Mixing is the reality of life; pure only exists in our imagination.
Humans have this love for purity and feel shame about the undeniable reality of mixing. While people in some parts of the world are proud of eating a ‘purely’ vegetarian diet, others list everything they could recollect from their harddisks to proclaim their superior ancestry. They are all right, but only for a negligibly short duration in history. Human history does not give a damn about vegetable eaters, and the same for any exclusive ancestry!
A landmark research paper came out in September 2019 in the journal Science titled, ‘The formation of human populations in South and Central Asia’. It was a report based on ancient DNA data from 523 individuals spanning the last 8000 years, from Central Asia and northernmost South Asia.
Migration of Yamnaya Steppe Pastoralists
The paper was primarily on the migration of the Eurasian Steppe to South Asia around 3000 years ago. The ‘Steppe Ancentry’ or Yamnaya culture was active around 5000 years ago in present-day Ukraine and Russia. The folks from that region had travelled to either side of the world, to Europe and South Asia. Today we talk about the guys and, perhaps some girls, who migrated to the east.
It is relevant here to talk about another DNA study published in Nature in 2009. This study genotyped 125 DNA samples of 25 different groups of India and did what is known as a Principal Component Analysis (PCA) of the data. Based on the similarities of the allele, they found a relationship between people of the North and South of India. An ancestral component, they call it ANI (Ancestral North Indian), varied from 76% for the North to 40% in the south. The remaining fraction is the ASI (Ancestral South Indians). Note that a ‘Pure’ ASI, closer to the earliest humans (travelled from Africa, of course), was not seen in that study.
Where are those people? That is next
Flashback
ASI was ‘ruling the land’ and Indus Valley Civilisation (IVC) was flourishing when the Steppe folks arrived in present-day India. But that would change soon, and the visitors would form a mix, which is the base of the continuous band from North to South that we saw earlier. So was ASI was the original one? The answer is a firm NO. ASI was a mix of what is known as AASI and a group of people with Iranian farmer ancestry. And who were this AASI? Well, they were the people who came 40,000 years ago, yes, from the cradle of homo sapiens, Africa. Of course, the Iranian farmers also went from Africa, but a few tens of thousands of years earlier.
Piecing All Together
The following picture, copied from the Science paper, summarises the whole story.
Why Is It Important?
It is always fun to learn more and more about the incredible spread of homo sapiens from Africa to the rest of the world. It is equally wonderful to note how dynamic was the intermixing of population. Also, notice one irony. These results, the vivid stratification of ANI and ASI, were possible due to their obsession with endogamy in the last few hundred years. That way, they preserved the signatures of the founders or else it would have been a complete mixing of genes.
The formation of human populations in South and Central Asia: Science
Reconstructing Indian population history: Nature
