If you go back sixty-four generations, to the time of the Romans, the number of people on whose cooperative efforts your eventual existence depends has risen to approximately 1,000,000,000,000,000,000, which is several thousand times the total number of people who have ever lived.
而在64代之前，也就是古罗马时期，决定你存在的祖先数将增到约10亿亿，这个数目是曾经在地球上生存过的人的总数的几千倍。

Clearly something has gone wrong with our math here. The answer, it may interest you to learn, is that your line is not pure. You couldn't be here without a little incest — actually quite a lot of incest — albeit at a genetically discreet remove. With so many millions of ancestors in your background, there will have been many occasions when a relative from your mother's side of the family procreated with some distant cousin from your father's side of the ledger. In fact, if you are in a partnership now with someone from your own race and country, the chances are excellent that you are at some level related. Indeed, if you look around you on a bus or in a park or cafe or any crowded place, most of the people you see are very probably relatives. When someone boasts to you that he is descended from William the Conqueror or the Mayflower Pilgrims, you should answer at once: "Me, too!" In the most literal and fundamental sense we are all family.
很明显，我们的统计出了一些差错。对于这个问题，正确的解释是——你也许对此感兴趣，你的这一线并不那么纯粹。如果根本没有一定程度上的亲戚的联姻——这种情况实际上是大量存在的，尽管出于遗传的原因小心翼翼地隔一代，你就不会在这里。你这一条线上有几百万个祖先经常会出现这样的情况，你母亲这一边的一个远亲和你父亲这一边的一个远亲结为夫妻。实际上，如果你现在的伴侣是你同一民族、同一国家的人，你们很可能就有着某种血缘关系。如果你在公共汽车上、在公园里、在咖啡屋中，或者在任何一个拥挤的地方环视四周，你所看到的大多数人很可能是你的亲戚。如果有人自吹是莎士比亚或征服者威廉的后代，你可以马上回答他说：“我也是！”无论从字面意义还是从本质来讲，我们都是一家人。
We are also uncannily alike. Compare your genes with any other human being's and on average they will be about 99.9 percent the same. That is what makes us a species.
我们也令人惊讶地相似。把你的基因和别的任何一个人对比，它们平均有大约99.9%是相同的，就是它们使得我们都属人类。