Here's just one of the problems he discusses, a problem I confess I had never heard of before reading the interview:
At King’s [College in London] the subject of my PhD thesis was the development of the red [blood] cell and it seemed to me there were aspects of red cell development which posed a severe challenge to the Darwinian framework.Denton, whose recent book The Miracle of the Cell describes a host of amazing cellular phenomena, also talks about another fascinating development in biology - the growing realization that everything in the cell affects everything else. Even the shape, or topology, of the cell determines what genes will be expressed and that the regulation of all of the cellular activities is far more complex than any device human beings have ever been able to devise.
The red cell performs one of the most important physiological functions on earth: the carriage of oxygen to the tissues. And in mammals the nucleus is lost in the final stages of red cell development, which is a unique phenomenon.
The problem that the process of enucleation poses for Darwinism is twofold: first of all, the final exclusion of the nucleus is a dramatically saltational event and quite enigmatic in terms of any sort of gradualistic explanation in terms of a succession of little adaptive Darwinian steps.
Stated bluntly; how does the cell test the adaptive state of ‘not having a nucleus’ gradually? I mean there is no intermediate stable state between having a nucleus and not having a nucleus.
This is perhaps an even greater challenge to Darwinian gradualism than the evolution of the bacterial flagellum because no cell has ever been known to have a nucleus sitting stably on the fence half way in/half way out! So how did this come about by natural selection, which is a gradual process involving the accumulation of small adaptive steps?
The complexity of the process — which is probably a type of asymmetric cell division whereby the cell extrudes the nucleus - is quite staggering, involving a whole lot of complex mechanisms inside of the cell. These force the nucleus, first to the periphery of the cell and then eventually force it out of the cell altogether.
It struck me as a process which was completely inexplicable in terms of Darwinian evolution — a slam-dunk if you want.
And there’s another catch: the ultimate catch perhaps? Is an enucleate red cell adaptive? Because birds, which have a higher metabolic rate than mammals, keep their nucleus. So how come organisms, which have a bigger demand for oxygen than mammals, get to keep their nucleus while we get rid of ours?
And this raises of course an absolutely horrendous problem that in the case of one of the most crucial physiological processes on earth there are critical features that we can’t say definitively are adaptive.... Every single day I was in the lab at King’s I was thinking about this, and had to face the obvious conclusion that the extrusion of the red cell nucleus could not be explained in terms of the Darwinian framework.
And if there was a problem in giving an account of the shape of a red cell, in terms of adaptation, you might as well give up the Darwinian paradigm; you might as well "go home." .... It’s performing the most critical physiological function on the planet, and you’re grappling around trying to give an adaptive explanation for its enucleate state. And the fact that birds get by very, very well (you can certainly argue that birds are every bit as successful as mammals).
So, what’s going on? What gives? And it was contemplating this very curious ‘adaptation’ which was one factor that led me to see that many Darwinian explanations were “just-so" stories.
It's all very fascinating stuff.
