Evolution in 1-2-3

1) Descent with modification
2) Adaptation and natural selection
3) Speciation


Example 2

Evolution of blood clogging

The concept of irreducible complexity is often raised as an argument against evolution. Darwin himself proposed this as a falsification criterion of his theory but also cautioned agains premature conclusions:

"If it could be demonstrated that any complex organ existed, which could not possibly have been formed by numerous, successive, slight modifications, my theory would absolutely break down.

But I can find out no such case.

No doubt many organs exist of which we do not know the transitional grades, more especially if we look to much-isolated species, round which, according to my theory, there has been much extinction. Or again, if we look to an organ common to all the members of a large class, for in this latter case the organ must have been first formed at an extremely remote period, since which all the many members of the class have been developed; and in order to discover the early transitional grades through which the organ has passed, we should have to look to very ancient ancestral forms, long since become extinct.

We should be extremely cautious in concluding that an organ could not have been formed by transitional gradations of some kind."

Since 1859, numerous attempts have been made to use this criterion to falsify Darwin's theory of evolution, one of which is the blood clogging system. However, as can be clearly seen in the illustration below, the claim that the blood clogging system is irreducibly complex has been thorroughly refuted. 



Step-by-Step Evolution of Vertebrate Blood Coagulation
R.F. Doolittle
Figure 6. Time-line phylogeny for appearance (and disappearance) of various clotting factors during the course of vertebrate evolution.
doi 10.1101/sqb.2009.74.001
Cold Spring Harb Symp Quant Biol 2009. 74: 35-40
Copyright © 2009, Cold Spring Harbor Laboratory Press


"Because fibrinogen, the mainstay of the clot, has never been found in any protochordate by any method, we must conclude that the invention of thrombin-catalyzed fibrin formation took place in the ~50–100-million-year window between the appearance of protochordates and the jawless fish."

In other words, there was a period of invention several million years ago. Any other explanation would be unscientific.

"Genomic data for hagfish are sparse, however, and for the moment, our study of clotting factors in this group is mostly limited to the lamprey. Even so, the system in these creatures is decidedly simpler than in mammals and serves as an illustration of how such a system can become more complex."

In other words, a simple system compared to a more complex system illustrates how one can evolve into the other, which in turn proves that it did because any other explanation would be unscientific.

Q. E. D.

See also The evolutionary origin of complex features, Nature 423, 139-144 (8 May 2003): "A long-standing challenge to evolutionary theory has been whether it can explain the origin of complex organismal features."

(The reason why you won't find the challenge in the scientific litterature is that any challenge to the theory by definition is unscientific. Challenges thus don't appear until they are refuted. This proves that there are no problems with the theory of evolution and that the scientific consensus concerning the theory is founded on science, not bias.)