1493 (Book)

This book is a sequel of sorts to Charles Mann’s 1491, but it’s on much firmer ground.  Mann is interested in discovering the roots of the global economy by following the transmission of New World products worldwide — silver, rubber, bat guano.  He has some fascinating letters from Spanish explorers trying to describe a game played by Aztecs with rubber balls without having a word for bounce.  And he speculates that the transmission of bat guano (used for fertilizer) from an uninhabited island off the Chilean coast in the same ships as potato plants may have played a role in the Irish potato famine.

The most interesting chapter, though, was the essay on malaria, which was brought to the New World by English settlers.  We think of malaria as a tropical disease, but all it needs is a malaria plasmodium variety and some anopheles mosquitos.  The fens (marshes) of East Anglia happened to house a particularly hardy variety of malaria (P. vivax) as well as the appropriate mosquitoes, and malaria was endemic to the region for centuries.  (Some historians now believe that Richard the Lionheart’s “tertian fever,” which he suffered from long before he went on Crusade, was actually malaria.)

The Elizabethans realized there was a connection between marshland and malaria, although they didn’t understand the role mosquitoes played in the transmission of the disease.  Attempts to drain the marshes in the late 16th C were incomplete, and in fact made things worse.   (It wasn’t until the 19th C that more modern drainage techniques finally ended this ancient scourge.)

Not surprisingly, in the 17th C, many folks living in East Anglia decided to emigrate to the new American colonies.  Many carried P. vivax with them (in their bloodstreams) to Virginia where, as (bad) luck would have it, there was an unemployed colony of Anopheles mosquitoes.   The colonists kept dying from malaria at frightening rates.  Native Americans were also very susceptible to the new disease.

African slaves,however, were not.  It’s well known that many Africans carry a gene for sickle cell anemia, which offers protection against many forms of malaria.  But it was recently discovered that a second genetic mutation, common in West Africans, made them almost completely immune to the “English” malaria.

Mann suggests that this differential malaria death rate might have had a role in the growth of slavery in the American colonies.  White indentured servants died at much higher rates than black slaves did.  Interestingly, the habitat of the Anopheles mosquito tracks pretty closely to what was later called the Mason-Dixon line.

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