Hi all, this is first time starting a thread on this site, so I decided to go with something simple and uncontroversial, so we can all get along in unanimous agreement.
Universal common ancestry.
I’ve been browsing a few different threads here recently and one topic that I’ve noticed pop up repeatedly is formal tests of universal common ancestry - whether they have been performed, or are even possible. One paper that is often brought up (and not surprisingly so given its title), is Douglas Theobald’s 2010 paper A formal test of the theory of universal common ancestry.
It’s worth a read if you haven’t already, but without getting into the details, I think it’s generally acknowledged at this point that Theobald’s statistical methods were flawed, so let’s put his paper to one side for a moment.
What other research exists to fill this void? Well, as it happens I wrote a blog post a while back outlining one such piece of research. I’ll let you read the blog post and/or paper to get the full explanation and data, but for now, here’s my brief summary:
In their 2013 paper, White and colleagues developed and implemented a test of common ancestry between different large clades based on ancestral gene reconstruction, based on the principal that divergence from a common ancestor means that earlier members of each new lineage would be less genetically diverged than modern members of the respective clades. The illustration of this principal I give in the blog post involves humans and chimps. IF humans and chimps shared a common ancestor 6 million years ago, then if we could go back in time 3 million years and look at members of each lineage (the on-the-way-to-chimp lineage and the on-the-way-to-human lineage), you’d find that they were less genetically distinct from one another than extant humans and chimps are today. After all, they’d only had 3 million years to diverge, whereas extant humans and chimps have had 6 million years.
We can’t go back in time, but we can perform ancestral sequence reconstruction. By comparing the ancestral sequences, as well as modern sequences, we can see if these ancestral sequences really are more similar to one another than the modern sequences are, as would be predicted if the 2 groups in question really did share a common ancestor in the past, or not. White and colleagues performed this test between several major clades across the eukaryotic tree of life, and found in each case that indeed the ancestral sequences were significantly more similar to one another than the modern sequences, confirming the prediction of universal common ancestry.
My blog post:
I link the paper in that post, but here’s the link again:
Where Theobald’s paper was met with critiques of the statistical methods, White et al’s paper has been met with more enthusiasm. In their 2016 paper critiquing Theobald’s 2010 paper, “Infinitely long branches and an informal test of common ancestry”, Leonardo de Oliveira Martins and David Posada write:
“It is worth noticing that another method has been recently proposed that can more directly test for ancestral convergence (White et al. 2013). This method does not seem to suffer from the drawbacks of [Theobald’s] UCA test…”
A rave review if I’ve ever heard one!
I’m curious to hear the thoughts of the members of this forum on this research (as well as my blog post describing it), particularly those of the resident ID researchers. As I say at the beginning of the blog post, I’ve yet to see any rebuttal to the conclusions of this particular paper, despite the fact that it was published 5 years ago now, and I really have looked. The only reasonable conclusion seems to be angiosperms share a common ancestor with gymnosperms, vertebrates share a common ancestor with echinoderms, etc.
One of the papers that cites this one is Baum et al’s 2016 paper: “Statistical evidence for common ancestry: application to primates”, published along with 2 complementary papers (in BioRxiv): “Statistical evidence for common ancestry: New tests of universal ancestry” and “Statistical Evidence for Common Ancestry: Testing for Signal in Silent Sites”. As the titles suggest, these too describe a suite of statistical tests for common ancestry. I haven’t delved into these as deeply as I have White et al’s, but again, these are proposed tests that I’ve not really seen brought up when people discuss common ancestry, so maybe we can consider these methods in this thread as well.