Evo-devo is a field of biology comparing the developmental processes of different organisms to discover the evolutionary relationship between them and to further understand how the developmental processes evolved within the organisms.
An evolutionary biologist can discover vital patterns from using an evo-devo conceptual framework. Understanding that the same master genes are found in fundamental body plans and parts across the animal kingdom will allow connections to be made within species. Determining the purpose of one gene in a species could allow a biologist to comprehend the gene in another species. For example, the BMP4 gene can signal cells to begin producing bone in birds, the more BMP4 protein produced, the thicker the beak of the bird. BMP4 acts in the same way with the jaw of fish. Most likely, this gene plays a role in the evolution of many other species dependent on the development of jaw changes such as lizards, rabbits, and mice.
The major finding of the Davis, et al, 2007 paper was that Polyodon, a basal actinopterygian, and tetrapods both show an inverted collinear expression of HoxD genes in the distal region of the appendage not found in teleosts. This similarity is a developmental hallmark of the autopod and is shown in tetrapods to be controlled by a ‘digit enhancer’ region. Therefore, the novelty in the appendages of lobe-finned and ray-finned fish has arisen by both changes in regulation, as in tetrapods, and by loss of portions of an ancient and conserved pattern of Hox expression in teleosts.
In the article “From a Few Genes, Life’s Myriad Shapes”, the author explains the theory that major events in evolution may be set in motion due to the right ecological situation where “such bold, new forms” will be beneficial. Does this process evolve through natural selection similar to mutations? Does increasing the protein from a few genes happen randomly and does it continue to appear if it is advantageous to the environment? What causes these genes to get turned on?
For more on a general picture of evo-devo, see Yoon, C. K. 2007. “From a Few Genes, Life’s Myriad Shapes.” The New York Times.
For more on the expression and function of genes implicated in the origin of the autopod in a basal actinopterygian, Polyodon spathula, see Davis, C. et al. 2007. “An autopodial-like pattern of Hox expression in the fins of a basal actinopterygian fish.” Nature 447: 473-476.