Too many papers, not enough time: each of these deserves a deep dive, but my list just keeps getting longer, so I’m going to have to settle for a quick survey instead. To give you an idea of what I’m up against, these papers were all published (or posted to bioRxiv) in July and August, 2016. By the time I could possibly write full-length posts about them all, there would probably be ten more!
Figure 6 from Hanschen et al. 2016. Multicellularity hinges on the evolution of cell cycle regulation in a multicellular context with subsequent evolution of cellular differentiation (here, cell size-based) and increased body size.
Remember how I said they’re prolific? Before I’ve even had a chance to write up my thoughts on the Gonium genome paper, Evolution News & Views has already published theirs. The story has also been picked up by the Washington Post, New Historian, GenNews, and ScienceDaily (that last one looks like just a reprint of the press release from University of the Witwatersrand). By the way, the genome paper is open access, so you don’t need a subscription to see it for yourself.
We already know that cdesign proponentsists are not fans of research into the evolution of multicellularity, and that they have trouble understanding it. In an unsigned article on the Gonium genome at ENV, they admit that
After reading this paper, we’re none the wiser.
That’s too bad. I’m here to help.
The so-called ‘Major Transitions’ framework is an attempt to explain the hierarchical structure of life on Earth: genes within chromosomes, chromosomes within cells, cells within cells (eukaryotic cells), individuals within sexual partnerships, cells within multicellular organisms, and organisms within societies. The best-known attempt to unify the origins of these relationships is a book by John Maynard Smith* and Eörs Szathmáry, The Major Transitions in Evolution.
First published in 1995, the book focused on the origins of these hierarchical levels, connecting them with the unifying theme that
…entities that were capable of independent replication before the transition can replicate only as part of a larger whole after it.
For example, after a transition from unicellular to multicellular organisms (there were several), cellular reproduction either contributes to the growth of the organism or to production of new multicellular organisms.
Dictyostelium discoideum. Photographed by Usman Bashir (Queller/Strassmann Lab, Washington University in St. Louis). CC-BY-SA-4.0 License. Image obtained from Wikimedia Commons.
In the Major Transitions class, the students keep pointing out that the transitions on Maynard Smith and Szathmáry’s list come in two flavors with very different properties. Sure, there are some important similarities between multicellular organisms and social insects, but they are quite different from cellular slime molds and the conspiracy of prokaryotes that make up eukaryotes.
[Read more…]
Figure 7 from Anderson et al. 2016. Evolution of GKPID’s new function by unveiling a latent protein-binding site. (A) The binding surface for Pins in GKPIDs is derived from the GMP-binding surface of gk enzymes. Homology models of Anc-gkdup (left) and Anc-GK1PID (right) are shown as white surface, with all side chains that contact either GMP or Pins as yellow sticks. In the AncGK1PID structure , substitutions at sites in the binding interface are shaded red, including key substitution s36P. (B) The structure of the hinge and GMP/Pins-binding lobes is conserved between the Pins-bound GKPID (blue, rat Dlg, 3UAT), the apo-gk enzyme (brown, S. cerevisiae guanylate kinase 1EX6), and the apo-gk-s36P mutant (gray, 4F4J), all in the open conformation.
Cdesign proponentsists really don’t seem to like research on the evolution of multicellularity. Pretty much any time real scientists learn something new about the origins of multicellularity, writers on intelligent design blogs Evolution News & Views and Uncommon Descent feel compelled to tell us why it’s wrong (for example, here, here, here, here, here, here, here, here, here, here, here, here, and here).
So I shouldn’t be surprised that Denyse O’Leary has weighed in on the latest work out of Ken Prehoda’s lab, in which Prehoda and colleagues identified a mutation crucial for forming and maintaining tissues in animals. Worse, from O’Leary’s point of view, the article describes the evolution of a new protein function, which is anathema to intelligent design thinkers. To say this post is badly argued is overly generous; it’s absolutely devoid of any substantive argument.