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What is some evidence for evolution?
Question Date: 2008-05-05
Answer 1:

There is an overwhelming amount of support for evolution-- in reputable scientific circles, questioning evolution is akin to claiming that the world is flat, and for similar reasons: the roundness of the Earth and the process of evolution are both overwhelmingly well supported by both observation and experiment. Let me quickly highlight a few of these observations and experiments, and tell you where else you could look:

The first network of evidence most people think of is the fossil record, and that's a good place to start. It has long been observed that fossilized animals (and plants!) found in sedimentary rock layers, show that in the past there were different animals than are on the Earth presently. Moreover, the fossils show that over time, the animals that were observed shifted-- at one point, there were dinosaurs. Then later in time, they were gone, and there were many small mammals. Even later in time (closer to the present), there were larger mammals, than animals that look similar to horses, dogs, and monkeys. And now, we see the rich diversity of life around us. Many of these snapshots show species with transitional features, somewhere between an older form and a newer form that we observe. But this evidence alone is not enough-- no scientific theory stands on one piece of data. Or even one group of data, but a wide ranging web of interlocking facts.

The next evidence we can look at is the chemical and anatomical similarities of related life forms. When biologists and biochemists look at the body structure or genetic information of modern animals,we quite clearly see patterns-- despite the overwhelming diversity of life, everything from amoebas in a pond to human beings are organized the same way: cells containing DNA that codes for all the proteins of the organism-- made of the same 20 amino acids across all of life.Moreover, when they look at the very finest details-- such as the exact composition and structure of essential components of life, such as the biological machinery that copies our DNA as we grow and multiply, they see that these are conserved as well-- and form a causal chain, with small differences between organisms conserved: a change between bacteria and multicellular life is shared by all multicellular life, and a difference between reptiles and mammals is shared by all mammals. By charting these small changes, we can construct trees that show what changes are shared between organisms,and even (by taking into account the known, constant rate at which genetic changes occur) figure out when in time various species separated.

Thirdly, we can look around and observe the geographic distribution of related species-- animals in nature aren't found randomly, but are dispersed according to their evolution. For instance, Australia has no native placental mammals (dogs, cats, horses, rats, etc) but only had native marsupial mammals (kangaroos, kangaroo rats, koalas, etc). And many small islands have no large mammals at all-- their geographic isolation prevented other animals from reaching them. And this separation allows species to separate. From genetic analysis or just by eye, one can tell that many island birds are closely related to continental species-- but they have changed over time to better suit their island environment (bigger beaks for nuts, etc). Eventually, these changes prevent the birds from mating with the original birds: speciation has occurred and there are now two species of birds. Which leads to one of the most important webs of evidence...

The recorded genetic changes in living organisms over many generations by scientists help confirm the theory of evolution. Scientists can,and do, cause simple organisms like bacteria to go through changes by changing their environment, eventually leading to unique species of bacteria. Similarly, mankind has introduced changes into larger species: domesticating wolves and creating dogs; and huge species changes have been made in plants, creating varieties of tomatoes,fruits, and more. (On a side note, this process of selective breeding leads to species with very different genetic traits-- and could be called genetic engineering just as much as a modern scientist introducing new DNA into a crop. Neither are, by themselves, bad or wrong. Just like any decision, the consequences must be evaluated to just the rightness of the action). Moreover, we observe that small species, such as bacteria, viruses,and insects, evolve very quickly-- this is why we must keep up by making new antibiotics, vaccines, and insecticides: the current generations have evolved resistance to the poisons.

This is only a brief introduction to the fascinating process of evolution. There are many good resources, but a very accessible one is the Wikipedia article on Evolution


It's worth noting that the current controv

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