[1] The discovery of a fossil combining features of two major groups is routinely hailed as a 'missing link,' a term that misleads more than it clarifies. [2] The phrase implies a single organism standing on the direct line of descent between an ancestor and its modern successor, a position no fossil can be shown to occupy with certainty. [3] What a transitional fossil actually demonstrates is that a particular combination of traits—some ancestral, some resembling those of a later group—once existed, and thus that the traits need not have evolved as an indivisible package. [4] A feathered forelimb paired with a toothed jaw, for instance, establishes that plumage did not await the loss of teeth, refuting the supposition that such characters evolved in lockstep. [5] The fossil's value lies not in marking a way station on a predetermined path but in dissolving the assumption that complex forms must have arisen all at once.
