THE EVOLUTION OF MILK
THE RISE OF THE RUMINANTS
All mammals produce milk for their young, but only a closely related handful have been exploited by humans. Cattle, water buffalo, sheep, goats, camels, yaks: these suppliers of plenty were created by a scarcity of food. Around 30 million years ago, the earth’s warm, moist climate became seasonally arid. This shift favored plants that could grow quickly and produce seeds to survive the dry period, and caused a great expansion of grasslands, which in the dry seasons became a sea of desiccated, fibrous stalks and leaves. So began the gradual decline of the horses and the expansion of the deer family, the ruminants, which evolved the ability to survive on dry grass. Cattle, sheep, goats, and their relatives are all ruminants.
The key to the rise of the ruminants is their highly specialized, multichamber stomach, which accounts for a fifth of their body weight and houses trillions of fiber-digesting microbes, most of them in the first chamber, or rumen. Their unique plumbing, together with the habit of regurgitating and rechewing partly digested food, allows ruminants to extract nourishment from high-fiber, poor-quality plant material. Ruminants produce milk copiously on feed that is otherwise useless to humans and that can be stockpiled as straw or silage. Without them there would be no dairying.
DAIRY ANIMALS OF THE WORLD
Only a small handful of animal species contributes significantly to the world’s milk supply.
The Cow, European and Indian
The immediate ancestor of Bos taurus, the common dairy cow, was Bos primigenius, the long-horned wild aurochs. This massive animal, standing 6 ft/180 cm at the shoulder and with horns 6.5 in/17 cm in diameter, roamed Asia, Europe, and North Africa in the form of two overlapping races: a humpless European-African form, and a humped central Asian form, the zebu. The European race was domesticated in the Middle East around 8000 BCE, the heat- and parasite-tolerant zebu in south-central Asia around the same time, and an African variant of the European race in the Sahara, probably somewhat later.
In its principal homeland, central and south India, the zebu has been valued as much for its muscle power as its milk, and remains rangy and long-horned. The European dairy cow has been highly selected for milk production at least since 3000 BCE, when confinement to stalls in urban Mesopotamia and poor winter feed led to a reduction in body and horn size. To this day, the prized dairy breeds — Jerseys, Guernseys, Brown Swiss, Holsteins — are short-horned cattle that put their energy into making milk rather than muscle and bone. The modern zebu is not as copious a producer as the European breeds, but its milk is 25% richer in butterfat.
The Buffalo
The water buffalo is relatively unfamiliar in the West but the most important bovine in tropical Asia. Bubalus bubalis was domesticated as a draft animal in Mesopotamia around 3000 BCE, then taken to the Indus civilizations of present-day Pakistan, and eventually through India and China. This tropical animal is sensitive to heat (it wallows in water to cool down), so it proved adaptable to milder climates. The Arabs brought buffalo to the Middle East around 700 CE, and in the Middle Ages they were introduced throughout Europe. The most notable vestige of that introduction is a population approaching 100,000 in the Campagna region south of Rome, which supplies the milk for true mozzarella cheese, mozzarella di bufala. Buffalo milk is much richer than cow’s milk, so mozzarella and Indian milk dishes are very different when the traditional buffalo milk is replaced with cow’s milk.
The Yak
The third important dairy bovine is the yak, Bos grunniens. This long-haired, bushy-tailed cousin of the common cow is beautifully adapted to the thin, cold, dry air and sparse vegetation of the Tibetan plateau and mountains of central Asia. It was domesticated around the same time as lowland cattle. Yak milk is substantially richer in fat and protein than cow milk. Tibetans in particular make elaborate use of yak butter and various fermented products.
The Goat
The goat and sheep belong to the “ovicaprid” branch of the ruminant family, smaller animals that are especially at home in mountainous country. The goat, Capra hircus, comes from a denizen of the mountains and semidesert regions of central Asia, and was probably the first animal after the dog to be domesticated, between 8000 and 9000 BCE in present-day Iran and Iraq. It is the hardiest of the Eurasian dairy animals, and will browse just about any sort of vegetation, including woody scrub. Its omnivorous nature, small size, and good yield of distinctively flavored milk—the highest of any dairy animal for its body weight—have made it a versatile milk and meat animal in marginal agricultural areas.
The Sheep
The sheep, Ovis aries, was domesticated in the same region and period as its close cousin the goat, and came to be valued and bred for meat, milk, wool, and fat. Sheep were originally grazers on grassy foothills and are somewhat more fastidious than goats, but less so than cattle. Sheep’s milk is as rich as the buffalo’s in fat, and even richer in protein; it has long been valued in the Eastern Mediterranean for making yogurt and feta cheese, and elsewhere in Europe for such cheeses as Roquefort and pecorino.
The Camel
The camel family is fairly far removed from both the bovids and ovicaprids, and may have developed the habit of rumination independently during its early evolution in North America. Camels are well adapted to arid climates, and were domesticated around 2500 BCE in central Asia, primarily as pack animals. Their milk, which is roughly comparable to cow’s milk, is collected in many countries, and in northeast Africa is a staple food.
THE ORIGINS OF DAIRYING
When and why did humans extend our biological heritage as milk drinkers to the cultural practice of drinking the milk of other animals? Archaeological evidence suggests that sheep and goats were domesticated in the grasslands and open forest of present-day Iran and Iraq between 8000 and 9000 BCE, a thousand years before the far larger, fiercer cattle. At first these animals would have been kept for meat and skins, but the discovery of milking was a significant advance. Dairy animals could produce the nutritional equivalent of a slaughtered meat animal or more each year for several years, and in manageable daily increments. Dairying is the most efficient means of obtaining nourishment from uncultivated land, and may have been especially important as farming communities spread outward from Southwest Asia.
Small ruminants and then cattle were almost surely first milked into containers fashioned from skins or animal stomachs. The earliest hard evidence of dairying to date consists of clay sieves, which have been found in the settlements of the earliest northern European farmers, from around 5000 BCE. Rock drawings of milking scenes were made a thousand years later in the Sahara, and what appear to be the remains of cheese have been found in Egyptian tombs of 2300 BCE.
DIVERSE TRADITIONS
Early shepherds would have discovered the major transformations of milk in their first containers. When milk is left to stand, fat-enriched cream naturally forms at the top, and if agitated, the cream becomes butter. The remaining milk naturally turns acid and curdles into thick yogurt, which draining separates into solid curd and liquid whey. Salting the fresh curd produces a simple, long-keeping cheese. As dairyers became more adept and harvested greater quantities of milk, they found new ways to concentrate and preserve its nourishment, and developed distinctive dairy products in the different climatic regions of the Old World.
In arid southwest Asia, goat and sheep milk was lightly fermented into yogurt that could be kept for several days, sun-dried, or kept under oil; or curdled into cheese that could be eaten fresh or preserved by drying or brining. Lacking the settled life that makes it possible to brew beer from grain or wine from grapes, the nomadic Tartars even fermented mare’s milk into lightly alcoholic koumiss, which Marco Polo described as having “the qualities and flavor of white wine.” In the high country of Mongolia and Tibet, cow, camel, and yak milk was churned to butter for use as a high-energy staple food. In semitropical India, most zebu and buffalo milk was allowed to sour overnight into a yogurt, then churned to yield buttermilk and butter, which when clarified into ghee would keep for months. Some milk was repeatedly boiled to keep it sweet, and then preserved not with salt, but by the combination of sugar and long, dehydrating cooking.
The Mediterranean world of Greece and Rome used economical olive oil rather than butter, but esteemed cheese. The Roman Pliny praised cheeses from distant provinces that are now parts of France and Switzerland. And indeed cheese making reached its zenith in continental and northern Europe, thanks to abundant pastureland ideal for cattle, and a temperate climate that allowed long, gradual fermentations.
The one major region of the Old World not to embrace dairying was China, perhaps because Chinese agriculture began where the natural vegetation runs to often toxic relatives of wormwood and epazote rather than ruminant-friendly grasses. Even so, frequent contact with central Asian nomads introduced a variety of dairy products to China, whose elite long enjoyed yogurt, koumiss, butter, acid-set curds, and around 1300 and thanks to the Mongols, even milk in their tea!
Dairying was unknown in the New World. On his second voyage in 1493, Columbus brought sheep, goats, and the first of the Spanish longhorn cattle that would proliferate in Mexico and Texas.
Milk in Europe and America: From Farmhouse to Factory
Preindustrial Europe
In Europe, dairying took hold on land that supported abundant pasturage but was less suited to the cultivation of wheat and other grains: wet Dutch lowlands, the heavy soils of western France and its high, rocky central massif, the cool, moist British Isles and Scandinavia, alpine valleys in Switzerland and Austria. With time, livestock were selected for the climate and needs of different regions, and diversified into hundreds of distinctive local breeds (the rugged Brown Swiss cow for cheese-making in the mountains, the diminutive Jersey and Guernsey for making butter in the Channel Islands). Summer milk was preserved in equally distinctive local cheeses. By medieval times, fame had come to French Roquefort and Brie, Swiss Appenzeller, and Italian Parmesan. In the Renaissance, the Low Countries were renowned for their butter and exported their productive Friesian cattle throughout Europe.
Until industrial times, dairying was done on the farm, and in many countries mainly by women, who milked the animals in early morning and after noon and then worked for hours to churn butter or make cheese. Country people could enjoy good fresh milk, but in the cities, with confined cattle fed inadequately on spent brewers’ grain, most people saw only watered-down, adulterated, contaminated milk hauled in open containers through the streets. Tainted milk was a major cause of child mortality in early Victorian times.
Industrial and Scientific Innovations
Beginning around 1830, industrialization transformed European and American dairying. The railroads made it possible to get fresh country milk to the cities, where rising urban populations and incomes fueled demand, and new laws regulated milk quality. Steam-powered farm machinery meant that cattle could be bred and raised for milk production alone, not for a compromise between milk and hauling, so milk production boomed, and more than ever was drunk fresh. With the invention of machines for milking, cream separation, and churning, dairying gradually moved out the hands of milkmaids and off the farms, which increasingly supplied milk to factories for mass production of cream, butter, and cheese.
From the end of the 19th century, chemical and biological innovations have helped make dairy products at once more hygienic, more predictable, and more uniform. The great French chemist Louis Pasteur inspired two fundamental changes in dairy practice: pasteurization, the pathogen-killing heat treatment that bears his name; and the use of standard, purified microbial cultures to make cheeses and other fermented foods. Most traditional cattle breeds have been abandoned in favor of high-yielding black-and-white Friesian (Holstein) cows, which now account for 90% of all American dairy cattle and 85% of British. The cows are farmed in ever larger herds and fed an optimized diet that seldom includes fresh pasturage, so most modern milk lacks the color, flavor, and seasonal variation of preindustrial milk.
Dairy Products Today
Today dairying is split into several big businesses with nothing of the dairymaid left about them. Butter and cheese, once prized, delicate concentrates of milk’s goodness, have become inexpensive, mass-produced, uninspiring commodities piling up in government warehouses. Manufacturers now remove much of what makes milk, cheese, ice cream, and butter distinctive and pleasurable: they remove milk fat, which suddenly became undesirable when medical scientists found that saturated milk fat tends to raise blood cholesterol levels and can contribute to heart disease. Happily the last few years have brought a correction in the view of saturated fat, a reaction to the juggernaut of mass production, and a resurgent interest in full-flavored dairy products crafted on a small scale from traditional breeds that graze seasonally on green pastures.
By Harold McGee in "On Food and Cooking", Scribner, New York, 2004, excerpts p. 8-12. Adapted and illustrated to be posted by Leopoldo Costa.
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