Why Some Diseases Only Traveled One Direction

> So any theory of "geographical stunting" would need to explain what changed in the geography after 1492. What changed was technology. Once you have ships going back and forth across the Atlantic, everything changes. Europeans introduced cows, sheep, pigs, chickens. The New World's only domesticable native animal is the llama, which is the main reason why civilizations sprung up in Central and the northern parts of South America, that's where llamas were. Now, to the Europeans, with vastly superior farming technology, the Caribbean and North America were veritable cornucopias of geopolitical possibility. Islands sheltered plantations. Europe could project real power only very closely to the shore, where the big naval guns could reach. The reason was supply. To maintain a group of soldiers requires not just food but adequate clothing, weapons, ammunition, and horses to carry all of that. It took over a century of growth for a colony to get to the point to where it could maintain and supply an army for deeper treks inland. By that time the colonies would have been deeply entrenched in native political systems. Because the warships protecting your colony could only hang around for so long, colonies were quite vulnerable to native military action, or even just having them hang around outside the settlement and killing whoever goes outside, say, to chop wood. It made sense for settlers to be nice to the locals, at least at first. CGPGrey just put out a fantastic video comparing t

Expanding on this, CGP Grey had this amazing video ( [VIDEO] ) of why European diseases in the Americas were so bad on the people that were already here when the two worlds met but you hardly heard of Europeans getting any super contagious illness from the people living in the Americas. Meaning European genomes had some adaptations (as well as antibodies?) from dense and unsanitary living, as well as animal farming in European prior to contact whereas that type of living setup was rarer in the Americas.

>Indians had no trouble crisscrossing America Well yeah there weren't any human infectious illness where... there aren't any humans. This video explains the history of man kind's infectious illness very well [VIDEO]

I recommend the following video by CGP Grey, largely based on the book "Guns, Germs and Steel" by Jared Diamond: [VIDEO] Now, history doesn't give a lot of merit to natives. The largest battle in the Americas, the siege of the Aztec capital Tenochtitlan, was won with the help of 80,000 to 200,000 Tlaxcalan natives, which amounted for 99% of the infantry used.

I remember being struck by his anecdotes of Papua New Guineans seeming just as smart as anyone else as supposed evidence of... What exactly? I don't think Neil Diamond is wrong but it's kind of baby's first reading on the differences between groups in the world. I think CGP Grey does a great job at communicating the actual meat of Guns, Germs, and Steel here [VIDEO]

CCP Makes a pretty good case regarding livestock - [VIDEO] America did offer a new disease that ravaged Europe. Syphillis.

Epidemics are a relatively new phenomenon as far as human evolution is concerned. Within a purely human set of hosts, germs don't feel evolutionary pressure to become more deadly. If anything, it's advantageous for a germ to be less deadly. The most successful viruses are the common cold viruses, not SARS or Ebola. Epidemics only really became a thing once we started domesticating animals and therefore being around live animals for prolonged periods of time. This allowed germs originally adapted to these animals the opportunity to jump over to human hosts, for which they may be more dangerous than for the original host animal. For more details on this point, I can recommend this video on why the native Americans were killed by diseases imported by the European conquerors, but the conquerors didn't bring any deadly diseases back to Europe: [VIDEO]

CGP Grey has a great video about this topic: Americapox: The Missing Plague - [VIDEO] TL;DR; You need big cities to keep plagues ongoing.