Your Ancestors Were African

One of my enduring interests has been evolutionary biology. It is a fascinating subject. Much of the credit for that goes to Richard Dawkins who is perhaps the best known writer on the subject, for making it so approachable. His book Selfish Gene, is a must read for anyone who wants to begin exploring this exciting subject. His latest book is God Delusion. As you can imagine, evolutionary biology and organized religion don’t get along.

Human evolution is perhaps one of the most interesting parts of evolutionary biology. In recent years, DNA testing has become the most important tool in our quest to understand the origins of man. The Genographic Project is an ambitious project that is trying to pull together enough data on individual human DNA to reach back into pre-history and understand the great migrations of man. It is now well established that homo sapiens first evolved in Africa and migrated to every habitable place on earth from there.

The way the Genographic Project works is quite simple. It is open to anyone although there are different testing setups in different parts of the world. In the US, you simply go to the website of the project, use your credit card to pay $100 and get a kit in the mail. The kit has the things you need to take a ‘cheek scrape’ (very gentle, no blood) sample and ship it back to the lab. The lab results are put online in a few weeks. The results are anonymous and unless you have the identification number that came on the kit, the website has no other way of knowing who sent which sample. The Project sponsors have been very careful with the privacy of participants’ data.

The lab identifies the key genetic markers for each participant. These genetic markers are mutations that have occurred since the origin of homo sapiens. Based upon these genetic markers each participant is put into a ‘haplogroup’.

Now knowing your haplogroup is interesting but doesn’t tell you much. But science is this wonderful thing. Using the genetic markers, scientists can tell you roughly when the mutations occurred and also what was the migration path that your ancestors took.

Mutations occur with tiny probabilities. Over a longer period of time, a larger number of mutations will occur. Effectively, a mutation that occurred earlier on the timeline of early man, will have more ‘dispersion’ (or a larger variety of mutations accompanying the early mutation). Based upon this dispersion and assuming a constant probability of mutations occurring, you can, with reasonable certainty, calculate the date of the mutation.

The way genetic markers are overlaid on the world map to get migration routes is also quite interesting. You may have heard this fact (or fiction, I don’t know) – 90% of humanity is born, married, lives and dies within a 5 mile radius. What this means is that while there may have been massive dispersion of people in a haplogroup, migration is gradual and geographically incremental. Till 10,000 years back, human beings could not migrate further than where their legs could carry them. Using the data gathered, therefore, it is possible to chart the earliest migration paths of human beings.

One last factoid here. Sexual reproduction in human beings mixes up the genome. At every point your biological ancestors go in two different directions in the family tree. If you go back n generations you will have 2^n ancestors to contend with. Obviously this won’t give you a definitive answer on where did your ancestors come from.

To solve this problem, the Project tracks the patrilineal descent for men using the Y chromosome. Since women don’t have the Y chromosome it is always passed down from father to son. In women, the Project tracks genetic markers in the mitochondrial genome which is passed on from the mother to the child in the egg.

The Project itself is a non-profit, jointly run by National Geographic and IBM. When my wife and I contributed our DNA to the project a year or so back, there was far less information than there is today. Clearly, the corpus of knowledge is growing. The more people who contribute, the better the data becomes and therefore the better the conclusions.

Shown below are my migration routes for my ancestors. The accompanying genetic history is here.

Here and here are my wife’s.