In 2002, the anthropologists Corey S. Sparks and Richard L. Jantz claimed that differences between children born to the same parents in Europe and America were very small and insignificant and that there was no detectable effect of exposure to the American environment on the cranial index in children.
2002年人类学家史巴克斯（Corey S. Sparks）和詹茨（Richard L. Jantz）宣称，由相同父母在欧洲和美国所生的孩子之间的差异極小且不显著，而且暴露於美国环境中，对孩子的頭骨指数并未發生可察覺的影响。