Ray,

You are right, we need more evidence, but we can speculate.

The thing to remember is that by 40,000 years ago when the Denisovans disappear, they had been around for nearly 800,000 years. That's a long time to develop their own unique physiology, mindset and material culture.

We, on the other hand, have only been around for 300,000 years, making us the new kids on the block when we entered central and northern Asia some 45,000-55,000 years ago. There is every reason to conclude the Denisovans were more advanced than we were at this time. Moreover, there is good reason to surmise that their legacy continued on through Denisovan-modern hybrid communities, or through any other type of hybrid community existing at this time. They, in turn, will have taken this legacy in every other part of the ancient world, and across into the Americas.