Tim Lewens

The Trials of Life: Natural Selection and Random Drift *

We distinguish dynamical and statistical interpretations of evolutionary theory. We argue that only the statistical interpretation preserves the presumed relation between natural selection and drift. On these grounds we claim that the dynamical conception of evolutionary theory as a theory of forces is mistaken. Selection and drift are not forces. Nor do selection and drift explanations appeal to the (sub‐population‐level) causes of population level change. Instead they explain by appeal to the statistical structure of populations. We briefly discuss the implications of the statistical interpretation of selection for various debates within the philosophy of biology—the ‘explananda of selection’ debate and the ‘units of selection’ debate.

The Natures of Selection

Elliott Sober and his defenders think of selection, drift, mutation, and migration as distinct evolutionary forces. This paper exposes an ambiguity in Sobers account of the force of selection: sometimes he appears to equate the force of selection with variation in fitness, sometimes with ‘selection for properties’. Sobers own account of fitness as a property analogous to life-expectancy shows how the two conceptions come apart. Cases where there is selection against variance in offspring number also show that selection and drift cannot be distinguished in the way Sober hopes for. These issues have significance beyond the parochial matter of the coherence of Sobers system. There is no good principled answer to the question of which features of a population should count among the contributors to fitness. This means there is no non-arbitrary account of the nature of selection. 1. Evolutionary Forces2. Selection and Drift3. Evolutionary and Newtonian Forces4. Is Natural Selection a Cause?5. An Ambiguity in Sobers Account of Selection: Variation in Fitness versus Selection-for6. A Second Problem: The Determinants of Fitness7. Conclusion Evolutionary Forces Selection and Drift Evolutionary and Newtonian Forces Is Natural Selection a Cause? An Ambiguity in Sobers Account of Selection: Variation in Fitness versus Selection-for A Second Problem: The Determinants of Fitness Conclusion

Adaptationism and Engineering

The rights and wrongs of adaptationism areoften discussed by appeal to what I call theartefact model. Anti-adaptationistscomplain that the use of optimality modelling,reverse engineering and other techniques areindicative of a mistaken and outmoded beliefthat organisms are like well-designedartefacts. Adaptationists (e.g. Dennett 1995)respond with the assertion that viewingorganisms as though they were well designed isa fruitful, perhaps necessary research strategyin evolutionary biology. Anti-adaptationistsare right when they say that techniques likereverse engineering are liable to mislead. This fact does not undermine the artefact modelprecisely because the same techniques misleadus for the same reasons when they are appliedunreflectively to artefacts. Thoseadaptationists who hold only that it isworthwhile to investigate organisms as thoughthey were artefacts and thoseanti-adaptationists who criticise simplisticdesign models have far more in common than thelabels attached to their positions mightsuggest.

Realism and the strong program

The four tenets of the Strong Program are compatible with a scientific realism founded on an externalist epistemology. Such an epistemology allows that appropriate norms of rationality may differ from time to time, and from community to community, and thereby enables the realist to embrace strong forms of the ‘symmetry principle’. It also suggests a fruitful collaborative research program in externalist social epistemology. Some of what the Edinburgh School says about truth can also be accepted. But the realist should reject the Schools argument for the claim that there is no distinction between being rational and being locally accepted as rational, which seems to rest on a kind of epistemological internalism. 1. Introducing the Strong Program2. Realism and the four tenets3. A stronger reading of symmetry4. Conflict and cooperation5. A note on discovery and justification6. Relativism and realism7. Truth8. Points of contention: the restriction of explanatory contrasts9. Points of contention: standards of rationality Introducing the Strong Program Realism and the four tenets A stronger reading of symmetry Conflict and cooperation A note on discovery and justification Relativism and realism Truth Points of contention: the restriction of explanatory contrasts Points of contention: standards of rationality

Sex and Selection: a Reply to Matthen

Mohan Matthen ([1999]) argues that when reproduction is sexual, natural selection can explain why individual organisms possess the traits they do. In stating his argument Matthen makes use of a conception of individual organisms as receptacles for collections of genes—a conception that cannot do the work Matthen requires of it. Either these receptacles are abstract objects, such as bare possibilities for organisms, or they are concrete. The first reading is too weak, since it allows selection to explain individual traits in both sexual and asexual contexts. The only concrete entities we might think of as receptacles for collections of genes are male or female gametes. It is true that in the sexual context selection explains why an individual gamete combines with a second gamete of one type rather than another; however, this is not to say that selection explains why an individual organism has the traits it does.

What Is Wrong with Typological Thinking

What, if anything, is wrong with typological thinking? The question is important, for some evolutionary developmental biologists appear to espouse a form of typology. I isolate four allegations that have been brought against it. They include the claim that typological thinking is mystical; the claim that typological thinking is at odds with the fact of evolution; the claim that typological thinking is committed to an objectionable metaphysical view, which Elliott Sober calls the ‘natural state model’; and finally the view (endorsed by Ron Amundson and Günter Wagner) that typological thinking—and specifically evolutionary developmental biology’s typological thinking—is committed to a peculiar form of causation that does not fit neatly into the causal models endorsed by population genetics. I argue that, properly understood, the typological thinking of evolutionary developmental biology does not run into any of these problems.

Enhancement and human nature: the case of Sandel

If we assume that “enhancement” names all efforts to boost human mental and physical capacities beyond the normal upper range found in our species, then enhancement covers such a broad range of interventions that it becomes implausible to think that there is any generic ethical case to be made either for or against it. Michael Sandel has recently made such a generic case, which focuses on the importance of respecting the “giftedness” of human nature. Sandel succeeds in diagnosing an important worry we may have about the use of some enhancements by some parents, but his arguments are better understood as opposing “procrustean parenting” rather than enhancement in general.

The risks of progress: precaution and the case of human enhancement

So‐called ‘enhancement technologies’ are technologies that promise to boost human mental and physical capacities beyond the normal upper range found in our species. Here it is argued that some of the most salient questions about the ethics of enhancement concern the ethics of risk, and precaution in particular. This paper uses recent work by John Harris to expose these risk‐based considerations, and it aims to temper Harris’s enthusiasm for enhancement. More specifically, it is argued that a defensible set of precautionary concerns can be isolated, which supports scepticism regarding the wisdom of adopting many enhancements in the near and medium‐term future. This way of understanding precaution can be generalised to justify a form of scepticism about promises of progress.

Development aid: on ontogeny and ethics

Abstract Human development is a matter of complex interactions between nutritional regimes, genes, educational regimes and other diverse developmental resources. I argue that there is no ethically salient difference between the contributions made to development by genes and the contributions made by these other resources. Since we think nutrition and schooling should be included in the calculus of distributive justice, we should include at least some genes in this calculus too. What is more, under the right circumstances genetic engineering may become a useful tool for the distribution of developmental resources. This said, attention to the parity of genetic and environmental causation can also help to articulate the legitimate suspicions many groups have of genetic engineering.

Natural selection then and now

One often reads the following claims: (1) The modern conception of natural selection differs from Darwins own conception only with respect to incidental features; (2) Natural selection is a very simple idea with enormous explanatory power. Both claims are problematic. R.A. Fisher famously argued that given a particulate view of inheritance, selection could proceed in a powerful manner even with frequent crossing, small fitness advantages and a low mutation rate. This is quite different from Darwins view, which (roughly translated into a modern idiom) insists on infrequent crossing, large fitness advantages and a high mutation rate. The modern conception of natural selection is not the same as Darwins, unless we describe natural selection in the most abstract manner. When so described, the ability of natural selection to account for adaptation is questionable.