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第1段
1 .<-NARRATOR:-> Listen to part of a lecture in an archaeology class.
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第2段
1 .<-FEMALE PROFESSOR:-> OK, so, as we know, archaeologists discover objects from past civilizations—
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2 .stuff like old pottery, old tools, even sometimes old bits of fabric...
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3 .and they examine these artifacts to learn about past civilizations.
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4 .But why are some artifacts preserved well enough to last for thousands of years
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5 .while others just wear away and disappear?
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6 .Well, a lot of it has to do with the environmental conditions in the area where the artifacts are found.
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7 .Artifacts are preserved better in environments where the bacteria that cause decay are less likely to grow.
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8 .So let's look at two environmental conditions that discourage bacterial growth
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9 .and thus help preserve archaeological artifacts.
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第3段
1 .One environmental condition that inhibits bacterial growth, and helps preserve artifacts,
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2 .is [slowly] aridity,
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3 .uh, lack of moisture.
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4 .Bacteria that cause decay can't survive well in dry environments,
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5 .and artifacts don't decay as fast in arid climates
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6 .without much moisture.
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7 .So, many of the best-preserved archaeological artifacts have been found in such climates.
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8 .For example, in the deserts of Egypt, archaeologists have found tombs more than two thousand years old
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9 .with brightly colored wall paintings in them.
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10 .And those wall paintings?
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11 .Well, their colors were still as clear and bright as a painting made today.
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第4段
1 .Another environmental condition is lack of oxygen.
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2 .Bacteria, like all living things, depend on oxygen to grow,
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3 .so when there's no oxygen present,
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4 .they can't grow and cause decay.
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5 .So artifacts are usually well preserved when they end up in environments that contain little or no oxygen
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6 .like, for example, the bottom of the ocean,
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7 .which is where archaeologists found an ancient ship that had sunk
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8 .and settled into the mud at the bottom of the Mediterranean Sea.
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9 .The ship was carrying vases,
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10 .and the vases were still intact and remarkably well preserved.
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