Note. If you’ve been to this page before, I’ve now (pm 5 december) edited the figures. Many thanks Larry.

 

I’ve just been reading E.A. Wrigley‘s Energy and the English Industrial Revolution which I highly recommend if you are interested in the transformation wrought by fossil fuels.

In passing, he gives these figures for the labor involved in growing maize in Mexico ca 1940. A hectare is roughly the area inside an athletic track.

Cultivating a hectare of maize by hand.   1,140 man hours

Cultivating a hectare of maize with an ox. 380 man hours (plus 200 ox hours)

His figures come from Cornell entomologist turned agricultural economist, David Pimentel “Energy Flow in the Food System,” in Pimental and C.W. Hall, eds.,  Food and Energy Resources (London, 1984).

They reminded me that I have always been frustrated that the “food system” so often ignores what happens after the harvest.  So here’s my effort to get an order of magnitude figure of the relative work expended by men and women in putting tortillas on the table prior to oxen, mules, tractors and mills.

In 1970, maize yield per hectare was 1,194 kg ( INEGI, 1999 cited in “El maíz en México,” by Massieu Trigo and Lechuga Montenegro).  Assume that you needed 1 kg of maize per adult per day when it was providing 65% of the calories, allowing for seed corn and wastage in storage.  Assume a family of two adults and four others, say three children and an old person (probably low), with the four others needing 1/2 kg of maize a day.  Multiplying 4 kg by 365 days and dividing by 1,194 you find that a plot of 1.2 hectares was needed.  And that means 1,368 man hours to grow maize for the family.

Now what about turning all that maize into sometime you could put in your mouth.  Assume that it took about 5 hours a day to grind the maize for a family of six.  Add in time to collect firewood, de-grain the maize, haul the water to nixtamalize it, and shape and cook the tortillas.  Say another hour a day for this (a low estimate I think).

That means 2190 woman hours to turn maize into tortillas for the family.

That is to say, processing maize took more time than growing it even prior to animal power. Once the man had the help of an ox or a mule, the woman spent four to five times as much time processing and cooking as the man spent farming.

Given what hard work grinding is, I would guess the woman spent at least four times as much energy processing and cooking as the man spent farming.

These are just back of the envelope calculations. Does anyone have any corrections or modifications to make?  Or any pointers to studies on the  relative energy involved in farming versus processing and cooking?

 

 

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