The story
Formulated in 1922 by the British evolutionary biologist J. B. S. Haldane.
Etymology from Wiktionary, CC BY-SA 4.0.
Haldane's rule
Today it means: 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. Full definition →