Hominid evolution: genetics versus memetics

摘要

The last few million years on planet Earth have witnessed two remarkablephases of hominid development, starting with a phase of biological evolutioncharacterised by rather rapid increase of the size of the brain. This has beenfollowed by a phase of even more rapid technological evolution and concomitantexpansion of the size of the population, that began when our own particular`sapiens' species emerged, just a few hundred thousand years ago. The presentinvestigation exploits the analogy between the neo-Darwinian genetic evolutionmechanism governing the first phase, and the memetic evolution mechanismgoverning the second phase. From the outset of the latter until very recently-- about the year 2000 -- the growth of the global population N was roughlygoverned by an equation of the form dN/Ndt= N/T*, in which T* is a coefficientintroduced (in 1960) by von Foerster, who evaluated it empirically as about twohundred thousand million years. It is shown here how the value of this hithertomysterious timescale governing the memetic phase is explicable in terms of whathappenned in the preceding genetic phase. The outcome is that the order ofmagnitude of the Foerster timescale can be accounted for as the product of therelevant (human) generation timescale, about 20 years, with the number of bitsof information in the genome, of the order of ten thousand million. Whereas theorigin of our `homo' genus may well have involved an evolutionary hard step, ittranspires that the emergence of our particular `sapiens' species was rather anautomatic process.