Monday, November 26, 2007

Evolution for Creationists Part Two

Continuing my series "Evolution for Creationists" I take a look at the nested hierarchy pattern of life and geographic distribution.

Evidence #3
The Nested Hierarchy Pattern of Life

Taxonomy, the classification of living things, supports evolution. This is probably one of the reasons that creationists are trying to construct a new system based on "kinds". EvoWiki explains it thus,

"'Nested hierarchy' refers to the way taxonomic groups fit neatly and completely inside other taxonomic groups. For instance, all bats (order Chiroptera) are mammals. All mammals are vertebrates. Likewise, all whales (order Cetacea) are also mammals, and thus also vertebrates.

While it might seem that this arrangement is obvious and unavoidable, it is not. Taxonomic groups are defined by traits and it should be possible to mix traits from multiple defined groups. An example from classical mythology is the Pegasus, a creature with features defined as both mammal (produces milk like a horse) and bird (has feathers). Mammals and birds are both orders, so, if Pegasus existed, it would be a violation of the nested hierarchy, a creature that belonged to two separate groups."

Now, I have heard creationists scoff at this as evidence of evolution. Isn't it ridiculous to demand a Pegasus or Mermaid to falsify evolution? Well, no, because we would not necessarily need something like that to falsify it. Ken Ham has implied that the Platypus falsifies evolution, because it shares characteristics of birds and mammals, and couldn't have evolved from both. But does it really? No it does not, because a close examination reveals that the similarities are superficial,

"The bill of a duck is a hard keratin structure, while that of the platypus is a soft flexible organ packed with electrical and touch sensors."

The bill of the platypus can be explained by convergent evolution: A similar looking structure evolved, but since genetic and biochemical similarities are not present, we should not assume that it was inherited from a common ancestor with birds.

So to recap: The more similar creatures are, the more recently they shared a common ancestor (we can verify this through fossils). All things can be grouped by similarity to greater and lesser degrees, and we never find any animal that cannot be grouped in this 'nested hierarchy' system, despite creationist claims. This is a falsifiable prediction of common descent.

If you are still having trouble understanding, try looking at this graph.

Evidence #4
Geographic Distribution

"Neither the similarity nor the dissimilarity of the inhabitants of various regions can be accounted for by their climatal and other physical conditions."

-Sir Charles Darwin

What, then, can account for the similarities/dissimilarities of creatures living in different regions? Why are marsupials found only in Australia? If plants and animals were created perfect, then why are they so different in conditions that are basicly the same?

Not suprisingly, we have more in common genetically with African Primates than with South American Primates. Evolution can explain this by telling us that our common ancestor with the South American primates lived longer ago than our common ancestor with African primates. How does creationism explain this?

The Kaibab squirrel became geographically isolated from the common ancestor with its closest relative, the Abert squirrel in the North Rim of the Grand Canyon about 10,000 years ago. Since then, several distinguishing features, such as the black belly and forelimbs have gradually evolved. Click here to see Photos of the Two Species

Frank Zindler, in "The Kiwi Question" explains,
"Despite the fact that most marsupial species seem to be out-gunned when they are forced to compete with placental mammals (hence the extinction of so many marsupial species after the introduction of European mammals), we are to suppose that wombats and wallabies, bandicoots and koalas, kept ahead of lions-'n-tigers-'n-bears all the way to Indonesia, and then - although the superior placental predators couldn't manage it - continued on to Australia. As if this were not mind-boggling enough, after all this implausible world travel, and after all the dust had settled, it turns out that the types of marsupials that made it to Australia just happened to form an ensemble able to fill all the ecological niches available!

Thus, there were marsupial moles, anteaters, mice, grazers, carnivores, frugivores, etc. - not one of which can be found anywhere else in the world. If this highly diversified marsupial population has descended with modification (evolved) from one or a few primitive, generalized marsupials which reached Australia by "sweepstakes dispersal" millions of years ago, this peculiar situation is understandable. But if all these creature had to journey from Turkey to Australia as an ensemble, it is incredible beyond computation."


David said...

Thanks for putting up all this material.

Dale Husband said...

"Why are marsupials found only in Australia?"

Actually, they are also found in the American continents too. But they should be everywhere if they came from Noah's Ark a few thousand years ago.

AIGBusted said...

Hi Dale,

You're right. They are in South America, most migrated to Australia through Antartica.

AIGBusted said...

By the way Dale, I am going to do a little more research and hopefully correct the thing about the marsupials.


Berlzebub said...

AiGB, there is also, at least, one marsupial in North America. The opossum is a marsupial that some believe branched off from the South American opossum around 100 million years ago.

Anonymous said...

So how do you explain away not finding any trasitional life forms in the fossil record?

EvoDevo said...

He addressed the transitional forms in part 1.