Geology of the National Parks

Main Topics, Unit 11


Overview of the main topics you will encounter in Unit 11.

It is a century now since Darwin gave us the first glimpse of the origin of the species. We know now what was unknown to all the preceding caravan of generations: that men are only fellow-voyagers with other creatures in the odyssey of evolution. This new knowledge should have given us, by this time, a sense of kinship with fellow-creatures; a wish to live and let live; a sense of wonder over the magnitude and duration of the biotic enterprise.
Leopold, Aldo:A Sand County Almanac, and Sketches Here and There, 1948, Oxford University Press, New York, 1987
For one species to mourn the death of another is a new thing under the sun. The Cro-Magnon who slew the last mammoth thought only of steaks. The sportsman who shot the last pigeon [this is the extinct passenger pigeon] thought only of his prowess. The sailor who clubbed the last auck thought of nothing at all. But we, who have lost our pigeons, mourn the loss. Had the funeral been ours, the pigeons would hardly have mourned us. In this fact, rather than in Mr. DuPont's nylons or Mr. Vannevar Bush's bombs, lies objective evidence of our superiority over the beasts.
Leopold, Aldo: A Sand County Almanac, and Sketches Here and There, 1948, Oxford University Press, New York, 1987

Easy Come, Easy Go--Evolution and Extinction

  • Kids include experiments—they are not identical to their parents
  • These differences affect the ability of the kids to survive to have their own kids (natural selection)
  • But, despite the differences, kids are quite similar to their parents—the kids just receive a bit more or less of what makes their parents biologically successful
  • This acting over time gives evolution—successful experiments accumulate, unsuccessful ones are eliminated, so that new generations are different from older ones
  • Changes to living organisms are not passed on (if you get a tattoo, your kids will still be born without tattoos)—just the reproductive experiments are passed on

The Unbroken Chain

  • The Law of Faunal Succession suggests evolution
  • Evolution predicts transitional forms over time, whereas special creation or catastrophism predict that there will not be transitions
  • Transitional forms have been found, strongly supporting evolution:
    • Transitional forms are common in commonly fossilized types
    • And less common in less-commonly-fossilized types
    • New species often emerge geologically rapidly from small populations (it is easier for a smaller group to change)
    • Transitional forms are found as often as evolution predicts; the fossil record is incompatible with competing hypotheses

Taking Care of Business

  • The theory of evolution is explanatory, predictive, and useful
  • Germs are evolving antibiotic resistance, and the scientists trying to keep us alive are using knowledge of evolution
  • Computer scientists mimic evolution to solve complex problems (evolutionary computing)

Teach the Conflict?

  • Scientifically, there is no conflict—there is much to learn and do, but with no serious problems or competitors
  • In particular, evolution is:
    • Consistent with the second law of thermodynamics, and all other known physical laws
    • Strongly supported by the fossil record and age dating
    • Not anti-religion (indeed, it is supported by many religious groups)
  • There is widespread scientific consensus that so-called competitors (e.g., “intelligent design”) are not science
  • Thus, “teaching the conflict” would require teaching non-science in science classes (note that a few years ago, to question evolution, the Kansas School Board invented a new definition of science, presumably because evolution was so scientific)

Extinction Can Ruin Your Whole Day

  • There has been a slow "background" rate of extinction, with species being lost about as often as new species appeared during most of geologic history (population fluctuations sometimes hit zero, which is extinct)
  • But occasionally there were mass extinctions, when species became extinct much much more commonly than new species arose, but these mass extinctions were followed by millions of years when new species arose slightly more often than species became extinct, thus restoring biodiversity:
    • end-Paleozoic mass extinction: heat-caused loss of ocean oxygen?
    • end-Mesozoic mass extinction: meteorite
    • a few others that we won't make you learn
  • The dinosaurs were doing just fine until meteorite got them
  • Their death freed ecological jobs (“niches”), allowing evolution to produce large mammals over the last 65 million years

The Dinosaur Killer

  • Evidence: the extinction event occurs with an odd sedimentary layer with much iridium (common in meteorites, otherwise rare on Earth), soot, high-pressure shocked quartz, melted-rock droplets, a giant-wave deposit in the Caribbean, and a giant crater of the right age on the Yucatan Peninsula
  • Mechanisms: the meteorite blasted things up, causing fire from the heat of fast-falling things, then cold from the sun-blocking effect of slow-falling things, with acid rain
  • A thought: there still are big rocks out there in space—averaged over millions of years (and presuming we humans hang around that long), they may kill as many people as commercial airline crashes, but not nearly so many as car crashes