3. What types of job did most of the first astronauts come from?

The selection was initially limited to military pilots. The earliest astronauts for both the US and the USSR tended to be jet fighter pilots and were often test pilots.

studies show tha in 7.5 billion years from now, the expanding sun will engulf, and destroy, the earth.

genetics is the study of how dna works, the methodologies defining the new recent technologies allow scientist to have a panoramic view of the entire dna landscape, especially how genomes interact with their environment, including off course, factors outside their organisms.

thus is very possible the existence of both scenarios, where populations of isolated individuals have different genetic traits, and share traits related to genetic mutation, due rats can easily travel overseas using human transport channels. so scientists could get a vast number of data, including human interaction, evolution of rodents, health development, spread of infections, development of new organisms, how genomes evolve in different environments and so on.