Dr Cochran argues that something similar happened to the Ashkenazim.Genes that promote intelligence in an individual when present as a single copy create disease when present as a double copy.

• Cochran博士认为，德系犹太人也面临着同样的情况，他们的某些基因如果以单组出现就可以提高智力，一旦以双组出现就会引起疾病。