Another fossil find. The fossil record is an important part of the reason evolution is considered a fact, not a hypothesis in need of more evidence. There are two aspects to using fossils to document evolution. One is the fossil itself, the things it tells us about the creature captured in stone for us to find millions of years later. The second is the dating of the fossil, to understand when it lived. Since the flow of time allows evolution to play out, we need the date to update the timeline of evolution.
The methods for dating fossils are various, but all are based in solidly established sciences like geology and nuclear physics. Geologists initially received as much grief from the fundamentalists as evolution would later receive. They were estimating the age of mountain ranges, seabeds, and other geologic formations by estimating the time it would take for things like erosion to whittle away at the hards surfaces of the earth. These preliminary estimates quickly placed the history of the earth thousands and even millions of years in the past, well past the six thousand years which the early Bible would indicate.
But this criticism eventually died out. One reason was that the evidence for an old earth continued to mount until there was no reasonable way to claim the earth was actually six thousand years old. Today, some fundamentalists hold onto the idea of a young earth, but they have absolutely no way to support this in the face of such a huge amount of evidence placing the earth approximately 4 billion years old.
When nuclear radiation was discovered and understood, this provided an independent way to test the dates which geology had proposed. The heaviest elements in the universe are often unstable, changing into other elements as they emit protons and neutrons from the nucleus. Some of these take a very long time to decay and so the amount of certain isotopes can lead to estimates of the age of the materials tested. The well-known carbon-14 dating process is just one example. But Carbon-14 is only valid for formerly living material which died no more than about 100 thousand years ago. Other elements, however, can be used to date rocks, sediments, and other parts of the earth's crust. The physics of nuclear decay and half-life determination is highly precise and beyond question as an accurate understanding of the basic building blocks of matter. Radioactive dating allowed more precise determination of the age of various parts of the earth's crust.
Even more confirmation of the earth's age came with the discovery of tectonic plates. Now geologists had a strong theory to explain all the things they had been documenting, such as fossils of fish at the tops of mountains, sections of one continent which fit perfectly into sections of other continents (Africa and S. America, for examle), and the ages of different parts of the crust. There is no question about the validity of plate tectonics. It has allowed us to know roughly how the planet looked at various times in the past. The continent of Antarctica, for example, was once along the equator and covered with tropical plants.
One aspect of plate tectonics which gave further confirmation to evolution was the correlation between when various continents broke apart, and when various species diverged from a common ancestor. Similar mammals exist in South America and Africa, which were once part of the same super continent. The estimates for when certain species diverged corresponds well to when geology says the continents split.
Between the fossil record and continental drift and geology, we can describe the various plants and animals which populated the earth and on which continents they lived and where those continents were and what kind of climate they experienced. This has given us a remarkable ability to "see" the earth as it has existed over the course of its 4 billion years.
When the big picture is seen in this way, it should be clear that no more fossils are needed to prove evolution. New fossils provide only more details allowing us to understand the manner in which evolution has shaped the populations of life on the planet.
posted by Coyote Z at 9:41 PM
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