First off, I was wrong when I mentioned that the (apparent) lack of marine resource remains was not that big of a deal, if they were just going to get medicinal seaweed. They write:
Here we report the recovery of three marine, two estuarine, and one terrestrial shoreline algae species new to the site and three additional stone artifacts, one with the remains of seaweed on a worked edge, that suggest a strong reliance on coastal resources for food and medicine.
So we'll have to see what sort of comestibles they were getting.
And we see what else they had apprarently been getting:
Other coastal resources collected from beaches and transported to the site were discoidal pebbles made into stone tools, bitumen used as adhesive to attach tools to wooden shafts, and marine fossils.
The stuff they analyze came from the hearths and floors of two structures, one of which they describe as a "medicinal hut" and a residential tent. Looks as if the medicinal hut interpretation comes from the remains themselves. They interpret the medicinal nature of the seaweeds and algae because they were found in the form of chewed cuds, but some were also found scattered in the hearth structure and may have been food as well. These sorts of things have been found before; chewed coca leaves, agave, etc.
What sort of medicinal uses?
All nine seaweed species recovered at Monte Verde II are excellent sources of iodine, iron, zinc, protein, hormones, and a wide range of trace elements, particularly cobalt, copper, boron, and manganese (23–29). Secondary beneficial effects of these seaweeds include aiding cholesterol metabolism, increasing the calcium uptake of bones, antibiotic effects, and increasing the body's ability to fight infection. These species have medicinal uses that closely correspond to common contemporary health problems in the study area today.
The latter two seem about the only two that might have been recognized by the inhabitants for more or less immediate beneficial effects. Two of the seaweeds were also inedible, thus their interpretation as medicinal only.
They conclude by offering the following general subsistence strategy:
. . .these new data indicate that the people inhabiting Monte Verde II were accustomed to frequently exploiting coastal resources year round, which, coupled with interior foods, allowed them to remain in the area. Prior evidence suggests that the Monte Verdeans also regularly moved up and down the Maullín basin to exploit resources and/or to exchange them with other people living in the area. Assuming that other late Pleistocene people operated under similar subsistence and settlement practices, our data imply that if groups traveled along the Pacific coast, they may have migrated slowly and exploited the interior resources of the hundreds of river basins descending the long mountain chain from Alaska to Tierra del Fuego to the sea. Several recent archaeological findings support the idea of early coastal migration and specialized maritime sites, but this evidence also indicates contacts with interior people or transhumance between coastal and interior areas and thus broad-spectrum economies.
I guess I'm still not bothered by the lack of extensive coastal food resources. They seem to have had an extensive terrestrial subsistence base anyway, so exploiting marine resources doesn't seem to have been either necessary or efficient, especially if you have to travel 90 km just to get some chow. Obtaining a few easily curated resources -- some seaweed, rocks, bitumen -- doesn't strike me as that out of bounds.
As for the migration aspect. . . .I think it's way too early to say much of anything about how people moved. The paucity of dated sites makes such interpretations really dubious, though admittedly they realize (as does everyone else at this point) that it's all informed speculation. We still have no idea when and in what numbers people moved into the Americas.