How a 6k-Year-Old Dog Cancer Spread Around the World
wired.com
wired.com
"Also, the majority of those mutations, including almost all of the recent ones, are neutral. They don’t seem to benefit the tumor in any way. Again, that’s very different from most cancers, which are constantly adapting to outfox their hosts’ immune systems, or to grow a little faster, or to spread to new areas. Not so with CTVT. “We think that the cancer is not adapting anymore,” says Adrian Baez-Ortega, who was one of the main researchers on the study. “Maybe it doesn’t really need to.”
Perhaps, early on in CTVT’s history, it found such thorough ways of escaping the immune system and jumping into new hosts that no further tweaks were necessary. Or perhaps it no longer imposes enough harm on its hosts to warrant a counterattack. It’s rarely fatal, after all, and if dogs are otherwise healthy, it doesn’t grow very fast. “The tumor and the dogs aren’t competing against each other anymore,” Baez-Ortega says. “They’re coexisting. The cells behave like cancer cells, but the ecology of the tumor is that of a parasite.” And a fairly benign one at that."
This is pretty much the story of any “old” virus; new viruses (new mutations, species jumping, etc) tend to kill, but they optimize towards coexistence, since killing the host reduces reproduction/spread opportunity.
So eventually they become benign within a population (both by their evolution, and adaptation of human immune system) and only become threatening again when encountering a new population (eg an “infected” city-man visiting rural populations).
Notably, due to the more rapid spread of disease in cities, due to higher density, city-folk tend to have more benign/evolved diseases than rural populations.
Which I think is also the answer to my childhood question: why did the europeans famously have diseases to spread and kill native americans with.. but the native americans could offer no such devastating disease in return? Both groups should have been encountering new diseases; my answer being that the native americans were carrying fewer suppressed diseases.
There’s of course the popular answer that europeans were more evil/willing to spread disease with things like chicken-pox blankets.. (and catapulting rotting animals), but it’s really difficult to imagine native americans would be so primitive that couldn’t learn/mimick the idea... or perhaps its just written out of the history books..
But I never found confirmation on this
America did offer a new disease that ravaged Europe. Syphillis.