Fundamentals of Evolution - O.P. Korzh - 2006

Part II. MACROEVOLUTION

Chapter 16. Modern Problems of Evolution

16.5. Micro-, Macro-, and Megaevolution

Today, There are two primary approaches to understanding the relationship between micro- and macroevolution. The first, developed by classical figures of the Synthetic Theory of evolution (Dobzhansky, Timofeeff-Ressovsky, Mayr, and many others), posits that virtually all macroevolutionary phenomena can be explained by the mechanisms of microevolutionary transformations. In other words, there is no need to introduce new supplementary mechanisms to account for The formation of supraspecific taxa, as nearly all evolutionary changes can be reduced to speciation processes.

According to the second approach, which is increasingly supported by modern scientists (Philippchenko, Gould, Zotin, Vorontsov, and others), macroevolution cannot be reduced solely to microevolutionary shifts, and such attempts should be viewed as reductionism. As N.N. Vorontsov argued, it is only recently that proponents of the synthetic theory of evolution have conceded that macroevolution cannot be reduced to simple changes in Gene frequencies. Similarly, V. Grant maintains that the definition "evolution is A change in gene frequencies in populations" is applicable exclusively within The Scope of microevolution.

Until recently, it was widely believed that there were no grounds for distinguishing a special macroevolutionary level of biological Organization, and that all evolutionary phenomena consisted entirely of microevolutionary events. The division of evolutionary science into micro- and macroevolution was always regarded merely as a methodological device designed to facilitate students' comprehension of the relevant material.

It should be noted, however, that There is a whole range of macroevolutionary phenomena that cannot be traced at the microevolutionary level.

This applies primarily to the patterns of evolution within organismal groups. For instance, the irreversibility of the evolutionary process is characteristic exclusively of the macroevolutionary level, whereas at the microevolution level, a reversion to the so-called "wild type" can occur. The rule of origin from unspecialized ancestors applies only to the macroevolutionary level, since any species—even a highly specialized one—can, in principle, give rise to a new species.

Of particular note is the relationship between the aromorphic and allomorphic pathways of organismal development. Speciation, intrapopulational genetic-automatic processes, and other phenomena that constitute The Essence of microevolution are invariably associated with allogenesis. Aromorphic transformations, which involve a group of organisms entering a new adaptive zone, occur exclusively at the macroevolution level. Microevolution and macroevolution can thus be distinguished as allogenesis and aromogenesis, respectively. This perspective aligns with Modern views on the periodicity of micro- and macroevolutionary transformations in nature (referring precisely to the succession of major evolutionary directions described by I.I. Schmalhausen's rule).

There is a series of purely macroevolutionary problems that were examined in the relevant section of this manual—such as the mechanisms of organ and function transformation, the Evolution of ontogeny, the Relationship between ontogeny and phylogeny, and Structure/149.html">The problem of progress. At the population level, investigating such problems is impossible due to the absence of the subject matter itself.

We have previously touched upon the problem of megaevolution, although it must be conceded that this term is not universally accepted. At the same time, a growing number of scientists conclude that the evolution of ecosystems deserves dedicated study, which has led to The Emergence of a new field: evolutionary ecology.

The properties of the biosphere are determined by the biogeocenoses that comprise it; therefore, evolutionary changes must begin with the transformation of the latter's structure. Consequently, only those macroevolutionary processes that fundamentally alter The structure of biocenoses can serve as the basis for megaevolution and global Changes in the biosphere. Due to Homeostasis (direct and feedback regulatory links within ecosystems) and the action of the stabilizing form of natural Selection, achieving this is by no means easy.

According to A.I. Zotin and A.A. Zotin, explaining macroevolutionary (and, consequently, megaevolutionary) changes through microevolutionary mechanisms is impossible. The explanations of these evolutionary transformations proposed by them (such as neo-catastrophism and "evolutionary winds") cannot be considered flawless either, and therefore they will not be discussed in detail here. We can only hope that in the near future this issue will find a more or less unified resolution.

A significant portion of microevolutionary processes can be repetitive and is largely predictable; whereas macroevolution is a historical process. This very historical nature accounts for the irreversibility of macroevolutionary events, whereas microevolution—at least ecologically—is reversible.