Pre-Columbian contact hypotheses

Pre-Columbian contact hypotheses relates to a series of claims that the Americas were visited by people from other parts of the world before the arrival of Christopher Columbus in 1492. Conventionally, this excludes the arrival of early populations over the Bering Straits, the initial peopling of the Americas, and subsequent movements of aboriginal people around the Arctic. But, includes ocean-going voyages by Asians, Africans, Europeans, and Oceanians. Most of these theories exist in pseudohistory or pseudoscience and are often based on superficial similarities between Old World and New World art, architecture, and linguistics. Some of these proposed events may be true, but were simply unrecorded, or of such little impact they can't be definitely proven. Most of these claims are probably not true.

At present there are three instances in historical times in which contact was made between Old World and New World peoples supported by robust archeological, genetic, and even written evidence.

Recognized Pre-Columbian contacts
A few instances of Pre-Columbian contact in historic times are now generally acknowledged as having happened. The most well established were those of the Norse around 1000 AD which were considered more legendary than factual until archeological digs in the 1960s showed otherwise. There are a few primary sources that mention islands called "Markland" and "Vinland" in old Norse documents. Likely, sometime after the Norse abandonment of North America Polynesian and Siberian people made contact with people in the Western hemisphere. Because none of those cultures involved had written languages little can be said about under what circumstances they met, other than that they did indeed meet somewhere somehow. In pre-historic times there now appears to have been a separate peopling of the America's that occurred from the South Seas around 20,000 years ago. Modern Amazonian peoples have a degree of Austronesian (though not necessarily Polynesian) ancestry.

Alleged "discoverers" of the Americas
The following claims are all considered much more dubious. This is not a complete list. A large number of other fringe theories on this topic exist including persecuted Roman Christians, ancient Greeks, Marco Polo, Basque fisherman, Japanese sailors, and basically everyone who ever existed except Christopher Columbus finding their way to the Americas before 1492. Interestingly, they all waited until after his voyages to let us know they had already done it. Many theories appear to be born out of cultural pride (We were there first!), rather than genuine fact.

Art historian Alexander von Wuthenau claimed a wide range of pre-Columbian contacts based on his view of facial similarities between pre-Columbian stone artwork and people originating from outside the Americas: Africans, Semitic (Jews and Arabs), Japanese, Polynesians, and Phoenicians. His analysis amounts to an pseudoscientific/pseudohistorical comparison because of convergent evolution.

The other way
Occasionally it has been suggested that New World populations visited the Old World. These theories tend to be dismissed as lacking credible proof.

It has been claimed that Egyptian mummies show traces of cocaine, which originated in South America. However, these theories are far more popular with the producers of wacky TV programs than with actual Egyptologists.

There are also suggestions of children or adults being brought back from North America or Greenland by Norsemen. This might have happened, although, as with most things on this page, there's no actual evidence. American Indian historian Jack Forbes argued in The American Discovery of Europe that American Indians traveled to Europe in the 1st century.

The elephant in the room: The Columbian exchange
The reconnection of two continents which had virtually no contact or knowledge of each other for more than 10,000 years changed the world's ecology, economy, and overall state of knowledge. Although Columbus wasn't the first to make contact with the New World, his voyages are correctly regarded as the most historically important because he stayed and permanently triggered two way exchange between both hemispheres. Within about one century of 1492, 75-90 per cent of all indigenous Americans had died of diseases previously unknown in the Americas including smallpox, plague, measles, mumps, yellow fever, typhus and whooping cough. Syphilis was originaly thought to have come from the Americas to the Old World. Newer evidence indicates that the Columbus and syphilis connection is unlikely since medieval DNA suggests Columbus didn't trigger a syphilis epidemic in Europe. Wheat, oats, barley, cabbages, lemons, sugarcane, truffles, horses, cows, sheep, cats, pigs, and other lifeforms were introduced to the Americas. European, Asian, and African agriculture were all radically changed in the 16th century with the introduction of maize (Zea mays), peanuts, potatoes, tobacco and squash. Invasive species like rats traveled on ships along with their human companions.

If there had been any intensive contact between the Old World and the New World before 1492, it would have been followed by a similar exchange of technologies, ideas, people, plants, animals, fungi, and diseases. The fact that it didn't happen is extremely strong evidence for the absence of any far-reaching outside influence on Pre-Columbian America and suggests any prior voyages would have been one-offs.

If you think a piece of pottery in Mexico that looks faintly Roman proves Roman colonization of Mexico, you'd have to explain why the Romans only exported ceramics, and not measles, horses, carrots, iron smelting, some genetic markers in modern Mexicans, and the Latin alphabet. The same goes for Egyptian, Chinese, or Phoenician failure to bring along oxen, plow cultivation, wheeled transportation or their own writing systems.