Comments on the Finches + GAME at the end of the post

"A fair result can be obtained only by fully stating and balancing the facts and arguments on both sides of each question. "

Charles Darwin

 So let's think about our experiment in class yesterday--modelling natural selection with spoons and scissors and macaroni and toothpicks and a bunch of other stuff.  What did it mean, and also what did it not mean?
Here is a shortened version of an article from this site, Truth in Science, which you or your parents might appreciate for a fuller discussion.

Darwin's Finches

Galapagos finches showing different beak shapes

On the Galapagos Islands in the Pacific Ocean, close to the equator, there are a variety of different finches, which vary in the shape and size of their beaks. It appears that the  finches colonised the Islands from mainland South America, and then diverged in form. The distance between the islands meant that the finches on different islands could not interbreed, so the populations on the different island tended to become distinct. Different populations also became specialised for different food sources, birds with thin, sharp beaks eating insects and birds with large, sturdy beaks eating nuts.

Darwin collected some of these finches when he visited the Galapagos Islands, and it is often stated that the finches were key to the development of his theory of evolution. They are used as evidence for his theory in many textbooks.

Were the Finches important to Darwin in formulating his theory?

When he was on the Galapagos Islands, Darwin did not notice that different islands had different finches. Neither did he realise that the finches were closely related despite their differences in beak shape. He did not match different beak shapes to different diets. Even after his return to London, Darwin's biographers note that he "remained confused by the Galapagos finches...unaware of the importance of their different beaks...He had no sense of a single, closely related group becoming specialized and adapted to different environmental niches." (p. 209, Darwin - A. Desmond and J. Moore).

So all Darwin did was speculate that the different finches had descended from a common ancestor and had changed to be able to do different things. He was never sure that the different species were from different islands. He certainly never came up with the detailed theory for how the finches diversified which the BBC suggests. ...


What do the Finches demonstrate about evolution?
Though the finches were not important in the work of Charles Darwin, they do tell us something about evolution. In particular, over the past few decades, two scientists have done an excellent long term study on the finches on one of the Galapagos Islands. This is accurately described by the textbook Advanced Biology. (Jones, M., and G. Jones. 1997. Cambridge University Press) The authors recount how from 1977 to 1982 there was a drought on one of the Galapagos Islands, and due to natural selection the average finch beak size became larger…

However, this proved not to be the end of the story. If it continued in this way, the average beak size of G. fortis would continue to get larger and larger. But this has not happened (p. 153)

This cumulative change does not occur for two reasons. (1) There are disadvantages to having a large beak, especially when a bird is young. This can outweigh [no pun intended!] the advantages. (2) The selection pressure on the island fluctuates. In 1982 the drought stopped and there was selection for birds with small beaks.

It can therefore be argued that the study shows natural limits to evolutionary change. Variation in a species is a good thing, as it gives them the ability to cope with environmental change, but variation does have limits.

Many textbooks do not go into such detail, and simply describe the finches as a good example of a range of species evolving from a common ancestor.

The Galapagos finches afford an excellent example of adaptive radiation. It is assumed by evolutionists that a stock of ancestral finches reached the islands from the mainland and then, in the absence of much competition, evolved to fill many of the empty ecological niches occupied on the mainland by species absent from the islands.” (p. 725) Advanced Biology. Roberts, M., M. Reiss, and G. Monger. 2000. Nelson

Conclusion
The Galapagos finches were not as important to Darwin as is often claimed, but they are a good example of micro-evolution. They show us that finches can vary in their morphology [shape], and that natural selection has a role in this.

This study does not give evidence for macro-evolution, and does not prove that natural selection and random mutation could produce the living world as we know it from simple single-celled ancestors.

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So here is a fun interactive that sums up what natural selection is--NOT NECESSARY to AGREE or to draw a conclusion--simply to understand the idea.
Who Wants To Live a Million Years? Game click here
Read, and then play the game until you can consistently win.