Originally Posted by mentor

If you were to graph sentience over the history of the earth, you would find an approximation of a mathematical curve which is fairly flat over most of prehistory, and then starts to accelerate upwards over the last few million years. It really takes off with the steps of language, writing, and finally modern electronic communication. Now it is accelerating skyward like a rocket.

Interestingly, not all humans are on board. In fact it seems normal for groups or individuals to get stuck at particular levels of evolutionary consciousness. But thankfully, new groups are always emerging on the cutting edge.

This evolution of sentience is undeniably tied to the evolution of technology. Already our consciousness has taken on certain "android" qualities, with vehicles to help us move, and computers to help us think. We will no doubt continue to make machines to perform mental and physical tasks. We'll create sentient machines if for no other reason than just to see if we can.

Sentience is the reason. And I don't think it cares what the substrate is.