war, the Fourth Men eventually reach the limits of their scientific abilities and discover that emotions and body are also necessary for complete understanding of the cosmos. Fifth Men. (Chapters 11–12) An artificial human species designed by the Fourth Men. "On the average they were more than twice as tall as the First Men, and much taller than the Second Men... the delicate sixth finger had been induced to divide its tip into two Lilliputian fingers and a corresponding thumb. The contours of the limbs were sharply visible, for the body bore no hair, save for a close, thick skull-cap which, in the original stock, was of ruddy brown. The well-marked eyebrows, when drawn down, shaded the sensitive eyes from the sun." After clashing with and finally eliminating the Third and Fourth Men, they develop a technology greater than Earth had ever known before. When Earth ceases to be habitable, they terraform Venus, committing genocide on its marine native race which tries to resist them. The Fifth Men do not cope well after the migration and eventually devolve and diverge into two species: the Sixth Men and a seal-like subhuman species. Sixth Men. (Chapter 13) "Sadly reduced in stature and in brain, these abject beings... gained a precarious livelihood by grubbing roots upon the forest-clad islands, trapping the innumerable birds, and catching fish... Not infrequently they devoured, or were devoured by, their seal-like relatives." After tectonic changes provide them with a promising land mass, they fluctuate like the First Men and repeat all their mistakes. Seventh Men. Flying humans, "scarcely heavier than the largest of terrestrial flying birds", are created by the Sixth Men. After 100 million years, a flightless pedestrian subspecies appears which re-develops technology. Eighth Men. "These long-headed and substantial folk were designed to be strictly pedestrian, physically and mentally." When Venus becomes uninhabitable, about to be destroyed along with the entire inner solar system, they design the Ninth Men, who will live on Neptune. Ninth Men. (Chapter 14) "Inevitably it was a dwarf type, limited in size by the necessity of resisting an excessive gravitation... too delicately organized to withstand the ferocity of natural forces on Neptune... civilization crumbled into savagery." After the Ninth Men's civilization collapses, the Ninth Men themselves devolve into various animal species. Tenth to Thirteenth Men. (Chapter 14) "Nowhere did the typical human form survive." About three hundred million years after the colonization