Your friends 'may be your fourth cousins' People tend to choose friends that are genetically similar to themselves, so much so that a person's social circle could be made up of their fourth cousins, scientists say. The research is based on the Framingham Heart Study in the northeastern US state of Massachusetts, which contains both extensive genetic detail - 1.5 million markers - and information about friends and connections. Scientists focused on 1,932 people and compared pairs of unrelated friends against pairs of unrelated strangers. Those in the same social circles shared about one per cent of their genes, much higher than the amount they shared with nearby strangers. Friends tended to be about as related as people who share great-great-great grandparents. "The increase in similarity relative to strangers is at the level of fourth cousins," researchers say, in a study published this week in the Proceedings of the National Academy of Sciences. Even though sharing one per cent of genes may not sound like a lot, co-author Dr Nicholas Christakis, professor of sociology, evolutionary biology and medicine at Yale University, says "to geneticists, it is a significant number." "We are somehow, among a myriad of possibilities, managing to select as friends the people who resemble our kin," he says. Most of the people in the Framingham study were white and of European descent. Researchers say they could tell from their analysis that the genetic ties among friends went above and beyond what would be expected among people of shared ancestry, or by people who tend to befriend those of the same ethnic group. They could also tell that friends were most similar in genes affecting the sense of smell, and most different when it came to genes that affect immunity against various diseases. Researchers do not fully understand how this happens. But they say perhaps friends might be most easily made among those who enjoy the same smells, such as the aroma of a coffee shop. On the other hand, the disparity in immune systems could foster survival in groups of friends by reducing the spread of dangerous pathogens. Christakis says he is interested in finding out why people have friends in the first place. "The making of friends is exceedingly rare in the animal kingdom," he says. "Certain other primates, elephants and whales are the only other mammals who do this, and this alone aroused our curiosity." ABC/AFP Special: The best from Australia
你的好友可能是你远方亲戚 科学家们揭示人们更愿意与基因接近的人成为朋友，或是伴侣，甚至可以说人们的社交圈是由远房亲戚组成的。 这项研究是基于美国麻省《弗雷明汉心脏研究报告》(Framingham Heart Study)数据的基础做出的。这项研究记录了150万人的基因资料以及这些人的朋友圈及亲属关系信息。 科学家们最终聚焦1932人，把两个朋友与两个互不相识的陌生人的基因进行对比。 那些同属于同一个社交圈内的人士有1%的基因是相同的。这远高于陌生人的基因共性。 这种基因共性意味着朋友是五代之内的亲戚。 这项本周发表在美国《科学院论文集》之中的研究报告作者，耶卢大学社会学、进化生物学及医学教授尼古拉斯·克里斯塔（Nicholas Christakis）博士说尽管1%的基因相同看起来没有太大的不同，但是遗传学家则认为这是一个很明显的不同。 他说："我们在选择朋友时，会选择那些与我们血缘关系更近的人。" 大部份在《弗雷明汉心脏研究报告》中的人都是欧裔白人。 研究人员说这些人所拥有的类似基因影响到他们的嗅觉、对不同疾病的免疫能力。 但是，科研人员并不完全清楚这到底是如何发生的。 也许那些有着相同嗅觉的人更容易在公共场，例如咖啡馆所成为朋友。另一方面，这些基因共性可能会帮助避免某些疾病的传播。 克里斯塔教授指出，他有意找到这些人是怎么起初成为朋友的。 他说："在动物世界，交朋友是很少见的现象。" "就哺乳类动物而言，大象和鲸鱼是这样做的其他两个动物，我对交朋友这种现象很感兴趣。" Related News
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