 Evolutionary biology as well became molecularized (Suárez-Díaz 2018). One important contribution was the theory of the molecular clock, which stated that the rate of evolutionary change in a protein remained constant such that the time of divergence of lineages could be estimated from data on amino acid sequences (Morgan 1998). This lent support to and was explained by the neutral theory of molecular evolution suggested, which was controversially discussed between molecular and traditional biologists in the 1960s (Dietrich 1998; entries on  ecological genetics  and  genetic drift).  In general, molecular biology opened a new perspective on evolutionary mechanisms, for instance, the notion that evolution builds upon events of duplication of genes, chromosomes, or whole genomes. On this view the duplicated elements could acquire new functions or alter the dosage of gene products (Morange 2020, Ch. 23).