身体里住着另外一个人吗

2015.10.29 from BBCIs another man living inside you?By David Robson You may think your body and mind are your own. In fact, you are a fusion of many organisms - including, potentially, another person. Words by David Robson, photography by Ariko Inaoka.Once upon a time, your origins were easy to understand. Your dad met your mum, they had some fun, and from a tiny fertilised egg you emerged kicking and screaming into the world. You are half your mum, half your dad and 100% yourself.Except, that simple tale has now become a lot more complicated. Besides your genes from parents, you are a mosaic of viruses, bacteria and potentially, other humans. Indeed, if you are a twin, you are particularly likely to be carrying bits of your sibling within your body and brain. Stranger still, they may be influencing how you act.A very large number of different human and non-human individuals are struggling inside us for control“Humans are not unitary individuals but superorganisms,” says Peter Kramer at the University of Padua. “A very large number of different human and non-human individuals are all incessantly struggling inside us for control.” Together with Paola Bressan, he recentlywrote a paperin the journal Perspectives in Psychological Science, calling for psychologists and psychiatrists to appreciate the ways this may influence our behaviour.Over the last 6 years, photographer Ariko Inaoka has captured the special connection between two Icelandic twins, Erna and Hrefna (Credit:Ariko Inaoka)That may sound alarming, but it has long been known that our bodies are really a mishmash of many different organisms. Microbes in your gut can produce neurotransmitters that alter your mood; some scientists have even proposed that themicrobes may sway your appetite, so that you crave their favourite food. An infection of a parasite calledToxoplasma gondii, meanwhile, might just lead you to your death. In nature, the microbe warps rats brains so that they are attracted to cats, which will then offer a cosy home for it to reproduce. But humans can be infected and subjected to the same kind of mind control too: the microbe seems to make someone risky, and increases the chance they will suffer from schizophrenia or suicidal depression. Currently, around a third of British meat carries this parasite, for instance despite the fact an infection could contribute to these mental illnesses. “We should stop this,” says Kramer.Infiltrating siblingsIn this light, it becomes clear that our actions are not entirely our own. Its enough to make you question your sense of identity, but the idea of infiltration becomes even more eerie when you realise that your brain has not just been invaded by tiny microbes but also by other human beings.Even non-conjoined twins could be sharing organs without realising itThe most visible example might be a case ofconjoined twins sharing a brain, says Kramer, but even regular twins could have shared organs without realising it. During early development, cells can be passed between twins or triplets. Once considered a rare occurrence, we now know it is surprisingly common. Around8% of non-identical twins and 21% of triplets, for example, have not one, but two blood groups: one produced by their own cells, and one produced by “alien” cells absorbed from their twin. They are, in other words, a chimera a fusion of two bodies and it may occur in many organs, including the brain.Developing together in the womb, twins may swap cells, making them even closer than wed previously realised (Credit: Ariko Inaoka) A chimera brain could have serious consequences. For instance, we know that the arrangement of different brain regions can be crucial for its function but the presence of foreign tissue, being directed by different genes carrying a different blueprint, may throw that intricate design into disarray. This may explain, for instance, why twins are less likely to be right-handed a simple trait that normally relies on the relative organisation of the right and the left hemispheres. Perhaps chimerism has upset the balance.Even if you do not think you ever had a twin, there are many other ways you might be invaded by another humans cells. Its possible, for instance, that you started off as two foetuses in the womb, but the twins merged during early development. Since it occurs at such an early age of development, the cells can become incorporated into the tissue and seem to develop normally, yet they are carrying another persons genetic blueprint. “You look like one person, but you have the cells of another person in you effectively, you have always been two people,” says Kramer. In one extreme case, a woman was surprised to be told that she was not the biological mother of her two children (See “Brother from another mother”, left). Alternatively, cells from an older sibling might stay around the mothers body, only to find their way into your body after you are conceived.However it happens, its perfectly plausible that tissue from another human could cause the brain to develop in unexpected ways, says Lee Nelson from the University of Washington. Shes currently examining whether cells from the mother herself may be implanted in the baby brain. “A difference in the amount, cell type, or the time during development at which the cells were acquired could all result in abnormalities,” she says.你的身体里住着另外一个人吗？也许你会认为你的身体和思想属于你自己。可实际上，你是一个多个有机体的融合物还可能包括-另一个人。 大卫 罗布森 以前，关于你是怎么来的是一个很容易理解的问题。你爸爸和你妈妈相遇，相恋，然后你就踢着手脚从受精的卵子里面咕咕坠地了。一半妈妈加上一半爸爸就有了完整的你了。 除此之外，那个单纯的故事现在就有些复杂了，而且，你的基因的源自父母，你是各种病菌，细菌还有可能其他人的一个拼接组合之物。实际上，如果你是一个双胞胎，你很有可能在你的身体和大脑里携带者一些另一个双胞胎的特征。陌生人也是如此，他们可能正在影响你的行为。 “人类不是一个单一性的个体而是一个超有机体，”帕多瓦大学的皮特克雷默说，“大量不同的人或非人个体在我们体内不停争取我们身体的控制权。”最近，他与鲍拉布雷森在心理科学杂志视角发表了一篇论文，号召心理学家和精神病学家能重视这些可能会影响我们行为的方式。 过去六年中，摄影师Ariko Inaoka一直捕捉一对冰岛的双胞胎之Erna and Hrefna间的特殊关系（照片来自：Ariko Inaoka） 听来震惊，可是我们很早就知道我们的身体是很多不同有机体混杂而成。你肠子里的微生物能产生神经传递来改变你的情绪；甚至有些科学家提出那些微生物还有可能影响食欲，因此你会渴求他们喜欢的食物。如果感染了一种叫弓形虫的寄生虫，可能会致命。实际上，微生物能改变老鼠的大脑因此会吸引猫，这样就为微生物的繁殖提供了温床。而且，人也会感染这种大脑被控制的微生物：这些微生物会让人爱冒险，增加他们患上精神分裂或自杀性的抑郁症的可能性。现在，三分之一的肉类携带有这种寄生虫，比如尽管这种感染会导致这些精神疾病。“我们应该阻止，”克雷默说。渗入的同胞这样说来，很明显我们的行为不是全然由自己控制的。这已经足够让我们质疑自己的身份了，但当我们意识到我们的大脑不仅被微生物入侵还被其他人入侵，这种