Evolution seems to have carried out some very strange experiments. Some of the earliest forms of animal life did not lead to further evolution, so they died out quickly. A few creatures have survived almost entirely unchanged, such as brachiopods. These look like small clams although they are unrelated. They appear in the oldest fossil beds and survive in exactly the same form to this day, living in ocean depths.
Some of the oddest failures in evolution were found in a layer of rock called the Burgess Shale, in Canada. This rock preserved the tiny remains of soft-bodied animals, which is an extremely rare occurrence. The animals amazed scientists because most of them had no relationship to any other known life form.
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