Suppose that a time machine allows you to go back in time (and to travel to and you have collected rabbits and myxoma from the years 1955 and 1980. once you are back in the twenty-first century, you infect both sets of rabbits with both sets of myxoma viruses. the most likely result will be (1) that the rabbits from 1955 injected with the 1955 virus will have a survival rate than those same rabbits injected with the 1980 virus; and (2) that the rabbits from 1955 injected with the 1980 virus will have a survival rate than rabbits from 1980 injected with the 1980 virus.

The best answer to your question would be as follows: The most likely result will be 1. That the rabbits from 1955 injected with the 1955 virus will have a lower survival rate than those same rabbits injected with the 1980 virus; and 2. that the rabbits from 1955 injected with the 1980 virus will have a lower rate than rabbits from 1980 injected with the 1980 virus.

Explanation:

The explanation as to why comes from the knowledge of evolution and especially with knowing that the Myxoma virus in European rabbits is the perfect example of virus-host co-evolution. Although according to the research published on this matter in 1998, Myxoma was not lethal to its natural rabbit hosts, it became so for the European groups that were in Australia. In the case of this hypothetical situation, evolution, and immune preparation to respond to a virus, to keep it in check, and for it not to be lethal is the key. In the 1955 rabbits, the exposure was just recent, therefore they had not had the time to develop defensive mechanisms, and much less evolutionary responses that would prevent the virus from being lethal. And in the second case, the virus from 1980 will have evolved much more than the 1955 rabbits to which it was injected, and therefore, again, a lethal situation will ensue.

"it built up in the atmosphere"

i think thats it, idk, i tried looking for this exact q& a for grad. and idk if i got this question right or sorry if im wrong