Old World

Biological life on the two continents probably began evolving separately around 100 million years ago.

That biological diversity, enabled by the breaking up of Pangea, has been an enormous boon for Homo sapiens as a species in the last 500 years, and also the cause of much suffering for individual humans in both the Americas and the Old World, Africa particularly.

In 1492, the entire population of the planet was probably between 450 and 600 million people.

The gap in the estimate explained in part by the still unresolved controversy over the pre-Columbian population of the Western Hemisphere.

We do know that by 1500, the population of Europe had not grown on a net basis since 1300.

There was plenty of hunger in most places outside of the New World, and every reason to believe that humans in the Old World had reached something of a limit in their capacity to grow or capture calories faster than their requirements for them.

On the website ourworldindata.org, one can find a graph of obviously estimated human population from 10,000 BC to the projected population in 2100.

Per the weirdly precise figures on that site, which apart from their faux precision look pretty plausible, from Common Era year zero to 1500, obviously just after Columbus's first three voyages, the world's population grew from 188.24 million people to 461.37 million.

Although the legendary explorer never reached mainland North America, his voyages had profound global consequences and quickly led to the opening up of the continent to massive changes and European colonization.

The Columbian Exchange was the widespread transfer of human populations, plants, animals, precious metals, commodities, culture, technology, diseases, religion, and ideas between North America in the Western Hemisphere and the Afro-Eurasian Old World in the Eastern Hemisphere.

It is named after the Italian explorer Christopher Columbus and is related to the European colonization and global trade following his 1492 voyage.

Some of the exchanges were purposeful; some were accidental or unintended.

Right

... for his journey.

So there were also political motivations in the Old World.

It's not to say that Columbus was guiltless, but if you look at the historical record, he was, simply on the point of the treatment of natives, he was a far greater defender of the natives than basically anyone else-