Blood clotting’s dependency on Vitamin K leaves us vulnerable
NOTE: This was first published here on 8.27.08, and is simply being re-published as a separate post now.
Bleeding disorders also accompany deficiencies in FSF, vitamin K, or α2-antiplasmin, which are not involved directly in clotting. DBB 89
As Behe stresses, the clotting cascade is rather complex, and is vulnerable to a number of disruptions. He wants to make this into an argument against evolution, and yet the dependency of the crucial function of blood clotting on not entirely dependable sources of vitamin K is clearly what would be more expected from the contingencies existing in “Darwinian” evolution, and not of some highly intelligent designer dealing with the issues of complexity and of vulnerability. While vitamin K deficiency is not typically a major threat to human life, in pre-industrial societies vitamin K deficiency is not uncommon precisely when humans are otherwise quite vulnerable, just after birth:
Newborns are especially prone to vitamin K deficiency. A nursing-mother’s milk is low in the vitamin; breast milk can supply only about 20% of the infant’s requirement. Infants are born with low levels of vitamin K in their body; they do not have any vitamin K-producing bacteria in their intestines. Their digestive tracts are sterile. As a result, a form of vitamin K deficiency, called hemorrhagic disease of the newborn, may develop. This disease involves spontaneous bleeding beneath the skin or elsewhere in the infant’s body, and occurs in about 1% of all infants. In rare cases, it causes death due to spontaneous bleeding in the brain.
What Behe deliberately tries to do is to blur the differences between evolution and design, mainly because all of the evidence is in favor of evolution. If he really wanted to make a scientific case for design, he’d sharpen the distinctions between the two, pointing out what evolution explains and what design could explain.
Since he dares not discuss the differences, I would like to point out that evolution is what is expected to co-opt already existing pieces into its complexity, so that the result is “good enough.” Sure, babies are vulnerable to insufficient blood clotting due to vitamin K deficiency, but most make it without medical intervention. Best of all, vitamin K was available to assist one step of the clotting cascade (p. 84 of DBB). Evolution is often constrained by a lack of needed components to its complexity. Evolution makes do with vitamin K, then, despite the fact that newborns lack crucial sources of vitamin K, and adults can run into deficiencies as well. The point is that already-available vitamin K works much better during evolution than having to evolve something anew from something lacking vitamin K’s abilities.
Design, on the other hand, looks ahead to difficulties and tries to make complexity robust against disruptions in nutrition. A designer actually might be quite happy to use vitamin K, then, but would give to mammals the ability to synthesize vitamin K, or otherwise prevent the vulnerabilities that dietary and bacterial supplies of vitamin K pose for us.
Behe fails to bring up these matters, because they would clearly underline the fact that the constraints on evolution that Behe likes to point to have indeed shaped what we are. The designer is concerned about constraints of operation, while evolution is “concerned about” (constrained by, in the more proper non-anthropomorphic terms) its severe restrictions of biochemicals and adaptive abilities to supply function. Thus evolution often fails to provide the kinds of functions that design could provide (although over time, and with reasonably good adaptive pathways to follow, highly efficient systems often do appear), but it does find its way to function in many cases (although many functions, like radio communications, are essentially precluded from biological adaptation).
Vitamin K was adopted during the course of evolution not because it would ensure the kind of clotting function that vertebrates need throughout their entire lives, but because it was already provided by diet and/or bacterial symbionts. It is a “good enough” solution, certainly, yet it is exactly the sort of “solution” that would be expected from undirected evolution, and not from a designer.
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.