The Role of Anecdotal Evidence in Zoology

One of the most controversial and divisive topics in the field of zoology is the role that anecdotal evidence plays in the discovery of new species. Some eager believers readily accept every claim, no matter how far-fetched or sketchy it is. Meanwhile, some militant skeptics claim that anecdotes are worth nothing at all. In my opinion, both of these opinions are erroneous. The truth lies somewhere in the middle.

Contrary to statements by many science journalists, anecdotal evidence has, indeed, had a significant role in the identification of several new species in the past. People who had been to Indonesia spoke of an enormous "land crocodile" that would devour large animals, including humans. In 1912, their claims were vindicated when the beast was finally identified by scientists. We now know it as the Komodo Dragon, Varanus komodoensis.

Likewise, travellers in equatorial Africa told stories about a tribe of giant, hairy men who would kidnap people and kill them. In 1847, these claims were confirmed when the Gorilla was discovered.

However, the skeptics are definitely right when they say that anecdotal evidence cannot be used to prove the existence of a species. According to accepted scientific protocol, the only way that a species's existence can be definitively proven is by obtaining a specimen -- either dead or alive.

So I conclude that anecdotal evidence can help indicate the existence of a given species, but it cannot prove the existence of a given species. 

A good analogy that I like to use is the smoke analogy; if a person sees smoke in the distance, the smoke indicates the possible existence of a fire, but the existence of a fire cannot be definitively proven unless the person walks up to the region where the smoke is emanating from, and checks to see if there is a fire.
When there is smoke, it is not unreasonable to suggest that there might be a fire that the smoke is emanating from. And when there is anecdotal evidence of an unknown animal, it is not unreasonable to suggest that there might, in fact, be an unknown animal behind the reports. However, the existence of a fire cannot be proven unless someone checks to see where the smoke is coming from. And the existence of an unknown animal cannot be proven until a specimen is obtained.

So anecdotal evidence is not total proof, like the true believers claim, but it is also not worthless, like the militant skeptics claim. As is so often the case in life, the extremists are wrong. It is the middle position that is the most scientific and reasonable.