The principle obstacle to human dominion over the rain forests is still the rich variety of parasites lying in wait for intruders. - William Hardy McNeill

When variations could be so extravagantly successful, displacement of one humanoid population by another even more effective group of hunters must have occurred frequently. Survival was more likely for the more formidable in battle as well as for the more efficient in the hunt.

Inferences and large dosages of imagination actually have allowed the construction of a far more adequate understanding of the cosmic and human past than earlier generations achieved. I believe that this is the central intellectual accomplishment of the twentieth century. Innumerable cosmologists, physicists, mathematicians, anthropologists, sociologists, historians, ecologists, ethologists, and other specialists have played their part; a few swashbuckling intellects led the way, and the outlines of an evolutionary worldview, uniting natural and human history, has begun to emerge. It may be convincing for generations to come—or again may not.

Religious history also offers another striking parallel between Rome and China. The Buddhist faith began to penetrate the Han empire in the first century A.D., and soon won converts in high places. Its period of official dominance in court circles extended from the third to the ninth centuries A.D. This obviously parallels the successes that came to Christianity in the Roman empire during the same period.