Haldane's rule

English Etymology Formulated in 1922 by the British evolutionary biologist J. B. S. Haldane. Proper noun An observation about the early stage of speciation, stating that if in a species hybrid only one sex is inviable or sterile, that sex is more likely to be the heterogametic sex. en 2018 w:Tim Flannery Europe: The First 100 Million Years 181 Penguin 2019 One study hints at the possibility that Haldane's rule may have been the cause of the lack of Neanderthal DNA on the Y-chromosome of hybrids, but currently we do not definitively know. en eponyms