Archeological Biomechanics

Union is opening a new Center for Bioengineering and Computational Biology this week, and the keynote speech was given last night by Steven Vogel of Duke, on "Power from the People: Life When Muscle Was Our Main Motor." Basically, this was an hour-long survey of some speculative ideas on what biomechanics can tell us about the ancient world.

Sadly, a quick Google search doesn't turn up anything coherent about this on the web, because it was a fun talk. Vogel started with the observation that to a good approximation, humans are all the same size and shape, and can exert about the same amount of force, and then considered how those limits influence what can be done using nothing but human muscle power.

Starting from that really simple beginning, he offered a lot of speculations about how various odd facts might be explained by biomechanics. He started with Neanderthals being replaced by modern humans, and worked up through the construction of the Pyramids, the size and shape of Mediterranean galleys, and the working of ancient artillery.

On the Neanderthal question, he noted that Neanderthals disappeared around the time that projectile weapons were introduced, and speculated that this might be due to the fact that modern humans are better suited to throwing spears than Neanderthals were. We have longer, lighter arms, which allow higher launch velocities, and logner throwing ranges. Neanderthals could compete and coexist with modern humans, he speculated, as long as both groups were using stabbing spears, but couldn't compete when throwing spears started to come in.

With the Pyramids, he suggested that the size of the blocks used for construction was determined by the maximum size that could conveniently be shifted in the quarries, and offered some simple calculations to support this. He argued that the rate limiting step in the production of blocks was the process of squaring and shaping them with bronze chisels and rudimentary rock saws, and thus the builders would be best served by using a smaller number of larger blocks, because the surface area is smaller.

In discussing galleys, he noted the odd fact that smallish boats seemed to be the norm, even though we know that longer boats are, in principle, faster than smaller ones. He argued that while this is true for modern boats with mechanical propulsion, boats that are rowed by human crews get slightly slower as they get longer, as the drag increases faster than you can add rowers.

The thing he was most fired up about was probably the ancient artillery. He discussed a couple of different types of trebuchet, but the main focus was on the ballista. Based on the mass of projectiles recovered from the site of Carthage, and information about the firing range, you can determine the amount of energy stored in the elastic ropes used, and how much work would be required to load it. Based on that, he estimates that the maximum firing rate would be something like one shot every seven minutes, for a two-man crew working all out.

This sort of points out the major flaw in the talk, though, which is that he didn't provide any information about actual firing rates of these devices. It's a fun plausibility argument for the firing rate, but there wasn't any data to compare it to. The same was true of most of the other lines of reasoning-- he didn't explain just how much of a difference arm structure would make for modern humans vs. Neanderthals, for example, or provide any real comparison between his models of how the Pyramid builders moved rocks around and actual archeological data. Everything remained very speculative, but it was still fun to see what you could do with a few scaling laws and simple approximations.

(This was a very physics-y approach to archeology, so it's no surprise that it appealed to me...)

I'd be interested to hear from some of our resident experts about what's actually known about these cases. As it was, I can't really evaluate whether he's right about any of this stuff, but it was a fun and interesting discussion of ancient technology.