Why is it hard to believe Christopher Columbus's story of men with tail?

Answer 1

During the Middle Ages and earlier, there was a long tradition of travel narratives in which every explorer "saw" these men with tails, or saw remnants of the kingdom of prestor John, or caught something about the fountain of youth. This came from a tradition of Greek and Roman sources, such as Pliny. Writers such as Ptolemy used valid sources for their histories, from many official and validated captains and travelers, but he never saw the creatures himself.

But these myths were an integral part of every travel narrative, and to make you story credible (e.g. your actual discoveries), you had to include something of this history. For example, Marco Polo (of whom Columbus read a lot), included some of these strange creatures.

By the time of Columbus, most people had started to disbelieve such myths, but the tradition was still there--I believe more so in Spain (which had strong ties to the Middle Ages) than England. For example, Patagonia (in South America) was named on account of the land of everlasting youth, and the discovery of Florida was precipitated by the search for El Dorado.

But to answer your question, these days we don't believe much without scientific proof. At the time, their scientific proof was the valid and accepted travel narratives and natural histories of the travelers and scientists of the time. People did not travel much and had no way of refuting them.