Theodosius Grygorovych Dobzhansky

DOB: January 24, 1900 DOD: December 19, 1975

Origin of species

In 1937 he published a book Genetics and the Origin of Species. In it, he described how species came into existence.

Genetically variable populations

While analyzing the genes of fruit flies, he discovered that they did not have the same genes. From this he concluded that the things that made a species was the fact that they primarily reproduced with each other.