The claim has been made that sperm counts in the West are declining alarmingly. A typical ejaculate might contain 100 million sperm; since only one is required to do the job, a reduction to (say) 50 million may not seem obviously critical. But human fertilization is chancy at best. Even trying hard, a couple can easily take many months to conceive. One explanation is that most sperm are infertile. Their job is to ward off or discourage rival sperm. In effect, they act as a large screen of warships escorting a small, crucial convoy of freighters.

Daedalus argues that both freighters and warships will put on a mighty spurt if challenged by a rival fleet. There is some evidence that a man with a sexual rival generates more sperm than he would do otherwise; but Daedalus reckons that the speed, efficiency and pugnacity of his sperm must rise as well. In many species sperm compete chemically, by putting out toxins or antigens against their rivals. Indeed, Daedalus once proposed to use human seminal toxins in a natural spermicidal contraceptive. He now has a converse strategy. DREADCO biochemists are studying human seminal toxins in the hope of developing a spermal ‘vaccine’. It will be a derivative of such a toxin, modified just enough to be harmless, but still sensed as a deadly threat by sperm encountering it. Spurred by this challenge, they will drive towards the ovum with extra speed and energy. This ingenious ‘conceptive’ will be welcomed by couples trying hard to have children. It will boost their chances greatly.

But Daedalus goes further. The sperm in a given ejaculate must be immune to their own toxin. They should even tolerate quite well the toxin of a close genetic relative carrying many of the same genes. But toxin from a genetic stranger must be a terrible threat. The DREADCO team are therefore mixing semen samples from different types and races of men, and studying their competition under the microscope. They will then plot the semen donors on a map such that the more fiercely antagonistic the sperm of any two donors, the further apart they are on the map.

The resulting human distribution will be far more fundamental than one based (say) on blood groups or pigmentation. It will reveal the classes of mankind as sensed by genetics itself. It should powerfully illuminate the stages by which we emerged from Africa, and our diversification since then.