People once believed culture was the bane of evolution. After all, when people solve all their problems with culture, such as medicine for a heritable disease, where does natural selection come into play?
They were wrong. Soon, scientists discovered many signs of post-agricultural evolution. Lactase production continuum in adults, for example. And even today, humans are getting less wisdom teeth and smaller, more efficient brains. And all of these, in just a matter of 10,000 years. And what of the future?
In this universe, man reaches out into outer space. Brave pioneers board ships, travelling generation after generation to explore new planets. A scientific revolution took place, as we learnt more and more about outer space, its wonders and its terrors. As we colonized planet after planet, star after star, all connected by ftl radio transmissions, humanity seemed unstoppable.
However, just at humanity's highest point, the galaxy andromeda collided with the milky way; and havoc ensued, as planets were ripped from their orbits, stars smashed into each other with mighty explosions, and all communications were destroyed. Thus, humanity entered a dark age. Each planet retained its human colony, but with no communication, each was completely isolated from the others, left to their own to survive in the turmoil.
A hundred years pass. A thousand years pass. A million years pass. Two million... seven million... twenty million...
Forty million years finally pass. Humanity is no more. Instead, each colony's inhabitants have evolved, each with their own culture and phenotype. And few understand the others.
Welcome to No Man's Space.