APR 24

24. APR 24

Assigned Work

• Montgomery, David. Chapter 2: "Skin of the Earth" Dirt(pp. 9-25); (16)
• Montgomery, David. Chapter 3: "Rivers of Life" (pp. 27-47) (20)

Montgomery, David. Chapter 2, "Skin of the Earth"

• Darwin's studies of worms. Worms are moving a heck of a lot of dirt. 10-20 tons per acre per year. digestive juices.
• Note the recentness of our lack of knowledge of this. Also why antiquities sink.
• Darwin's calculations were off: underestimated the time scale for effects. Didn't know about isostasy - a process which lifts rock as well. But did understand soil formation as breakdown of minerals.
• 15: overview of soil ecology relationships. read. even theories that soil formation was involved in first forms of organismic life.
• guanine and cytosine in clay-rich solutions.
• 15-16: overview of plant colonization of cooling earth (350 mya). earth plant life accelerated soil formation. lots of other physical and chemical processes (17). Gophers, roots, termites, ants….
• nitrogen fixation (18): note mechanism. "nitrogen fixing plant" a misnomer.

• effects of agriculture:

• tilling releases nutrients, but also disrupts soil life, short-rotation farming reduces soil diversity, increases vulnerability to parasites,

• p. 20: Connection bt farming methods and soil erosion and soil health.

• Note how starting your account of food (vs. “Agriculture as Human Innovation”) from soil gives you deeper sense of your trophic relationships.

• You are what you eat. You are what you eat eats.

Montgomery, Dirt, Chapter 3, "Rivers of Life"

• connection between humanity and soil in language: adama (earth) hava (living). We are living earth. In Latin "homo" from "humus", living soil.

• suggest myth of the garden represents transition to agriculture, climate change.

• Long history

• 20,000 years ago - last major glaciation (though not a single event). Europe freezes, Africa dries.
• 2 million years ago - earliest evidence of migration of homo erectus from Africa. separation from Neanderthal (note some evidence that we ate 'em [1]),
• 300,000 year ago - first modern humans.
• 45,000 years ago - another wave of migration from Africa (movement occurred in both directions).
• 30,000 years ago - sharp stone tools (much later than the handaxe .5 mya) and at 23,000 yrs bows and arrows
• Human Evolution Timeline

• modifications in skin color and other features a response to UV radiation and Vitamin D production, selection effect.

• Emergence of agriculture

• oasis and cultural evolution theories.

• oasis theory - post glacial drying in Middle East restricted food sources to wetter flood plains.
• cultural evo thesis - agricultural innovation independent of environmental change.

• problem with oasis theory - food variety in mid-east expanding at time of agriculture, esp from N. Africa - seeds.
• problem with cultural evolution theory -- not everyone adopted ag (though in other examples, like hand axes, everyone does adopt).

• 3rd possibility: increasing population density -- agriculture a forced option. Note climate of the Levant 13 - 11,000bc - major food abundance. could have supported population explosion.

• mini-glaciation at 10,000 bc called the Younger Dryas -- recovered pollen samples drop by 3/4 -- decrease precip. forests recede.

• site evidence from Abu Hureyra, on Tigris -- evidence of cultivation of grains, drought tolerant ones (drought sensitive ones disappear from the record), for example.

• more work to produce a calorie at start of agriculture --(recall crucial calculation here). population grew to six thousand. evidence of settlements chosen for ag condition.

• note -- using evidence from burnt food remains, we can track the migration of food, independently of human migration.

• agriculture developed in several places, but we missed this because in some places it developed before settled towns. Mesoamerica, China.

• Spread of Agriculture

• spread through Levant and Turkey. Growth allowed defeat of nearby hunter/gatherers in contest for territory.

• The dog - 20k. The cat 4K. (Google “human evolution and dogs” for research on dog/human convolution.)

• Domesticated livestock a huge leap - animal labor, fertilizer, and stored food — on the hoof.

• after agriculture, population doubles every 1,000 years. 200 million by 0 CE. 2,000 years later 6.5 billion.

• Sumeria / Mesopatamia

• by 5,000 bc, evidence of overcultivation in Tigris valley, hillside erosion. emergence of irrigation. 37

• Also, early agricultural infrastructure and control by governing elites. Emergence of class, armies, fight for territory.

• very interesting: Mesopotamian religious elite controlled food production and distribution. (Later we'll see that Jewish authorities do the same in the Levant). More population growth.

• Uruk grows to 50,000. agriculture brings property, inequality, class, gov't administration, (philosophers). Writing 3,000 bc - (mention Field Museum in Chicago - a “must see”).

• back to the environment -- Babylonian Empire emerges from Sumerian cities around 1800bc. But irrigation led to salination of the soil, silting of rivers -- 39-40 evidence of lack of understanding of soil. Babylon falls! Pop peaks at 20 million. Temple records tell the story.

• Egypt

• story in Egypt - p. 40 on: short story, the Nile fed civilizations for 7,000 years in rough sustainability, ideal combination of new silt and humus (Blue Nile and While Nile). Harvests increase over time.
• But, desire to grow grain for export led to year round irrigation. 1880's salination extreme. Then Nasser damn. (Thinking about the logic of export crops for maximizing revenue. Very similar to situation of local over population leading to exploiting the soil.)
• Irony of Nasser dam producing electricity to make synthetic fertilizers that are now needed because of the dam and poor soil management. Read at 42.

• China

• story in China - interesting, administration of ag recognized many grades of soil. Yellow River (name from mineral erosion upstream) damned and diverted starting 340 bc. Process of raising levees around the river led to 30 foot levies by 1920s. 19th century floods killed millions. Also .5 million in early 20th century.

• story of Walter Lowdermilk -- 1922 - working on famine prevention. First to write about soil management and civilization. Follows major river up stream documenting 400 miles of levies and evidence of ancient mismanagement of early ag sites. Erosion from farming steep grades.

• thesis going forward: Civilizations are defined by their management of soil. And, everyone has messed it up eventually, even the Egyptians.