biodiversity fossils

A Geologist's Tale

The Endangered Species Act is bad law because it fails to provide any positive incentives for conservation; it “takes” beneficial economic use of private property without just compensation; it prevents economic opportunity on public land; and it seeks the unnatural. Preservation is unnatural because things change; nature itself creates species and kills them off, most notably in 5 known mass extinctions in the last 500 million years and in at least two other mass extinctions before that. But, after each mass extinction, speciation and biodiversity increased, because the most robust lived and evolved to occupy the newly empty life niches.

It is, perhaps, only natural to want to preserve the status quo, but some environmentalists carry this to ridiculous extreme and even yearn for some imagined Eden that never was. Whatever their motives may be, they derive them in part from ignorance about life on earth. So let me tell you a story.

In the first half of the 19th century, when the science of geology was young, a British geologist, Adam Sedgewick, was working in Wales. He noticed that certain strata contained abundant fossils of marine life that formed a characteristic life assemblage which was, later, to be recognized throughout England and Europe. He named these strata “Cambrian” after the Latin name for Wales. He also noticed that successive layers of rock contained a slightly different characteristic assemblage of fossils. Life was evolving. Later dating would place the beginning of the Cambrian period at about 540 million years ago.

But there was a mystery. The Cambrian rocks showed an “explosion” of abundant and varied animal life. The strata below the Cambrian (called Precambrian) was apparently devoid of obvious life. This vexed Charles Darwin whose new theory of evolution demanded that the Cambrian animals should have evolved from earlier life forms.

Of course, Darwin was right; there are Precambrian fossils, but they weren’t discovered until 1940 because they weren’t obvious. It’s hard to make a fossil out of a jellyfish. I’ll get back to that later.

So let’s now go back to the beginning and take up the story, as we know it, in chronological order.

 

Life leaves a signature. We now know that life began on Earth almost 4 billion years ago, and it left a signature consisting of a special combination of carbon isotopes. The first known life-form on Earth was the bacterium. You’ll notice that bacteria are still with us. That’s because they are good chemists. They don’t change body shape, but they do change chemical processes in response to the environment.
 

 

 

The first bacteria developed and lived at crushing ocean depths near undersea volcanoes where they derived sustenance from hydrogen sulfide emitted by the volcanoes. Gradually these earliest bacteria worked their way to shallow water near land, and started to use carbon dioxide and sunlight. The oldest known fossils are microfossils called stromatolites, which are remnants of bacterial mats. The earliest stromatolites are dated at about 3.5 billion years before present. For about one billion years, bacteria were the only life-form on earth.

Bacteria give off oxygen, and after a billion years, that process caused an environmental crisis. About 2.5 billion years ago, oxygen levels in the ocean reached some critical level which caused iron and manganese to precipitate. All of the world’s large iron deposits, called Banded Iron Formations, formed between 2.5- and 1.8 billion years ago, and none have formed since. After oceanic iron was used up, oxygen increased in the atmosphere. The oxygen began to destroy methane, a very powerful greenhouse gas, and the reaction produced carbon dioxide, which is 62 times less effective at warming the surface of the planet. Loss of methane plunged the planet into a profound ice age that lasted for about 30 million years. The bacteria retreated to equatorial habitats and again toward warm volcanic vents. Populations became isolated and some changed; they became more organized into a new life form called Eukaryotic microbes. Fossil Eukaryotes appear in the iron formations, initially as single cells, then as multicellular chains up to 4″ long. Life was getting big. The Eukaryotes would eventually become animals, plants, and fungi. Algae appear in the fossil record beginning about one billion years ago.

Planet Earth suffered another series of ice ages between 750 million and 600 million years ago, which caused at least three separate mass extinctions including most of the stromatolites. Another extinction occurred 560 to 500 million years ago, right at the start of the Cambrian Period. But with each extinction, life bounced back, became more diverse, and bigger. And that brings us back to the discovery in 1940.

In 1940, an Australian geologist, R.C. Sprigg, found some fossils in Precambrian sandstone in southern Australia. These “Ediacarans” resembled jellyfish, worms, and stalked sea anemone-like creatures. Some of these fossils were nearly three feet long. Similar fossils have since been found worldwide. The Ediacarans appeared about 580 million years ago and were largely gone by 550 million years ago. As I said, it’s hard to make a fossil out of a jellyfish. The early Ediacarans were preserved in bacterial mats, stromatolites. When the stromatolites disappeared, so did the means of fossilizing Ediacarans.

The next evidence of animal life are trace fossils, not the critters themselves but squiggles and tracks left by relatively large animals capable of locomotion. Next came SSFs, small shelly fossils, evidence that animals first formed hard parts that are easily fossilized. These critters appeared beginning about 545 million years ago. The “abundant life” in Sedgewick’s mid-Cambrian assemblages didn’t appear until 522 million years ago. Genetic work from molecular biology studies, and more-recent fossil discoveries suggest that a major diversification in animal life took place at least 50 million years before the Cambrian, and that the Cambrian “explosion” represented the second major diversification. So you see, there is a continuous line of fossil evidence for evolution; it just took us a while to recognize it.

Abundant, visible life was present on planet earth by 500 million years ago, and nature tried to kill it off several more times. Here are the major events.

The Ordovician and Devonian mass extinctions of 440- and 370 million years ago caused extinction of 20% of marine families. The Permo-Triassic mass extinction event of 250 million years ago appears to have been the most catastrophic. It is estimated that 80% to 90% of all species became extinct during this event. These extinctions are associated with Ice Ages.

About 50% of genera were eliminated in the end-Triassic extinction 200 million years ago. This one may have been caused by cooling associated with an asteroid impact. The Cretaceous/Tertiary extinction, 65 million years ago which eliminated the dinosaurs and about 50% of other species is attributed to cooling events caused by vulcanism and asteroid impact.

Finally, megafauna, such as the mammoth, became extinct about 10,000 years ago following the last period of glaciation. The time of extinction coincides with a major cooling event called the Younger Dryas. Some attribute this event to asteroid impact.

Life on earth is risky, but resilient, and each extinction was followed by more speciation and greater biodiversity. The old order gives way to new.

So that’s my story. Put all that against the feeble folly of the ESA. Do you see now why the plight of pygmy owls and other “endangered” species doesn’t impress me? Lots of things kill off life on earth, including us. We are part of Nature. Notice also, that most extinctions were associated with cooling; not warming.

Bottom Line: The Endangered Species Act reflects only our own hubris, and is just so much wasteful foolishness because Nature is the ultimate impartial and ruthless arbiter of life on earth.