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Teleonomy and Evolution


In a new paper, “Evolutionary Teleonomy as a Unifying Principle for the Extended Evolutionary Synthesis,” in the journal BIO-Complexity, Jonathan Bartlett of the Blyth Institute revisits an old idea first proposed by Ernst Mayr and Colin Pittendrigh. It is a way around biologists’ continued use of teleological (goal-directed, functional) language, despite the supposed lack of teleology in the Modern Synthesis (neo-Darwinsm). Bartlett writes:

For more than a century, biology has struggled with the concept of teleology. Teleology is the orientation of objects (often organisms) towards ends. That is, organisms have purposes which are reflected in their behaviors. What makes biology unique as a subject is that while the study of rocks or atoms rarely makes reference to purpose, the study of biology is almost exclusively concerned with purpose….

[T]he idea of evolution by natural selection seemed to remove teleology from biology as well. There was nothing in natural selection that referred to purpose — only to reproduction. The whole of evolution was therefore devoid of purpose. If teleology was not needed in physics, and now it is not needed in biology, then it seems like there is no need for it at all.

Thus, the whole concept of purpose fell out of favor with biologists. It was thought of as an old-fashioned concept — a leftover relic that would soon go the way of alchemy. By the beginning of the twentieth century, biologists were actively avoiding any sort of purpose-oriented language, sometimes to the point of ridiculousness.

As reported by Pittendrigh,

“Biologists for a while were prepared to say a turtle came ashore and laid its eggs, but they refused to say it came ashore to lay its eggs [emphasis in original].”

Pittendrigh and Mayr sought a way to deal with the problem of apparent function in biologists’ use of language:

In order to alleviate the situation, Pittendrigh and later Mayr suggested using the term teleonomy instead of teleology to describe this sort of purposive behavior.

Mayr suggested that we can use the term teleonomy to represent something that operates according to a purpose because of a program. Specifically, Mayr says, “It would seem useful to restrict the term teleonomic rigidly to systems operating on the basis of a program, a code of information. Teleonomy in biology designates ‘the apparent purposefulness of organisms and their characteristics,’ as Julian Huxley expressed it.”

That is, to the extent that organisms operate according to their genetic programming, “purpose” can simply refer to the actions of the program behind the organism. [Emphasis in the original.]

And of course, the program was, to their minds, an inherited program, the result of variation, natural selection, and drift. Mayr was concerned that the idea of teleonomy might be turned back toward the idea of design or purpose, so he made it abundantly clear:

Only three processes are known to [change the genetic pool]: mutation, fluctuation in genetic frequencies, and differential reproduction. The first two of those processes are not oriented toward adaptation. They are in that sense essentially random, and are usually inadaptive, although they may rarely and coincidentally be adaptive. By “differential reproduction” is meant the consistent production of more offspring, on an average, by individuals with certain genetic characteristics than by those without those particular characteristics…

If an organism is well adapted, if it shows superior fitness, this is not due to any purpose of its ancestors or of an outside agency, such as “Nature” or “God,” who created a superior design or plan.

“Note that here, Mayr explicitly decries not only the influence of outside purposes (i.e., divine teleology) in evolution, but also the influence of inside purposes (i.e., biological purposes present within ancestors),” says Bartlett.

But ideas sometimes morph into new forms. As our understanding of evolutionary processes has grown, it has become apparent that sometimes change happens too fast, or in a seemingly directed fashion, much more than a purely neo-Darwinian process can account for. Enter the Extended Evolutionary Synthesis (EES), a scientific program that seeks to explain longstanding evolutionary problems that the Modern Synthesis hasn’t been able to successful address.

In a paper published in Nature in 2014, “Does evolutionary theory need a rethink? Yes, urgently,” a number of EES proponents came together to list the features that they think make the EES distinct. These include:

  1. Extended inheritance: organisms inherit more than just genes and more than just by physical inheritance. Organisms not only have genetic and epigenetic inheritance, they have inheritance of behavior based on the nurturing of parents and biological communities.
  2. Reciprocal causation: organisms shape their environment, which then acts on themselves.
  3. Non-random phenotypic variation: organisms are biased in certain evolutionary directions rather than others, as reflected by available evolutionary phenotypes.
  4. Variable rates of change: the effects of mutations are non-linear, and therefore have the potential for saltational effects.
  5. Organism-centered perspective: organisms themselves have a larger causal role in the Extended Evolutionary Synthesis, as opposed to the gene-centered approach of the Modern Synthesis.
  6. Macro-evolutionary processes: the additional modes of inheritance will also lead to additional macro-evolutionary processes.

Says Bartlett, “This list maintains the cautious approach typically taken by those favoring the Extended Evolutionary Synthesis, making it unclear whether it deserves to be treated as a new synthesis. Is this really new, or are they merely tweaking around the edges? The architects of the Extended Evolutionary Synthesis are adamant about the need for a new synthesis but highly cautious about how it is described.”

There are differences, though, that open up the EES to teleonomy. One of the primary areas where the Extended Evolutionary Synthesis differs from the Modern Synthesis is in the number of modes of inheritance available for evolutionary action. These modes of inheritance each appear to incorporate some amount of teleonomy in their operation.

These modes include niche inheritance, sexual selection, epigenetics, and developmental processes.

Another concept common to EES is evolvability. Bartlett writes:

Shapiro, Caporale, and Noble [three of the main EES proponents] show that many systems within organisms can direct the evolution of specific genes. These evolvability systems are encoded by the genome, targeted by gene products, and produce effects that benefit the evolution of offspring. In every way they match the concept of Evolutionary Teleonomy.

If one considers the idea that there is an internal program governing each of these processes, and directing the organism’s response to its changing environment, then one has arrived at the idea of teleonomy. Bartlett says, “As is evident, Evolutionary Teleonomy plays a central, unifying role in nearly every aspect of Extended Evolutionary Synthesis.”

Is the idea of teleonomy actually useful to biology? According to Bartlett, teleonomy works well with the way biology is analyzed and described: “In nearly every other aspect of biology, the presumption of function is used as a heuristic for understanding how biological systems work.” That is, except in evolutionary biology, where up until now any hint of goal-directedness was barred by the Modern Synthesis. However, perhaps it is time for that to change. Bartlett explains: “[F]urther developments in the theory of evolution over the last several decades show that Evolutionary Teleonomy should be returned to a central place in evolutionary thinking.”

For example, it might make a difference in Dan Graur’s analysis of the percentage of our genome that is functional. It certainly makes a difference if you think that mutations are teleonomic or not, in how his calculations work out. See Bartlett for an explanation.

It would indeed be useful to have an idea that links together the many evidences that organisms respond to challenges in apparently goal-directed means. The difference that matters, though, is where those goal-directed systems actually came from. Did they evolve, pushing the problem back a step or two, or were they designed? Bartlett leaves that question unanswered.

Photo: Leatherback turtles hatching, by Elise Peterson (Own work) [CC BY 3.0], via Wikimedia Commons.