The Past is a Foreign Country: The evolutionary potential of “living fossils”

Are evolutionary distinct species – what may fancifully be called “living fossils” – more or less likely to diversify in the future? The various forms of evidence and argumentation for how evolutionary distinctness may be a predictor of evolutionary potential are mixed. Depending on the scientific discipline and the data, these taxa may either be doomed to extinction or primed for future diversification. With an increasing focus of conservation effort towards the evolutionary distinct, such a question is of growing importance. If it is shown that these “living fossils” have higher rates of extinction and lower rates of speciation, then it may be argued that time and resources should not be spent on these evolutionary dead-ends. Conversely, if these groups can be identified as evolutionary fuses then it may be argued that their conservation is key to safeguarding future biodiversity. Here we map the fates of mammalian clades through time to their evolutionary distinctnesses. We find that taxa that are evolutionary distinct have increasing measures of evolutionary distinctness through time. This indicates that these groups have lower rates of speciation but also lower rates of extinction and, as such, represent neither dead-ends nor fuses. Our finding recasts the conservation arguments: protecting the evolutionary distinct will not secure the future of life; it will, however, not be a wasted effort either.