It is proposed that the loss of ability by humans to synthesize ascorbic aicd may have markedly enhanced the survival opportunities of early man living in a malarial infested environment. This hypothesis is based on biomedical evidence which indicates that glucose-6-phosphate dehydrogenase (G-6-PD) deficient individuals display enhanced sensitivity to ascorbic acid induced hemolysis which has been fatal at sufficiently high doses and that the G-6-PD deficient trait has been selected for in malarial environments.