Key points of Wagner's theory of innovation

Question

What are the key points of Andreas Wagner's "theory of innovation" from his book The Origins of Evolutionary Innovations?

Specifically:

• What is new in his theory?
• What problems in evolutionary theory does it address*?

Answer 1

Wagner does not propose any new theory. He uses the word innovation to mean evolutionary adaptations that manifest qualitatively different traits. In fact, he has himself not defined it properly in the mentioned book. This is what he has written about the term innovation:

It may be difficult to define rigorously what an evolutionary innovation is [538,616]. However, these and countless other examples show that it is usually easy to recognize: a new feature that endows its bearer with qualitatively new, often game changing abilities. These may not only mean the difference between life and death in a given environment (just think of biosynthetic abilities), they may also create broad platforms for future innovations, as did innovations of photosynthesis and of complex nervous systems.

However the examples he cites in the introduction are not as obvious as he says. Lets say the evolution of nervous system. The innovation that would have led to evolution of nervous system could have been the evolution of electrically excitable cells.

Actually, throughout the introduction he does not actually clarify the meaning of innovation. In page-3 he does list some features of innovation but it is all still vague. Without a rigorous definition nothing is easy to recognize and classify (especially in theoretical terms).

I do not have the book and cannot look through the entirety of it. However, based on what I have read in some of his papers I can comment something about what he possibly means by innovation.

In certain dynamical systems, some parameter changes can lead to qualitative differences in the output (bifurcations). Steven Strogatz's book on Non-linear Dynamics and Chaos is a nice and easy read on this topic.

If you look at some of Wagner's research papers, you would understand this idea better. Some of these papers are about how some parameter changes can affect the overall outcome (which may be drastic). For example, in this paper the authors talk about how differences in cell division rates can affect the outcome of a cell differentiation event.

He also talks about metabolic innovations which refer to changes in metabolic reactions and network leading to new products/optimized growth etc. Details of this can be found in his lab's papers on Metabolic Flux Balance Analysis.

There is nothing new or drastically different about all of this. This is just an addition that was unknown during Darwin's time. All that he says is still quite in agreement with the current evolutionary theory. (But personally, I find the opening of the book too vague).

As far as empirical corroboration is concerned, you may have a look at his lab's research papers.

Answer 2

What is new in his theory? What problems in evolutionary theory does it address?

No major problems really. The problem he is claiming, or at least how it is portrayed, doesn't really exist. To borrow from my answer to your since closed question (see that answer for more):

"Wagner appears to suggest that Darwin's theory relies on novel mutation arriving after selection changes, which it does not.."

Put simply, selection acts on genetic variation. Novel selection can occur through two principle routes: acting on standing genetic variation or novel mutations. In the case of standing genetic variation, variants exist in a population and then the adaptive landscape changes, introducing selection (fitness differences) between the variants. In the case of novel mutations, there is a standing potential for fitness differences but there is no genetic variation underlying the trait, until a mutation arises.

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Side note: examples of how standing genetic variation and novel mutation affect adaptation

Imagine that there is standing genetic variation for heat tolerance, but this variation is outside the normal range of temperatures (allele 1 allows tolerance of up to 30 C, allele 2 allows tolerance of up to 40 C, but the environment never exceeds 20 C). There may then be a shift in the environment which means that it sometimes exceeds 30 C. This means selection suddenly acts on the previously neutral standing genetic variation. It is not a new idea that previously neutral genetic variation can come under selection.

"Alternatively, a pre-existing neutral allele can drift to intermediate frequency and can later become advantageous when selection pressures change owing to environmental change or to colonization of a new habitat."

Conversely, imagine that higher sperm motility would increase reproductive output, but there is no genetic variance for sperm motility. In this case there is no selection on sperm motility (selection occurs only when there is genetic covariance with fitness), but if a novel mutation arises which does affect sperm motility, suddenly we have selection.

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What Wagner's idea does suggest is that, because genes act in interacting networks (see epistasis), previously neutral standing genetic variation can be brought in to play for selection. If novel mutations arise in one gene that allow standing genetic variation in another interacting gene to affect fitness then selection acts on both loci. It's not so much a problem he is dealing with, just an additional idea of how genetic variation can accumulate in populations and allow rapid adaptation. It is this idea of harbouring genetic variation that can be brought in to play that is the novelty of the work.

"Wagner has emphasized how epistasis – interactions among genes that shape the adaptive consequences of mutations – allows neutral variation to modulate the effects of other mutations, producing a vast range of possible mutant phenotypes that may lead to an adaptive innovation."