 His 1937 work "Genetics and the Origin of Species" was a key step in bridging the gap between population geneticists and field naturalists.It presented the conclusions reached by Fisher, Haldane, and especially Wright in their highly mathematical papers in a form that was easily accessible to others.Further, Dobzhansky asserted that evolution was based on material genes, arranged in a string on physical hereditary structures, the chromosomes, and linked more or less strongly to each other according to their physical distances from each other on the chromosomes.