Was the atmosphere's pressure much higher before the Flood, explaining longer lifespans and larger creatures?

I do not object to it; it could have been. We do have some scientific evidence that, up to a point, the body functions better under somewhat higher pressure, and that could be why the men lived so long: Adam lived to 930 years, and after the flood Shem lived to 600, then Peleg, Eber, and the rest to about 400 for a while, then 200, down to Abraham at 175. What is causing that decline? One possibility is that the atmospheric pressure, once much higher, was dropping, and that is how God would begin trimming down the human lifespan. So scientifically it does work.