Every woman alive today received her mitochondria from her mother. If we trace the passage of the mitochondria back one generation to the mothers, we have fewer women than today. If we trace back another generation, we find an even smaller number, and with each previous generation this number decreases. Eventually this traces back to a single woman from whom all women alive today received their mitochondrial DNA. Mitochondrial Eve lived approximately 200,000 years ago. It is believed that she lived in Africa and from her all of the tribes of the world were created. Although, many races developed after some of her descendents migrated  to other regions, all races have a connection because of this common ancestor.