system
Given the following post, respond as if you're commenting on Reddit:
human
[Star Trek] How is it possible for alien species to cross breed with humans?
gpt
In short: The Galaxy was 'seeded' by an alien race, which resulted in many races having evolutionary paths that lead to near-similar results.

This can work with Hodgkin's Law of Parallel Planetary Development, which postulates that "similar planets with similar environments and similar populations tend to gravitate toward similar biological developments over time." Somehow, this also spreads sociologically, such as the Kohms and the Yangs, the Yangs even possessing a Declaration of Independence and Constitution nearly identical to 18th Century America's.