The thrust and parry of human-malaria evolution did not build anything–it only destroyed things. Jettisoning G6PD wrecks, it does not construct. Throwing away band 3 protein does likewise. Sickle hemoglobin itself is not an advancement of the immune system; it’s a regression of the red blood cell. Even the breaking of the normal controls in HPFH doesn’t build a new system; it’s just plugging another hole in the dike. Edge of Evolution 42
Behe has a creationist view of these matters, so that hemoglobin remodeled to confer partial immunity to malaria for those who are heterozygous for sickle cell anemia is “regression.” Scientifically and philosophically, that is nothing other than nonsense. The other mechanisms we have evolved that are mentioned in the above quote have varying degrees of deletion (which science would consider to be a functional regression, if still an improvement to fit current conditions) and/or change. Leaving those aside at the present, let us just note here that the changes that cause sickle cell anemia in homozygotes is definitely an improvement for heterozygotes, and his comparisons to a utopian defense against malaria of the kind a true designer (especially his omniscient “designer”) might produce has no place in understanding evolution.
The larger concern involves something quite different, which are the constraints of evolution. Even Behe mentions the constraints, oblivious to the fact that we accept evolutionary theory precisely because it fits the constraints seen in life. He writes:
Darwinian processes are incoherent and highly constrained. EoE 19
Well, Behe is incoherent, because in other places he claims that evolutionary processes mimic intent (also not true), which is typically not incoherent, even if incoherent statements are the norm in intentional ID arguments). Yet he is correct that evolution is highly constrained. Indeed, why else would the basic elements of our adaptive immune system remain the same for nearly half a billion years (though many of the parts have been significantly modified, added, or deleted)?
Beyond that, well, why can’t gazelles run 433 miles per hour, and cheetahs run somewhat faster, if evolution is constantly selecting both to optimize speed? Said that way, it sounds absurd, as if there are no limits to animal speed, let alone limits to what can evolve. Nevertheless, Behe’s “argument” about malaria and humans not evolving better “strategies” to attack and to defend, respectively, is about as intelligent and apropos as claiming that gazelles ought to run at least 433 mph by now.
What is more, chordates have evolved what is really quite a wonderful immune system, first evolving the innate immune system, and then a supplement to it which uses many of the same components, the adaptive immune system. That he denies that this is the case is hardly of any consequence, for the evolution of the adaptive immune system fits the constraints that he himself brought up, that “Darwinian evolution requires physical precursors.” DBB, 45 If not all such precursors have been found (and it is likely that not all will be, as extinctions of gene lines are not unexpected or uncommon), many have been, and the cladistic patterns map out to evolutionary expectations.
Importantly for our purposes, the complexity of our immune system evolved in stages, and according to the “nested hierarchies” predicted of organisms which are mainly limited to vertical transmission of information. The odds against evolution producing the innate and adaptive immune systems all at once are decisively against, and innate system precursors were needed for the adaptive system to operate and to evolve (not all adaptive system precursors come from the innate system, according to the evidence).
My previous post in this category (Darwin’s Black Box), and this one, are leading up to future posts dealing with the evidence of the evolution of immunity, framing the issue. After all, Behe manipulates the argument by framing everything according to his perspective, which truly does amount to dishonest framing. I am indeed framing (in the way more writers on these matters should do), by restoring the context that Behe stripped away from his own discussions of these things, and I do not doubt that this is quite an honest frame. The immune system is very important in both of his books, so I have an additional point to bring in as introduction, which is that the evidence of the evolution of the immune system goes directly against Behe’s claims of the inadequacy of evolution, in both of his books–but especially in Edge of Evolution (which is why this post is also in the EoE category, and will be put on the EoE cumulative post).
So I want to make clear how Behe’s criticisms of the “inadequacy” of evolution in response to malarial infection in humans fail so badly, since I will be bringing in good evidence that adaptive immunity did evolve. Crucially, we already have evolved an immune system that is both complex and to a considerable degree optimized. This is where the gazelle analogy comes in, for while gazelles run very fast and often leave cheetahs hungry, they can’t just simply keep evolving to run ever faster, due to physical limitations and to evolutionary limitations (indeed, evolution gave birds a better breathing system than it gave mammals, a typical non-design, makes-sense-only-in-the-light-of-evolution, limitation).
It is foolish to ask why evolution has the observed limitations, when the meaningful question is why Behe’s “design” seems to have so many limitations–and notably the same ones that evolution has. Furthermore, Behe still has absolutely no answer to the question of how he can determine what evolved and what has not. This is all the more true in Edge of Evolution, where he brings up the possibility that mutations “look accidental” but are not.
On the science side, I would like to get into a likely problem for evolving the immune system to better resist malaria, which is that Plasmodium falciparum, like many other parasites, actively subverts both the innate and the adaptive immune systems. This is not as important as the above points, in my opinion, but it is likely to play a role in the difficulty of evolutionarily responding to malarial infection.
One way malaria avoids our defenses is that it has an alternative method for taking up iron, that bypasses the body’s sequestration of iron (iron is a crucial element to nearly all life, especially so to growing life which has a high metabolic rate) effected to starve pathogens of iron.
A couple more ways that P. falciparum thwarts the immune system are mentioned in the quotes below:
In vitro studies involving human cells have shown that macrophage functions, including phagocytosis and ROI [reactive oxygen intermediates] generation, are severely impaired after uptake of an insoluble degraded host hemoglobin, called homozoin, generated during blood-stage malarial infection.
From the same source:
One of the more consistent and striking dysfunctions observed in macrophages infected with protozoan parasites [which include P. falciparum] is their inabililty to produce IL-12, which–as the main physiological inducer of interferon-γ (IFN-γ) and T helper type 1 (TH1) cell differentiation–is an essential cytokine for the development of acquired resistance to most intracellular pathogens. Nature immunology
The same paper details how malarial (and other parasitic protozoa) down-regulate many of the signaling pathways, particularly but not exclusively those involved with IL-12 (interleukin-12), and apparently also prevent maturation of the crucial dendritic cells. Again, I do not think that going into the details is especially instructive, since one can always use the link given, or search engines, to find out about those.
The question pertinent to this subversion of our immune system is: how are the highly evolved protozoan abilities to bypass or suppress our immune response really supposed to be countered by evolution? No doubt evolution has indeed tweaked our immune response to malaria, but our immunity is not an infinite god, it is a limited system whose adaptations are met with even more malarial adaptation. The very complexity of immunity likely inhibits further evolution, and, in any case, no gazelle will be able to evolve to run 433 mph. We have never outrun all parasites in our evolution, and likely we never will.
However, we do manage to fend off pathogens better than most ocean bacteria can, as their death rate is enormous at the hands of viruses. And they can evolve much more quickly than we can. The fact that our adaptive immunity has evolved to allow our line to exist for nearly half a billion years is certainly a testimony to the importance of of that evolution.
The ability of P. falciparum to be able to avoid much of the powerful effects of our immune system is merely one of the many stories of evolution wherein a “stalemate” of sorts has appeared. It is no fault of evolution that gazelles have topped out at around 50 mph, nor that our immune systems are able to handle most infections fairly well, but not the subversive virulence of P. falciparum. That evolution can recruit other changes in parallel with immune system evolution only speaks to the power–and the limitations–predicted of evolution.
Thus it is that the evidence of the evolution of our immune systems is crucial both to demonstrate what evolution can do, and, of course, what it cannot do. While one would like to endlessly ask the IDists how they account for the limitations of organisms, until they either reply to at least one crucial question or learn to keep quiet, the fact is that they will avoid all of the hard questions.
We, on the other hand, can answer a great deal about evolution’s abilities and limitations, so I plan for the next post to begin to lay out the evidence that the adaptive immune system evolved from the innate immune system. Evolution of the innate immune system could also be discussed (and may be in a limited way), but we almost certainly know more about how adaptive immunity evolved, and it is the part of immunity that Behe claimed could not evolve, even as he ignored the evidence that it evolved substantially out of the innate system.
This is part of a series of posts that I am combining into one long post, which may be found at Darwin’s Black Box.
Behe Fails Weblog 