Генри Райдер Хаггард - Allan and the Ice-Gods

This novel is the final volume of the Allan Quatermain saga. Once more Quatermain takes the hallucinogenic taduki drug, as he did in previous novels, and he finds himself reliving as Wi, an civilized man living in the barbaric ice age as part of a clan of cavemen. The novel has been noted as a treatment of the topics of eugenics and evolution in literature and culture.