By the 1930s, however, the work of geneticists, especially Thomas Hunt Morgan, revealed the importance of chromosomes and genes for controlling development, and the rise of the new synthesis in evolutionary biology lessened the perceived importance of the field hypothesis.
Morgan was a particularly harsh critic of fields since the gene and the field were perceived as competitors for recognition as the basic unit of ontogeny. With the discovery and mapping of master control genes, such as the homeobox genes the pre-eminence of genes seemed assured.
But in the late twentieth century the field concept was "rediscovered" as a useful part of developmental biology. It was found, for example, that different mutations could cause the same malformations, suggesting that the mutations were affecting a complex of structures as a unit, a unit that might correspond to the field of early 20th century embryology.