Our ships, however organic, do not have the ability to breed. The artificial pathogen that initiates and controls the ship-growing process has been virtually unchanged since our first war with Atlantis. Each lineage and its sub-factions have their own strains, true, but the changes made to the strain mainly concern living space configurations.

As they cannot speciate without our meddling, their evolution, as you might say, has been stalled for over ten thousand years.