The primary biological role of human skin pigmentation is as a mediator of penetration of ultraviolet radiation (UVR) into the deep layers of skin and the cutaneous circulation. Since the origin of Homo sapiens, dark, protective constitutive pigmentation and strong tanning abilities have been favored under conditions of high UVR and represent the baseline condition for modern humans. The evolution of partly depigmented skin and variable tanning abilities has occurred multiple times in prehistory, as populations have dispersed into environments with lower and more seasonal UVR regimes, with unique complements of genes and cultural practices. The evolution of extremes of dark pigmentation and depigmentation has been rare and occurred only under conditions of extremely high or low environmental UVR, promoted by positive selection on variant pigmentation genes followed by limited gene flow. Over time, the evolution of human skin pigmentation has been influenced by the nature and course of human dispersals and modifications of cultural practices, which have modified the nature and actions of skin pigmentation genes. Throughout most of prehistory and history, the evolution of human skin pigmentation has been a contingent and non-deterministic process.

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人类皮肤色素沉着的演变涉及遗传、环境和文化变量的相互作用

人类皮肤色素沉着的主要生物学作用是作为紫外线辐射 (UVR) 渗透到皮肤深层和皮肤循环的介质。自智人起源以来、深色、保护性组成性色素沉着和强晒黑能力在高 UVR 条件下受到青睐，代表了现代人类的基线条件。部分脱色的皮肤和不同的晒黑能力的演变在史前时期已经发生过多次，因为人口已经分散到具有较低和更多季节性 UVR 制度的环境中，具有独特的基因和文化习俗的补充。深色色素沉着和色素脱失的极端进化很少见，并且仅在极高或极低的环境 UVR 条件下发生，这由对变异色素沉着基因的正选择和有限的基因流动促进。随着时间的推移，人类皮肤色素沉着的演变受到人类传播的性质和过程以及文化习俗的修改的影响，它们改变了皮肤色素沉着基因的性质和作用。在史前史和历史的大部分时间里，人类皮肤色素沉着的演变一直是一个偶然的和非确定性的过程。