Recently, PZ Myers accused me of lying about the views of molecular evolutionist W. Ford Doolittle in a debate on Canadian public television. Before I respond to PZ’s baseless charge, let’s see what mental image the following proposition generates:
All organisms on Earth have descended from a single common ancestor.
I’ll bet “single common ancestor” caused you to picture a discrete cell. And if you opened a college biology textbook, to the diagram depicting Darwin’s Tree of Life, you’d find that same image.
Moreover, if someone asked you to summarize the arguments for the single-Tree topology, you’d say (for instance) that multiple independent originations of the same basic biochemistry — e.g., the 64 trinucleotide genetic code — are too unlikely. It’s far more parsimonious to postulate a single cell as the universal ancestor of life.
That’s the historical topology Jerry Coyne described for Canadian television viewers, which he accepts, and which W. Ford Doolittle does not.
Now, one may equivocate, and say that by “single common ancestor” Doolittle actually means an indefinitely large population of organisms, but such word-jigging is shameful. Significant differences exist, both empirically and theoretically, between single-Tree (monophyletic) and multiple-Tree (polyphyletic) topologies. If the question were just a quibble over words — okay, let’s agree that “great-grandfather” can mean pretty much anything, such as an actual guy in Sweden, several such guys, or the entire male population of Stockholm, it doesn’t really matter — the “heated argument” described in this article wouldn’t have occurred.
Did the Dalhousie University writer of this news article lie? Of course not.
Doolittle and I have never met, although I’ve been a student of his thinking since the late 1980s. I’ve always taken care to describe him as fully supporting evolution by natural processes, as rejecting intelligent design in toto, and as well within the Darwinian fold, broadly defined. Hence, the description “cautious revolutionary” above. Don’t miss the sidebar in the Dalhousie article.
And consult the figure in this post. Rejecting Darwin’s single Tree does not mean one accepts intelligent design. Nor does the acceptance of the single Tree mean one thereby endorses the sufficiency of natural processes to explain life. If it did, Mike Behe wouldn’t be arguing for ID.
Come on, people, let’s grow up and take on some sophistication about these questions. Bashing me for describing the diversity of possible evolutionary views is just plain silly.