7 - Time for a Change?

Summary

Turn now to those who think natural selection is vastly overrated as a cause of evolutionary change. It is at best a clean-up process after the real creative work has been done. It is little surprise that these critics come from within the organismic model, implicitly or explicitly. At the scientific level, we have encountered already the most (and properly) distinguished of them all, the American population geneticist Sewall Wright. Remember his “shifting balance theory,” where the key lay in genetic drift, as gene levels fluctuated randomly in small subpopulations, and then, when new adaptive features appeared, the subpopulations rejoined the larger group (probably the species), and through a form of group selection the new feature spread through the whole group. This is highly Spencerian – infused with a solid dose of Bergsonian vitalism – as equilibrium is disturbed and then regained at a higher level, part of an overall progressive process, presumably ending in humankind.