It's just weird to think that we drove them all to extinction so quickly and so effectively in a relatively short space of time. Long before we had agriculture or non stick-and-rock technology. How did we do it? A few Homo sapiens wander into Eurasia, which already has a population of millions of Homo, and all the other Homos die off?

I'm not advancing an alternative theory or saying its wrong, I'm just saying its surprising.

It's also possible that Neanderthals prevented modern humans from leaving Africa until their populations were already in decline for other reasons (disease? inbreeding? infighting? overhunting?). In that case we may have just sped up the inevitable.

Climat changes were very important, populations varied greatly, and many regions became uninabited and inhabited again many times over.

There are minor "ice ages" on 40 000 and 100 000 year long cycles. Every time these happen (especially when they combine) - animals and plants change, and hunter-gatherers have to migrate or starve (most starve anyway). It's almost like game reset. So neanderthals advantage wasn't that big.

Survival of the fittest.

Since we have ~2% Neanderthal DNA, I don't think you can say they're quite extinct.

Exactly. The current theory, I believe, is that humans didn't "exterminate" Neanderthals, we just out bred them. This might be due to differences in "character". I can't reproduce the argument here, and I don't have a link, so I'm being a bit vague but the point is, something in the Human mental make up caused us to form more successful communities than the Neanderthals. The several Hominins running around Europe in the past seem to have coexisted for some time, and interacted enough that some interbreeding took place. Over time, Neanderthal faded away, leaving only the bits of DNA we got from them.

There were never more than a few thousands Neanderthals. The rising tide from Africa just diluted them to 2%. They're not gone; they're here in you and me and Aunt Hilda.

We have 99% of chimpansee DNA and 60% of banana DNA. I don't understand how they measure the 2%, obviously it's a different metric.

EDIT: so apparently there is a way to distinguish DNA that originated in Neanderthals and we got it from them as opposed to DNA we both got froum common ancestors.