If there were more oxygen in the air, how would it change humans?

Question

I know that one reason the dinosaurs were so big was because they had a lot more oxygen in the air than there is now.

If there was as much oxygen in the air now as there was when dinos were walking, what dramatic changes would happen to man?

Would we be bigger? Could we run a lot more efficiently? Would it change the way we look? Etc.

Answer 1

Actually there was more carbon dioxide in the atmosphere during the time of the dinosaurs, not oxygen. The increased carbon dioxide produced a much greater biomass, specifically plants. Plants need carbon dioxide to grow and the greater amount of carbon dioxide allowed plants to flourish. The increased food source is what allowed dinosaurs to grow so large. It is also what we have to thank for the oil we use today. Experiments have shown that even today plants will grow faster and larger if the amount of carbon dioxide in the atmosphere is increased.

Answer 2

That would depend on what mutations turned out to be advantageous.  Mutations are random.  I believe it was during the Jurassic that the Earth's atmospheric oxygen content rose quite a bit and dinosaurs became considerably larger.  However its difficult to say what would prove advantageous for humans.  Humans are more culture driven than biological.  

Answer 3

Well, size wasn't directly attributed to the amount of oxygen;  it was mostly a question of defense and available food.  I would imagine that human lungs would be smaller, and probably the cells of our bodies wouldn't be quite as porous as they are now...  The amount of oxygen in the air would change the quality of sound as well, but only slightly, so our ears may have been a little less developed, but overall, I would suspect a human to look pretty much like a human in a high oxygen environment.  

The *amount* of oxygen in the atmosphere can only increase a little - I forget the number, but if it's more than 30 or 35%, things burn a *lot* easier... to the point of lightning setting off flash fires without even striking the ground.  

Answer 4

Our breathing and other functions would be slower!