Is it possible that humans live longer, on average today, because there are less radioactive emissions than there were in ancient times. Since all of these evil emission-producing elements have given half-lives, wouldn’t it make sense that early humans had shorter lives because they were constantly bombarded by radiation many times more powerful than today’s?
Seth
P.S. I have the stomach flu, so if my thoughts are less than coherent, don’t blame me. 
Wow, I have no response to that other than:
** WHAT??? **
Please, please, please, for the love of God, stop watching the Discovery Channel.
To answer your question, no, it is not possible.
Tris
Umm…but haven’t lifespans pretty much gone up since we started mucking around with nuclear power plants and above-ground bomb tests and stuff? I’m not suggesting that a chest X-ray a day keeps the doctor away or anything, but I really think the increase in average lifespan is due to better nutrition, better sanitation, antibiotics, and stuff like that.
I can see the logic, but most of the really nasty stuff was already long gone by the time that humans arrived on the scene. There’s still traces of plutonium, for instance, in the Earth’s crust, but that’s entirely because it’s a daughter element of U-238, and it’s reached a steady state. For the things that aren’t being continually replenished, half of a very small amount is also a very small amount, and there’s not so much difference. Does that make sense?
Lifespans have gone up because we generally live healthier than we did back in the day. There’s better food and better medicine. As for radiation, there’s SO much radioactive stuff in the earth that I doubt much has changed since humans have been around (compared to other life on this planet, not very long.) Humans as we are today have been around for (I think) about 10,000 years, and most radioactive elements that show up in nature have half-lives on the order of tens of thousands to millions of years.
We need figures. What is the half life of earth’s background radiation? Is it even known?
OK, this site answers most of the questions raised:
http://www.umich.edu/~radinfo/introduction/natural.html
I am inferring this from the data, but… The only significant sources of terrestrial radiation that have been around for a long time are Uranium and Thorium. The rest are daughter products, and as said above their level is stable. So, it would seem the whole background has been stable for the last 2 million years or so man has been evolving. Right up until 1945, that is.
More important for us today is the info on the increase in background radiation at altitude, due to higher cosmic radiation levels. It appears airline crews can get higher annual dose rates that nuclear plant workers and A-10 pilots.