Class, Caste, and Genes 阶级、种姓和基因 作者:Henry Harpending @ 2012-01-13

译者:尼克基得慢(@尼克基得慢)

校对:辉格(@whigzhou)

来源:West Hunter, https://westhunt.wordpress.com/2012/01/13/class-caste-and-genes/ An article by Sabrina Tavernise appeared in the New York Times a few days ago describing increasing perceptions of class conflict in America, and there is a lot of recent commentary in the press about this report from the Pew Charitable Trust that claims there is less class mobility here than in several other northern countries.   It is not very clear to me what the complaints really are or what alternatives exist. If there is any substantial heritability of merit, where merit is whatever leads to class mobility, then mobility ought to turn classes into hereditary castes surprisingly rapidly.

几天前，Sabrina Tavernise一篇描写美国阶级矛盾越发明显的文章刊登在了《纽约时报》上，这份来自皮尤慈善信托基金（the Pew Charitable Trust）的报告宣称美国的阶级流动性少于其他几个北方国家，最近的新闻对此有很多评论。但是我并没有搞清楚他们究竟在抱怨什么或者存在什么可行的替代选项。假设存在实质性的个体优势遗传，同时个体优势总会导致阶级流动，那流动性应该会迅速地把阶层转化为世袭的种姓式分化。

A start at looking into genetic consequences of meritocracy is to create the simplest possible model and follow its implications. Consider free meritocracy in a two class system, meaning that each generation anyone in the lower class who has greater merit than someone in the upper class immediately swaps class with them. Mating then occurs at random within class. There are no fitness differences, no selection at all, everything is neutral.

要开始调查精英制度的遗传后果，应该建立尽可能简单的模型并遵循其推论。设想有两个阶级系统的自由精英制度，这意味着每一代中任何身处较低阶级的人，都可立刻与更高阶级中能力弱于自身的人互换阶级。然后阶级内随机通婚。这里没有健康程度的不同，也完全没有自然或人工选择，所有都保持中性。

It is convenient to discuss what happens in terms of IQ because IQ is familiar and, in northern industrial nations, closely related to merit. On the other hand we have to keep in mind that our focus on IQ is like that of the drunk searching for his keys under the lamppost: we can measure IQ but have no good way to measure honesty nor time preference nor conscientiousness and so on.

方便起见，不妨从IQ的角度来讨论由此引出的结果，因为IQ广为人知，而且在北方工业国家中，IQ跟个人优势紧密相关。另一方面，我们也必须谨记，我们对于IQ的关注就像醉汉在路灯下找寻钥匙：我们可以测量IQ，却没有好方法来测量诚实、时间偏好或者尽责性等特质。 This figure shows an initial population with normally distributed merit. A new merit based class system is imposed such that the two new classes are of equal size. In this free meritocracy everyone with merit exceeding the population mean moves into the upper class and everyone with merit less than the average moves into the lower class. The second panel of the figure shows the resulting merit distributions by class before reproduction and the bottom panel shows the distributions after endogamous reproduction. This model assumes that the reshuffling of genes during reproduction leads to normal distributions in the next generation within classes.

上图的顶层显示了个体优势呈正态分布的初始人口。一种基于阶级系统的新优势被引入进来，据此划分的两个新阶级的人口数量相当。在这种自由精英制度中，每个能力超过人口平均值的人都进入上层阶级，每个能力达不到平均值的人都进入下层阶级。上图的中层表示在生育前所处阶级导致的个体优势分布，底层则表示在同阶级通婚生育后的个体优势分布。这个模型假设生育过程中的基因重组会导致同阶级的下一代在个体优势上的正态分布。

The process continues for several generations. By analogy with IQ the additive heritability of merit is set to 0.6 so there are substantial random environmental effects. The second figure shows the evolution of class differences over four generations or about 100 years in human terms.

这个过程持续了几代的时间。通过类比IQ，个体优势的可加性遗传率设为0.6，所以这就有了大量随机的环境影响。下图展示了四代（人类角度的大约100年）时间内阶级差异的演化。 Class mobility after the first generation is 30% while after four generations it has declined to 10% and continues to decline after that.  The average merit in the two classes is about -1SD in the lower and +1SD in the upper on the original scale, corresponding to IQs of 85 and 115.

第一代之后的阶级流动性是30%，而四代之后这个数字就已跌至10%并且之后继续下降。相较于原始水平，较低阶级的平均个体优势降低了一个标准差，较高阶级的平均个体优势增加了一个标准差， 对应的IQ数值为较低阶级的85和较高阶级的115。

Recall that there are no fitness differences in this model. Still, after four generations, about 70% of the variance is between classes, which can be compared to  about 35% of the variance among continental human groups for random genetic markers, i.e. colloquially class differences are twice neutral race differences. (The familiar among-population figure of 15% made famous by Lewontin refers to gene differences while here we are comparing genotype differences of diploids, hence the difference between 15 and 35.)

回想下这模型中是没有健康水平的差异的。但在四代之后，阶级之间的方差仍到达了70%，这都可以与随机遗传标记的跨大陆种群间35%的方差相比了，例如，通俗语境中的阶级差异是纯粹种族差异的两倍。（Lewontin提出的著名的种群间15%的差异数据是指基因差异，而这里我们是比较二倍体的基因型差异，因此差别在15到35之间。）

A surprise to me from this model was the rapidity with which classes turn into castes: most of the action is in the first generation or so. In retrospect this seems so obvious that it is hardly worth saying but it wasn’t so obvious to me when I started toying with it.

这模型让我吃惊的地方在于阶级转化为世袭种姓的速度之快：大部分转变在第一代左右就已发生。回想起来，这过程看起来如此明显以致于都不值得谈论，但是一开始我很随意地思考时，我并没有注意到这点。

Even though everything here is selectively neutral, I wonder about the extent to which this free meritocracy mimics selection. Any mutant that boosts merit in carriers will be concentrated in the upper class and vice versa. Greg and I discuss in our book how environmental change initially selects for dinged genes that are “quick fixes” in carriers but detrimental in homozygotes, citing sickle cell in humans, broken myostatin in beef cattle, and numerous others. Does this social system mimic selection?

即使这里的每件事情都是有选择地设为中性，我很想知道这个自由的精英制度与选拔制相似到什么程度。任何让携带者具有个体优势的基因突变都会聚集在较高阶级，反之亦然。Greg和我在我们的书【 编注：Greg是Gregory Cochran，作者与他合著了《万年大爆炸》一书，West Hunter是这两位作者的合作博客 】中讨论环境改变最初如何选择出了那些丧钟般的“临时补丁”基因，他们能为携带者快速解决一些问题，但对纯合子有害，造成人体内的镰状细胞，菜牛内残缺的肌肉生长抑制素，和很多其他坏处。这个社会系统也模仿选择机制吗？

A correlate of IQ in humans is myopia, one idea being that IQ boosters relax early developmental constraints on CNS growth resulting in eyeballs too big for the socket, leading to myopia. I have read somewhere that myopia is positively related to income in the US. Time to try to find that literature.

跟人类IQ相关的是近视，一种观点认为IQ超群者放松了对中枢神经系统生长的早期发展限制，导致了眼球相比于眼窝过大，于是成了近视。我在某处读到，近视在美国跟收入是正相关的。该去试着找到那篇文献去了。

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