Today's New York Times has a series of articles up about various aspects of evolution. One that caught my eye was this essay by paleontologist Douglas Erwin. It discusses various challenges to the Neo-Darwinian synthesis. Not the silly, brain-dead challenges of the creationists and ID folks, but the serious challenges from people who actually know what they are talking about.
Erwin begins by explaining the basics of Neo-Darwinism:
To understand the current tumult it helps to understand how our evolutionary framework developed. It was constructed from the 1930s to 1950s by early geneticists, paleontologists and others, who disagreed about the efficacy of natural selection in driving evolutionary change (Darwin's big idea) and about the nature of the underlying genetic variation upon which natural selection could act. What they came to agree on was called the modern synthesis, and it established an intellectual zeitgeist that continues today, and has been continually adapted, in the best evolutionary fashion, to encompass new discoveries.
That synthesis holds that mutations to DNA create new variants of existing genes within a species. Natural selection, driven by competition for resources, allows the best-adapted individuals to produce the most surviving offspring. So adaptive variants of genes become more common. Although selection is often seen, even by biologists who should know better, as primarily negative, removing poorly adapted individuals, Charles Darwin understood that it was a powerful creative tool.
It is the primary agent in shaping new adaptations. Computer simulations have shown how selection can produce a complex eye from a simple eyespot in just a few hundred thousand years.
We should probably note that the paper being referred to in that last sentence did not actually involve a computer simulation. It did, however, provide strong evidence that the vertebrate eye coud have evolved gradually in the time available.
So far so good. But now Erwin writes this:
In the past few years every element of this paradigm has been attacked. Concerns about the sources of evolutionary innovation and discoveries about how DNA evolves have led some to propose that mutations, not selection, drive much of evolution, or at least the main episodes of innovation, like the origin of major animal groups, including vertebrates.
Erwin goes on to discuss the importance of evo-devo, contraints on the direction of evolution, hierarchical selection and the underappreciated role of ecology.
These are all fascinating points, but it looks to me like the biggest aspect of Neo-Darwinism is not being disputed by any of this. Specifically, even if all the challenges Erwin discusses are integrated into a new, more powerful theory of evolution, it will still be true that complex systems like eyes and immune systems evovle gradually via natural selection acting on small genetic variations. I see nothing in Erwin's essay that challenges that central principle.
Perhaps because I spend so much time arguing with creationists, I tend to agree with Richard Dawkins that explaining the origin of complex systems is the most important challenge a theory of evolution must face. Once you've done that, everything else is a matter of filling in details. And if Neo-Darwinism is right on that point, and everything I've read suggests that it is, then I have a hard time seeing any of these challenges as representing a nascent paradigm shift.
Erwin closes his article as follows:
Does all this add up to a new modern synthesis? There is certainly no consensus among evolutionary biologists, but development, ecology, genetics and paleontology all provide new perspectives on how evolution operates, and how we should study it. None of these concerns provide a scintilla of hope for creationists, as scientific investigations are already providing new insights into these issues. The foundations for a paradigm shift may be in place, but it may be some time before we see whether a truly novel perspective develops or these tensions are accommodated within an expanded modern synthesis.
Sounds about right to me, and you can number me among those who think these tensions will be accommodated within an expanded modern synthesis.
I suppose it is inevitable that someone over at Uncommon Descent will present that brief mention of creationism as the obligatory anti-creationist statement in an essay otherwise supportive of the idea that modern evolutionary theory is collapsing. But Erwin is quite right to present things in this way. If all of the challenges Erwin discusses really do turn out to be as important as their supporters think, that will only make the situation far worse for anti-evolutionists. Basically, the substance of these challenges is that evolutionary theory has far more explanatory options at its disposal than has previously been recognized. That realization makes it far harder to argue that evolution is such an unfathomable mystery that we need to invoke God to explain it.
The word paradigm has long since been completely debased. None of the current challenges, even added together at their most ferocious, could change more than a paranickel.
A paradigm is defined as the degree of disconnect when you have disagreement between a paradox.
I thought paradigm was another name for paraquat!
I came away from the article seeing more of a tune-up than a paradigm shift. It isn't exactly ground-shaking stuff... interesting and well-founded, sure. My mind has not been blown.
I agree, Jason. The significant thing about paradigm is that there is no requirement for any external agency. I don't accept it, but it is certainly dominant. If darwinism can develop to explain more with no requirement for external agency, then the paradigm hasn't shifted, even if the content of darwinism shifts.
Of course, Dawkins, who seems to have a strong intellectual commitment to a thoroughly gradualistic darwinism, may not agree with this analysis - I think his position would be seriously undermined if the traditional neodarwinist perspective were overturned.
And if it were to be the case that proponents of ID were to successfully show that complex biological systems could not evolve, then this would cause a paradigm shift. However, from what I've seen, the darwinist community will take all available steps to prevent this happening.
It is the primary agent in shaping new adaptations.
And how is the new paradigm supposed to challenge this statement? Adaptations are, by definition, selected for. How does Erwin think that organisms develop a match with their environment except by selection?