Computer modeling is big in population biology. The great thing about a model is that you can just relabel the parts and make it about something else. For example, we can
revise the "wave-of-advance" model so that it describes the uptake of advantageous technology through a population rather than describing the spread of advantageous genes through a population. The key is that
any trait that preexists alongside the advantageous one could be carried along with it, such as genetics or language, regardless of any intrinsic superiority.
In applying this "cultural hitchhiking" model to food production, the
authors found that the two traits can be decoupled wherever geographic "inhomogeneity" halts the spread of the carrier trait. Two such "inhomogeneities" are
the "subsistence boundary," land so poor that the wave of advance is halted, and the temporary "diffusion boundary" where the wave cannot move into poorer areas until its gradient becomes sufficiently large.
So, for example, indigenous people in poorer lands beyond a diffusion boundary can adopt technologies selectively, effectively erecting a cultural boundary.
If a model like this seems a little too ad hoc, perhaps a new version can be coupled with the counterfactual approach of
some economic historians. Counterfactual histories have their own problems--they tend to oversimplify systems or overestimate the importance of one or two components. Yet there is a time-honored method of learning to think deeply about complex systems: games. That's why my next grant application will include a game console.
History is a field with many challenges. It would be nice to be able to ask Darwin what he actually meant in paragraph two of page 236 of
Origin of the Species. But he's dead, so we can't. And even if we could, there's no telling whether we could trust his word (250 years is a rather long time to remember accurately). In that sense, it's actually helpful that the subjects of history are usually dead--dead people can't change their minds about what they've done. But often enough, they changed their minds during their lives. Put this together with our innate desire to connect events together in a linear (progressive) narrative, and we have quite the recipe for disagreement. Sometimes, there's very little archival material to go on, a fact with its own trade off. On one hand, it can be hard to tell how representative the extant materials are. On the other, there's less substance to disagree about. If somehow all of these difficulties are resolved, Deleuze offers a suggestion to keep us all in work: it is our job to determine what goes unsaid. I'll say no more on that.