematically tested, conclusively showing that infanticide is the driver of monogamy,” trumpeted Christopher Opie, a researcher in anthropology. “This brings to a close the long-running debate about the origin of monogamy in primates.”
Well, not so fast! Another study, published in the journal Science, used a similar analysis, but across a wider sample — about 2,500 mammal species. Those authors, Dieter Lukas and Tim Clutton-Brock, found no correlation between infanticide and monogamy. They suggested that monogamy is about location and supply. “Monogamy develops where females live at low density,” says Lukas. Males cannot fend off rival suitors from more than one female at a time because they’re too spread out. To ensure their young are the ones the female is carrying, they stick with one female. “It’s a consequence of resource defense.” This study notes that in monogamous mammalian species, the females tend to be solitary and intolerant of other females. Unlike those of ungulates, who are rarely monogamous, these mammals’ nutritional needs are greater, and they therefore shoo off competitors for food resources.
As for human monogamy, the PNAS study is more comfortable extrapolating its results. Because humans have big brains, their infants take longer to nurture and are vulnerable for longer. Therefore, human males needed to protect their child-rearing female until breeding was done. So how important were kids in man’s move towards monogamy? It’s a fascinating fight, but ultimately, whether monogamy is natural is less relevant than whether it’s desirable. Human monogamy seems to be both an acquired taste and a social necessity. The question remains whether it’s worth the cost of learning it.
P2:
一个原因:
PNAS的报告:与female在一起的male保证他们的年轻孩子不被其他male杀死,以延续基金。
基于230中主要品种抚育和父母的表现,研究者觉得males平衡了基因池对抗需要保护年轻后代被杀死的传播的需求。进攻的males需要杀死年轻的后代,以此breed他的母亲。所以父亲在周边保护基因链,帮助抚育子嗣,母亲还能再很快生育。
这是evolution of monogamy理论首次被系统的测试,结果显示出infanticide是monogamy的驱动。
P3:
另一个研究:(反驳前一个原因)
Science杂志:用相似的分析方式,但是用了更大的样本(2500种物种)。
Dieter Lukas and Tim Clutton-Brock:infanticide和monogamy没有关联,而是location and supply影响的。
-Monogamy在females低密度的地方产生。这是资源斗争的结果。
females会对其他females不可忍耐,不像rarely monogamous的物种,这种哺乳动物的营养需求更大,所以与竞争者竞争食物资源。
引出问题(为什么有哺乳动物会一夫一妻):一夫一妻制是违反动物天性的,减少繁衍率。
原因1:PNAS认为ensure the survival of their babies. CO :still long-running debate
原因2:DL TC repute reason1,suggest:location and supply of low density.(resource defense)
人类一夫一妻:protect childing-rearing female. Author:more desirable.
Monogamy - uncommon due to decrease offspring
Why?
1.Ensure their young were not killed>> survived to carry gene
- balanced spread vs protection
Kill young to breed with mother >> father to protect >> mother reproduce sooner
2.Wdier sample: no connection b/w infanticide and monogamy >> location + supply
- females live at low density, too many suitors
>> to ensure female only care about his own child
Resources defense: females intolerant of other females
Ungulates >> nutritional needs great >> fight for resources
Human: take longer so need to protect children
Questions remain