Ultimate Factors for Divergent Trajectories

Key Insight

The divergent historical trajectories between Eurasia and the Americas can be attributed to several ultimate factors. Eurasia enjoyed a significant head start in human occupation, having been inhabited for approximately one million years, compared to the Americas, settled around 12000 B.C. Food production in Eurasian homelands began about 5000 years earlier than in the Americas. A more profound factor was the Americas' limited suite of wild animals and plants suitable for domestication. The Late Pleistocene extinctions drastically reduced the number of large mammals, making early food production less competitive against hunting-gathering in the Americas compared to Eurasia, where animal domestication closely followed plant domestication, creating a more robust food-producing system with benefits like fertilizer and plow traction. American wild plants also posed challenges; for instance, corn required thousands of years and drastic genetic changes to evolve from wild teosinte into a productive crop, unlike Eurasia's rapid development of wheat and barley.

Diffusion of animals, plants, ideas, and technology was significantly easier in Eurasia due to its east-west major axis, which allowed spread without major changes in latitude or environmental variables. The Americas, in contrast, possessed a north-south major axis and were constricted at the whole length of Central America and especially at Panama. Furthermore, the Americas were fragmented by extensive ecological barriers unsuitable for food production or dense populations. These included the rainforests of the Panamanian isthmus separating Mesoamerican societies from Andean and Amazonian societies; the deserts of northern Mexico separating Mesoamerica from U.S. southwestern and southeastern societies; dry areas of Texas; and deserts and high mountains fencing off U.S. Pacific coast areas. These barriers severely limited or slowed the diffusion of domestic animals, writing, political entities, crops, and technology between New World centers like Mesoamerica, the eastern United States, and the Andes/Amazonia.

The impact of these barriers was profound: food production from the U.S. Southwest and Mississippi Valley never reached California or Oregon, leaving those Native American societies as hunter-gatherers. Andean domesticates like the llama, guinea pig, and potato never reached the Mexican highlands, nor did Mesoamerican domestic turkey reach South America or the eastern United States. Mesoamerican corn and beans took 3000 and 4000 years, respectively, to cover the 700 miles from Mexico to the eastern U.S. farmlands. While Eurasian crops spread rapidly, preempting parallel domestications, American barriers led to many such parallel domestications. Similarly, Eurasian writing systems spread widely, but Mesoamerican writing never reached complex Andean or eastern U.S. societies. Mesoamerican toy wheels never combined with Andean llamas for wheeled transport. Unlike vast Eurasian empires, American empires had no political relations or awareness of other distant complex societies, highlighting the profound fragmentation reflected even in linguistic diversity, with the Americas lacking the large, easily recognized language families typical of Eurasia, except for Eskimo-Aleut and Na-Dene.