The role of indirect evidence and traditional ecological knowledge in the discovery and description of new ape and monkey species since 1980

Although empirical data are necessary to describe new species, their discoveries can be guided from the survey of the so-called circumstantial evidence (that indirectly determines the existence or nonexistence of a fact). Yet this type of evidence, generally linked to traditional ecological knowledge (TEK), is often disputed by field biologists due to its uncertain nature and, on account of that, generally untapped by them. To verify this behavior and the utility of circumstantial evidence, we reviewed the existing literature about the species of apes and monkeys described or rediscovered since January 1, 1980 and submitted a poll to the authors. The results show that circumstantial evidence has proved to be useful in 40.5% of the examined cases and point to the possibility that its use could speed up the process at the heart of the discovery and description of new species, an essential step for conservation purposes.