There’s a very very interesting article with the title of this post, on the topic of molecular genetics and molecular evolution, published in the most recent edition of “Nature” by London science writer Philip Ball. I intend to cite it, or at least some of the articles it references, in my thesis. Well worth a read if you’re into this stuff (perhaps noone who reads this blog is though) and have access via a university library or such.
Amongst other things, he dares to highlight the fact that there is debate over the capacities of natural selection to explain molecular evolution – he notes neutral evolutionary processes as another option, but that it is all generally unclear. For what it’s worth, I’m inclined to think that there is yet more going on.
“On the 60th anniversary of the double helix, we should admit that we don’t fully understand how evolution works at the molecular level, suggests Philip Ball.”
“In short, the current picture of how and where evolution operates, and how this shapes genomes, is something of a mess. That should not be a criticism, but rather a vote of confidence in the healthy, dynamic state of molecular and evolutionary biology.”
“Barely a whisper of this vibrant debate [[on the nature of the gene]] reaches the public. Take evolutionary biologist Richard Dawkins’ description in Prospect magazine last year of the gene as a replicator with “its own unique status as a unit of Darwinian selection”. It conjures up the decades-old picture of a little, autonomous stretch of DNA intent on getting itself copied, with no hint that selection operates at all levels of the biological hierarchy, including at the supraorganismal level2, or that the very idea of ‘gene’ has become problematic.” [[It’s no big secret that Dawkins is overly simplistic (at best) in his science, as well as in his philosophy]]
phylogenetic tree image from tree.bio.ed.ac.uk
Update: earlier this month, in the Proceedings of the National Academy of Sciences (PNAS), another interesting paper was published (at least one!). This one argues that the concept of junk DNA must be retained. There are various interesting issues concerning function and the wide range of ‘DNA elements’ which this paper raises and which I hope to ponder more, but here is one quote that raises interesting teleological possibilities (I’m over-using the word ‘interesting’, I know):
“If the human genome is junk-free, then it must be very luckily poised at some sort of minimal size for organisms of human complexity. We may no longer think that mankind is at the center of the universe, but we still consider our species’ genome to be unique, ﬁrst among many in having made such full and efﬁcient use of all of its millions of SINES and LINES (retrotransposable elements) and introns to encode the multitudes of lncRNAs and house the millions of enhancers necessary to make us the uniquely complex creatures that we believe ourselves to be. …” – from “Is junk DNA bunk? A critique of ENCODE” by W Ford Doolittle.
another quote: “it cannot in general be the case that selection operating at the level of ﬁtness of individuals within a species can favor the origin or maintenance of traits that incurs selective cost at that level, while offering only the remotest hope of future beneﬁt to the individual and its descendants.” [the author then goes on to discuss mechanisms outside of ‘selection at the organismal level’]
Another interesting point: gene duplication can help facilitate expression which is specific to a particular cell type or tissue.