Fact list: putting racial difference into context and dispelling myths.
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Did you know?
• There are more differences between individuals within a population than there are between populations
• 93% of genetic variation is between individuals within a population; 7% is between groups
• Even people with 100% African ancestry have widely varying skin pigmentation. Although skin colour can be an indicator of proportions of African and European genetic contribution, the bottom line is ‘you can't tell by looking’
• Scientist’s best estimates put the level of ‘European’ Americans with West African ancestry at around 10%, each having about one great grandparent of African ancestry
Evolutionary Tree of Life:
• 6 million years ago humans and chimpanzees shared a common ancestor
• 1 million years ago Homo erectus was the human that lived throughout the world, smaller brained than us but with many human characteristics
• 500,000 archaic Homo sapiens evolved in Africa from Homo erectus
• 50-70,000 years ago the first humans – possibly as few as 100 - left Africa. All humans outside Africa descend from this first group. They are the ancestors of all non-Africans alive today. As they left Africa, because they were such a small group, they left a lot genetic diversity behind. More diversity was lost the further they travelled and this is seen today, South American Indians are much less variable than Asians, who tend to be less variable than Europeans who in turn are less variable than Africans.
Out of Africa: The first ‘races’ evolve:
Around 50-70,000 years ago as few as 100 people may have left Africa to spread out and people the world, settling in different parts of the world. The descendants of these new settlers evolved physical traits needed to survive in their new environmental niches.
This was a time of climatic change within and without Africa. Those who stayed in Africa continued to evolve and adapt to their changing continent and as temperatures warmed, skin colour darkened close to the equator; malaria resistance and immune resistance to other pathogens continued to evolve. But the biggest physical changes were among those who moved out.
Outside Africa, many new physical characteristics evolved to match the new environments. As people travelled north their skin became lighter to allow lower levels of sunlight to penetrate through to produce vital Vitamin D; those migrating to the far north evolved smaller and more rotund bodies for better thermoregulation. One of the last places people migrated into was the Amazon rain forest and here they evolved resistance to many indigenous pathogens and a more efficient small-bodied stature. Every new environment carried new pathogens and parasites, driving evolution of the immune system. In these new environments people found new sources of food, causing changes to the digestive system - those who found tougher roots to chew on developed stronger jaw muscles to help them grind it down.
Download a PDF of Race Facts.
Discover more about the Race: Science's Last Taboo season.
