Modern Versus Ancient Extinction pt 2

Rock Volume
Ok let's think a little more about Jack's curve.

Remember we're counting fossils here. The number of fossils you have is going to depend on the amount of rock that you have. The younger the rock, the more of it there is. So there is a lot more Tertiary (the "T" on the graph) rock out there than say Cambrian (the "C" with a line through it) so there are more Tertiary fossils than Cambrian fossils. You can compensate for this but it's always going to be very tricky. So that huge run up of in diversity that you see at the end of Jack's curve might not be "real" just because we have so much more rock for those more recent time periods. So the general shape of the curve is a little suspect. With respect to extinction, I'm not saying that extinction events in the paleontoloogical record are simply a result of not having rock for those time periods, but certainly the volume of rock is going to affect how severe we view the extinction as being.
Next time: taphonomy and counting issues

Modern Versus Ancient Extinction pt 1

I've been meaning to get to this for a while. It hits on something that comes up from time to time in Paleontology. Writing in the New Yorker Elizabeth Colbert says:

The fifth, the end-Cretaceous event, which occurred sixty-five million years ago, exterminated not just the dinosaurs but seventy-five per cent of all species on earth. Once a mass extinction occurs, it takes millions of years for life to recover, and when it does it’s generally with a new cast of characters. In this way, mass extinctions have played a determining role in evolution’s course. It’s now generally agreed among biologists that another mass extinction is under way.

What these biologists are doing is jumping from ancient extinction events to a modern "extinction". This is much trickier than most people think so lets look at it. Let's begin, as Anton Ego would say, with some

Perspective.


This is Jack Sepkoski's Family diversity curve with all five of the major extinctions numbered. Jack generated this curve by going into the literature and tabulating the number of taxonomic families through time. Paleontologists spend a great deal of time pouring over curves like this one so we can understand the broad sweep of life's evolution. We also spend a great deal of time looking at extinction events in great detail. So with that sort of perspective it is certainly fair to ask what can paleontologists or the paleontological record tell us about the current biological crisis.
The answer.... not much.
Why next time.

Two graphs noted without comment

... mostly because it's just depressing.

This chart depicts the public acceptance of evolution theory in 34 countries in 2005. Adults were asked to respond to the statement: "Human beings, as we know them, developed from earlier species of animals." The percentage of respondents who believed this to be true is marked in blue; those who believed it to be false, in red; and those who were not sure, in yellow.

It's a little small click to embigen if you need to.

Still more...

A very interesting extension of the pattern I noted below. See it HERE

Geology Controls Everything

I was looking at the electoral map by county and I saw a familiar pattern. It's most obvious of the picture below that shows the counties that Republicans made gains in this election.


I know it's a little blurry but that's ok we're just looking at at VERY general trend. I've circled the area we're interested in. Now look at the geologic map of the United States. I've circled the same area.


See how the Mc Cain voting pattern ends as the rocks that make up the Appalachian mountains end? Here's a closer pic of the region.


Back in the good old days when dinosaurs roamed the Earth there was a giant inland sea called the Sundance Sea (or Western Interior Epicontinental Seaway for those of you who like the words). In the central Alabama Georgia region this sea lapped up against and weathered the rocks that make up the Appalachian mountains, depositing the younger (green) rocks. Geologically what we're dealing with here are older (Pennsylvanian, about say 300 millionish years old) rock of the Appalachian mountains truncated by and overlain by much younger (Cretaceous, about say 80 ish million years old) rock.
Geopolitically I'm sure there are a number of factors that play into why Appalachia is Republican country (and if there's a political scientist out there who would like to collaborate on something get in touch) my guess is that a lot of them are controlled by the underlying geology.
Interesting that on this map anyway the political boundary and the Geologic boundary coincide.