Scientific facts require that their laws be immutable, thus the existence of merely one counterexample disproves the truth of the rule. Evolution, as a theory, is a science open to development and is based on observable patterns. Based on all available evidence (including some modern examples of speciation), scientists conclude that there does exist some mechanism for evolution, and that the set of living spicies on the planet is not a subset of all species which once existed.
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As scientific theories require that their laws be immutable, the existence of merely one counterexample disproves the truth of the rule. Thus, if evolution fails to account for any one of these items (or countless others), it must be discarded.