Did we breathe nitrogen??

I was trying to look up some things we know about how creatures, even man may have breathed in the past. I thought I'd throw it out.
I think that massive changes happened, leaving our universe in a different state after the flood sometime. Before this I think evolution could happen very fast.
So, I was considering what evidence exists that might say we MUST have used to breathe as we now do, absorbing the oxygen, etc. Could we tell by any evidence anywhere that this was the case? (and I don't mean looking at a chest cavity, and speculating how it must have worked if the past were the same)

One example that made me think of this is trees. In the past, with a different light, and growing process, from what I can tell of the bible (as in the future) trees grew superfast. In a week or so, in cases.

Could they have did something like absorb the nitrogen, and give off more carbon, or some such? If so, looking at carbon levels in the past in trees would yield no results with any real bearing on any real time.

I hear nitrogen is used in keeping apples fresh over the winter. If we are looking for possible causes of man being able to live for a thousand years almost in the past, could this be one area to explore?
If, say, (I don't know, just guessing here) an apple can be kept pretty fresh for up to 7 months, instead of a week or so on our counter, that is a fantastic difference. 7 days on the counter, in this example, versus 210 days with the nitrogen process. Or, a thirty fold increase in "lifespan"!!
If we now live 80 years, rather than, say 950 years, that means about almost a 12 fold decrease in lifespan.

Can this idea, that we adapted to absorb gases differently be ruled out?