Tag Archives: evolutionary biology

The continuing relevance of David Hull’s “On Human Nature”

I am honored and pleased to have been asked to select the reading for this week’s meeting of the Lewis and Clark philosophy reading group, and I wanted to make sure to select a paper that’s relevant, a good read, and that fits with the group’s interests. I have been wanting to re-read David Hull’s “On Human Nature” [PDF] for some months now. I think most people would agree that it’s well-written: although there’s some science, and although it’s pretty tightly argued, a start-to-finish first read is profitable and enjoyable. The group’s interests are broad; moreover, “On Human Nature” dovetails with last week’s reading, Bloomfield’s “Tracking Eudaimonia,” for some of the same reasons the Hull paper remains relevant, or is perhaps even more so, since its initial publication in 1986.

To elaborate concerning the paper’s continued relevance: Hull considers the concept of human nature from the point of view of biological taxonomy and the nature of biological species, foregrounding diversity and variation in his account. This stands in contrast to those who foreground adaptation and natural selection. Bloomfield, for instance, emphasizes adaptation and proper function in a biological reconstruction of the classical notion of eudaimonia. Steven Pinker is another prominent advocate of the view that adaptation, also seen as establishing some traits as innate or instinctive, is the biological basis for human nature. I get the sense that both Bloomfield and Pinker see grounding human nature in evolution by natural selection as a way of resisting what they might see as a pernicious kind of social constructionism or relativism, or, worse yet (from their point of view) nihilism about human nature. I would think that sociobiology and evolutionary psychology, considered broadly, also represent points of view according to which what human beings are adapted for is the basis for our nature, rather than their membership in the species simpliciter.

Our cultural and political moment requires that we tease apart the roles of evolution, variation, and natural selection in our conception of human nature. Earlier this Spring, I attended a training seminar on Diversity, Equity, and Inclusion, with a special focus on intersectionality, sexual orientation, gender identity, and transgender issues. This is the occasion on which it occurred to me that it would be worth looking at “On Human Nature” once more. At the training seminar, at a major cultural institution and visitor attraction in Portland, the presenter boldly declared that the existence of variation in gender identification was to be promoted because variation as such is always good for the species. The presenter seemed to have the view that any variants of a trait present in the human population must have some history of natural selection, and the view that traits with a history of natural selection should be preserved; and, I got the sense that the presenter also thought that natural selection, in general, works to preserve the species. Together, these claims seemed intended to inform the following line of thought: variation is worth preserving, if all variation is due to natural selection, because natural selection works to preserve the species; and, preserving the species is intrinsically worthwhile. Clearly, these premises cannot stand in justification of promoting or protecting variation among people. At least, I hope this much is clear to those who consider themselves well-informed about evolutionary biology: not all variation is adaptive; not all variation results from natural selection; and natural selection does not, in general, work to preserve a species. We will need to do better, if we are going to look to evolutionary biology in our argument that diversity in the human population is worth preserving. Indeed, perhaps there is no such argument to be made.

All this just points to the continued relevance of Hull’s paper. I’m excited about the discussion at this week’s meeting.

A quick question about evolutionary psychology

I recently read Paul Bloomfield’s “Tracking Eudaimonia,” in which that argument is made that evolutionary biology, by means of the concept of proper function, can provide an empirical basis for the semantics and knowledge of virtues. A key element of the argument is that human beings have the genetic endowment, due to natural selection, for capacities for behavior and cognitive life, that explain why we are able to act in virtuous ways. For instance, our ancestors acted in certain ways we now identify as virtuous, such as exhibiting other-regarding behavior, which contributed to their success in natural selection; this is why we have these capacities nowadays; and so the portions of our genome have the proper function of encoding for those aspects of our physiology, etc., which form the basis for those capacities.

Evolutionary psychology plays a central role in filling in details of Bloomfield’s proposal, because the discipline is devoted to discovering psychological and behavioral adaptations. In considering how evolutionary psychology might be used in the service of virtue ethics, the following question occurred to me. If behavioral capacities for virtues evolved by natural selection in the ancestral environment of the human species, as is a central principle of evolutionary psychology generally about behavioral adaptations, what maintains them, now that we are no longer in that environment? In general, adaptations will decay, when selection is relaxed; or adaptive traits will change, in response to changing environments. Now that our environment has changed significantly, shouldn’t our psychological adaptations be expected to decay or change, in our new environment?

Qualified support for evolution in New York

The standards for high school biological sciences curricula in New York State are described in The Living Environment Core Curriculum. (“LE Standard,” hereafter) The Living Environment curriculum is Standard 4 in a set of 7 describing the science curriculum in New York State. “Key Idea 3” in the LE Standard describes the central point instructors in Living Environment courses are supposed to make about evolution.

Individual organisms and species change over time.

There are many ways in which this statement and the associated Performance Indicators fail to describe, even in broad outline, what we know about evolution. For one thing, they almost all concern natural selection. For instance, there is no mention of random drift or historical contingency, or the use of evolution in explaining taxonomy and biodiversity. While this deserves further comment, what I would like to call attention to here are two points at which the LE Standard qualifies support for teaching evolution.

Use of “theory”

Key Idea 3 is further elaborated in the LE Standard as follows.

Evolution is the change of species over time. This theory is the central unifying theme of biology.

The problem here is “theory,” which is widely misunderstood, and which does not appear anywhere else in the LE Standard. Teaching evolution is often attacked on the grounds that scientific knowledge about evolution is “just a theory.” This is not how scientists use “theory,” which, in proper scientific parley, indicates a well-confirmed statement or set of statements of general or universal application, such as Newton’s theory of gravitation, or Einstein’s theory of relativity. Although both of these have been modified with time, no one attributes either to Newton or Einstein as conjectures or guesses. They are understood as describing facts about physical objects derived from initial claims made by Newton and Einstein. Glenn Branch, in a recent blog post, explains the cognitive status of evolutionary biology in depth, and provides some useful links.

The LE Standard ought to state that “The central, unifying theme of biological science is that all living things have relationships of descent with one another.” 

Belief vs. acceptance

Key Idea 3 is also explained with:

According to many scientists, biological evolution occurs through natural selection.

This is the only point in the LE Standard at which the level of support among scientists for a scientific claim is mentioned. Indeed, it would be absurd to preface “Organisms from all kingdoms possess a set of instructions (genes) that determines their characteristics,” the explanation of Key Idea 2, about heredity, with “According to many scientists.” Any scientist that denies this would not be deemed worth of the name. The aim of the LE Standard should be to state what the best scientific evidence provides rational warrant for, which is that evolution has occurred and will continue to do so. Formulating the standard in terms of how many scientists would affirm that evolution occurs by natural selection suggests that there is a parallel between religious belief and acceptance of evolution. This is not the case, as explained in a National Academy of Sciences FAQ.