The human population contains a great variety of genetic variation, but drugs are tested on just a few thousand people.
人类群体中有各种各样的基因变异，但是药物只在几千人身上进行测试。
2
Their allele frequencies at numerous genetic loci gradually become more and more different as new alleles independently arise by mutation in each population.
随着新等位基因在每个群体中独立突变产生，它们在许多遗传位点上的等位基因频率逐渐变得越来越不同。
3
The best information on early population movements is now being obtained from the 'archaeology of the living body', the clues to be found in genetic material.