The phylogeny of blogs, and other things

There's a nice little discussion on Science and Sensibility about the evolutionary relationships between science blogs (which he kindly, and unrealistically, classifies my blog as). In doing so, David, the author, introduces some of the techniques used to generate trees as classifications. There's some discussion in the comments worth reading.

It raises a deep question for me. A tree diagram can be seen as a classification based on resemblance, or a classification based on causal processes that generate lineages. "Lineage" is a term used to denote any ancestor-descendent chain. Now it isn't the case that blogs spawn other blogs, and in culture generally a lot of the problem of historical influence lies in determining what actually gave rise to what (for instance, in meme theory). So is the fact that PZ Myers (or whatever the spelling is) outed my initial blog a causal process? Not really. I've been an opinionated sumbitch for years, and I didn't need Paul to encourage me to share my "insights". A general lull in background noise is enough for me to do this.

So is a cladogram/phylogram sufficient to classify these relationships, or should we use a network rather than a tree? It's a tough question.

But it seems the same problem is to be found in actual biology, too, what with Lateral Genetic Transfer, endosymbiosis, and other "phylogenetic signal" obscuring processes being discovered and taken into account. Was Darwin's metaphor of a tree a good idea? Or should we have stuck with his "coral" metaphor, which lacked the structure of a tree, with its always-articulating and never-reticulating branches? [I love the fact that a net is reticulus and the gladiators who used nets were reticulari. The classical allusions of biology are great fun.]

In cultural evolution, we expect, or so many say, that there will be lots of horizontal transfer. It is a key disanalogy between biology and culture. And yet, when it comes down to it, most of the time we chart influences, traditions, schools, languages, and the like as, you guessed, tree diagrams. It may be simply that evolutionary processes make trees over time, but I think it more likely that we can "see" trees through time unless there is too much confusion of the signal. So I think that when two traditions merge or share their "memetic" material too greatly, we simply lose sight of them. Otherwise, we can differentiate them from each other, and "see" a tree.

Phylogenetic signals, are, in other words, the retention of sufficient history for us to see what happened in the past. And this allows us to use tree diagrams to represent that history...

A Sunday musing.