[permaculture] Major histocompatibility complex (MHC)

Marimike6 at cs.com Marimike6 at cs.com
Wed Mar 12 09:34:36 EST 2003

Dear Anne--

I think the main thing to keep in mind is that people not only inherit MHC 
characteristics, they develop them by exposure to pathogenic organisms, 
toxins, environmental irritants, etc.  A breast-fed baby has a double dose, 
having not only the MHC inherent in his genetic structure but that given to 
him in his mother's milk-- particularly the colostrum.

The thing about Amazonian Indians is that at the time of Columbus, neither 
they nor any of their ancestors had ever been exposed to any pathogens or 
allergens other than those of Amazonia. This makes theirs a very small MHC 
zone. By contrast, a Peace Corps volunteer, foreign correspondent or any 
world traveller has been exposed to a range of irritants from the entire 
world. Every time you walk through an airport you join the members of the 
worldwide MHC zone, frequently coming back with a new form of the flu as a 
memento of your journey.

A number of years ago visitors to odd corners of the world, like backpackers 
in rural Ladakh or Bolivia, used to have to take care as they could so easily 
infect unexposed populations to things like the measles or our common cold, 
which could be fatal to a population with no endemic resistance. It works the 
other way as well. Go to the back end of Gabon and you may very well come 
back with a fierce case of the trots, dengue or Lassa fever, to which you had 
not previously been exposed and were thus much more vulnerable than the local 

In the global village though, the most hardy weeds that have established 
themselves all over the world tend to be those that come from the Eurasian 
landmass. Being widespread in their total range, they already have very 
strong resistance to most pathogens, and can outcompete other species. The 
white man is a good example of such a hardy weed. Purple loosestrife is 
another. Local populations tend to be shoved aside when encroached upon by 
these aggressive invaders.

Mike Elvin
Fuquay-Varina, NC
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