A reflection on human history
First of all, my excuses for the word "arse". I just could not resist after seeing some episodes from the BBC sitcom "Mrs. Brown's Boys" where the word is used often. You can check out the first episode of the show here.
But let's get started now: Why was I thinking about the consequences of Christopher Columbus being a lazy arse (sorry again)? It has to do with a recent paper in Science (on Valentine's Day by the way, which is actually totally irrelevant here). In this paper Garrett Hellenthal and his colleagues used modern genetic data to look for ancient admixture events between human populations. They managed to identify the genetic impact of many important historical events, such as Arab slave trade and European colonialism.
This research shows the urge of humans to explore the world. As a matter of fact, my sister is on a world trip with her boyfriend at the moment (but again irrelevant here). But what if explorers, like Columbus of Marco Polo, did not set out to discover the world? What would be the impact on human genetics?
Admixture events between human populations would be rare. And if you look at the route our species followed (out of Africa, over the Bering Sea and down to the most Southern Point of South America), it looks a bit like an incomplete circle (see picture, taken from the book "Guns, Germs and Steel" by Jared Diamond).
So, could humans have become a so-called ring species? A ring species, is a connected series of neighbouring populations, each of which can interbreed with closely related populations. But the two ends of the ring (in this case Africa and South America) are to distantly related to interbreed. Examples are gulls (genus Larus) around the polar circle, and the Greenish Warbler (Phylloscopus trochiloides) around the Himalayas.
But because of our historical curiosity to explore and discover the world, we shall never find out. Although a mariage between an African and a South American is quite rare. If you do know such a couple, give me a ring!