Amphibians, such as frogs and salamanders, marked the attempt to station vertebrates on land. Still, they were transition products; they had to stay near the waters where they reproduced. Reptiles were the first truly adapted to a terrestrial environment.

Reptiles were so successful that they ruled the Earth for a long period. During the Jurassic age, however, while tyrannosaurs stomped the ground, Eternons started experimenting with mice-sized prototypes of mammals. When a cataclysm wiped out dinosaurs, Eternons made no effort to reintroduce them: they had more exciting structures to work on. They even renounced to further improve snakes, lizards, crocodiles, and tortoises.

Birds, also launched during the age of dinosaurs, were high-tech marvels. Feathers and thin-walled bones reduced weight. A super efficient metabolic system delivered sheer muscular power. Birds could almost magically escape gravitation.

But it was mammals upon which Eternons had decided to focus their attention. Mammals presented the highest potential among all living beings. It was not because internal gestation had replaced the insufficiently protected egg; nor because glands produced milk for reliably feeding the newborn; nor because an ingenious thermostatic system regulated body temperature; nor because of hundreds of similar wonders. It was because, in mammals, Eternons had given emphasis to the brain and to its software: in other words, to intelligence.

From now on, Eternons would privilege the "Mammalian Research & Development Program," and the progress would be amazingly rapid. It had taken billions of years of arduous work to come to this point. In a few million years, Eternons would pack into the human structure an incredible amount of knowledge and capabilities.

Why, after such progress, do Eternons continue to assemble forms of life simpler than us, from microbes to whales? We can answer by observing our own behavior.  Although we have powerful computers, we continue to produce much needed pots, chairs, nails, pens, etc. Likewise, Although  Eternons have us, they continue to produce over a million distinct species, all having a place and use on Earth.