But, as Dr Tilghman points out, some species emerge more rapidly than this hypothesis can explain.

ECONOMIST: Genes are not all there is to heredity

Shirley Tilghman and her colleagues correlated this abnormal growth with disruptions of the methylation patterns on the hybrid offspring's genes.

ECONOMIST: Genes are not all there is to heredity

Other recipients of doctorates were Dame Rosalyn Higgins, DBE, The Rt Hon Lord Rothschild, GBE, Dr Arno Penzias, and Professor Shirley Tilghman.

BBC: Oxford honours arts figures

Molly Tilghman of Chestertown, Md.

WSJ: What Life Was Like in 1776