今天这种极其显著的平均化——每个人的生存机会和子女数量都相同——意味着，与部落相比较，自然选择在印度中上阶层已经失去了80%的效力。
The grand mediocrity of today - everyone being the same in survival and number of offspring - means that natural selection has lost 80% of its power in upper middle class India compared to the tribes.
这药的效力几个小时后会自然消失。
The effects of the drug naturally wear off within a few hours.
因此，它似乎在法律领域更加'自然'，电子邮件收到而有其效力应当适用。
Therefore it seems more 'natural' that the law of the place where the E-mail is received and where it has its effect should apply.
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