Why Diversity Is the Only Path Forward: Sarah Tishkoff on African Genomics

Are you lactose tolerant? If you’re of Northern European ancestry this is because of a stretch of DNA in a gene enhancer that developed some 9,000 years ago. That's the same time Northern Europeans began domesticating cattle for milk. If you’re of African ancestry, you may have one of three mutations which appeared independently of the European mutation--and of each other--about 6,000 years ago, again when dairying began.