To die of hunger is the bitterest of fates. ~ Homer, in the Odyssey
The climate turned cold in North Africa and the Fertile Crescent 12,800 years ago. Forests and woodlands dwindled. Small stands of wild grasses and other seed foods became an increasingly valuable food source.
Drier weather drove people to better-watered locations. Increased population density focused efforts on bettering food production.
Early agriculture was a survival strategy. Plant and animal domestication for food began in response to bitter climatic elements that would eventually relent. Crop cultivation was a response to overexploitation of local resources by a growing population.
Agriculture engendered settled communities. This undoubtedly intensified conflict between neighboring tribes for the best land and water rights. Disputes were especially acute when harvests were paltry.
Food has long been a check on population growth, and a spur to diaspora. The oomycete that caused potato blight in Ireland in the late 1840s traveled by ship from America. The resulting famine sparked an Irish diaspora, which sent many back to the fungus’ source.
Early scholars documented farming techniques during the days of the ancient Greeks and Romans. Much of what was believed about soil and nutrition was incorrect, but it provided the foundation for farming during the medieval period. As these ideas remained much the same from Greco-Roman times until the 19th century, crop yields stayed low.
There were many incremental improvements to food production in the Middle Ages. The heavy plow was invented in the 6th century; an innovation which spread across Europe over the course of the next 4 centuries.
The benefit of such metal implements was alloyed. Using iron plows polluted the soil, and the food that was harvested using such tools. Heavy metal pollution in the South China Sea from inland farming was significant as early as 4,000 years ago.
Monasteries in medieval Europe acted as agricultural knowledge centers. Nonetheless, growing populations were fed only by increasing the acreage of land under cultivation. Continuous cultivation of the same area lowered soil fertility.
Despite mechanical improvements, the pressure of population spelled soil overexploitation, and established a vicious cycle. Soil fertility in arable fields could only be maintained via animal manures, but the supply of livestock was limited by lack of fodder crops. Animals had to be slaughtered in the autumn because of an acute shortage of winter feed. As livestock population declined, so too fertilizer supply, and with it crop yields.
For almost everyone, food meant vegetables. Meat was rare except for the upper class. China was no different than Europe on this account. Only near rivers or on the coast was fish ever on the menu; and then, even by the 16th century, signs of overfishing were apparent.
Grain to feed livestock was scarce. Where animals were kept, their output was low. A medieval cow produced less than 20% of the milk and 25% of the meat of a modern one.
Exchanges between Christians and Muslims in medieval times were fruitful, both in new crops and farming techniques. Arabs introduced the Europeans to the benefits of slave labor for intensive cultivation on plantations: a model carried forward to the New World that afforded white American prosperity, especially in the Old South.
Malnutrition meant that mortality remained high. In the late 17th century, over 20% of French infants died before their 1st birthday, half before they were 20, and only 10% survived to the age of 60. In the 2,000 years before the 20th century, there were famines in China every year in at least 1 province. Until around 2 centuries ago, in every part of the world, nearly everyone lived on the edge of starvation.