But because of these global change concerns, there's been a lot of work, certainly medical studies looking at increase in cancer and so on, looking therefore at the molecular mechanisms of UV damage. But there's also been a fair amount of work on the biology of phytoplankton. The interest here is what is this going to do to aquatic productivity, particularly the ocean if you start having more UV effecting particularly phytoplankton, which is the base of the food change in the ocean.

During the 1970's, there was a conclusion that UV has not really been important in evolution for the last 2.5 billion years. The reason for that is they estimate that about 2.5 billion years ago, we had about one percent of the present atmospheric level of oxygen and that was good enough to start to form an ozone shield. I'm going to argue the rest of the talk that, well yes, it may have started to form an ozone shield and it may have been better than the good old days before that when all this UV got to the surface of the Earth, but even today we're hearing about these serious UV effects on organisms. And throughout evolutionary history, UV has had an effect. And if you don't think that UV still has an effect today, look at my face from the light. I was out in the boat yesterday morning, it was completely overcast and I still got sunburned.

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