Paleontologists at the University of Leicester have been conducting a decidedly unpleasant scientific study—and one whose purpose may not be clear at first. Researchers spent 200 days watching dead fish rot under controlled conditions, carefully recording the patterns of decay and observing which body parts disappeared first.
Decay bias may lead to incorrect identification and distort (supposed) evolutionary history.
The point? The team hoped to better understand the process of decomposition in order to ascertain what anatomy the fossil record may systematically omit. That is, if the same fishy parts always rot away quickly, the fossil record will have relatively fewer examples of those parts—perhaps leading scientists to believe such parts were rarer than in reality.
“Decay bias” is the term the researchers use for this problem, which was illustrated by decaying lampreys that the team observed. “[C]ertain parts of the brain and the mouth that distinguish the animals from earlier relatives begin a rapid decay within 24 hours,” ScienceNOW reports. Because the scientists believe those parts are more recently evolved, fossils missing them appear “more primitive than they would have been in life.” Therefore decay bias may lead to incorrect identification and distort (supposed) evolutionary history.
Yale University paleobiologist Derek Briggs, who was not involved in the study, notes that the research reveals “important constraints on the interpretation of rare fossils, including some of our earliest ancestors” and that the problem “can be applied to the interpretation of soft-bodied fossils in general, and particularly to determining their true place in the tree of life.” Indeed, the study is a reminder of the assumptions required for one to infer biological history based on a very incomplete record of imperfectly preserved fossils. More importantly, the research suggests that—at least in some biological taxa—there may be a systematic bias making fossils appear more “primitive” than they actually were; and by decreasing the frequency of supposedly primitive fossils, evolutionists have even less of an example of progressive evolution over time.
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