Modern humans evolved in Africa and successfully colonised the globe only in the last 100,000 years or so, a feat made possible by cultural and genetic adaptation. Human habitats differ dramatically in climate, available foods or pathogens, and genetic adaptation was mediated both by mutation and by interbreeding with archaic humans such as Neanderthals and Denisovans. Besides representing a mark of our past, these adaptations contribute to diversity in living people in traits such as skin colour and immune function.