THE FIDELITY OF THE FOSSIL RECORD: THE IMPROBABILITY OF PRESERVATION

Abstract:  The fidelity of the fossil record reflects how accurately it preserves the history of life. Since Darwin's time any mismatch between our theories and the fossil record has been attributed to the imperfections of the record. For over a century scarcity of gradual evolutionary trends was explained in this way until the punctuated equilibrium model was proposed. A null hypothesis that all morphological patterns in the fossil record are unbiased random walks can be rejected because it predicts far more apparent trends than exist. Current best estimates suggest that trends occur in at most 5% of characters. When an organism dies either it becomes fossilized or it doesn't. To be confident a species has not been preserved the probability against preservation must be significantly larger than the total number of individuals of that species that ever existed. For skeletized species preservation was the norm not the exception. Nevertheless, fossils must then avoid subsequent destruction and be discovered to be useful.