no the European neolithics had the whole of Europe ,Asian and a,short boat ride away Africa, they wernt by any means hemmed in
I would contend that they were.
Mountain ranges require that you have foodstuffs you can carry, which means storage, which means you have to be beyond hunter gatherer.
Seas (a short boat ride) need the same, but they also need boats of a size capable of carrying more than a few people - you can't develop a longship if you're nomadic because you can't carry it.
So, to get past those 'hemmings' means you have to have reached a level of stability and security that the indigenous peoples of larger areas never needed (or weren't able) to reach.
If that weren't the case, and everyone in Europe, Africa and Asia could just wander between each area, everyone would look the same.
Because they were 'hemmed in', a Frenchman looks different to a German, who looks different to a Spaniard, who looks different to an Asian - who all look different to a native American, who looks different to an aboriginal Australian, who looks different to an African.