Claim CB200.2:
The biochemistry of blood clotting is irreducibly complex, indicating that
it must have been designed.
Source:
Behe, Michael J. 1996. Darwin's Black Box, New York: The Free Press, pp.
74-97.
Response:
- The blood clotting systems appears to be put together by using whatever
long polymeric bridges are handy. There are many examples of
complicated systems made from components that have useful but
completely different roles in different components. There is also
evidence that the genes for blood clotting (indeed, the whole genome)
duplicated twice in the course of its evolution (Davidson et al. 2003).
The duplication of parts and co-opting of parts with different
functions gets around the "challenge" of irreducible complexity
evolving gradually.
- Blood clotting is not irreducibly complex. Some animals -- dolphins,
for example -- get along fine without the Hagemann factor (Robinson et
al. 1969), a component of the human blood clotting system which Behe
includes in its "irreducible" complexity (Behe 1996, 84). Doolittle
and Feng (1987) predicted that "lower" vertebrates would lack the
"contact pathway" of blood clotting. Work on the genomes of the puffer
fish and zebrafish have confirmed this (Yong and Doolittle 2003).
- Irreducible complexity is not an obstacle to
evolution and
doesn't imply design.
Links:
Acton, George, 1997. Behe and the blood clotting cascade.
http://www.talkorigins.org/origins/postmonth/feb97.html
Behe, M. and K. Miller. 2002. Transcript: American Museum of Natural
History April 23, 2002 (Part 7).
http://www.ncseweb.org/resources/articles/7819_part_07_dr_michael_behe_dr_10_31_2002.asp
Dunkelberg, Pete, 2003. Irreducible complexity demystified.
http://www.talkdesign.org/faqs/icdmyst/ICDmyst.html
EvoWiki, 2004. Blood clotting.
http://www.evowiki.org/wiki.phtml?title=Blood_clotting
Musgrave, Ian, 2005. Clotted rot for rotten clots.
http://www.pandasthumb.org/pt-archives/000884.html
References:
- Davidson, C. J., E. G. Tuddenham, and J. H. McVey. 2003. 450 million
years of hemostasis. Journal of Thrombosis and Haemostasis 1:
1478-1497.
- Robinson, A. J., M. Kropatkin, and P. M. Aggeler. 1969. Hagemann factor
(factor XII) deficiency in marine mammals. Science 166: 1420-1422.
Further Reading:
Doolittle, Russell F., 1997. A delicate balance. Boston Review
(Feb./Mar.), http://bostonreview.net/BR22.1/doolittle.html
Ussery, David, 1999. A biochemist's response to "The biochemical
challenge to evolution". Bios 70: 40-45.
http://www.cbs.dtu.dk/staff/dave/Behe.html
created 2001-2-17, modified 2005-9-24