The sources of adaptive variation

Abstract

The role of natural selection in the evolution of adaptive phenotypes has undergone constant probing by evolutionary biologists, employing both theoretical and empirical approaches. As Darwin noted, natural selection can act together with other processes, including random changes in the frequencies of phenotypic differences that are not under strong selection, and changes in the environment, which may reflect evolutionary changes in the organisms themselves. As understanding of genetics developed after 1900, the new genetic discoveries were incorporated into evolutionary biology. The resulting general principles were summarized by Julian Huxley in his 1942 book Evolution: the modern synthesis . Here, we examine how recent advances in genetics, developmental biology and molecular biology, including epigenetics, relate to today's understanding of the evolution of adaptations. We illustrate how careful genetic studies have repeatedly shown that apparently puzzling results in a wide diversity of organisms involve processes that are consistent with neo-Darwinism. They do not support important roles in adaptation for processes such as directed mutation or the inheritance of acquired characters, and therefore no radical revision of our understanding of the mechanism of adaptive evolution is needed.

Animal learning as a source of developmental bias

“…Recently, the suggestion (associated with the extended evolutionary synthesis) that "novel phenotypic variants will frequently be directional and functional" (Laland et al, 2015, p. 10) excited considerable contention (e.g., Charlesworth, Barton, & Charlesworth, 2017). Recently, the suggestion (associated with the extended evolutionary synthesis) that "novel phenotypic variants will frequently be directional and functional" (Laland et al, 2015, p. 10) excited considerable contention (e.g., Charlesworth, Barton, & Charlesworth, 2017).…”

On reciprocal causation in the evolutionary process

“…Nevertheless, the increasing interest in epigenetic inheritance is certainly justified and will most likely lead to new empirical insights. Clear cases of epigenetic inheritance now exists (Dias and Ressler 2014) and it is now mainly an empirical issue to understand the importance of such effects and how widespread they are (Charlesworth et al 2017). Here, I take issue with some of the claims by Laland et al (2015), and I argue that their characterization of MS and SET provides a wrong, or at least a very biased, picture of the state-of-theart research in modern evolutionary biology.…”

“…With respect to Laland et al's (2015) claim of the preeminence of natural selection in contemporary evolutionary biology, it must be emphasized that most evolutionary biologists today, including many molecular population geneticists would strongly disagree (see Welch 2016 and;Charlesworth et al 2017 for further discussion). On the contrary, leading molecular population geneticists are highly critical of what they consider an excessive adaptationist research programme in some areas of evolutionary and behavioural ecology.…”

“…On the contrary, leading molecular population geneticists are highly critical of what they consider an excessive adaptationist research programme in some areas of evolutionary and behavioural ecology. Some leading evolutionary biologists would instead argue that random processes such as genetic drift should more often be used as a null modell and point of departure, before invoking natural selection (Lynch 2007;Charlesworth et al 2017). Historically, and from the very beginning of the MS, the non-adaptive process of genetic drift was considered to have a much more powerful evolutionary role than it perhaps deserved to have, something which only became clear after extensive empirical investigations in both the field and in laboratory studies (Provine 1986).…”

“…The call for an EES has also been criticized from several other different angles and perspectives, by both biologists and philosophers (Gupta et al 2017;Lu and Bourratt 2017;Charlesworth et al 2017;Futuyma 2017). Among these criticisms against the EES are that these phenomena and processes have already been successfully accommodated by contemporary evolutionary biology and that so-called "soft inheritance" is unlikely to be important in evolution (Brodie 2005;Dickins and Rahman 2012;Welch 2016;Gupta et al 2017;Lu and Bourratt 2017;Charlesworth et al 2017;Futuyma 2017).…”