Simulating Coastal Migration in New World Colonization

Todd Surovell modeled coastal migrations along the Pacific Coast to try and solve a perplexing problem. Paleo-Indians were in inland South America at Monte Verde 1000-2000 years before the Clovis culture was established in continental North America. There are possible pre-Clovis sites in eastern North America, however these sites aren't fully established and wasn't the topic of Todd's paper. The Monte Verde II problem is that there isn't any pre-Clovis sites on the Pacific Coast of North America. Obvioulsy paleo-Indians would have had to sail down the coast of North America in order to reach South America. But scant archaeological evidence has been found in North America to support this. Todd used a mathematical model to simulate coastal migration to see if it would be feasible for paleo-Indians to make it down to inland South America before venturing inland in North America. The model consisted of five parameters: cell width (there are 77 of them arranged linearly 200km long each), maximum population growth rate, leapfrog distance, and two functions relating population density to return rates for coastal and inland ecosystems. No migration could occur until optimal return rates were reached and a subpopulation would then move down the coast. The migrants would stay on the coast only if the return rates on the coast were higher than if they moved inland. Todd's conclusion from the model was that a coastal migration theory could not explain the spatio-temporal discrepancy between Monte Verde and early North American sites. In order for the model to predict what is seen in the archaeological record 7 criteria must be met: Initial migration must be coastal as opposed to the ice-free corridor, inland return rates were unrealistically low in inland North America, only in South America were inland return rates higher than on the coast, the optimal population densities were excessively low, people were highly mobile and leapfrog rates were massive, population growth was very slow, and the occupation of coastal lands extended considerably inland without leaving an archaeological trace (in North America). The model predicts paleo-Indians moving inland in North America long before South America is reached. And yet there isn't any archaeological traces of this before Monte Verde. A lot of this subject is beyond the scope of what I want to talk about. I have some problems with the model he used 9it isn't his model by the way). It is a linear model and I think a nonlinear model would be more accurate. I can't say off hand what the nonlinear terms would be but it would have something to do with when humans would move. I disagree that humans would only have moved because return rates reached an optimal point. Humans are unpredictable and tying them down to what resources they have access to is an inadequate assumption for this model. I offer criticism yet no solution beyond some weak assertions. But this problem jumped out at me when I first read the atricle. It's a good article all the same and it tries to make sense of a thorny issue between the coastal migration theorists and the Clovis ice-free corridor theorists.

Surovell T. Simulating Coastal Migration in New World Colonization. Current Anthropology. 2003. Vol 44, no 4, (580-591).