Adam and the Snake

I am finally a Postgraduate. Yipeee! The last few weeks have been very hectic. My thesis left hardly any time for anything else.

My thesis, on the occurrence of distinct mutations on the Y chromosome in North Indian men, left many people confused. Admittedly, I was one of them. It all boils down to one particular mutation: M17.

This marker confounds me still. Here's why:

• Every single North Indian Brahmin I sampled (including myself) carried M17. Gaur, Saraswat, Kanyakubj... all were M17.
• Off the record, I heard some of the results of the NRY (Non recombining Y Chromosome) typing of some South Indian samples. These results are not in the public domain, and I'm not supposed to know this. It seems an ancient Brahmin settlement somewhere in Southern Tamil Nadu (I wasn't told which) turned up ALL M17s. This in itself is amazing news.
• I heard from my Guide, who is the South Asia Principal Investigator for the Genography Project, that M17 is turning up in unexpected numbers in Central Asia.
• In Eastern Europe, about half of all men carry M17.

Based on such figures, M17 has been called the Indo-Aryan marker. The frequency of M17 diminishes down the caste hierarchy, which further cements this presumption.

However, some recent data on Microsatellites on the Y Chromosome seems to complicate matters. Microsatellites are repeating segments of 2 or 3 nucleotides.... eg, AGAGAGAG..... they may be 10 repeats, 30, or 300. The genome is littered with thousands and thousands of distinct Microsatellites. The repeat number is mutable within the span of generations, so individuals with the same (or similar) repeat numbers are more closely related. Sample large enough numbers of people, and you can start to build something of a family tree. Now, simply put, if within a population, you find wildly different repeat numbers for a particular MS, that would mean that the population is more diverse, or in other words, more ancient. Here's where the story of M17 in India gets complicated. Look at Microsatellites on M17 men, and you'll see that there is enormous diversity, vastly more than was expected. Even Central Asia, the presumed birthplace of M17, doesn't have this much diversity. So what does this mean? On the face of it, this would imply M17 originated in India. If so, then how do you account for its presence in Eastern Europe? The Aryan Invasion Theory, or Sons-of-India?

Some scientists like to use popular terminology to explain concepts. Among them, Genetic Adam. Simply put, all men alive today share a single male common ancestor, dubbed Adam. He was the patriarch of a lineage that eventually dominated all other human lineages, till none survive. It is believed Adam lived somewhere in East Africa 40-60 Thousand years ago.

So one stormy night, while I contemplated Adam on my way back to the hostel, I nearly stepped on this Snake.

This is a Saw Scaled Viper, AKA the Carpet Viper. Kills more people than any other snake in the world.