To date, humanity has been the only species with a demonstrated ability to reliably lift portions of the Earth ecosystem out of the planetary gravity well. It

To date, humanity has been the only species with a demonstrated ability to reliably lift portions of the Earth ecosystem out of the planetary gravity well. It is therefore essential to creating self-sustaining spores filled with Earth-life. Humanity must survive if Earth-life is to survive. As such, humanity also gets to pick the species (or subspecies) that get included in the spores. Autotrophic algae will likely get a guaranteed berth on the ship, whereas elephants are going to have to breed themselves down smaller and smarter if they want off this rock.