This question seems a bit like the age old question: “Which came first, the chicken or the egg?” Did our current atmosphere help bring life to our planet or did early life influence and change our atmosphere? There is a good deal of current evidence suggesting that current life, both human and non-human, is changing our atmosphere, and perhaps not for the better.
One thing for sure is that we need the oxygen in our atmosphere to survive. This is often the point I need to make so patients realize that unless they have a normal oxygen level in their blood they really cannot live long or well on this planet. The biggest hurdle I usually need to overcome with a patient is convincing him or her that oxygen therapy is a medication and, like all medication, needs to be used in the right amount and on the proper schedule to get benefit. The need for oxygen therapy may not always be apparent to the patient but can easily be found by checking their oxygen level with a finger probe or a blood test called a blood gas test.
Most patients think that oxygen therapy is a treatment for their lungs but it is really a treatment for their heart and other organs that require normal levels of oxygen to function properly or they will fail. Remember, if your oxygen level is not adequate you are not fit to live long or comfortably on this planet.