A Primer on the Tree of Life (Part 1): The Main Assumption
Evolutionists often claim that universal common ancestry and the "tree of life" are established facts. One recent opinion article in argued, "The evidence that all life, plants and animals, humans and fruit flies, evolved from a common ancestor by mutation and natural selection is beyond theory. It is a fact. Anyone who takes the time to read the evidence with an open mind will join scientists and the well-educated."1 The take-home message is that if you doubt Darwin's tree of life, you're ignorant. No one wants to be ridiculed, so it's a lot easier to buy the rhetoric and "join scientists and the well-educated."
But what is the evidence for their claim, and how much of it is based upon assumptions? The truth is that common ancestry is merely an assumption that governs interpretation of the data, not an undeniable conclusion, and whenever data contradicts expectations of common descent, evolutionists resort to a variety of different ad hoc rationalizations to save common descent from being falsified.
Some of these ad hoc rationalizations may appear reasonable -- horizontal gene transfer, convergent evolution, differing rates of evolution (rapid evolution is conveniently said to muddy any phylogenetic signal), fusion of genomes -- but at the end of the day, we must call them what they are: ad hoc rationalizations designed to save a theory that has already been falsified. Because it is taken as an assumption, evolutionists effectively treat common ancestry in an unfalsifiable and unscientific fashion, where any data that contradicts the expectations of common descent is simply explained away via one of the above ad hoc rationalizations. But if we treat common descent as it ought to be treated -- as a testable hypothesis -- then it contradicts much data.
The Main Assumption
As noted, the first assumption that goes into tree-building is the basic assumption that similarity between different organisms is the result of inheritance from a common ancestor. That is, except for when it isn't. (And then the similarity is purportedly said to be the result of convergent evolution, etc.) But even if we take this claim at face value -- that similarity between different organisms is the result of inheritance from a common ancestor -- let's recognize it for what it is: a mere assumption. But are there other possibilities?
I'll explore more problems with the tree of life and other possibilities in a series of five total posts in this series.
[1.] Perry Mann, "The Dinky Insect That Helps Demonstrate Darwin's Theory," at http://www.huntingtonnews.net/columns/090427-mann-columnsmanntalk.html (April 27, 2009).