Prem Kumar ji,
Thanks for the link to Neelakandan's rebuttal.
In addition to your point regarding Poznik's erroneous conclusion, here is something else.
In his email communication, Dr Underhill cautioned against jumping to conclusions with quite a few caveats:
It is important to realize that haplogroup R1a1 is just one piece of genetic information that informs the conversation about the peopling of Eurasian as well as Indian. It is also important to keep in mind that the Y chromosome locus is sensitive to founder effect and high frequencies may over-emphasize the magnitude of the impulse relative to other genetic data. For example while the Y chromosome might indicate a large degree of replacement of other Y chromosomes in a region, while other genetic data may indicate that the degree of replacement and mixing was not as great as reflected by Y chromosome data alone.
What is the "founder effect"?
Well, when you have a population that gets suddenly and catastrophically diminshed, say by some natural disaster or climatic effect, then afterwards, only a small proportion of the original population remains.
Let's say you have a population of ants on your terrace. Most are brown, a few are black, a few are red, and a very small number are white.
One day you spray DDT on the terrace. The vast majority of the ants die!! They will never contribute gene pool to the DNA of the ant population again. You have effectively created what is known as a "population bottleneck".
Let us say four of the original (1000+) ant population are hiding somewhere, and survive the population bottleneck imposed by spraying DDT. Just by chance, three out of these four are white ants!
As a result of this, over the next several months/years, the new ant population that grows on your terrace will have a HUGE proportion of ants carrying white-ant DNA (because three out of four possible parents following the bottleneck were white ants). This is what is known as a "founder effect".
Martin Richards and his gang claim that, because some sub-clades of the R1a-M417 haplogroup (such as Z94-Y40-Y37) which showed rapid expansion in India are relatively "young" sub-clades (about 4000 years old), therefore the Y chromosomes bearing the markers for these sub-clades MUST have been first brought into India by Eurasian-origin "Aryans" about 4000 years ago (2000 BCE).
This is bad science and reeks of confirmation bias.
Indeed, according to the above quote from Underhill that Neelakandan cites, the MUCH more likely explanation is a population bottleneck followed by a founder effect, as I illustrated above.
In this case we would be talking about an Indian-origin human population (not an ant population), that had been living in the Indus-Saraswati Valley (ISV) for many thousands of years prior to 2000 BCE.
Many members of this Indian-origin human population would have been been members of various R1a subclades, including R1a-M417, R1a-M780 (which in fact has not been found ANYWHERE in the world except India), etc. Among the R1a-M417 people, a small proportion would also carry the marker Z94-Y40-Y37. These would be analogous to the "white ants" in my example.
Now there has been much controversy regarding the exact causes of the demise of the ISV civilization, but most of them center on climate change, environmental degradation, and natural disasters.
The very same things that cause the ends of civilizations also cause... guess what? Population bottlenecks!
When a large and diverse population loses the majority of its members in a catastrophically short timespan, the distribution of various sub-clade markers (M417, M780, Z94-Y40-Y37 etc. etc.) amongst the small number of survivors could be extremely different from the distribution of those same markers in the original large population.
The population in whom the Z94-Y40-Y37 marker had relatively recently emerged, could have suddenly gone from being a tiny minority of the overall Indian R1a-carrying population to an overwhelming majority of the small group of survivors. Like the white ants after spraying of DDT.
It stands to reason that most of the currently living Indian population who carry R1a on their Y chromosome, would also carry Z94-Y40-Y37. Just as the overwhelming majority of ants on your terrace a few years after you sprayed DDT will carry white-ant DNA. This is the founder effect at play.
And as Underhill has emphasized, data from a Y-chromosome locus (which is what R1a and all its sub-clades are) is especially sensitive to founder effect.
That Martin Richards has utterly disregarded this explanation (founder effect) for the "rapid expansion of relatively young Y-chromosomal subclades in South Asia", shows that he is a bad scientist. That Richards has, furthermore, tried to shoe-horn his observations to fit the notion that Z94-Y40-Y37 carrying Y chromosomes MUST have been brought to India by steppe Aryans riding on horseback and brandishing the Rigveda, shows that he is intellectually anesthetized by a degree of confirmation bias that even Herbert Risely would have found hard to justify. He is drawing conclusions about the genetic makeup of a population that existed BEFORE the bottleneck, using data that emerged as a result of founder-effect expansion AFTER the bottleneck.... a thoroughly unscientific method, as made explicitly clear by my analogy of the ant populations before DDT (mostly non-white) and after DDT (mostly white).
And meanwhile, how about the "other genetic data"
that Underhill suggests could be used to temper conclusions drawn from the unusually founder-effect-prone
Y-chromosome marker distribution?
Those would include mtDNA data (which have long supported the idea of no significant gene flow into India since 12500 ybp), and the autosomal data analyzed by Singh, Tamang, Thangaraj, Chaubey and others-- on which the scenario of 45000 y/o ANI admixing with 60000 y/o ASI is based.
But why should Richards allow these burdensome facts to temper the sensationalist conclusions he can draw by regarding the Y-chromosome data, unreliably, in isolation?
Bad science, at best, offers no improvement in our understanding of the world. At worst-- in the hands of intellectually dishonest, politically motivated, poisonously anti-Hindu propagandists like Tony Joseph-- it becomes an instrument for perversion of the truth itself.