Where Did I Come From?
Like every other human, I came from Africa ultimately. But anthropologists have long known that early humans branched off as they left Africa and spread throughout the world. My particular lineage takes my ancestors out of Africa and through the Middle East. At this point, roughly 40,000 years ago several groups split off – one going south into India and eventually making its way to Australia, while another ends up in China. My ancestors, like most Europeans, moved west and populated most of Europe. During the last ice age things got so bad that my ancestors migrated south into a pocket of southern Spain known as the Iberian Refugium. Once the glaciers receded they moved north and repopulated most of western Europe.
The marker in my Y-chromosome connects me to 70% of the men in southern England and as much as 90% of men in Spain and Ireland. Pretty cool, huh? How do I know this? Because I participated in the Genographic Project being run by National Geographic and IBM. It’s an ambitious program to process a wide variety of genetic samples from people from around the world and create the ultimate database of human genetic history.
You can see a short video of the project in action here…
How do they do it? By sequencing DNA and looking for genetic “markers.” DNA for the most gets combined by parents to produce a hybrid form in offspring – this is why we have similarities with our parents but aren’t carbon copy duplicates. Mitochondrial DNA is a small piece of the puzzle that has the unique quality of being passed down by mothers and doesn’t really change, in essence creating a simple note that can be tracked through populations.
Alice J. Dunn has a more detailed explanation:
Scientists who trace modern human origins often talk about a special kind of DNA, mitochondrial DNA (mtDNA). But do you know what mitochondrial DNA is? And do you know what mitochondria do? Mitochondria are tiny structures found within the cell that resemble grains of rice. They produce the energy that cells need to function, and they have their own small complement of DNA, containing just 37 genes in humans. Compare this to the human nuclear genome (the entire set of genetic instructions found within the nuclei of all the cells), which contains some 30,000 genes. But mitochondrial DNA is especially powerful for studying the ancestry of modern humans. While the nuclear genome is reshuffled with each new generation as the father’s and mother’s DNA recombine, mitochondrial DNA is passed directly from a mother to her children. As a result it preserves patterns of ancient markers that thelp scientists map the path modern humans have taken around the world.
So by collecting samples and looking for these mtDNA markers, scientists can identify and track the lineage of a person along a well established migratory path from Africa. Over the years it’s been established that early humans migrated out of Africa and many groups have branched off from those initial groups, as seen in the map below:
Which one are you a part of?