巨猿、化石人和智人牙齿的波动不对称：人类进化中压力源变化的意义

Fluctuating Dental Asymmetry in Great Apes, Fossil Hominins, and Modern Humans: Implications for Changing Stressors during Human Evolution

波动不对称（FA）是压力的随机性引发双侧完美对称偏离的现象，这是个体无力免受发展中不利因素（如早期营养不良）侵害的一个标志。比较个体口腔两侧牙齿的大小是一种测量FA的方法。本研究汇集了10个物种共296名个体的牙齿测量结果，测量对象包括黑猩猩（学名Pan troglodytes）、猩猩（学名Pongo pygmaeus）、大猩猩（学名Gorilla gorilla）、智人（学名Homo sapiens），以及许多化石人。分析发现，猩猩样本牙齿的FA水平要显著低于大猩猩、黑猩猩、直立人、尼安德特人和智人样本的FA水平。而与之相反的是，智人与尼安德特人样本的牙齿FA水平要显著高于其它任何一种巨猿样本的FA水平。该文提出了有关缓和的选择压力的解释。

Fluctuating asymmetry (FA)， defined by random， stress-induced deviations from perfect bilateral symmetry， is an indication of the inability to buffer against developmental disturbances， such as poor early nutrition. One method of measuring FA involves comparing individual tooth sizes on opposing sides of the mouth. In this study tooth measurements were compiled for 296 individuals from 10 species， including chimpanzees (Pan troglodytes)， orangutans (Pongo pygmaeus)， gorillas (Gorilla gorilla)， modern humans (Homo sapiens)， and a number of fossil hominins. The orangutan sample had significantly lower levels of dental FA than the gorilla， chimpanzee， Homo erectus， neandertal， or modern human samples. In contrast， the human and neandertal samples had significantly higher dental FA levels than any of the great ape samples. Some explanations relating to relaxed selection pressures are suggested.