Our ancestors lost their fur about 1,9 million years ago, so our lineage has been ‘naked’ for a long time. Fur protects most mammals from the sun, so why would we lose our protective layer? Humans sweat … a lot. Sweat evaporates more efficiently off an uncovered surface, and it is most likely that this adaptation allowed us to lose heat and avoid overheating while running long distances. This development has left our skin exposed to the sun for around 75 000 generations. Plenty of time for evolution to get to work.

It is quite clear that human skin has adapted to sunlight in a highly optimized way. Skin tones match the levels of UV radiation almost perfectly, with lighter skin tones in low UV zones like Europe and Asia and darker skin dominating around the equator. Tanning evolved to ensure that skin can adapt to the change in seasons, darkening by adding melanin in response to the higher UV radiation in summer and lightening again to allow Vitamin D synthesis in winter.

So, until around 4 generations ago, human skin had a finely-tuned adaptation to sunlight – around 10 hours of it every day. With the advent of the industrial age, we started to spend much more time indoors and currently in ‘developed’ nations people spend 87% of their lives indoors and 6% in enclosed vehicles. This is a very large shift in exposure and 4 generations is nowhere near enough time for our genetics to adapt. What does this mean for your skin?