Too Many Males: A Fast Lane to Extinction?
<FONT color=#0008ff><STRONG>摘要：</STRONG> <BR>    挪威生物学家的一份最新研究结果显示，如果一个物种中，雄性个体的数量过多，将会导致雌性个体受到更多的性侵犯，最终这一物种还可能因此而走向灭绝。 <BR>    A new study suggests that having too many males of one species could lead to more sexual aggression toward females and ultimately the extinction of the species.</FONT><FONT color=#840084> </FONT>
<FONT color=#840084>    </FONT>挪威生物学家的一份最新研究结果显示，如果一个物种中，雄性个体的数量过多，将会导致雌性个体受到更多的性侵犯，最终这一物种还可能因此而走向灭绝。
    据美国《国家地理》杂志日前报道，大多数生物学家认为，在一个物种中，性别比例会基本保持稳定。因为个体间的竞争甚至可以消除任何性别比例上出现的偏差。然而，这项新的研究成果却对这一生物学的基本理论提出了挑战。挪威科学家研究发现，雄性数量过多将导致种群内个体数量直线下降。他们是通过研究蜥蜴得出此结论的。
    为研究动物如何对其性别比例偏差做出反应，挪威科学家们对两组普通的蜥蜴进行了监控。两个蜥蜴种群中，个体的性别比例都被设定为有很大的偏差。其中一个种群中有四分之三的雄性蜥蜴，另一个种群有四分之三雌性蜥蜴。这些蜥蜴被安置在围栏中，上方还设有保护网，以防止外界（鸟类捕杀）对它们数量的影响。
    1年之后，研究人员们看到了惊人的结果。雌性蜥蜴占大多数的种群中，蜥蜴数量从73只增长到了118只；而在雄性蜥蜴占大多数的种群中，蜥蜴数量减少到了只有区区35只。另外，原本雄性就偏多的这个种群，其性别比例甚至发展得更为极端。研究人员发现，这个种群中的雌性蜥蜴更容易死亡，而且它们的繁殖能力也呈现出下降的趋势。这些雌性蜥蜴平均只能产3或4只后代，而在通常情况下，应该产5只小蜥蜴。与此同时，这一种群中的雌性蜥蜴在雄性试图与之交配时，更容易受到身体上的伤害。而在雌性蜥蜴占大多数的种群中，这种现象就会少很多。
    对此，研究人员表示，雌性蜥蜴可能是由于雄性蜥蜴富有侵略性的交配行为对其产生了巨大的压力而死亡的。这项研究的负责人、挪威奥斯陆大学的生物学家加里阿德表示，“（这一研究）证明了有关种群灭绝的一个新奇而重要的行为因素：由于雄性个体数量过多，其对异性的性侵犯也随之加剧。”他说，雄性数量过多，雌性个体的生存及繁殖能力都受到了巨大的负面影响，而这将把整个物种推向灭绝的快车道。
    研究人员表示，从蜥蜴身上得到资料信息甚至可能同样适用于人类。在韩国和印度等国家，男性数量大大超过了女性，而这种现象的出现主要是由于当地人通常较偏爱男孩的缘故。
    也有科学家认为，人类性别比例在出现偏差时，会自行重新恢复平衡。因为，群体中女性数量的不足将让人们给予女孩子更大的价值，而这将使人们偏爱男孩的现象有所下降。然而，这项研究也同时指出，男性的侵犯行为以及男性之间对女性竞争的加剧，可能会导致女性对婚姻的不满意，并最终导致人口数量的降低。
    报道说，这一研究结果被发表在最近出版的新一期美国《美国国家科学院学报》上。
    （国际在线独家资讯 王高山）
本稿件为国际在线专稿，媒体转载请注明稿件来源和译者姓名。
英文见第二楼

  <FONT face=Arial color=#840084>  A new study suggests that having too many males of one species could lead to more sexual aggression toward females and ultimately the extinction of the species. </FONT>
<FONT face=Arial color=#840084>    Researchers studying lizards have shown that an excess of males will cause populations to plummet as the survival and fertility of female lizards drop dramatically. </FONT>
<FONT face=Arial color=#840084>    "[This study] is evidence for a novel and important behavioral factor of population extinction: male aggression toward females exacerbated by male population bias," said lead researcher Jean-Fran?ois Le Galliard, a biologist at the University of Oslo in Norway. </FONT>
<FONT face=Arial color=#840084>    The lizard data might even apply to human populations. Countries such as China, South Korea, and India have a significant excess of males in the population, mainly due to a preference for male babies. </FONT>
<FONT face=Arial color=#840084>    The study was reported yesterday in the journal Proceedings of the National Academy of Sciences. </FONT>
<FONT face=Arial color=#840084>    Most biologists have argued that sex ratios in a species are stable, because competition among the dominating sex will even out any deviations. </FONT>
<FONT face=Arial color=#840084>    The new research, however, challenges this basic tenet of biology. </FONT>
<FONT face=Arial color=#840084>    To study how animals respond to sex ratio bias in their population, the scientists monitored two groups of common lizards. The reptiles were kept in enclosures covered by nets to stop birds from munching the lizards. </FONT>
<FONT face=Arial color=#840084>    Each lizard population was skewed to either three-quarters male or three-quarters female. </FONT>
<FONT face=Arial color=#840084>    After a year, the group of mostly female lizards had grown from 73 to 118, while the population with excess males had declined to just 35. </FONT>
<FONT face=Arial color=#840084>    The mostly male population became even more skewed toward a male majority, as adult and yearling females in that group died four times more often and produced three or four offspring instead of the usual five. </FONT>
<FONT face=Arial color=#840084>    In addition, the females in the male-dominated group had two to three times as many scars and wounds inflicted by the males during mating attempts as females in the female-biased group. 　</FONT>
<FONT face=Arial color=#840084>    The researchers say the females may have died of stress caused by aggressive male copulation attempts. </FONT>
<FONT face=Arial color=#840084>    The findings suggest that male aggression puts the whole population on a fast lane to extinction. </FONT>
<FONT face=Arial color=#840084>    "This paper uses direct observations and population models to show that an increase in the fraction of adults who are male can actually grow over time," said Shripad Tuljapurkar, a population biology professor at Stanford University in Palo Alto, California. </FONT>
<FONT face=Arial color=#840084>    "As the male fraction continues to increase, females are subject to intense competition that reduces reproductive success, and the population can collapse," said Tuljapurkar, who was not involved with the research. </FONT>
<FONT face=Arial color=#840084>    Some rare species with skewed sex ratios may find it harder to recover if males show aggression to females. Researchers believe male aggression is, for example, a threat to population persistence in the Hawaiian monk seal, one of the most endangered seal species in the world. </FONT>
<FONT face=Arial color=#840084>    A more speculative connection is to sex ratios in humans. </FONT>
<FONT face=Arial color=#840084>    In China planned birth programs and selective abortion have caused rapid changes in the sex ratio at birth. Since the early 1980s, males have far outnumbered females among newborns in China. </FONT>
<FONT face=Arial color=#840084>    "Whether and how these populations will respond to increasingly male-biased sex ratios could depend on their ability to implement rules that protect females efficiently against sexual harassment," Le Galliard, the lead study author, said. </FONT>
<FONT face=Arial color=#840084>    Researchers have argued that the sex ratio will rebalance itself because of so-called competitive feedbacks. A shortage of females will lead to a greater value being placed on daughters, causing male preference to decline. </FONT>
<FONT face=Arial color=#840084>    This study suggests, however, that male aggression and increased competition for available females could make marriage less desirable for females, ultimately contributing to a fertility decline. </FONT>

动物都是些法盲，从它们身上得到的信息怎么能适用于人类呢

上次世界人口大会也提到了人口失调的问题。(转述，非政府文件)
在中国，到本世纪中页，男性将比女性多几百万，这将导致有几百万男人打光棍。
除此之外，相应的各种问题也会随之而来。

天涯何处无芳草，国内没有还可以上国外找吗