Disappearing Neanderthal Y chromosomes

At https://www.livescience.com/health/genetics/the-mystery-of-the-disappearing-neanderthal-y-chromosome … the human genome is thought to preserve Neanderthal DNA, so much so it effects health amongst the modern human population. There is, however, a bit of a mystery as the Y chromosome of the Neanderthals is missing. Females carry two copies of the X chromosome and males only one of X plus one of the Y chromosome. The Y chromosome can only be passed from father to son. So, why might  the bit of Neanderthal DNA have vanished? The consensus was that it was lost over time as a result of several inter breeding escapades between humans and Neanderthals. This sounds like a hastily thought up response. It has now been found that 3 of the Neanderthal genes common to modern humans seem to be part of the immune system – which has been inherited. Cutting a long story short it has been found that around 100,000 years ago the Neanderthal Y chromosome was completely replaced by one that modern humans have inherited. Martin Petr, a Danish researcher, suggests Neanderthal populations may have shrunk, at some point in time, allowing mutation to accumulate within the gene pool. On the other hand, a catastrophic event may have led to a population bottleneck and at the same time, mutation occurred as a result of radiation – or something like that. If this happened 100,000 years ago it would have coincided with the last Interglacial period – presumably at the point it came to an end.