 He was born Hugo Hellmut Iltis to Anni (née Liebscher) and Hugo Iltis, a botanist and geneticist who was a life sciences teacher at the German-language gymnasium of Brünn (Brno).His father was also the first biographer of Gregor Mendel and a vocal opponent of Nazi "racial science".In the fall of 1938, the Iltis family was granted visas to enter the United States thanks to the intercession of the Emergency Committee in Aid of Displaced Foreign Scholars, along with affidavits of endorsement from Albert Einstein and Franz Boas.