I dont think an intelligent species would ever get past the philosphical debate as to whether to go back and introduce the life or not, you could argue that both cases are right, 'we are here so we don't need to introduce life', and 'we are here because we DID go back and introduce life!'. Both arguments hings on 'we are here', so whatever we did was right, but we have not done that thing yet! So what do we choose.
But thankfully by the time we work out how to time travel we will understand that 1) time travel is impossible and 2) if it was possible it would be a REALLY bad idea and really boring!.
It's not possible because we live in a universe that does not have temporal time! That's right, we only have spatial time. PAST and FUTURE do not exist, and seriously does not exist, you go back 1 second in time you turn up and there is not even a universe there... AT ALL. it's just nothing, no space, no objects, no spacetime.. nothing.
If fact, that only thing you can consider a universe is YOU, you are the only thing in that otherwise non existant universe.
2), We dont have temporal time, the only time we have is a function of the length of space, this is SPACETIME, any 'real time' event is delayed to you by the length of space, that means at the speed of light it takes time for an event to get to you. That delay is spacetime.
Also we are aware of a past because that past is continuously 'imprinted' on spacetime (or over space created time), a book is information (past, history, information), that is imprinted over space (the pages of the book).
Just like you would instantly go to some point in space and view a past event, because that event is being distributed (imprinted) over space.
Lastly time as with space is always a positive value, you cannot go backwards in space (just forward in the opposite direction, which is arbitary), and you cannot go backwards in the length of time either just forward. It's a length you can't go minus 1km, and you can't go minus 1 minute. They are absolute numbers.
THe speed of light is constant because the length of time is derived from the length of space, and both are the same length. Making c constant.. Time is the length of spacetime that corresponds to the length of space. Speed is the length of space over the length of time. c is the highest speed you can go as it represents all the available length of space over all the available length of time.
Length of space / Length of time = 1