Creating a genetic map of Asia: A Book Talk

Posted By Damjan DeNoble

I am currently reading Steve Olson’s “Mapping Human History” and there is a part of the book that deals with the genetic mapping of Southeast Asia, a history that is very relevant to our work here at AHCB.  In essence Steve Olson provides a layman’s explanation of where our genes come from, and why all humans on Earth are related.  I want to share some of the thoughts in this book, but I also want to add my two cents.  Below you will find two sections. “My Two Cents” gives some of the thoughts I have had while reading Olson’s book, and I originally included it as the concluding paragraph of the next section,”The Long of It“  an explanation of where Southeast Asia’s people came from.

My Two Cents

Healthcare wise, I think that the fact we are all genetic relatives should dampen the current trend of popular nomenclature in Asia and elsewhere to refer to modern, science-based medicine as “Western Medicine”.  Perhaps we should just shorten it down to “Modern Medicine”, a much more inclusive term. It is the eponymous representation of science-based medicine’s universal applicability to a modern human civilization that shares a common genetic ancestry.  “Western Medicine,” on the other hand, subtly implies that science-based medicine is a preference of Western civilization.

I am also beginning to wonder about the role of traditional medicine as a propaganda vehicle.  Some of its value derives from the fact that medicine encapsulates the collective wisdom and heritage of a nation.  But, medicine, like history, is a mysterious  branch of knowledge. So, it makes sense to me that someone would choose to emphasize the importance of history through the lens of traditional medicine  in order to  muddle the origin of the former, thereby leaving more room for official state interpretation of a society’s genetic and racial origins.

The Long of It

Genetic mapping has fascinated me ever since I attended a presentation by Mary Claire-King, the famed geneticist who pioneered the use mitochondrial DNA sequencing to identify surviving family members of  Argentina’s lost children.

The sequencing technique used by Claire-King derives its name from a very important component of the human body called a mitochondria.  This mitochondria can be thought of as the battery of the animal cell.

Long ago,  mitochondria were self sufficient organisms, but now they are dependent on the animal cell for survival.  And, we know that they were once independent of the cell because they have their own DNA, a  loop of nucleotides about 16,500 nucleotides long. Every human body has trillions of them and in almost all known cases, all mitochondria within a single human body have the exact same  DNA sequence.  However, as Steve Olson points out “the DNA sequence of my mitochondria probably differs from the DNA sequence of yours, which is where the story gets interesting.”

During reproduction,  mitochondrial DNA is passed on through the egg, and usually the DNA sequence of the mitochondrial cells in that egg is an exact duplicate of the mitochondrial DNA in the mother’s cells.  But, sometimes, as the mother’s cells are duplicating their DNA to pass on to the egg, a mistake happens, and the DNA in the mitochondrial DNA of the egg ends up with a few differences in its nucleotide genome.  This is called a mutation, and according to geneticists like Olson “these mutations are the key to reconstructing our genetic history“.

The presence of these mutations leads to an inevitable conclusion, every mitochondria in existence today can be traced to the mitochondrial DNA of one human female known as Mitochondrial Eve, our most recent common human ancestor.  It’s not that she was necessarily the first modern human being, it’s simply that her mitochondrial DNA is the oldest surviving mitochondrial DNA within all humans on Earth.  (To find out exactly why her existence is fact, go here.) Similarly, we can use the same line of logic to trace all people on Earth back to a Y-Chromosome Adam since the Y chromosome is only passed through men, but I digress.

We can calculate when Mitochondrial Eve was around by examining all the variation in modern day mitochondrial DNA (distinct DNA sequences are called haplotypes) and calculate the number of generations that it must have taken to produce the necessary mutations to produce so much variation.  We end up with a figure that dates Mitochondrial Eve’s existence to somewhere around 150,000 years ago.  This means that from 150,000 years ago on,our mitochondrial DNA simply built upon the DNA of Mitochondrial Eve.  Studies have confirmed that all humans on Earth share Mitochondrial Eve’s basic haplotype, which also means that humans on Earth are all related. One way to conceptualize this is  in terms of car models.  First imagine two mustangs side by side, the first generation mustang from 1964, and the all new 2009 mustang drop top.

The cars clearly share similar characteristics, and look like relatives.  But, the 2009 car is not a direct evolution of the 1964 model.  There are many intermediary steps, and all those steps share varying degrees of resemblance to the 1964 model.  Also, all of the car models built upon and in some cases even improved upon the previous design. Realizing that there are also intermediary steps between the DNA of Mitochondrial Eve or Y-Chromosome Adam and the DNA of today’s humans, is the key to creating a genetic map of the world.

To take the car visualization one step further, lets line up all the Mustang models ever built, side by side, with the oldest car on the West, and the newest car on the East.  And lets say that each space on that line is representative of a geographic area that the particular car model occupies, and that no two cars can sit on top of one another so that they all have to occupy a different space.  Let us also prominently display the date models were built below each vehicle.   Three things become obvious.  First, the further one goes East from the 1964 mustang, the newer the cars get.  Second, each model car corresponds to both a time and a place. Third, there is only one oldest model.

Now, lets pretend that everyone in the world was to suddenly hold hands and we could take a freeze frame picture.  Looking from West to East, where would the oldest model of mitochondrial DNA be?  Where are its geographic origins and at what time were they created?   In which direction would one go to find the newer versions of mitochondrial DNA?  If  one were to do this, like many geneticists have, all the signs would point to Africa as the cradle of human civilization because that’s where the oldest mitochondrial DNA sequences are located.  From central Africa and on up through the Middle East, Europe, Southeast Asia, and Australia the haplotypes only get newer.  Furthermore, by looking at the dates of various haplotypes within geographic regions we can come to better understand how civilizations of humans there formed, where they came from, and how they interacted.

Of course, the analogy between cars and DNA haplotypes is an overly simple one.  There are, in truth, many other factors that go into dating civilizations, like, for example, the number of haplotypes in a particular region; usually the greater the number of a particular gene haplotype in a region the longer that region has harbored civilization. But I will let geneticists explain that elsewhere, and in a much more clear way than I have.

So when did humans come to Asia?  By looking at various gene haplotypes and archaeological remains scientists are fairly certain that humans successfully left Africa between 100,000 and 65,000 years ago, and made their way along the coast of Asia down to Australia some 65,000 years ago.  Around 40,000 years ago humans started living in the interior of Asia, and by 26,000 years ago groups made it as far inland as Beijing.

Japan is an interesting case because there seem to have been two main migrations to the island.  Around 10,000 years ago Japan was populated by people that were close descendants of the humans that populated New Guinea and Australia.  Then, 2,300 years ago, another group of humans from mainland China and/or Korea came to the island and mixed with the original group.

Steve Olson makes the point that the genetic evidence contradicts the claims of the Chinese paleontology establishment.  Chinese paleontologists almost universally claim that the Asian people descended from Peking Man – a skeleton some 500,000 years old, unearthed near present day Beijing in the 1920′s.  Much of this adherence is the political remnant of some three and a half thousands years of propaganda by Northern warlords that intermittently united and fractured China over the centuries.  It bears point out, however, that it is also a point of racial pride.  The idea that one’s race is somehow different from other races, is an appealing one because proof of difference is proof of uniqueness and, when times call for it, of superiority.