Darwinians Cannot Agree on What Natural Selection Is
Controversies 159 years after Darwin have rendered his ‘mechanism’ a mystical idea, nebulous and incomprehensible. Has natural selection become the phlogiston of the 21st century?
Are we tired yet of hearing “All scientists agree that evolution is a fact, like gravity”? How about “Nothing in biology makes sense except in the light of evolution”? A leading Darwinian, publishing in America’s prestigious journal the Proceedings of the National Academy of Sciences (PNAS), has just staged a new version of natural selection that is almost literally a song and dance. Before we get to that, listen to why W. Ford Doolittle feels it is necessary to critique Darwin’s mechanism again, so many years after biologists began assuming that Darwin had solved evolution with his “law-like” notion of natural selection. Prepare for a jolt:
Many practicing biologists accept that nothing in their discipline makes sense except in the light of evolution, and that natural selection is evolution’s principal sense-maker. But what natural selection actually is (a force or a statistical outcome, for example) and the levels of the biological hierarchy (genes, organisms, species, or even ecosystems) at which it operates directly are still actively disputed among philosophers and theoretical biologists.
Now that everyone is awake, consider what has been going on in scientific circles behind the scenes. Simplistic presentations of evolution, like this one at Live Science, shield the public from deep controversies among Darwinians about evolution, or try to downplay their significance. This new PNAS paper, co-authored by S. Andrew Inkpen (with Doolittle at the University of Halifax, Nova Scotia), was reviewed by Douglas Futuyma, another long-time Darwian theorist. And it’s full of controversy!
Among the points of controversy is the so-called “unit of selection.” What does nature select? What kind of entity does it act on? The question was posed this way by Charles Lineweaver in New Scientist back in November, 2012. Asked if life could be defined as ‘anything that undergoes Darwinian evolution,’ he responded,
We pretend that makes sense, but if you look at it, it makes no sense at all. What is the unit of Darwinian evolution? Is it the gene? Is it the cell? Is it a multicellular organism? Is a city evolving? How about Gaia? Is that a life form?
Doolittle is trying once again to make sense of the concept that Dobzhansky had triumphantly claimed made sense of everything in biology. But like Lineweaver six years ago, Doolittle shows continuing doubt in the Darwin Party’s assumption that common formulations of natural selection make any sense at all. Particularly troubling is the concept of units of selection:
Most formulations of evolution by natural selection emphasize the differential reproduction of entities at one or the other of these levels. Some also recognize differential persistence, but in either case the focus is on lineages of material things: even species can be thought of as spatiotemporally restricted, if dispersed, physical beings. Few consider—as “units of selection” in their own right—the processes implemented by genes, cells, species, or communities.
The PNAS paper by Doolittle and Inkpen is full of very damaging admissions about natural selection. Before we consider their song-and-dance rendition which they dub “ITSNTS thinking” (wait till you see what that means), it’s worth summarizing their complaints about standard ENS (evolution by natural selection):
- Natural selection lacks a theory of how it acts on communities.
- Standard views of natural selection do not address adaptation and function of “multispecies collectives.”
- Natural selection cannot explain stable or redundant bacterial communities.
- Natural selection cannot explain processes that benefit communities of dissimilar reproducers.
- Natural selection cannot explain how processes that benefit multiple communities re-establish themselves.
- Dupre agues that “much of contemporary biology embraces a generally mechanistic and reductionist ‘thing’ (or ‘substance’) ontology.”
- The commonplace textbook focus on reproductive success of individuals is a habit of thinking that overlooks the contingent history of the modern synthesis and population genetics.
- Some formulations of natural selection are vague because the proposed units of selection have “too many parents” (Godfrey-Smith’s complaint). This muddies concepts of inheritance.
- Natural selection is ambiguous about what “beneficial” means. “It is not clear that any property can be considered ‘beneficial’ to impermanent and nonreproducing communities.”
- Some formulations of natural selection violate William’s Principle that states, “adaptation at a level requires that there was selection at that level.”
- Some functions “are more stable or ecologically resilient than are the taxonomic compositions of the assemblages carrying them out.” This demands an evolutionary explanation.
- ENS does not easily account for redundancy.
- ENS is vague on the question of which is more relevant to evolution: the allele frequency in the population or the individual carrying it?
- Biologists are undecided on whether memes undergo natural selection. Sperber is one such ‘meme-skeptic’ that Doolittle mentions.
- Biologists also debate whether language or culture undergo natural selection.
- It’s difficult to determine if natural selection constitutes a mechanism or a logical necessity (an a priori assumption).
- Sober argues that ENS is “a priori true in the sense that no experiment could disprove it.”
- Niche construction theory is another ‘mechanism’ of ENS that is in dispute among evolutionists.
- Evolutionists face “awkward transitions in retelling the history of life,” such as the step from unicellularity to multicellularity.
- What’s more important: differential reproduction or differential persistence? Which makes more sense and is more ‘satisfying’?
- The difficulty of establishing lineages relevant to ENS can be illustrated thus: “I am my father’s son, but my heart is not the offspring of my father’s heart.”
- At what ranges can ENS be compared? Is the evolution of microbe community functions across guts analogous to the evolution of lizards across islands?
- Before Doolittle’s proposal, there was lacking “a sensible way of discussing adaptations and functions relevant to communities and ecosystems generally.”
- Some evolutionists have said there is an “urgent need for a general framework” to decide what constitutes the “health” of a system.
- An important problem in evolutionary theory is the role of abiotic components in ecosystems. These may play important roles but are not reproduced biologically. Bouchard remarked, “Evolution as change in allelic frequencies does not seem to apply to systems that have a motley crew of alleles and abiotic material interacting in a systematic way.”
- For a century, biologists have been debating at what levels Darwin’s ‘law-like principle’ of natural selection operates. Does it operate on processes as well as things?
These are some of the controversies facing evolutionists. Natural selection seems like such an intuitive idea the way it’s typically taught, until you start asking these types of questions. Since Darwin, evolutionists have been called on to interpret weird situations like obligate parasitism, lateral gene transfer, and quasi-species in terms of Darwin’s mechanism. Some evolutionists want to pare down the unit of selection; others want to ramp it up to explain whole ecosystems and biospheres, including natural cycles with abiotic elements, and phenomena that overlap with intelligence, like languages and memes. Even the basic terminology of neo-Darwinism generates controversy: what is meant by fitness? survival? reproduction? mechanism? selection? individual? collective? life itself?
Science needs clarity. The problem with hazy words and concepts is that they can explain everything, masquerading as explanations when they might be just a priori conclusions (things that have to be true), or contingencies (chance occurrences) masquerading as laws (cf. “Stuff Happens Law” in the Darwin Dictionary). When a fuzzy theory becomes an entrenched consensus, it becomes very hard to dislodge. History provides a classic example: phlogiston theory. In his new book Heretic: One Scientist’s Journey from Darwin to Design, Matti Leisola (a Finnish research biochemist with co-author Jonathan Witt) recounts the sad tale. For over a century, phlogiston theory was patched up with absurd notions such as “negative weight” as observational problems mounted. “The story of phlogiston,” they say, “shows how an established paradigm may persist in the face of contrary evidence because its supporters patch it up ad nauseum instead of following the evidence.” Then they close in for the kill:
The Darwinian theory of evolution is the phlogiston of our day, festooned with a myriad and growing number of patches. Evolution is slow and gradual, except when it’s fast. It is dynamic and creates huge changes over time, except when it keeps everything the same for millions of years. It explains both extreme complexity and elegant simplicity. It tells us how birds learned to fly and how some lost that ability. Evolution made cheetahs fast and turtles slow. Some creatures it made big and others small; some gloriously beautiful, and some boringly grey. It forced fish to walk and walking animals to return to the sea. It diverges except when it converges; it produces exquisitely fine-tuned designs except when it produces junk. Evolution is random and without direction except when it moves toward a target. Life under evolution is a cruel battlefield except when it demonstrates altruism. Evolution explains virtues and vice, love and hate, religion and atheism. And it does all this with a growing number of ancillary hypotheses. Modern evolutionary theory is the Rube Goldberg of theoretical constructs. And what is the result of all this speculative ingenuity? Like the defunct theory of phlogiston, it explains everything without explaining anything well. (pp 198-199)
Before we examine Doolittle and Inkwell’s proposal, we should note that nowhere in their paper is there any hint of how natural selection might create something new that is complex and functional. Whatever version of ENS is discussed, they all concern impertinent things like “differential reproduction” or “differential processes” or “units of selection” without ever answering the big question: How could Darwin’s blind, unguided mechanism (if it can be charitably called a mechanism at all) get humans from bacteria? Leisola and Witt recall Graham Budd’s remark at the Altenberg 16 conference (a kind of alt.Darwin movement): “When the public thinks about evolution, they think about the origin of wings and the invasion of the land… But these are things that evolutionary theory has told us little about.”
Will Doolittle and Inkpen be able to end the controversy and unite all the Darwinians around a new, all-encompassing version of natural selection? We’ll look at their proposal next time.
All we can warn you about next time is: hold onto your hats! Prepare for one of the craziest versions of natural selection you have ever heard, courtesy of W. Ford Doolittle, who years ago said that natural selection predicted junk DNA. Well, guess what. Junk DNA is disappearing as a myth.
Either great minds think alike, or (as I contemplate might be possible), Leisola or Witt read my account of evolutionary theory and decided to imitate it in their own words. Compare the line “Evolution made cheetahs fast and turtles slow” and the rest of the quote above with my version in “Evolution Goes Forward, Backward and Sideways” (15 June 2014):
The Story of Evolution
Evolution explains more complexity, and more simplicity. It explains why flight arose in some birds, but was lost in others. With evolution, organs and genomes can become more complicated, or more streamlined. Eyes emerge through evolution, but eyes are also lost by evolution. Evolution makes the cheetah fast but the sloth slow. By evolution, dinosaurs grow to skyscraper size, and hummingbirds grow tiny. With evolution, peacocks grow more flashy and crows more black, giraffes tall and flatworms flat. Evolution explains predator and prey, loner and herder, light and dark, high and low, fast and slow, profligacy and stinginess, terrorism and altruism, religion and atheism, virtue and selfishness, psychosis and reason, extinction and fecundity, war and peace. Evolution explains everything.
I’m flattered by the imitation if that’s what this is, although it could be a case of “convergent design” instead.