The Neolithic period, often called the New Stone Age, marks a profound transition in human history defined by the shift from a nomadic hunter-gatherer existence to settled agriculture. This change, beginning approximately 12,000 years ago, was predicated on the human ability to control the reproduction and growth of both plants and animals. Animal domestication is a sustained, multi-generational, coevolutionary relationship where humans assume significant influence over the care and breeding of another species. The result is a population of animals genetically modified to provide a predictable supply of resources, leading to mutual benefits for both the human domesticator and the animal domesticate.
The Process of Domestication
The process of domestication is a population-level phenomenon distinct from merely taming an individual wild animal. Taming is a behavioral modification where an animal is conditioned to tolerate the presence of humans but retains its wild genetics. Domestication, conversely, is a permanent genetic change across a lineage, established through human-controlled selective breeding over many generations. This selection favors traits that predispose the species toward human tolerance and utility.
A species had to possess a specific suite of behavioral and biological traits to be successfully domesticated. These animals needed a flexible diet, enabling them to thrive on the food humans could easily provide. A rapid growth rate was also beneficial, allowing generations to quickly reach maturity within a human lifespan. Species that naturally exhibit a manageable disposition, lacking a strong tendency to panic or flee when startled, were viable candidates for sustained cohabitation with people.
The most successful domesticates also had a hierarchical social structure, which allowed humans to easily assume the role of the dominant leader in the group. Furthermore, the species had to be willing to breed readily in captivity. Animals with complex or ritualistic mating behaviors could not be easily managed in pens or herds. Only a small fraction of animal species met these specific criteria.
The First Domesticates: Timing and Geography
The earliest animal to enter this coevolutionary relationship was the dog, diverging from the gray wolf lineage between 15,000 and 30,000 years ago, well before the start of the Neolithic period itself. This initial domestication occurred when humans were still primarily hunter-gatherers. Dogs were first valued for their behavior as hunting companions and camp guards. The primary suite of Neolithic domesticates, those linked directly to the agricultural revolution, first arose in Southwest Asia in the area called the Fertile Crescent.
Following the dog, sheep and goats were the next species to be domesticated, with archaeological evidence pointing to their management around 10,500 to 10,000 years ago. Their wild ancestors were prevalent in the mountainous regions of modern Iran and Turkey. The remains of early managed herds, exhibiting a shift in culling patterns, are found at sites like Ganj Dareh in Iran, demonstrating that humans were deliberately controlling their populations.
Cattle and pigs followed shortly after, with initial domestication occurring around 8,500 to 8,000 years ago, also centered in the Fertile Crescent region. The wild ancestor of cattle, the aurochs, was a significantly larger and more dangerous animal, making the selective breeding for docility a necessary step. Pigs, descended from wild boars, were likely first drawn to human settlements as scavengers before their breeding was controlled.
While Southwest Asia was the earliest hub for most domesticated livestock, other cultures independently domesticated animals outside of this core area. In East Asia, the wild red jungle fowl was domesticated into the chicken, and pigs were domesticated independently in China. Much later in the Neolithic timeframe, New World peoples in the Andes mountains domesticated the llama and alpaca for transport and wool.
Biological and Behavioral Transformation
The sustained selection for docility and specific utilitarian traits resulted in physical changes known collectively as the domestication syndrome. This suite of traits appears repeatedly across various domesticated species, even though they were not directly selected for by humans. One consistent change is a reduction in the size of the animal’s brain, which is often linked to a decrease in the size of the adrenal glands and a reduced fear response.
Physically, domesticated animals often exhibit a loss of defensive structures, such as the reduction in the size of horns. They frequently develop piebald or mottled fur patterns, a trait rarely seen in their wild counterparts, and morphological changes like floppy ears and shorter muzzles. These changes are hypothesized to be an indirect consequence of the selection for tameness, which influences the development of embryonic neural crest cells. These cells contribute to various tissues, including the adrenal glands, pigment cells, and parts of the skull.
These transformations made the animals more manageable and predictable within a human-controlled environment. The smaller body size and reduced aggression made livestock safer to handle and required less feed to sustain. The genetic changes created a species that was biologically adapted to a life of dependence on and cohabitation with humans.
Beyond Food: New Uses for Domesticated Animals
The initial domestication of animals focused on their primary products: a reliable supply of meat, hides, and bone. However, the realization that animals could provide renewable resources led to a profound shift in their management. This transformation, referred to as the Secondary Products Revolution, centered on the exploitation of milk, wool, and traction power.
The ability to milk animals like goats and cattle provided a continuous source of high-protein food that did not require the animal to be slaughtered. This new resource significantly improved the nutrition of Neolithic populations and supported the growth of larger, settled communities. Similarly, the development of sheep breeds with thick, woolly coats provided a raw material for textiles, leading to the development of weaving and new forms of clothing.
The use of large animals, particularly oxen and cattle, for traction was the most impactful development. Harnessing these animals to pull plows allowed farmers to cultivate larger tracts of land and significantly increase agricultural yields. This power also facilitated the invention of wheeled transport and allowed for the easier movement of goods, which fundamentally altered the scale of agriculture and the complexity of Neolithic society.