| Abstract: | The horns of a dilemma are usually on the same bull–Spanish proverb. A plague o' both your houses–Veronese imprecation. Although some hypotheses explain the world better than others, making ‘pluralism’ an untenable position, it is the case that scientists frequently set up as alternative hypotheses, one of which must be rejected, models which are merely compatible aspects of some other valid hypothesis that embraces them both. For example, Miillerian mimicry was once supposed to evolve either by a single large change or by gradual convergence (the assumption of gradualism is such that the second alternative has usually been regarded as correct). Yet our genetical research with Heliconius indicates that both processes take place, one after the other, when Miillerian mimicry evolves. A reconstruction of the most plausible route, through time and space, for the evolution of mimicry in Heliconius erato and H. melpomene is used to suggest that two currently popular controversies are similarly futile: the allopatric and parapatric models of race formation are considered to be the extremes of what in nature is a continuum of populations showing varying degrees of partial isolation (ecological change rather than stoppage of gene flow being the driving force in race formation); and it is shown that jerky evolution of the type now interpreted as evidence for ‘punctuated equilibria’ and ‘hopeful monsters’ can be produced by changes in the frequencies of major but ordinary gene mutations in response to changing ecological conditions, a phenomenon well accounted for in neo-Darwinian theory. |
