As you may be aware, people have 2 biological parents, which means that for ever n generations, they had 2
So, while the mitochondrial Eve, a woman who lived some 200,000 years ago, is the ancestor of basically every human alive today, she was not the only living woman of her time. The other women's mitochondrial lines died out when either they had only sons (who would not pass on the mitochondrial DNA) or no children at all, leaving only hers. Same for the Y chromosome Adam, an ancestor of all men alive today who lived 60,000 years ago. He was not the only man alive, but the other men's lines all ended across the 60,000 years when they either had only daughters (who do not have a Y chromosome) or no children at all. This was further sped up by Genghis Khan, a Mongolian ruler who had a lot of children, who in turn had many more children. He is the ancestor of 16 million people today. Being a powerful Emperor probably did have a part of the ladies interest in him, as did his reputation for being wealthy and benevolent.
However, some signs show that our genetic bottlenecks may be disastrous for us. The Y chromosome has been shrinking over time, which may slowly damage male fertility (should those genes, located in the Y chromosome, be lost), or perhaps even end altogether, leading to an all-female humankind. (We could technically survive, but it would be...inconvenient.) The shrinkage is mostly due to interference from the Y chromosome's rival, the X chromosome, which you need to live. The most critical of the Y chromosome's genes are a group called SRY, which is responsible for 99% of what people think of when they think of men. In some species, the Y chromosome has been destroyed, but their SRY migrated out, so they still have males.
So to improve the genetic state of humankind, I would like to see some volunteers, dissatisfied with the genes they inherited, undergo a retrovirus-based retooling of their genome. This would hopefully prove helpful to them, in some way or other, and their new genomes would make them genetically unrelated to anyone on earth, and thus the best person to marry if you want to avoid inbreeding.
There is one particular group of pacific islanders, I can't remember their name right now, who would be the most interested, as their tribes have a tradition of marrying passing sailors as a way of avoiding incest on their tiny, historically isolated, island. (Children of an outsider are less genetically related members of the tribe, and thus more eligible for marriage, see?)