SUMMARYWilliam Bateson's background and training suggest sympathy with the black emancipation movement. Yet the movement's success is attributed more to battles between political figures, than between scientists with contending views on the biology of racial differences. Perhaps, in the long term, Bateson's contributions to slavery and eugenic issues will be seen as no less important than those of politicians. Mendel's discovery of what we now know as "genes" languished until seized upon by Bateson in 1900. For six exhausting years he struggled to win scientific acceptance of these biological character-determining units. Later, he pressed the Mendelian message home to the general public, opposing simplistic applications of Mendelian principles to human affairs, and arguing that minor genic differences that distinguished racese.g. skin colour -can seldom initiate new species. Indeed, the spark that initiates a divergence into two species can be non-genic. We are one reproductively isolated population, the human species.