Sun, skin and the deadly politics of medical racism

Dark skin evolved more than 2 million years among early hominids as they lost their fur.2 Living close to the equator, where intense sunlight prevails for most of the year, early members of the genus Homo had a darkly pigmented integument.3 4 Dark skin pigmentation, a phenotypic feature common among those who are racialised as Black, presents many advantages in this environment, including the protection of folate from photodegradation.3 Folate is important for many significant biological processes including DNA synthesis, cell division and healthy fetal development.5 Plentiful epidermal melanin also protects skin from free radical damage caused by ultraviolet (UV) radiation, which lowers the risk of skin cancer.6 In sunny regions, dark skin is an important trait for the survival of individuals and the health of their progeny. Pale skin evolved approximately 8000 years ago among people who migrated north from Africa as an adaptation to maintain cutaneous vitamin D synthesis in environments with less sun exposure due to weaker sunlight7 and also less skin exposure due to the clothing required in colder temperatures.2 Vitamin D is important to several biological processes including calcium and phosphorous homeostasis, immune system modulation and maintenance of cardiovascular health,8 thus, in geographies with limited sunlight, such as the northern parts of Europe, this genetic polymorphism presented a significant competitive advantage. The pursuit of global power spurred the development of early sunscreen products in the mid-20th century for the protection of American military personnel serving in tropical theatres of World War Two and the Korean War.12 The American Air Force, alongside the American Medical Association Council of Pharmacy and Chemistry, led ‘top secret’ research in the 1940s to identify substances which could protect pale skin from the harm of UV exposure.13 Effective sunscreen products have since become readily available in the private market, and clinical research investments have significantly improved skin cancer outcomes. Social factors identified include physician misperception about skin cancer risks for patients with dark skin, reduced access to healthcare among Black people in the USA—a downstream consequence of structural racism that may contribute to the increased proportion of late diagnoses among this group—and inadequate efforts to sensitise Black communities to skin cancer risks.16–18 These factors are further compounded by th