The total population of the Americas at the point of Columbus’ voyages is a matter of extreme dispute.

In the 1960s, some historians with an interest in demography explored all the evidence they could find that related to population. Some respected historians argued that the pre-Columbian population was a hundred million. This revised previous estimates of ten millon.

The debate has a political edge. We do know that the population of American natives dropped very sharply, probably by more than 90% in many places. If the population was in fact a hundred million, then the Spanish colonization was the greatest crime in human history.

The diseases brought by the Spanish were common ones most Europeans had resistance to, but that caused virgin field epidemics in the Americas—influenza, smallpox, measles, and so on. The populations losses were highest in the densely populated areas like the Valley of Mexico and the Andes highlands of the Incas. Diseases were not the only causes of American mortality: the wars of conquest were rather bloody, and the enslavement of Indian populations had disastrous consequences.

More recent and probably more accurate studies have cut into that estimate of a hundred million. Serious study of the human carrying capacity of pre-Columbian environments, given the technologies and crops of the time, suggests a considerably lower figure, perhaps 25 million, maybe even 50 million.

So the answer to the question is no, but a qualified one. There were probably not 90 million people in the Americas so it was not a third of the world’s population. But there were substantial numbers, and whether 25 or 50 million, it was still a considerable fraction of the world’s people at that time.

[Edited to correct a typo]