Built in maps

Bill Idsardi sent me this piece on bird navigation. It seems that Swainson thrushes have genetically built in maps that get them from Canada to Mexico and parts of south and central America. Moreover, it appears that these maps come in two flavors, some taking a coastal route and others taking a more medial one. As the author puts it, these routes can overlap and when they do (well let me quote here) "they have a chance to (ahem) mingle." Mingling has consequences and these consequences can apparently end up with mixed maps. As the researchers put it: "it is believed birds have genetic instructions on which direction they need to head and how long they need to fly," though, as conceded "it’s still a mystery how, exactly, a bird’s DNA tells it where to go."

This is interesting stuff (the area of study is called "vector navigation"). I bring it to your attention here for the obvious reason: whatever is genetically coded is very fancy: maps and routes. And despite the fact that the scientists have no idea how it is so coded does not stop them from concluding that it is so coded.  

This is quite different from the attitudes in the the study of humans, as you all know. Chomsky has pointed repeatedly to the methodological dualism that pops out whenever human mental capacities are studied. Were thrushes humans the usual critics would be all over themselves arguing that postulating such inborn mechanisms is methodologically ill advised (and not at all explanatory), that DNA could not possibly code for maps and routes, and that there must be some very subtle learning mechanism lying behind the attested capacities (almost certainly using some Bayesian  learning procedure while still in the egg!). In other words, standard scientific practice would have been suspended were thrushes humans.  You draw the relevant moral.