Evolution of Evolution — Text-only | Flash Special Report
Interview with Gerilyn Soreghan
Does Darwin get the credit he deserves for his impacts on geology?
You know what, I don’t think he does. People focus very much on the word evolution and on descent with modification, but imbedded in his appreciation of the history of the biological record were all these other aspects that he – that led – you know, that appreciation of the biological record led him to really probing these other aspects that we had no inkling of, how long the history of the earth was, the interconnectedness of change, the magnitude of change. So, I think those are things that are under-appreciated by most.
What do we know about a changing earth that we didn’t know in Darwin’s time?
Well, a whole lot. We did just begin to have the idea that the earth’s climate had changed quite recently. It turns out only about 20,000 years ago and we were dealing with a much colder world at that time, a world with a lot of high latitude ice. That is now such a part and parcel of our collective conscience that Pixar makes movies about it, you know, but that was not something that was very well known at the time. It was starting to come into its own then. Now, however, we appreciate that earth’s climate has changed way beyond those extremes. Instances of palm trees growing in Wyoming or times when the earth may have been nearly consumed by ice.
Did an evolving climate affect Earth’s scientific processes?
What Darwin was really getting at, the immutability of process came from Charles Lyell and the concept of uniformitarianism that processes that have operated in the past operate today. The physical laws have not changed. Gravity happened then the way it does today. What has changed are the boundary conditions around which those laws were operating. So, for example, today we know we have physical laws that tell us about the greenhouse effect, for instance. We have a certain amount of CO2 in the atmosphere today. In the geologic past, the amount of CO2 has been much different.
Is a planet teeming with life during the late Paleozoic evidence of Earth’s heating and cooling?
There’s two – there’s really two aspects to looking at climate of the time. There’s sort of the broad aspect that overall that was a cold world but, in detail, on the details of, say, 10,000 years here or 10,000 years there, there may have been times that were – there certainly were times that were warmer and times that were colder within that overall cold episode. As far as what caused it, that’s something that – there are things that we know about that time and there are things that we’re still struggling with. We know that CO2, atmospheric CO2, was quite low, for instance, which would push the planet cooler. We know that solar luminosity was weaker by a few percent and that would’ve made the planet a bit cooler as well.
Are we getting to a point now where we have too much CO2?
Remarkably, when you look at all of the geological record for which we have data and imprints as models, CO2 today is on the low side geologically speaking but it’s on the high side when we look at the history of the last several tens of millions of years.
You also note evidence of former glaciation on the equator?
Well, first, I have to offer a disclaimer. That’s a hypothesis, and it’s a controversial one at that. The kind of evidence that we’re bringing to bear on it is really similar to the kind of evidence that people were looking at back in Darwin’s time, which is the preservation of a landscape that we think dates to the late Paleozoic and that we think may have been carved by ice. That’s one of the more sort of spectacular ones, if it bears out.
What will be the next big discovery in geosciences?
I have to say that one of – that I think it has to come from the appreciation that the planet really is a system, an interconnected system, of components that operate together; the biosphere, the atmosphere, the hydrosphere, the cryosphere, and the solid part of the planet. It’s something that we’re appreciating more and more. It’s breaking down the barriers between different disciplines and it’s where the big discoveries will come.