Big Ancestor

In a galaxy where countless alien civilizations thrive, humans stand out as the only species capable of interbreeding across thousands of light‑years. A curious alien pilot, Taphetta the Ribboneer, meets a small team of human specialists—a Neanderthal‑like archaeologist, an Earth‑born biologist, a linguist, and a mathematician—who are trying to explain this baffling genetic unity. Their discussion centers on a bold hypothesis: humanity didn’t evolve independently on each world but originated once, then spread far and wide, leaving behind a “big ancestor” that links every human colony.

The scientists present their “adjacency mating principle,” a model that maps how different human races could still produce offspring if they were once physically adjacent in evolutionary history. As they lay out the data, Taphetta weighs the evidence, skeptical yet intrigued by the possibility that a single, ancient lineage could account for the galaxy‑spanning family tree. Their debate sets the stage for a journey that could reshape how all sentient beings understand humanity’s place among the stars.