Past Humans
The recordings from the past are real(live action), but everything else is animated and cartoony?
What is the deal with that?
I'm pretty sure it's because they wanted to show the difference between humans of the present day (or the near future) that grew up and lived on Earth and were relatively active physically, and humans that have been living in space for generations under low gravity conditions, growing fatter and lazier due to their sedentary nature and being waited on hand and foot by robots.
There would be a clear difference.