Hey gang! I apologize for my absence of a few weeks. I have been very busy with work lately, and I hate to write something that I haven't been able to research properly, so I haven't posted anything in this series for three weeks now. This week's installment will be a brief one, but certainly one that should provide interesting fodder for further thought and research.
Previous articles:
Retroviral sequences: http://www.jehovahs-witness.com/6/86797/1.ashx
Cytochrome c: http://www.jehovahs-witness.com/6/87238/1.ashx
What evolution is not: The role of randomness: http://www.jehovahs-witness.com/6/87711/1.ashx
Mitochondrial DNA, part 1: http://www.jehovahs-witness.com/6/87781/1.ashx
Mitochondrias DNA, part 2: Neandertals: http://www.jehovahs-witness.com/6/88271/1.ashx
Atavisms and Vitamin C: http://www.jehovahs-witness.com/6/88649/1.ashx
My entry this week will be on the phenomenon of species that exist in only one place in the world. There are many instances of this. For example, kangaroos exist only in Australia (in fact, marsupials as a whole are found only in Australia and the surrounding islands). There are 900 species of insects in Hawaii that have been shown to be descended from a single ancestor. Large inland lakes, such as Lake Tanganyika in Africa also provide an interesting study in this phenomenon.
Some quick facts about Lake Tanganyika, from http://www.africaguide.com/facts.htm:
Take Tanganyika is the deepest lake in Africa reaching at its greatest depth is 1,436 m (4,710 ft), making it the second deepest freshwater lake in the world after Lake Baikal.
Interestingly, Lake Tanganyika is home to many species of fish that exist nowhere else in the world. http://www.cichlid-forum.com/articles/lakes_east_africa.php says that there are about 200 unique species of cichlid fish. Just to give these guys a face, here are a few pictures:
Okay. Now, the phenomenon of unique species is pretty interesting, especially when they occur in isolated bodies of water. Why should a species occur in this lake and nowhere else in the world? How is that even possible?
From a creationist point of view, if I may be so bold, it is impossible to explain in a convincing manner. Even if we say that God created 200 species just for this particular lake, what happened during the flood? Remember "the waters covered the highest mountain." So these fish were no longer confined to their lake. They swam around uninhibited for a year, and then somehow all ended back back in the same lake? Definitely hard to swallow.
What makes it even harder to swallow is that several DNA studies in situations like this have shown that the unique species are genetically related.
DNA studies of 16 species, representing the major Malawian cichlid groups, suggest that all the Malawian cichlids arose from one single species within the past 700,000 years.
-- http://www.hagblomfoto.com/article_evolution.htm
Regarding the same phenomenon in Lake Victoria:
In the October 11th (1990) issue of Nature, Meyer et.al. present of paper aimed at establishing if the cichlid fish species of Lake Victoria (Africa) are monophyletic or polyphyletic. (If they all share a recent common ancestor in that lake or came from separate lineages that invaded the lake). In their paper they sequenced a 363 bp part of the cytochrome b gene and a 440 bp segment of mitochondrial DNA from what is called the control region. They sequenced these genes from several species of fish in the lake and a few species from relatively nearby lakes.
What they found was the sequences in the Lake Victoria species of fish were all very similar, but they were different from the sequences of fish in nearby lakes. All the sequences are listed in the paper.
They came to the conclusion that this indicated the cichlid species of Lake Victoria all derive from a recent common ancestor in the lake.
-- http://www.talkorigins.org/faqs/evolution-research.html#cichlid-fish
So what we have are a family of isolated species that can be shown to be genetically related, and which exist nowhere else in the world. This is about as solid a set of evidence for evolution as one could ever expect to see. There simply is no reasonable explanation except that evolution is a real phenomenon that is actively creating new species.
So that's it for this week! Think, discuss, enjoy!
SNG