What are some contributions that scientists have made in our understanding of the DNA structure

Chargaff's realization that A = T and C = G, combined with some crucially important X-ray crystallography work by English researchers Rosalind Franklin and Maurice Wilkins, contributed to Watson and Crick's derivation of the three-dimensional, double-helical model for the structure of DNA.

the fossil record provides evidence of a common ancestor to many species.