Philosophy and evolution

One of the problems that many people have with evolution is not religious, but philosophical. If evolution is true, they think, then we are at sea - nothing is fixed, nothing is determinate, all coherence is gone, as Donne famously lamented of the death of the two-sphere universe and physics. This is, I believe, a valid worry. But it is not new or due to evolution: Heraclitus worried about it, as did Parmenides, and the solutions given by Plato and Aristotle against the atomists were in effect ways to deny that what really counted was changing. They called change "degeneration" or "corruption". The true reality was the forms (εἶδη) that never changed. It was at first not a widely adopted solution, but with the collapse of the Stoic philosophy in the late Roman period, and the rise of Catholic Christianity, it made a comeback and was the "default" view of the next 1200 years.

What in fact does evolution add to the mix of philosophical unease?

Over the past 50 years or so, there have been many attempts to give a general metaphysics of evolution, ranging from axiomatisation (by Mary Williams, at the height of the "theories are axiomatic systems" period*), to "logical necessity" cases (such as Lewontin's three conditions for natural selection), to "units of selection" arguments, most closely associated with George Williams and RIchard Dawkins. In each of these, and other, attempts, there has always been the presumption that there is a fixed hierarchy of ranks and units in biology. These are the "forms" of biology: replicators, interactors, species, genes, cells, and so on.

The odd thing about this is that as people were asserting that essentialism is dead (see the article on species linked above), they were being essentialists about concepts and units and ranks. Ernst Mayr, for example, who asserted that species individually (the species taxon, as he put it) have no essences, nevertheless asserted that the concept of species (the species category) did so. He was an essentialist about the species concept. Likewise, the gene centrism of a Dawkins is essentialist about the replicator concept. And so on.

Now one of the reasons why people adopted the hard and fast categories is that they usually were specialists in groups, such as mammals, birds or insects, where these categories had a real purchase. This is often referred to, mostly by botanists, as the "fur and feathers" or "vertebrate" or just "animal" bias. But another is just that they were seeking what used to be called the Characteristica Universalis, or the most general universal and formal language for the domain in question. It is a general disposition of those in the west to do this (and despite suggestions to the contrary, I cannot see how one might apply the Eastern metaphysics fruitfully in the domain of science). It is a constant temptation to try to ground ideas in unchanging and agential categories. We like species because they do something. We like replicators because they are the ultimate doers. These categories apply in ways that make sense of both the world, and our need for constancy. Coherence is not gone.

Until you stop focussing on the "obvious" cases, and start paying attention to as many as you can find. I have what I call the "esoteric method": look for cases that don't fit the current categories and then go look and see if that is more general than you might think. For example, in his 1942, Ernst Mayr referred to nonsexual organisms as "aberrant" when discussing the adequacy of his "new" "biological" species concept (122, 129). Today we know that not only are most organisms not sexual, which would mean most of them are not arrayed in species, but that the sexuality of species even in the small twig of the phylogenetic tree that is metazoans is not constant: many groups have either got hybridisation, or asexuality, or both. Nor is gene exchange confined to sexual species - between species gene flow is common, and even among asexuals lateral transfer is frequent. In fact the sort of species Mayr expected to exist are rare, except among some groups of vertebrates (oddly, the group Mayr studied, birds, often hybridise).

Over the past 50 years these essentialistic categories have become harder and harder to support empirically, as we have learned of more and more exceptions. Some, such as John Dupré, have argued for a pluralism of conceptions in biology due to the polytypic nature of the instances to which these categories are applied. It's just a brute fact of biology that none of these categories are universal, and so biologists must avail themselves of whatever conception works in a particular case (to make this more concrete: species are sexual isolates when that works, but in, say, bacteria, they are phenetic clusters or something else).

Some years ago, I published an idea that I think might be the resolution to this (2003) in which I argued that species is like any other property of organisms, something that has evolved in its own way. The reason there is no universal notion of species for the same reason there is no universal notion of leg: species, like legs, are the outcome of evolution. In other words, these kinds themselves evolve. This applies also to other apparently universal aspects of biology: genes, or rather replicators, cells, individuals, and so on. It is not the case that, as Dupré thinks, that anything goes, but that there are evolved modalities, as I called them - ways of being whatever it is that we are trying to understand. This applies not only to the organisms and their traits, but to the kinds of organisms, and even to the kinds of kinds. Taxa, units, ranks, entities, systems - all these are evolved, and so to understand what it means to be, say, a bird species or a eukaryote gene, you need to understand the evolutionary relations of that group.

Last year, Peter Godfrey Smith published an interesting book that argues that the sole precondition for a Darwinian perspective on the world is that there are populations. Because we are disposed to see biology in terms of agency, we want agents, but that is, PGS holds, a remnant of the oldthink of teleology that Darwinism replaced. I think he's well on the right track, although he still thinks that this means we cannot have types or classes. I think that classes are merely local and evolved. We are in a reading group covering his book right now, so as we work through it, I'll probably add some more.

One thing I do want to say now, though, is that there is a prior problem knowing what a population is. For instance, to know that an ensemble of individuals form a population, you need, minimally, to show they are of the same species because you don't get a population that spreads across two or more species, unless they are causally connected reproductively (in which case they might be classed as the same species anyway). Moreover, you already need to know the sort of object/organism that counts as an individual for that group in order to identify it as a population. This is not always so easy, in the case of colony organisms. While PGS is rightly arguing that there are no ranks or special units, only populations (which comprise individuals that have heredity and ecological differences, leading to evolution**), it seems to me that he still requires there to be some sort of types or equivalence classes, even if there are no universal kinds of types.

In part, this is something that comes out of the death of the essentialism story: it is often assumed that if one abandons essentialism, one loses access to any kind of equivalence class in biology (i.e., natural kinds; we aren't worried about conventional classes or functionally defined classes), and that is what PGS assumes too. But it is my view that biology always uses types, which are defined or rather ostended by identifying an exemplar and then looking for clusters of properties. This is what PGS says we should be doing, but he does not see these as types. I do. By finding these clusters of properties (and even more the underlying developmental traits and heredity), we are then able to determine what a population is, and what individuals are, by a process of iterative induction (start with a case that is presumably exemplary and then make inductive generalisations from that until they fail).

What bothers people who think in terms, not of binaries as Chris Schoen suggested, but of absolute levels or entities that do not change, is that evolution leaves us gasping and dealing with vague boundaries, shifting kinds and so on. I feel for them, but it is really biology that does this, and always has. What really is novel about evolutionary thinking is that we know not only that the appearances change, but that the forms, and the forms of forms also change. However hard to come to grips with, we must. And the solution to this vagueness is phylogenetic thinking. If you know where a species or an organism is placed on an evolutionary network (allowing for the moment that the tree topology sometimes fails), then you know what sorts of sorts it will fall into, or if you find that it doesn't, that sets up an interesting research project.

More as it occurs to me.

* Williams was a student of the originator of the Axiomatic Method for the sciences, Joseph H. Woodger.

** Evolution includes a lack of change by stabilising selection or developmental entrenchment (which I think may be a subset of the former). We need not presume that selection always causes change (but if there is a lack of change, I think we should presume that is due to selection).

More like this

The living world, it seems to me, causes no end of trouble for those who would classify it. Its levels, ranks, hierarchies and units all seem to be clear enough, until we encounter troublesome cases. Then they get very troublesome indeed. So I want to say, there are no ranks or set units in…
Well after reading many papers by various bacteriologists, mycologists, and other non-vertebrates specialists, I have come to the conclusion that there is no single set of conceptions or criteria (that much abused word!) for something being a species in non-sexual organisms, which I am here…
Here is a working list of species concepts presently in play. I quote "Concepts" above because, for philosophical reasons, I think there is only one concept - "species", and all the rest are conceptions, or definitions, of that concept. I have christened this the Synapormorphic Concept of Species…
Rob Wilson has a new entry up at the Stanford Encyclopedia of Philosophy, entitled "The Biological notion of an individual". It discusses an interesting problem, one that goes back to discussions by Julian Huxley in 1911. What is an individual in biology? The term "individual" means,…

stasis is dynamic. keep saying that, students of evolution, over and over again.

I Would guess that stabilizing selection is the large majority of selection.

I've worked quite a bit with hybridization in fishes; some thousands of examples in the literature. There are instances where hybrid swarms have been maintained for as long as we have been aware of them. However, I think there are very few instances where hybridization has been important in speciation of biparental species. Also, I think, after examining the evidence, that hybridization between two species usually has little effect on how we view the two species. By this I mean that hybridization has resulted in little or no gene flow between the two species. For some reason, it seems that mitochondrial genes introgress more than nuclear genes.

I don't think there is a useful procrustian universal species concept. Perhaps species is like an electron, sort of a fuzzy sphere of probablity as to position and nature. Said sphere looking different depending on which species is being examined.

By Jim Thomerson (not verified) on 19 May 2009 #permalink

Jim, I think you should ask a botanist if hybridisations is rarely the cause of new species in biparental species. Also, you might find that it works differently in different groups - I understand that reptiles have a higher frequency of hybrids than other land verts. Cichlids are also thought by some to be freely hybridising, although from what I have seen that may just mean introgression. Corals certainly. Ferns and fern allies most definitely. Don't know about insects, although I think I saw one on Drosophilids and mosquitoes. The Grants argued that bird speciation by hybridisation is frequent, if not common (and we know ducks massively hybridise). And so on. The apparent lack of it in animals may just be due to the fact that people weren't until recently looking for it.

I think I read that some 25% of higher plant species are of hybrid origin. So obviously a botanist would think differently about species than I do. I have been a semi-serious hobbyist with amaryllis, and various succulents. So I have looked at their taxonomic lterature from my professional perspective. I am clear that botanical taxonomy and fish taxonomy are quite different.

By Jim Thomerson (not verified) on 19 May 2009 #permalink

I cannot see how one might apply the Eastern metaphysics fruitfully in the domain of science

I'm not inclined to disagree with this with any haste.

But the history of the scientific enterprise is fairly short and recent, and I also wouldn't want to overdetermine what it may and may not encompass down the road.

My main aim in raising the subject is not to try to propagandize for the superiority of eastern over western metaphysics (to the extent these are even valid categories), but to reach for a system of relations with sufficient contrast to our own to throw it into relief, allowing a meaningful evaluation on its own terms. So-called eastern metaphysics is a ready-made world picture, the first that comes to hand.

Lots to click through to here, and lots to chew on.

The odd thing about this is that as people were asserting that essentialism is dead (see the article on species linked above), they were being essentialists about concepts and units and ranks.

Interesting idea about essentialism (or the lack thereof). Perhaps I misunderstand, but I assume it's standard thinking in philosophy that nothing has meaning by itself. No idea, concept, or thought appears to exist ex nihilo alone in a vacuum - the "meaning" of something always stands in relation to other things. An isolated idea is meaningless. The same appears to be true in the physical world (which I suppose would make the entire universe meaningless, if it's truly isolated). A "form" in biology is relative to other forms, in other "species" and forms in different times, as well as forms which exist in a relation of composition (genes, etc). The same is true of physics, at the quantum level. As expressed by Bohr, "Isolated material particles are abstractions, their properties being definable and observable only through their interactions with other systems."

But if you say there are no essential absolutes, that is an absolute in itself, isn't it? Can you really get rid of essentialism?

I think that if Eastern metaphysics is understood in a critical and secular way (which is permissible for eastern metaphysicians) and selectively used when it proves helpful (which is what many of the smartest Chinese and Japanese do, while also appropriating Western approaches as needed), Buddhist and Taoist approaches to anti-essentialism are usable.

One impediment is that all interpreters of the East to the West (regardless of whether they are Western or Eastern in origin) have their axes to grind, and while this is inevitable and not necessarily a bad thing, from the scientist's point of view most of them are grinding the wrong axe. Some of the missionary groups that come over are often the Eastern equivalents of Mormons or Jehovah Witnesses in terms of their take on Eastern philosophy, and Western appropriators can be as bad or worse than that.

Besides anti-essentialism, another thing that evolution brings to philosophy and science is contingency and an open future (expressed vividly in Gould's "A Wonderful Life"). Along with essentialism comes eternalism (e.g. Platonism) -- the idea that everything really real was already there in the beginning, and that new things are just recombinations of old things. One philosopher still thinks that, but he had to conclude that the only really real things are quarks, and that everything else is just a seeming reality.

Some of these themes were developed by Whitehead, whose ideas stand behind Bohm's (mentioned above) and are not widely accepted in professional philosophy.

One of the best attempts to come up with a science-Taoism combination was that of R.G.H Siu in "The Portable Dragon", "The Tao of Science", and "Ch'i: a neo-Taoist approach to life". Siu had a successful scientific career ("MICROBIAL DECOMPOSITION OF CELLULOSE With Special Reference to Cotton Textiles"), mostly at the administrative end, and his development of Taoism is very hard-headed and real-world.

The "Tao of Physics" is probably to be avoided. Likewise the TV show "Kung Fu", which is a primary reference for many.

By John Emerson (not verified) on 20 May 2009 #permalink

Probably the best solution to this apparent paradox is Niklas Luhmann's version of systems theory, which focuses on communications instead of structures.

This is very hard to understand (at least, I found it hard to understand, and struggled with it for months)

Peter Andras and I tried to summarize it in the Appendix of our book The Modernization Imperative -

Probably the best solution to this apparent paradox is Niklas Luhmann's version of systems theory, which focuses on communications instead of structures.

This is very hard to understand (at least, I found it hard to understand, and struggled with it for months)

I tried to sumarize it in the Appendix of my online book The Modernization Imperative -

John E.,

It's been years since I read it, but I think the Tao of Physics gets a bad rap, in part because it is judged based on some of the people who were influenced by it. (As one blogger recently wrote on the same dynamic in reference to another topic [Strunk and White's Elements of Style], this is sort of like blaming the White Album for the Tate-LaBianca murders.) Frijof Capra is a "real" physicist, after all, not a mere mystically inclined populizer, and many of the great names in quantum physics--Heisenberg, Bohr, Pauli--advocated similar metaphysical views, though none of them went on to write systematically about them.

Thanks for the Siu reference; I'll look for him.

Hi John,
I agree with a lot of this. One question, though: where did I say that 'anything goes'? What goes is what shows up in biology. You want to call the clusters of more or less similar entities that evolve within different lineages 'species'. I (and others) point out that these clusters are very diverse, for example with respect to the factors that maintain the similarities to one another of the elements in the clusters and their differences from other entities. Apart from different degrees of comfort with the word 'type' I'm not sure what we need to disagree about.


I meant it in a nice way - that scientists can avail themselves of any concept that works for their needs (with which I also agree). You're right - we are not disagreeing. See the disclaimer in the profile...