GEOSC RockOn #11

The picture above shows:

A right-side-up dinosaur track. This is a dinosaur track, from dinosaur ridge, and the dinosaur stomped down into the mud, so the track is right-side-up.

In Pennsylvania today (or at most other places on the world's land surface):

The land surface is accumulating sediment in a few small places, building up records of geologic history, but most places are eroding. Today in Pennsylvania (and across most of the land surface of the planet), sediments are accumulating in a few human-made lakes, a few natural wetlands or natural lakes, along some streams and in some caves, but almost everywhere else is eroding. This is the typical state of affairs, so you need to correlate events across large regions to get a good geologic record.

The extinction of many types of dinosaurs occurred about:

65,000,000 years ago. Humans were trotting around 65,000 years ago, and met dinosaurs only in The Flintstones. 650,000 years is barely enough time for evolution to have changed large animals a bit, and although 6,500,000 years is enough time for noticeable change of large animals—increase in maximum size of members of the horse family, for example—the huge changes since the dinosaurs needed 65,000,000 years. 650,000,000 years goes back before any land creatures, and before all but the simplest of multi-celled organisms.

A widely accepted scientific idea usually is based on:

An interlocking web of important experimental results or observations that support the correctness of the idea. At last observation, Pepsi commercials were not highly scientific, even if science is involved in figuring out what sells. It is a romantic notion that you could overturn great knowledge with a single observation; however, observing nature is not easy, and nature occasionally fools us (you can, rarely, flip an honest coin twenty times and get twenty heads), so if a single observation disagrees with a lot of other information, that single observation will be checked in various ways to see if the new result "stands up" before the older body of knowledge is discarded. Before an idea gains wide currency, that idea is tried in various ways, in many labs, in many places in nature, while models are run and theory is developed. The interlocking of all of these provides the confidence that scientists can use in doing things successfully. Although received wisdom from sacred books can be used for inspiration, scientific ideas must be tested against nature. Social scientists have quite rightly learned that scientists are affected by their prejudices, their funding sources, their mating habits, and other things, and that the path of science is not nearly the straight-ahead road to understanding presented in some textbooks. Unfortunately, some of those social scientists have then gone off the deep end and claimed that science is no more useful than any other human story—claiming that astrology and astronomy are equally valid, for example, or palm-reading and modern medicine. These same social scientists seem to know where to find a real doctor when they get in trouble, however. Science is appealed to nature, and builds on the learning of people from around the world. Airplanes that fly, computers that calculate, small devices that make big explosions, etc. are not socially conditioned ideas but instead are demonstrations of the success of science coupled to engineering.

The picture above shows a beautiful specimen of Araucarioxylon arizonicum, a fossil tree from the Mesozoic rocks of Petrified Forest National Park. Based on the discussions of evolution in the class materials, it is likely that:

Araucarioxylon arizonicum is related to, but recognizably different from, trees still alive today. Evolutionary theory indicates that living things change from generation to generation, but that all living things are related. Consistent with this, Araucarioxylon arizonicum is recognizably similar to, yet different from, Araucaria trees such as monkey puzzle that are native to southern South America today.

What cause probably was not important in contributing to extinction of most species on Earth, including the dinosaurs, in a very short interval of time at the end of the Mesozoic Era?

Cold from the change in Earth's orbit caused when the meteorite shoved the planet farther from the sun. Robert Frost once wrote "Some say the world will end in fire, some say in ice". For the dinosaurs, both were probably true, with acid thrown in. But the meteorite was not nearly big enough to change the planet's orbit noticeably. Frost went on "From what I've tasted of desire, I hold with those who favor fire, But if it had to perish twice, I think that for destruction ice, Is also great, and would suffice."

Considering long-term averages, and assuming that we don't deploy space-based defenses against incoming meteorites, a reasonable estimate of the chance of an average U.S. citizen being killed by the effects of a meteorite or comet impact is that this risk is about the same as the chance of being killed by:

Crash of a commercial airplane Nobody that we know eats Pepsi cans, and while there are still meteorites in the solar system that can hit and kill, there are no dinosaurs left except on "The Flintstones". A reputable study found that a meteorite impact might not occur for millions of years (or might occur next year...) but then might kill billions of people; plane crashes usually kill a few to a few hundred each year. Add up the deaths over a sufficiently long time, and plane crashes and meteorite impacts likely are similarly dangerous. But car crashes, smoking, and being fat and lazy are way more dangerous to us.

Evolution produces new types, and extinction gets rid of them. The scientific evidence summarized in the text and in class shows that:

Evolution and extinction are usually more-or-less in balance, but occasional mass extinctions reduce biodiversity, and subsequent evolution faster than extinction increases biodiversity until a new balance is reached. Numerous extinctions have occurred over the history of the planet, but extinctions have been especially rapid during the short "mass extinctions" including the one that killed the dinosaurs. After mass extinctions, evolution fills the empty niches, increasing biodiversity back to a more-or-less stable level.

Scientists promote the teaching of evolutionary theory, in part to raise new scientists to help use evolutionary theory. How are scientists using evolutionary theory in efforts that can help people?

Evolutionary theory is being used to understand, and help fight, the emergence of antibiotic-resistant diseases and other new diseases, and even to guide thinking in computer science. As antibiotic resistance appears in disease organisms, evolutionary biologists are helping doctors find better strategies to keep us healthy. The processes behind evolution—try new things, keep the ones that work, repeat—has been used intentionally for guidance in many human endeavors, including "evolutionary computing" in computer science. Ecologists trying to rescue ecosystems are informed by understanding of the evolutionary processes that made, and are changing, those ecosystems. Even regulations for sport fishing are guided by our understanding of evolution. In the same way as other successful ideas in science, evolution is useful in many practical ways in the real world.

Religion and science always disagree.

False Pope John Paul II said that the Catholic Church has no problem with evolution, and Baptist Jimmy Carter also supported evolution, so it is clear that religion and science can agree.

Which of the following is not part of the evidence that the odd layer marking the extinction of the dinosaurs was caused by a large meteorite impact?

High concentrations of silica found in the layer. We have seen several times that silica is very common, so its presence in a layer would not indicate much of anything. Features really observed in the layer that are associated with meteorites but not common elsewhere in rocks include shocked quartz from the impact, soot from wildfires, iridium from the meteorite, and a giant-wave deposit because the meteorite hit water as well as land at the edge of the Yucatan Peninsula.

The pictures labeled I and II show fossils from a sediment core collected from the floor of the Atlantic ocean, east of South Carolina. The sediment has not been disturbed by landslides or mountain building or other processes. The pictures were taken by Brian Huber, of the Smithsonian Institution, using a scanning electron microscope. The two samples in the sediment core were separated by the unique layer marking the extinction that killed the dinosaurs. Which is correct?

II is younger than the unique layer, and thus sat above the unique layer in the sediment on the sea floor. Before the impact, biodiversity was high, as shown in I, which includes fossils from below the unique layer and thus deposited before the meteorite hit. After the impact, most of the living types were killed, giving rise to the limited diversity seen in II from above the unique layer after the impact.

Which of the following is not a part of the modern theory of evolution?

If the body of an adult living thing is changed by its environment, those changes usually are passed on biologically to children. You can get a tattoo without worry that your children will be born with that same tattoo, but all the rest of these contribute to evolution.

Reasons why fossils of transitional forms are missing in some lineages that humans especially care about include:

Rapid evolution often occurred in small populations, and fossilization is less likely in smaller populations. Although more searching could be valuable, lots of scientists have looked for transitional forms, which are expected based on evolutionary theory. The common occurrence of transitional forms in commonly fossilized types shows that "Ford-Mustang-type" catastrophism did not occur, but the data also show that evolution often occurred rapidly in small, isolated populations that are hard to find, and that might not be fossilized in rarely-fossilized types.

There are many large mammals on Earth today. This is because:

Small mammals were not able to outcompete the dinosaurs for big-animal jobs, but after the dinosaurs were killed, some large mammals evolved from small mammals to fill the large-animal jobs. There are "big-animal" jobs—eating tall trees, eating smaller animals, etc. But the total number of big-animal jobs is limited. The dinosaurs filled the big-animal jobs before mammals really got going, and mammals were not able to displace the dinosaurs. Some small mammals survived the meteorite that killed the dinosaurs, and then evolved to give big mammals over millions of years and longer. There were almost no big mammals before the dinosaurs were killed off, volition has nothing to do with evolution, and running away doesn't avoid acid rain.