Thursday, February 19, 2009

Biogeography shows that evolution is true

This subject was discussed earlier as evidence against the flood story in the Bible but it deserves to be mentioned again as positive evidence for evolution. In fact, many people consider this to be the single most powerful argument in favor of evolution.

Specifically “biography” is the distribution of plants and animals throughout the Earth.

If living things had not evolved, it would seem reasonable to expect that they would live wherever that organism’s natural habitat existed. You should find the same desert animals in all deserts, the same jungle animals in all of the jungles, and so on.

Or, more particularly, if they all came from Mt. Ararat in Turkey after a global flood, they would have found and settled into the natural habitat closest to where the Ark settled. Turkey itself has a desert environment ideal for many species of animals that instead chose to live as far away as North America. The closest jungle is found in Africa, not South America.

But, as specific evidence of evolution, what should we see in terms of biogeography?

The talkorigins web site provides this excellent description:

"Because species divergence happens not only in the time dimension, but also in spatial dimensions, common ancestors originate in a particular geographical location. Thus, the spatial and geographical distribution of species should be consistent with their predicted genealogical relationships. The standard phylogenetic tree predicts that new species must originate close to the older species from which they are derived. Closely related contemporary species should be close geographically, regardless of their habitat or specific adaptations. If they are not, there had better be a good explanation, such as extreme mobility (cases like sea animals, birds, human mediated distribution, etc.), continental drift, or extensive time since their divergence. In this sense, the present biogeographical distribution of species should reflect the history of their origination[1]. "

If that’s what we should see if evolution is true, what do we actually see?

Of course we see exactly that!

A well-known example is the fact that marsupials (mammals with pouches to hold their young) live nearly exclusively on the continent of Australia. This is also an example of an exception that “proves the rule”. The non-Australian marsupials are few in number and they all live in South America. South America was once attached to Australia as a single continent.

Similarly there are New World monkeys that all live in the Western Hemisphere, and Old World Monkeys, which all live in the Eastern Hemisphere. The monkeys are distinctly different from each other.

How did that happen if not through evolution?

[1], referenced on May 29, 2008

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