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In 1958, Hessel de Vries in the Netherlands showed there were systematic anomalies in the carbon-14 dates of tree rings.His explanation was that the concentration of carbon-14 in the atmosphere had varied over time (by up to one percent).To get a mass large enough to handle, you needed to embed your sample in another substance, a "carrier." At first acetylene was used, but some workers ruefully noted that the gas was "never entirely free from explosion, as we know from experience."(4) Ways were found to use carbon dioxide instead.
Some speculated that such irregularities might be caused by variations in the Earth's magnetic field.After a creature's death the isotope would slowly decay away over millennia at a fixed rate.Thus the less of it that remained in an object, in proportion to normal carbon, the older the object was.As for still earlier periods, carbon-14 dating excited scientists (including some climate scientists) largely because it might shed light on human evolution the timing of our development as a species, and how climate changes had affected that.(2) It was especially fascinating to discover that our particular species of humans arose something like 100,000 years ago, no doubt deeply influenced by the ice ages.(3) A few scientists noticed that the techniques might also be helpful for the study of climate itself.
From its origins in Chicago, carbon-14 dating spread rapidly to other centers, for example the grandly named Geochronometric Laboratory at Yale University.
For example, Hans Suess relied on a variety of helpers to collect fragments of century-old trees from various corners of North America.