Dark Skin Evolution in Early Humans: Revisiting the Skin Cancer Hypothesis Through Migration-Related Mismatch.

Area of Science:

• Human Evolution
• Cancer Biology
• Dermatology

Background:

• The role of cancer as a selective force in human evolution is underexplored.
• The skin cancer hypothesis suggests UV-induced skin cancers favored darker skin in early hominins.
• Evolutionary mismatch involving fair-skinned individuals in high-UV environments has been cited as evidence.

Purpose of the Study:

• To evaluate the skin cancer hypothesis regarding the evolution of human skin pigmentation.
• To test the migration-related mismatch component of the hypothesis using contemporary data.
• To explore alternative explanations for the selective pressures on skin color.

Main Methods:

• Review of existing literature on cancer, evolution, and human adaptation.
• Analysis of current skin cancer incidence rates in Australia.
• Examination of UV radiation's impact on human physiology and life history.

Main Results:

• Skin cancers with metastatic potential are common in Australia but typically manifest after reproductive age.
• This finding challenges the direct selective pressure of skin cancer on the evolution of darker skin.
• UV-related risks like thermoregulation and water barrier integrity are proposed as more likely selective factors.

Conclusions:

• The skin cancer hypothesis, in its direct form, is unlikely to explain the evolution of darker skin.
• Selection for darker skin was probably driven by other UV-related factors crucial for survival and reproduction.
• Lethal skin cancers may have indirectly influenced human evolution through social structures involving post-reproductive individuals.