FIGURE 2.6 Students on a field trip examining possible fossil finds in Tertiary Period rocks of central Georgia, USA. Their descriptions and hypotheses were independently tested through peer review (with each other), then presented as a single hypothesis in modified form to an expert (the author of this textbook), who conditionally accepted their hypothesis but then presented it to another expert (another geologist at the field site) who was more of an expert on the rocks in that area than the author. This geologist reconfirmed the hypothesis of the students: they had found fossil plant leaves. All of this process, from discovery to reconfirmation, took about 15 minutes.
untrained people often label large oval objects as dinosaur eggs. In such cases, both novice and expert alike should remember that clouds sometimes resemble horses or dragons. Field partners can provide instant reality checks that prevent imaginations from running wild.
Paleontologists discover quickly and early in their careers that fossils are rarely preserved as complete specimens and more likely to occur as mere fragments (Fig. 2.5). With enough correcting of observations and accounting for variations in fossil preservation (Chapter 7), however, identifications become easier. A search pattern is a mental image used by geologists, wildlife biologists, and ecologists, in which they scan an area with certain shapes or colors in mind, based on previous experiences, looking for matching objects. In some cases, these items correspond to what the observer is looking for. In all cases, scientific methods can be applied instantly to the observation in the form of the simple but very appropriate question "What is this?" (Fig. 2.6).
When an object is found that is identified tentatively as a fossil, a paleontologist will normally observe everything about it that comes to mind. This is the description phase, which has worked well for previous generations of scientists. The paleontologists will gather both qualitative and quantitative data by drawing, photographing, measuring dimensions, describing shapes, and noting any resemblance of a possible fossil to known objects. If the object was not lying on the ground surface, they also will especially document how it was found in the context of its host rock. All these observations will connect in some way with a hypothesis; this is the interpretation phase, an attempt to explain the data that may or may not reconcile with a hypothesis held by the observer before going into the field. If possible, this hypothesis can be tested initially in the field while the source of data is still in front of the observer. As mentioned earlier, a skeptical field partner is a big help to paleontologists in this respect. In the case of the solitary professional paleontologist or amateur collector, thorough descriptions become even more essential for communicating results to other paleontologists for evaluation. In this case, measurements (quantitative data) are among the most important descriptors for absolute comparisons and testing of a hypothesis. They can also be used later for calculating ratios, areas, volumes, or statistical tests, which can all be used in hypothesis testing.
When making these types of comparisons, the larger a sample set of measurements, the more meaningful the description. For example, if some paleontologists have multiple measurements for what they hypothesize is the same type of fossil, such as dinosaur tracks, an average value is useful. They can also report a range of values, which is the maximum number coupled with the minimum number, to give an approximation of the variability of the data. An average, also called the mean, is calculated through the following formula:
n where X x is the sum of all values measured and n is the number of values. An example of how average and range can be demonstrated is by using seven measured dinosaur tracks with the following lengths: 80, 64, 78, 72, 82, 75, and 69 cm.
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