Fossils and Dating

The "fossil record" refers to the placement of fossils throughout the surface layers of the Earth. Older fossils are buried more deeply than younger ones. Scientists use the placement of fossils as a guide for determining when life forms existed, and how they evolved. For example, we know that flowering plants evolved from non-flowering plants because, in the fossil record, we see flower fossils becoming more and more primitive the deeper we go, until they disappear all together. There are no flower fossils below a certain depth. This shows us that flowering plants evolved from non-flowering plants, then began to diversify themselves. This kind of progression is found throughout the fossil record.

[ References: Wikipedia: Fossil Record ]

Transitional fossils bridge gaps between two species. Due to the difficulties in creating fossils in the first place, and the fact that speciation sometimes occurs very quickly in small groups, transitional fossils can be rare in the fossil record. However, even given these circumstances, there are still thousands of transitional fossils known to science, including those illustrating the evolution of modern fish, the transition of fish to amphibians, amphibians to reptiles, reptiles to birds, reptiles to mammals, and the evolution of human beings (as well as many other species).

Please see this video for great examples of transitional fossils: http://www.evolutionfaq.com/videos/transitional-fossils

Also, see this Wikipedia page detailing just a partial list of transitional fossil examples: http://en.wikipedia.org/wiki/List_of_transitional_fossils


The concept of a "missing link" between humans and apes arose in the 19th century, when the fossil record was largely incomplete. Large gaps separated species, casting doubt on the theory of evolution. But in the last 130 years, a plethora of fossils have been discovered, greatly narrowing the gaps between species. The Australopithecus afarensis fossil known as "Lucy" is considered to be a key fossil bridging the gap between humans and primitive hominids.


Based on the experimental data of numerous independent dating techniques, we know the Earth to be approximately 4.55 billion years old.


Radiocarbon dating is just one of many "radiometric" dating techniques. While contamination in the laboratory might happen on rare occasions, radiometric dating remains a trusted and reliable method of determining the age of a sample. The technique relies on the constant rate of decay of certain radioactive elements in the sample. For example, rubidium-strontium dating relies on the decay of rubidium-87 to strontium-87. Rubidium-87 has a half-life of 50 million years (the amount of time for half its mass to decay into strontium). Using this figure, scientists measure the amount of rubidium and strontium in a sample to determine its age.

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