on common ancestry and jars of clay

It’s not the most exciting start to a blog post, but I’m currently thinking about how to calculate the genetic diversity that has accumulated over the course of an exercise in experimental evolution in yeast. This led on to considering measures of the genetic distance between two organisms; and from there, the concepts of homology and common ancestry flitted in to join in with this impromptu brainstorming session with topic “life”.

I’ve also recently been thinking about 1) differences in complexity, and how the complexity in organisms can be divided into ‘what’s in the DNA’ and ‘the other stuff – like sub-cellular compartmentalization & form’, and 2) the ethical difference between a rock and an organism. I’m interested in the ties between a “proper function” account of ethics and natural law theories – on such accounts, broadly, the form of things has some connection to their ethical use. Form matters…


This all coalesces such that it occurs to me that a stone jar and a rock have quite similar chemical compositions. You could easily enough produce formal tables charting the proportions of the various elements or types of material present in each; they could be 100% similar in those terms, or certainly close enough. But the stone jar still quite clearly evinces ‘design’, while the rock, from which it may have been hewn, doesn’t.  Perhaps, in a kind of similar way, even though two creatures may share a significant proportion of their molecular make-up (measured in terms of their DNA sequences), and even though they share a common ancestry, they are still able to evince design? If one is the ancestor of the other, the process could have been laden with that unpopular word, ‘intention’ – mere similarity clearly does not dispel that possibility. The same deal as that for the rock presumably could be applied to the Scriptural metaphor of the clay jar, which can be compared to the clay from which it was shaped, but clearly arose from intentional processes nonetheless.

As it comes to mind, here’s an epilogue: if I was to write a book on these things, I’d want to discuss at least these topics:

*The failures of reductionism in describing life.
*Biochemical fine-tuning.
*The various ways in which DNA is optimised for its function (including the triplet code, & chromosomal packing).
*Measuring the total information content of organisms (not just that in the DNA).
*The pervasiveness of “exaptation” in evolutionary history.
*Evolutionary convergence at the organismal and molecular levels.
You saw it here first, folks!

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