Did you know that some people “understood” genetics before scientists understood genetics?

By Shaun Richard McCann

Did you know that some people understood genetics before scientists understood genetics? Since Biblical times observers have commented that some people continued to bleed after relatively minor injury. However the Talmud provides insights into the genetics of bleeding disorders many millennia before scientists/physicians began to understand the underlying haemostatic deficiencies which have only been unravelled relatively recently. There are descriptions in the Talmud of bleeding disorders in males and which were transmitted by apparently ‘normal’ females. The Rabbi Judah the Patriarch said that the decision to circumcise could be waived if two brothers bled abnormally and died after circumcision.

Much later Moses Maimonides (1135-1204) said that if a woman married for a second time, her sons by her second marriage should be exempt from circumcision if any sons from her first marriage had bled abnormally following circumcision.

This may be the first recorded recognition of an inherited bleeding disorder which occurs only in males and which we now call Haemophilia due to a mutation in the factor VIII gene on the X chromosome.

The circumcision of Jesus. Public Domain. Artist: Ludovico Mazzolino (1480-1528).



Jacobs J, Fischberg M. ‘Morbidity’, in JewishEncyclopedia: the Unedited Full-text of the Jewish Encyclopedia, 1906. http:// -morbidity, 2011

McCann Shaun R. A History of Haematology. Oxford University Press 2015. ISBN 9780-19-871760-7.