[dwaltrip]

Previously, human groups were like two separate containers, one containing coffee and one containing milk. Now, through technological advancements and many other developments, they have been brought together into a single cup. The laws of physics demand that the two liquids in the cup combine into a homogeneous mixture.

This is an imperfect metaphor -- in reality, the separate containers have only been partially brought together, and human individuals are more complex than beverage molecules. But I think the idea expresses noteworthy amounts of truth.