He left in 1910 to join the University College London where he studied biometrics under Karl Pearson, a proponent of Social Darwinism and eugenics.

[4] After the Armistice he returned to the Zoology department of the University of Oxford, taking an interest in ecological issues, especially population and overpopulation.

The population problem arose -according to Carr-Saunders hypothesis- from the fact of having high reproductive rates among primitive people with low mental and physical qualities.

In the 1946 New Year Honours, Carr-Saunders was appointed a Knight Bachelor (Kt) in recognition of his role as Director of the London School of Economics and Political Science.

[2] In the 1957 New Year Honours, he was appointed a Knight Commander of the Order of the British Empire (KBE) "for services as Director of the London School of Economics".

[13] Carr-Saunders was married and lived at a 16th-century mansion, Water Eaton, Oxfordshire, age 52, when his son Nicholas Saunders was born in 1938.