Yeah, Alon briefly mentions that line of study as well, although he doesn’t discuss it much. Personally, I think connection costs are less likely to be the main driver of biological modularity in general, for two main reasons:
If connection costs were a taut constraint, then we’d expect to see connection costs taking up a large fraction of the organism’s resources. I don’t think that’s true for most organisms most of the time (though the human brain is arguably an exception). And qualitatively, if we look at the cost of e.g. signalling molecules in a bacteria, they’re just not that expensive—mainly because they don’t need very high copy number.
Connection costs are not a robust way to produce modularity—we need a delicate balance between cost and benefit, so that neither overwhelms the other. Given how universal modularity is in biology, across so many levels of organization and basically all known organisms, it seems like a less delicate mechanism is needed to explain it.
I do find it plausible that connection cost is a major driver in some specific systems—in particular, the sanity checks pass for the human brain. But I doubt that it’s the main cause of modularity across so many different systems in biology.
Yeah, Alon briefly mentions that line of study as well, although he doesn’t discuss it much. Personally, I think connection costs are less likely to be the main driver of biological modularity in general, for two main reasons:
If connection costs were a taut constraint, then we’d expect to see connection costs taking up a large fraction of the organism’s resources. I don’t think that’s true for most organisms most of the time (though the human brain is arguably an exception). And qualitatively, if we look at the cost of e.g. signalling molecules in a bacteria, they’re just not that expensive—mainly because they don’t need very high copy number.
Connection costs are not a robust way to produce modularity—we need a delicate balance between cost and benefit, so that neither overwhelms the other. Given how universal modularity is in biology, across so many levels of organization and basically all known organisms, it seems like a less delicate mechanism is needed to explain it.
I do find it plausible that connection cost is a major driver in some specific systems—in particular, the sanity checks pass for the human brain. But I doubt that it’s the main cause of modularity across so many different systems in biology.