© 1986 by The Society for Integrative and Comparative Biology
Whither Mankind? The Choice Between a Genetic Twilight and a Moral Twilight1
Department of Genetics, University of California, Davis Davis, California 95616
SYNOPSIS. The biological evolution of mankind continues at present, even though for the lastfew millennia mankind's mode of adaptation has been primarily cultural. The necessary and sufficient conditions for biological evolution are genetic variability and differential reproduction (natural selection). The genetic variation of human populations is immense: no two individuals developed from different eggs can ever be genetically identical to each other. The two components of natural selection—differential mortality and differential fertility—continue unabated in modern mankind. Cultural changes fuel human biological evolution, which may well be faster now than it has ever been.
The genetic endowment of mankind may be deteriorating precisely owing to the advances of modern health care, although this is not occurring as fast as some would have it. The eugenic measures proposed to improve the genetic lot of mankind may be classified into four broad categories: genetic counselling, genetic surgery, germinal selection, and cloning. The first two can be used as measures of negative eugenics, that is, to prevent the spread of harmful gene mutations. The goals of negative eugenics would seem unobjectionable, and so would be their voluntary application; compulsion would violate fundamental human rights. Germinal selection and cloning are primarily proposals for positive eugenics that seek the multiplication of desirable genetic characteristics. Positive eugenic proposals are unacceptable on biological, ethical, and sociopolitical grounds.