Frequently asked questions about palaeontology
(Adapted from University of California Museum of Paleontology, Berkeley)
Q. What is palaeontology?
Q. How does palaeontology differ from archaeology and anthropology?
Q. What are the practical uses of palaeontology?
Q. How do palaeontologist know how old their fossils are?
Q. What is palaeontology?
A. Palaeontology is the study of fossils. A fossil is described as any trace of a past life form. Thus, although wood, bones, and shells are the most common fossils, under certain conditions soft tissues, tracks and trails, and even coprolites (fossil feces) may be preserved as fossils. Although most of the fossils that palaeontologists study are several thousands to several billions of years old, there is no absolute minimum age for a biological structure to be a fossil.
Palaeontologists study these fossils and attempt to use them to reconstruct the history of the Earth and the life on it. Some study the ecology of the past; others work on the evolution of fossil taxa.
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Q. How does palaeontology differ from archaeology and anthropology?
A. Archaeologists primarily work with human artefacts—objects that have been made by humans—and with human remains. Anthropologists work with humans—their cultures, societies, languages, and ways of life, in addition to their bones and artefacts. Some paleontologists do study the fossil record of humans and their relatives. However, palaeontology as a whole encompasses all life, from whales to bacteria. Palaeontology does not usually deal with artefacts made by humans.
However, archaeologists and palaeontologists might work together. For instance, a palaeontologist might identify fossil animal bones or plant pollen associated with an archaeological site to find out what the people who lived there ate, or a palaeontologist might be called on to analyze the climate at the time a particular archaeological site was inhabited.
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Q. What are the practical uses of palaeontology?
A. First of all, a number of natural resources are in fact fossils, or derived from fossils. Coal, oil, and peat are derived from fossil plant material; marble is metamorphosed limestone, which is often biogenically deposited; diatomaceous earth (used as an abrasive and in gardening) is made up of fossil microscopic siliceous skeletons of certain algae. To study these resources—and to identify areas and rock layers that are likely to contain them—requires in-depth knowledge of sedimentary rocks and of the fossils contained in them. Some palaeontologists work for the petroleum industry and use fossils to interpret sequences of sedimentary rocks.
Palaeontologists who work on relatively recent fossils have developed approaches to reconstructing past climates and environments. Today, environmental change, global warming, and so on are household words. Palaeontologists can provide historical data on past climates and apply it towards understanding future trends and their likely effects. If we understand the effects of climate change, for instance, on our world in the past, we can understand our probable effects in the future.
Finally, palaeontology is an increasingly important component of historical biology. The life around us today has been shaped through its long history, and understanding its past is important to understanding its present situation. There are a number of techniques and fields that deal with reconstructing the past, but palaeontology provides hard data on past events. Palaeontology can potentially provide much data on the evolutionary relationships of organisms, which in turn gives a deeper understanding of biodiversity.
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Q. How do palaeontologist know how old their fossils are?
A. A complete answer to this question would require a book-length response. Briefly, palaeontologists deal with two types of dating, absolute and relative. Absolute dating, which estimates the age of a rock or fossil in years, is most usually done by measuring the amounts of a radioactive isotope and its decay product; since isotope decay rates are known to be constant, the age can be calculated from the relative amounts of parent isotope to daughter product. Fossils up to about 40,000 years old can be dated using carbon-14 if there is enough organic matter present. Older rocks can be dated using potassium-40, which decays to argon-40, or uranium-235, which decays to lead-207. However, many sedimentary rocks cannot be dated directly by these methods; dates usually are obtained from igneous rocks within a sedimentary sequence, such as lava flows or ash beds. Such dates are maximum age estimates for fossils above the dated beds, or minimum estimates for fossils below the beds.
Relative dating has been practiced for nearly 200 years, arising from the observation that different layers of sedimentary rock contain different fossils, and that this sequence can be recognized in other rocks at other localities, even those far away. This allows fossil-bearing rocks to be dated relatively; on the basis of its fossils a rock might be placed in, say, the Ordovician, which predates the Cambrian and was followed by the Silurian. This technique does not depend on knowing the actual numerical ages of the rocks. Not all fossils are equally useful for relative dating, or correlation; some are rare, restricted to small geographic areas or to particular environments, difficult to recognize, or have such long ranges as to make precise correlation impossible. Fossils that are most useful for correlation tend to be widespread, found in many rock types, easily recognizable, and short-lived enough to permit precise placement in the geologic column.
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