Concluding Remarks

Much of the debate between the sufficiency of microevo-lutionary mechanisms to account for macroevolutionary phenomena stems from looking at problems at different spatial or temporal scales. By analogy, while nobody doubts that macroeconomic phenomena ultimately arise as a consequence of individual decision-making processes, nobody argues that macroeconomic phenomena are not real and that large-scale human institutions have emergent properties that can be studied and understood in their own right. In the same way, biological phenomena are 'real' and need not be reduced to physics and chemistry to be understood, even though no biological processes contradict the laws of chemistry or physics. In fact, it is often more instructive to study biological phenomena at their own scale and level of organization than by reducing them to the underlying physicochemical interactions.

By analogy, although most if not all patterns of interest of macroevolutionists (apart from catastrophic environmental changes that are more questions of geology than of biology) have their origins in the genetics and variational properties of ancestral species, this does not imply that problems such as the invasion of new ecological niches, or the distribution of characters in phylogenies, are best understood by studying population genetics. It simply means that these phenomena are not in violation of microevolutionary processes, and do not require the discovery of previously unknown mechanisms any more than the emergent properties of living organisms violate the laws of chemistry and physics.

Along similar lines, changes in regulatory genes that have major effects on phenotype differ quantitatively and qualitatively from those genes that have minor effects on size or color within species, yet it would be difficult to justify the claim that such major changes in phenotype are caused by fundamentally different processes at the molecular level than those that lead to the more typical material of intraspecific variation. Yet even though such variants are subject to the same underlying population biology and the same forces of natural selection, one can probably learn more about these processes through an understanding of developmental genetics than from population genetics theory. One must distinguish the claim that macroevolutionary phenomena do not contradict microevolutionary (almost certainly the case) from the claim that macroevolutionary events are simply epi-phenomena of the former, which is harder to justify given the qualitative differences in time and scope.

See also: Ecological Niche; Physiological Ecology; Units of Selection.

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