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Perspectives in Biology and Medicine 47.2 (2004) 314-316
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The evolutionary synthesis in biology was a major achievement. However, it had one major failing: it did not involve much in the way of synthesis. The founders of the synthetic theory integrated the genetics of their day with traditional evolutionary theory, but all they did was show that the emerging synthetic theory was not incompatible with the rest of biology. Contrary to what some paleontologists might claim, paleontology did not contradict the synthetic [End Page 314] theory. Neither did other areas of biology, such as embryology. Non-contradiction is something, but it is not quite a synthesis.
The problem with integrating embryology and evolutionary theory at the time was that embryology, for all its empirical data, lacked the sort of unifying principles that might be integrated into traditional evolutionary theory. During the past few years all that has changed as the advocates of evo-devo begin to deliver on earlier promissory notes. Some of these advocates contend that traditional evolutionary theory must be rejected because evo-devo is incompatible with it, but cooler heads urge a synthesis, and "synthesis" does not require that these theories remain unchanged in the process. Just as in the reduction of Mendelian genetics to molecular biology, modifications in both theories are likely to be required.
The authors of the book under review seek to expand this synthesis by urging increased attention to a long-neglected process in evolution: niche construction. One important difference between evo-devo and niche construction is that until recently we lacked the knowledge of development necessary to pull off a synthesis between embryology and evolutionary theory, whereas knowledge of what present-day biologists call "niche construction" has been around since Darwin. After all, Darwin discussed it at some length in his best-selling book on worms. Worms modify the soil in which they live in ways that benefit not only themselves but also organisms belonging to other species, as well as later generations of their own and other species. Organisms do adapt to their environments, but they also sometimes modify their environments to suit their needs. Such occurrences are far from inconsequential. One of the major transitions in the living world was from anaerobic to aerobic atmosphere, a transition caused by the evolution of oxygen-producing organisms.
As important and prevalent as niche construction has been in the evolution of life, relatively little attention has been paid to it—at best it has been viewed as a minor auxiliary process. In Niche Construction:The Neglected Process in Evolution, Odling-Smee, Laland, and Feldman expand upon the importance of niche construction. Natural selection is one of the two major processes in evolution; niche construction is the other. From the perspective of standard evolutionary theory, organisms transmit their genes from generation to generation, with natural selection acting on phenotypes. Co-evolution is a step in the direction of niche construction, but even here the only kind of inheritance involved is genetic. Even the feedback between modifications that organisms make in their local environment and their success in reproduction is not enough for niche construction.
In addition, genetic inheritance must be replaced by ecological inheritance. In ecological inheritance persistence is what counts. Spiders construct webs, but these webs are not adequate for ecological inheritance because they are destroyed frequently, perhaps daily. The consequences of niche construction, if they are to have any effect, cannot be erased every generation—they must persist [End Page 315] from generation to generation, as do the tunnels that certain organisms construct, use, and modify. In such cases, each generation inherits from ancestral organisms both genes and a legacy of modified selection pressures. The selected environments encountered by descendant organisms stem partly from independent environmental agents, but they also stem in part from sources of natural selection that have previously been modified by ancestral niche construction.