More Science Labs: The OOL Question

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Here’s an interesting back-and-forth volley on the subject of intelligent design and science; first an article by Gordy Slack on What neo-creationists get right.

Then, evolution advocate Nick Matzke (who was featured in that video I posted yesterday on the Dover School District controversy) replies to Slack’s article in an essay on what scientists really know about one of the most fundamental questions, the Origin of Life (OOL): What critics of critics of neo-creationists get wrong: a reply to Gordy Slack - The Panda’s Thumb.

Read the whole thing, but here’s one section that deals with an issue that’s been raised in LGF comments over and over:

OOL Discovery #1. All known life can be traced back to a single common ancestor which, compared to what most people think of as present-day life (i.e. plants and animals), was relatively simple – microscopic, single-celled, perhaps as complex as an average bacterium or perhaps somewhat less so.

Because a lot of creationists, and sometimes others, are a bit thick in the head on correctly understanding this point, let me bash away at some common misconceptions. The phrase “single common ancestor” does not, and never has for people who were paying close attention, referred to a literal single individual organism. Think about a phylogenetic tree with humans and chimps on the branches. When you trace the tree back to the “common ancestor” of chimps and humans, does that node represent a literal single individual? No, of course not! Everyone (well, everyone paying attention) realizes that that ancestral node represents a species or population sharing genes in a gene pool. Ditto for all of the other ancestral nodes in a phylogenetic tree, including the Last Common Ancestor of known life.

With this understood, the debate initiated by Ford Doolittle and others over the precise nature of the Last Common Ancestor – they argue that it was a population of unicells that were rampantly trading genes – can be put in the correct context. It’s basically a debate about how wide or narrow the bottleneck the Last Common Ancestor represents, and whether (for example) modern life might contain some genes derived by lateral transfer from pre-LCA lineages that are now extinct. These debates are fascinating and highly technical, but they don’t undermine at all Point #1. Somewhat ironically and counterintuitively, those who say that there was rampant lateral transfer – this is supposed to be the “radical” position that “uproots the Tree of Life” when its proponents get their blood up – are actually pushing the LCA to something more and more like a traditional gene pool, i.e. species, i.e. what every other node in a phylogenetic tree represents.

Any way you slice it, all known life (with minor derived exceptions, and excepting viruses) shares a suite of protein and RNA genes, a DNA-RNA-protein system and a mostly standard genetic code (again with minor derived exceptions), etc. Even if various other bits of modern life came from other ancestral lineages (unlikely for most features in my opinion but there may be some exceptions), this shared system indicates that all known life, i.e. all the stuff that’s not extinct, descends from a pretty good bottleneck where these features were fixed in the “population.” And this reconstructed ancestor is maybe as complex as a typical bacterium and probably less so. It could be that in the last 50 years science discovered that known life had for-real multiple origins, or that at the root of the tree was a complex multicellular organism with 30,000 genes and huge, elaborately regulated, genome, but instead we get a unicell with a relatively small & simple genome. Various caveats, important to scientists but irrelevant to beginner-level education and dealing with creationists (e.g., somewhat more genes may have been passed through the bottleneck in some but not all organisms if the LCA was more of a gene-trading community) should not be allowed to distract from the Main Point: science has confirmed the hypothesis, going back at least to Darwin, that the ancestor of modern life was much less complex than life today.

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