2021-06-26:非洲基因组计划为何意义重大

Know thyself 认识你自己

Why the African genome project is so useful 非洲基因组计划为何意义重大

To map the ascent of man, begin at the beginning从头开始绘制人类演进图

Jun 24th 2021 |

RACISM MAY often run deep, but one of the most depressing things about it is how superficial it really is. In most parts of the world it is literally a matter of black and white. A person’s skin colour, however, has little biological significance. It is merely a balance between defending the lower layers of the dermis from cancer-causing ultraviolet light (which favours dark skin) and promoting the beneficial role of ultraviolet in the synthesis of vitamin D (which favours light skin). The farther someone’s ancestors lived from the equator, the paler their skin evolved to be.

种族歧视往往根深蒂固,但其中最令人沮丧的一点是它其实非常肤浅。在世界大多数地方,它实际上仅就是黑白问题。然而,一个人的皮肤颜色几乎毫无生物学意义,而不过是在保护真皮下层免受紫外线照射而致癌(倾向于深色皮肤)与促进紫外线在合成维生素D上发挥积极作用(倾向于浅色皮肤)之间达到一个平衡而已。谁的祖先住得离赤道越远,他的皮肤颜色就会进化得越浅。

Go back far enough, though, and everyone’s ancestors lived in Africa, the continent where Homo sapiens originated. Most non-Africans alive today trace the bulk of their ancestry to Africans who burst forth on an unprepared world about 60,000 years ago. Indeed, the oldest representative of the species yet found in Britain retained the dark skin of his African forebears. Africa is where humanity grew up—and where the bulk of human genetic diversity is found to this day.

但是,只要往远了追溯,所有人的祖先都住在非洲,智人就发源于这片大陆。如今大多数活着的非非洲人的大部分祖先都可以追溯到6万年前突然出现的一群非洲人那里。事实上,英国迄今发现的最古老的代表人种还保留了其非洲祖先的深色皮肤。非洲是人类成长的地方,到目前为止在非洲发现了大部分的人类遗传多样性。

Only now is a serious effort beginning to explore Africa’s genetic richness. Better late than never. The Three Million African Genomes (3MAG) project, a continent-wide endeavour, proposes to do for the place what has already been done for Europe, North America and parts of Asia—namely to catalogue and analyse the genetic diversity of those who live there. That will be scientifically fascinating, for it will help elucidate how H. sapiens evolved. But it will be medically important, too. It may even help erode that black-and-white excuse for racism.

对非洲丰富的遗传基因进行严肃探索,直到现在才开展起来。但姗姗来迟总比什么都不做好。三百万非洲基因组计划(3MAG),致力于覆盖整个非洲大陆,计划在这一地区开展在欧洲、北美及亚洲部分地区已经完成的工作——即对非洲的人类遗传多样性进行归类和分析。这在科学上极具吸引力,因为这将有助于解释智人是如何进化的。在医学上也有重大意义。更甚,它也许能帮助动摇种族歧视那套黑与白的托辞。

Genetic diversity brings with it diversity of genetic disease. Cystic fibrosis—in any case rarer in Africa than in Europe—is often caused there by a different mutation from the one involved in the European version, and is thus missed by tests developed in the West. A mutation responsible in Ghana for 40% of inherited deafness is unknown in South Africa. And so on. It also brings a diversity of genetic response to disease. Some of the molecular details of the immune system, for example, vary with geography. Understanding that variation in Africa will improve understanding of immunity to infection, helping Africans and non-Africans alike.

伴随遗传多样性的是遗传性疾病的多样性。囊肿性纤维化,在非洲绝对比在欧洲罕见,非洲的病例往往是由一个与其欧洲版本不同的基因突变引起的,因此由西方研发的检测项目就会忽略掉它。一项在加纳造成40%的遗传性失聪的基因突变,在南非反而不存在,诸如此类。随之还有对疾病的遗传反应的多样性。比如,免疫系统的一些分子在细节上会随地理变化而变化。理解非洲存在的这种差异能使我们更好地理解免疫系统如何应对感染,从而帮助到非洲人和非非洲人。

More genetic information will also cast light on evolution. Early H. sapiens migrants from Africa encountered other species of human being on their travels. These were descendants of previous migrations out of Africa of archaic members of the genus. At least two of these other types of human, the Neanderthals and the Denisovans, interbred with the newcomers, and some of their genes are still found in modern Asians and Europeans, doing various jobs including protecting them from disease. Preliminary analysis suggests that those who remained behind in Africa similarly interbred with yet another species of human—but one of which no fossil record remains.

获取更多遗传信息也有助于理解进化过程。从非洲迁出的早期智人在旅行中遇到了其他人种,他们是以前从非洲迁出的同属里更古老的成员。至少有两种其他分支,尼安德特人和丹尼索瓦人曾与这些初来乍到者交配,在现代亚洲人和欧洲人身上仍能发现他们的一些基因,这些基因功能多样,比如保护免受疾病侵扰等。初步分析显示,那些留在非洲的人也曾与其他人种(没有留下任何化石记录)混合交配。

There is an irony in all this. Xenophobia has probably existed for as long as people have. But racist attitudes were reinforced in the 19th century by an enthusiasm for physical anthropology and eugenics. The former attempted to classify human beings on the basis of visible characteristics, such as skin colour, head shape and facial features, that are genetically inherited. If this had been a neutral analysis, it would have been unexceptional. But often it was not neutral. It not only classified, but ranked. White-skinned Europeans put themselves at the top—and black-skinned Africans at the bottom. Add eugenics to that mix and the result was toxic.

这就极具讽刺意味了。排外主义也许和人类的历史一样长。但种族主义偏见则是在19世纪出于对体质人类学和优生学的热衷而得到加强的。前者试图以可见特征为基础对人进行分类,比如皮肤颜色、头骨形状和面部特征,这些都是由遗传继承下来的。若分析不带偏见,那也就不值一提。但这类分析往往并非不带偏见。它不仅把人分类而且会排出三六九等来。白皮肤的欧洲人把自己列在前面,把黑皮肤的非洲人列在最下面。再加上优生学,结果荼毒四海。

The 3MAG project will not, alone, overthrow the legacy of these misadventures and the prejudices they reinforced. The thinking that gave rise to them is still too deeply ingrained in too many minds for it to do that by itself—even, probably, for it to come close. But to those whose minds are open, a group of 21st-century African scientists revealing that the true, glorious genetic diversity of human beings lies in their own continent more abundantly than in any other will be a superb rebuttal to the doctrines of those misguided Victorian European gentlemen. ■

仅靠三百万非洲基因组计划,颠覆不了这些不幸遭遇以及因之加强的偏见之祸患。其源头思想在很多人头脑里扎根太深而无法自行拔除——甚至可能都无法接近做到这一点。但是有一群思想开放的人,一群21世纪的非洲科学家揭示出人类真正的、光辉的遗传多样性就存在于他们自己的大陆之上,且比任何其他地方都更加丰富,这对于那些误入歧途的维多利亚式欧洲绅士所抱持的教条思想,是绝佳的反驳。

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