Also the chemical makeup of the canopy is unknown which may have some bearing on the heat factor. The lush vegetation coupled with fewer & smaller oceans over the entire globe including the poles would also consume much CO2 and increase the O, perhaps supportive to the long life as recorded for the preflood era.
Again just a point of thought. Higher concentrations of oxygen in the atmosphere is not a good thing for mammals in general. Being exposed to higher concentrations in general just messes with the pulmonary system as well as numerous other systems in the body (i.e. it can cause . The biggest thing though is that adding more oxygen into the air does very little to affect the human lifespan. One could argue that actually higher concentrations of oxygen in the air would actually be adverse to human life expectancy as it increases general oxygenation of muscles etc, which can potentially lead to an increase of Radical Oxygen Species which are implicated in genetic/protein/membrane mutations which lead to cancers and other very unpleasant conditions that can considerably shorten a person's life span. (As much as the body does have a number of mechanisms to reverse or prevent damage from these types of attacks, the mechanisms are eventually overwhelmed). (sorry about splitting the reply to your message)
Oxygen Toxicity
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