The independent emergence of similar features in phylogenetically non-allied groups of organisms has usually been explained as the result of similar selection pressures particular to specific environments. This explanation has been more or less helpful in elucidating convergent resemblances among organisms since the times of Darwin. Nevertheless, intensive research has brought new knowledge on the emergence of structural similarity among organisms, especially during the last two decades. We now have manifold evidence of the phenomena of evolutionary re-entries or re-evolution, which (...) happens when a particular character present in one organic taxon also appears in another taxon which does not share an immediate ancestry. This is not the re-appearance of the same character, but rather of a similar one. Here I propose a model of threefold origin of similar phenotypic features in unrelated organisms stemming from intrinsic, extrinsic and semiosic causation. It is suggested that neither externalist nor internalist explanations per se, nor any combination thereof, are sufficient to cover all the manifold instances of character re-evolution. There is also a special group of resemblances that consists of what is originated, shaped, and retained in evolution due to meaning attributed to them by particular organic subjects. These cases cannot be fully understood without inviting a biosemiotic approach. Integrating Uexkull’s theory of meaning with the recent evolutionary developmental perspective could complete our understanding of phenotypic re-evolution. (shrink)

A number of authors have pointed to “convergent evolution” as evidence for the central role of natural selection in shaping predictable trajectories of macroevolution. However, there are numerous conceptual and empirical difficulties that arise in broadly appealing to the frequency of homoplasy as evidence for a non-contingently constrained adaptational design space. Most important is the need to distinguish between convergent (externally constrained) and parallel (internally constrained) evolution, and to consider how the respective frequencies of these significantly different sources of homoplasy (...) affect a strong adaptationist view of life. In this paper, I critically evaluate Simon Conway Morris’s use of the homoplasy literature to support his argument for a non-contingent, counterfactually stable account of macroevolutionary pattern. In so doing, I offer a conception of parallelism which avoids the charge that it differs from convergence merely in degree and not in kind. I argue that although organisms sharing a homoplastic trait will also share varying degrees of homology, it is the underlying developmental homology with respect to the generators directly causally responsible for the homoplastic event that defines parallel evolution and non-arbitrarily distinguishes it from convergence. The notion of “screening-off” is used to distinguish the proximal generators of a homoplastic trait from its more distal genetic causes (such as a master control gene). (shrink)