The emergence of plant and animal domestication represented a monumental change in the ways that humans interacted with Earth’s resources: the rate at which Earth’s surface was modified and the rates of human population growth. The development of agriculture was accompanied by fundamental changes in the organization on human society: disparities in wealth, hierarchies of power, and urbanization.

Phrases like “plant and animal domestication” and “the invention of agriculture” create the impression that humans made the transition to cultivating plants and tending animals rather abruptly, maybe with a flash of insight. Most scholars don’t think so. It seems more likely that humans used and manipulated wild plants and animals for many hundreds of thousands of years. The transition to gardens, fields, and pastures was probably gradual, the natural outgrowth of a long familiarity with the environmental requirements, growth cycles, and reproductive mechanisms of whatever plants and animals humans liked to eat, ride, or wear.

For years, scholars argued that the practices of cultivation and animal domestication were invented in one or two locations on Earth and then diffused from those centers of innovation. Genetic studies are now showing that many different groups of people in many different places around the globe learned independently to create especially useful plants and animals through selective breeding. Probably both independent invention and diffusion played a role in agricultural innovation. Sometimes the ideas of domestication and cultivation were relayed to new places. In other cases the farmers or herders themselves moved into new zones, taking agriculture or improvements such as new tools or new methods or new plants and animals with them.

Scholars used to assume that people turned to cultivating instead of gathering their food either because they had to in order to feed burgeoning populations, or because agriculture provided such obviously better nutrition. It now seems that neither of these explanations is valid. First of all, the risk attached to exploring new food sources when there were already too many mouths to feed would be too great. Second, agriculture did not necessarily improve nutrition or supplies of food. A varied diet based on gathered (and occasionally hunted) food probably provided a wider, more secure range of nutrients than an early agriculturally based diet of only one or two cultivated crops. More likely, populations expanded after agricultural successes, and not before.

Richard MacNeish, an archaeologist who studied plant domestication in Mexico and Central America, suggested that the chance to trade was at the heart of agricultural origins worldwide. Many of the known locations of agricultural innovation lie near early trade centers. People in such places would have had at least two reasons to pursue cultivation and animal raising; they would have had access to new information, plants, and animals brought in by traders, and they would have had a need for something to trade with the people passing through. Perhaps, then, agriculture was at first just a profitable hobby for hunters and gatherers that eventually, because of market demand, grew into the primary source of sustenance. Trade in agricultural products may also have been a hobby that led to trouble.

E. N. Anderson, writing about the beginnings of agriculture in China, suggests that agricultural production for trade may have been the impetus for several global situations now regarded as problems: rapid population growth, social inequalities, environmental degradation, and famine. Briefly explained, his theory suggests that groups turned to raising animals and plants in order to reap the profits of trading them. As more labor was needed to supply the trade, humans produced more children. As populations expanded, more resources were put into producing food for subsistence and for trade. Gradually, hunting and gathering technology was abandoned as populations, with their demands for space, destroyed natural habitats. Meanwhile, a minority elite emerged when the wealth provided by trade did not accrue equally to everyone. Yet another problem was that a drought or other natural disaster could wipe out an entire harvest, thus, as ever larger populations depended solely on agriculture, famine became more common.

种植植物和驯化动物的出现代表着人类和地球资源的相互作用发生着巨大的改变：地球表面被修缮的速度和人类人口数目增长的速度。农业的发展伴随着人类社会组织的根本性改变：财富差距、权利等级以及城市化。 像“种植植物和驯化动物”和“农业发明”这样的短语给人留下了一种印象，那就是人类使得培育植物和饲养动物这样的转变突然发生，或许这是一种瞬间洞察力。许多学者却并不这么认为。他们觉得人类可能在千百年来一直都在使用和操控着野生动植物。向花园、田野和牧场的转变可能是渐进的，自然的产物是要长期熟悉环境要求、生长周期以及繁衍机制，无论是人类喜欢吃的、骑的和穿的各种动植物。 多年来，学者们认为，植物耕种和动物驯化的做法是在地球上的一个或者两个地方出现的，然后从这些创新地点向周围传播。现在，遗传学研究表明地球上许多不同地点的不同人群通过选择性育种，特别是通过有用处的动植物，独立地学习创造。独立发明和传播在农业创新中都可能有着重要作用。有时，驯化和耕种的想法被传播到了新的地方。在其他情况下，农民或者牧民自己搬到了新的地区，会采取农业或改善的措施，如新的工具或新的方法或新的动植物。 过去，学者们认为，人们转而开始耕种，不去收集食物的原因要么是为了养活增长的人口，因为他们不得不这么做，要么是农业显然为他们提供了更好地营养的食物。而现在看来，这些解释都站不住脚。首先，当有太多的人口需要养活时，去寻找新的食物来源的风险很大；其次，农业并不一定会提供他们好的营养和粮食。收集到的（或偶然捕猎到的）多样的食物可能会给他们提供更多种更安全的营养，而不是仅有一到两种农作物的早期农业基础食物。更有可能的是，人口的增长发生在农业成功之后，而不是之前。 研究墨西哥和中美洲植物耕种的考古学家理查德•马尼士表示，贸易的可能性是全球农业起源的核心。许多已知的农业创新地点位于早期贸易中心附近。这些地方的人至少有两种理由耕种和饲养动物：一是，他们将有机会获得新信息并通过贸易者引进动植物，并且他们需要东西来和路过的人做贸易；二是，农业起初只是猎人和采集者有利可图的一种嗜好，最终因为市场需求，成为了主要的食物来源。农产品贸易也可能是一种引起麻烦的嗜好。 安德森在写到中国农业的开端时表明，用于贸易的农业生产可能对于几种全球形势是一种推动力，但目前也成了问题:人口快速增长、社会不平等、环境退化和饥荒。简单地说, 他的理论表明, 群体转向饲养动物和种植植物是为了在交易中赚取利润。由于供应贸易需要更多的劳动力, 人类生出更多的孩子。随着人口的扩大, 为了生计和贸易，越来越多的资源被用来生产粮食。逐渐地, 狩猎和收集技术被摒弃了，因为出于对空间的要求,人们毁坏了自然栖所。与此同时, 当并不是每个人在贸易中都能有同样的收益时, 就出现了少数精英阶层。还有一个问题是, 旱灾或其他自然灾害会使人们颗粒无收,因此,随着人口的增加，如果人类只依赖于农业, 饥荒会变得更加普遍。