When looking at the SBPM proteins, they have high similarity between different subspecies of the Crotalus genus and between different individuals of the same subspecies. This indicates, according to the Radis-Batista et al. 2003 study, that the crotamine gene and other SBPM genes have evolved recently.
The homology among SBPM proteins across various Crotalus subspecies and individuals of the same subspecies implies that these genes have evolved relatively recently, as concluded by Radis-Batista et al. in their 2003 investigation.