Projects like menstrual cycles

A friend recently made the observation that no matter how many projects we have running concurrently in our development center they all seem to slide into lock-step and arrive at phases and milestones simultaneously. The analogy she used was that this seemed similar to the way that menstrual cycles of women in close quarters tend to synchronize over time. I find a lot of truth in this and don’t exactly know how to explain it. The extremes don’t seem to apply — if you are in the design phase of one project and launching another you’re obviously too far apart — but projects with only a few months offset do seem to synchronize, somehow. This is most noticeable when you realize that an entire entire category of skilled resource is busy simultaneously. (How come all the information architects are swamped all of the sudden?)

Why does this happen? Could be coincidence, but what if it a kind of macroscopic inability of an organization to truly multi-task? That is, what if there is some underlying tendency which drives teams working in close proximity to maximize productivity by shifting timelines slightly so that they are all in the same phase of a project at once? One benefit would be a kind of lateral development support. (Need help solving this particular design problem? Look at the team next door.) Other than that, though, it seems to me to be a trend fraught with downside: vertical resource shortages, projects completing at the same time (putting large numbers of people on the bench, potentially), and organization-wide single points of failure (if something should happen to prevent some step of the project methodology from being able to proceed.)

Maybe it has to do with pheromones. Thoughts?