• Health policy
• Medical demography
• Public Health
• Cancer

As we reflect on the skin we live in, we consider its powers and its vulnerabilities. At the nexus of environmental and societal pressures lie genetic adaptations central to the progress of humans over time. Thousands of years of evolutionary adaptation driven by varying environmental conditions—including sun exposure1—have led to the emergence of some characteristic phenotypic differences among geographically distinct groups. Drawing on this phenomenon, we explore the medical consequences of advantages in the physical environment that are penalised in the social environment. We examine skin pigmentation through environmental and social lenses to illuminate the effects of racist societies and the opportunities for mitigation within the medical profession.

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. Pale skin and northern European heritage are racialised as white, generally speaking. The social constructs of race and human biology are linked through these adaptive processes, even if the broader relationship between these two categories is contested.

Whether pale or dark, skin pigmentation confers substantial health advantages in the physical environments to which it is adapted. In recent centuries, however, migration has disrupted the evolutionary alignment of skin pigmentation and the natural environment, whether coerced, forced or voluntary, as has happened due to enslavement, colonial policies or economic reasons, for example. Traits produced through natural selection in one region of the world may pose health risks in other settings. Pale skin prone to burning following sun exposure is a significant risk factor for skin cancer. This increased risk is reflected in both the incidence and spatial distribution of skin cancer in the United States of America (USA), where more than 9500 new diagnoses are made every day.9 Non-Hispanic white people in the USA are 28 times more likely to be diagnosed with skin cancer than Black people during their lifetime, and the US counties identified as having the highest skin cancer vulnerability indices for this group are located in the southern and western regions of the country, where UV exposure is high.10 11

In response to the risk of skin cancer posed to those with pale skin, the medical and scientific communities have built an industry dedicated to the protection of vulnerabilities linked to this trait. 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.

While overall survival from melanoma, the most deadly form of skin cancer, has improved in recent decades, the persistent racial disparities in melanoma-specific survival for localised disease reveals a divergent pressure from the social environment despite the natural advantages provided by dark skin.14 Despite being at significantly lower risk of developing melanoma, survival rates for Black people are far lower than for those who are white. Only 66% of Black people diagnosed with melanoma survive 5 years or more, compared with 90% of white people with melanoma at a similar site.15 Recent research has uncovered the complexity of factors contributing to this disparity. 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 the relative infrequency of the disease among Black people and the propensity for the disease to occur in non-sun exposed skin such as the palms of the hands, soles of the feet, toenails, genitals and the inside of the mouth,19 which increases the likelihood of diagnosis during late stage of disease because of low awareness of skin cancer at these sites.20 Even when the disease is identified at an early stage, Black people have been shown to have worse survival outcomes compared with those who are white,15 highlighting the presence of continuing deficiencies in care that extend beyond diagnostic delay.

In this example, the health risks posed to Black people differ greatly from those affecting individuals with pale skin. Those with dark skin should enjoy advantageous protection in sun rich environments and have lower risks associated with skin cancer than those with pale skin in the same settings, yet, in this circumstance, rather than the physical environment posing the greatest risk, it is the social environment that confers the greatest threat to Black survival. While factors related to the location and stage of skin cancer at diagnosis may influence disease outcomes among the Black population, the negative social environment plays a significant role in undermining the protection that increased skin pigmentation offers. The effects of the social disadvantages that marginalise many people racialised as Black are so strong that they have reversed the competitive advantage in the physical environment provided millions years ago by natural selection. Discriminatory societal forces underpin far worse skin cancer outcomes for those with Black skin.

Inequalities in health for Black people are not limited to skin cancer; disease-specific morbidity and mortality, metrics of good health and life expectancy are commonly worse for Black people in the USA compared with those who are white. Society often robs the protection that dark skin offers through systemic and structural racism. Additionally, the medical community does not consistently identify prejudices against those who live within dark skin as a risk factor for poorer outcomes, instead labelling their Blackness as a cause.

Comparing coronavrus disease (COVID-19) mortality in non-Hispanic Black people in the USA to that of Black people on the African continent provides a pertinent illustration of how differing societal influences can vastly alter disease outcomes among individuals considered as belonging to the same racial group. While COVID-19-specific mortality rates in many African nations remained low throughout the pandemic,21 non-Hispanic Black people in the USA were much more likely to die from the disease than their white counterparts, even after adjusting for age, comorbidities and sociodemographic disparity.22 23 The low number of deaths due to COVID-19 seen in Africa is thought by some to be due to favourable demographic and biological characteristics of the African population, including younger population average age and lower prevalence of cardiovascular disease,21 however, the over-representation of Black people among those with poor COVID-19 outcomes in the USA cannot be explained easily in such terms. Although the higher rate of cardiovascular disease among Black people was suggested as being contributory,24 this too is a condition which derives from suboptimal preventive care, lifestyle differences stemming from unequal neighbourhood and socioeconomic circumstances, and physician bias resulting in differential treatment.25 26 Additionally, pervasive structural inequalities such as discrimination, poverty and residential segregation which impact Black people’s access to timely medical care were identified among the societal reasons responsible for the disparate COVID-19 outcomes in the USA24—factors that also impact skin cancer outcomes among Black people.

The negative social environment manifests its pernicious effects on the health of Black people not only through the structural impediments imposed by racism, but also through biological mechanisms such as ‘weathering’ and accelerated telomere attrition due to the stress of discrimination, both of which have further deleterious consequences for health.27 28 Despite the work of many scholars to bring light to the material effects of racism on the health of Black people in the USA,27 29 there is often a failure to account for the many ways in which these factors degrade health and the significant impact they have of health outcomes.

The skin we live in presents both powers and vulnerabilities. Both our physical and social environments determine our skin’s strength and weaknesses, yet, as we have seen with the risk of skin cancer among individuals with pale skin, such risks can be modified favourably. Despite the social threats to Black people’s health, the medical community has not responded to provide the same protection against these factors as for those from the natural environment that increase skin cancer risks for those with pale skin, yet, it is imperative that we do so. Threats in the natural environment are not always modifiable, but those in the social environment are completely caused by people’s bias, both conscious and unconscious, which influences their decisions and the structures they put in place. It may be a difficult process to change these behaviours and dismantle these systems, but it is not an insurmountable task. To mitigate the effects of the social environment on the health of Black people, the medical and scientific community must strive in equal measure to combat the racism that compromises the health of those with dark skin. We have begun to see such efforts emerging, including the reimagining of medical illustrations to include representations of Black people, clinical handbooks showing skin dermatological conditions on Black and Brown skin, and even medical school initiatives seeking to address bias in medical education by promoting inclusive anatomical representation.30–32

These initial steps are welcome but insufficient. A unified acknowledgement within the medical profession of the impact of racism, discrimination and imperialism would be an important first step for implementing the changes necessary to mitigate society’s harmful effects on Black health. Democratising medical education to support the inclusion of more Black and Brown people, among both medical educators and students, is essential to improving the profession’s clinical performance. Medical professionals have organised effectively against threats to population health before, by opposing products with carcinogens such as lead or tobacco. A racist society is also harmful to health and yet, no similar organised response has been forthcoming. This lapse points to deep faults in the medical profession itself, from admissions and training programmes to the delivery of care and public communications. The worse clinical outcomes for Black people with skin cancer reveal one aspect of the harmful failure of the medical profession to identify and oppose racist biases within its ranks and in wider society. Only by recognising the deep ties between racism and poor health can a coordinated response be woven into both the teaching and practice of the medicine within our society that so urgently, so desperately quests for change.