Post provided by ELIZABETH BOAKES

The indisputably extinct Dodo (Raphus cucullatus). ©Ballista

A species is either extant or extinct – it exists or it does not exist. Black and white, a binary choice. Surely it should not be difficult to assign species to one of these two categories? Well, in practice it can be extremely challenging and a plethora of methods have been developed to deal with the problem.  This of course leads to a second challenge – which of the plethora should you use?! (More on this later…)

There are a few well-studied cases where we can assert extinction confidently. For example, the chances of the Dodo (Raphus cucullatus) having existed undetected for upwards of 300 years on an island now densely populated by humans are infinitesimally small. However, many extinctions are far harder to diagnose. Species typically become extremely rare before becoming extinct. If taxa are particularly cryptic or are found across a huge geographic range it is quite plausible that the few remaining individuals may exist undetected for decades. An extreme illustration of this is the 1938 discovery of Latimeria chalumnae, a deep-sea member of the Coelacanths, the entire order of which was believed to have become extinct 80 million years earlier! Continue reading →