How many ancestors does a person have

Of course not. Many people do not know the answer to that question. Care to guess? The number of ancestors is simple to calculate as it is a simple mathematical progression: every person has two parents, four grandparents, eight great-grandparents, sixteen great-great-grandparents and so on.

The number doubles with each generation. Because of the random reshuffling of genes in each successive generation, some of your ancestors contribute disproportionately to your genome, while others contribute nothing at all. According to calculations by geneticist Graham Coop of the University of California, Davis, you carry genes from fewer than half of your forebears from 11 generations back. And your genealogical connections to the entire globe mean that not too long ago your ancestors were involved in every event in world history.

So the next time you hear someone claim to be descended from royalty, take heart: you are, too. Credit: Nick Higgins. Already a subscriber?

Sign in. Thanks for reading Scientific American. Create your free account or Sign in to continue. See Subscription Options. Go Paperless with Digital. Get smart. Sign up for our email newsletter. Sign Up. I know it appears impossible to have that many people 67 generations ago, but someone had to produce the offspring in order for the line to continue, people don't appear out of thin air.

Stephen Wiles, Right, but if those two parents were, for example 4th cousins, they shared a common set of grandparents a certain number of generations back. Dear Mercedes, You have composed a brilliant article, above. So sorry but I found it to be a little sad. This is because you have stated that "pedigree collapse" is found in every family.

I think that "pedigree collapse" is the same as incest. Incest is quite negative. Incest can lead to mental retardation, in offspring. I feel worried that my ancestors indulged in incest.

Is there not a better theory to explain numbers in our ancestry and exclude incest? Alternatively, is it even true that incest with distant relatives is alright for the offspring to be fine biologically? Anonymous, I appreciate your comment! From a technical standpoint, you are correct that pedigree collapse would be the same as marriage between very close relatives.

That is not what this article is really discussing, however. Marriage between distant relatives i. When I mentioned that we all have pedigree collapse in our trees, I really mean that at some point, somewhere in our tree, we have ancestors related in some way to each other.

Fortunately, scientists are only really concerned about children born to more closely related parents like second cousins or closer , especially if this occurs generation after generation. Marriage between close cousins has been illegal in most places for a long time, so I think most of us don't have anything to worry about. Thank you for sharing your perspective, Mercedes. I have a question. How far back would you have to go to find a common ancestor of everyone living today?

This is a great question! We all do share common ancestors, and I think there would be some variation in the answer. However, I found these two links interesting. They suggest two different answers.

One suggests that about 20 generations would be enough to find a common ancestor shared between a group of people. The other article says that about 1, years that's about 40 generations.

I think that these are great explanations, but that we might have to go back further in history to find common ancestors shared between populations that have been geographically isolated from each other for many thousands of years.