For most of human history, we have foraged (hunted, fished, and collected wild plants) for food. Small nomadic groups could easily supply the necessities for their families. No one needed more, and providing for more than one’s needs made little sense. The organization of such societies could be rather simple, revolving around age and gender categories. Such societies likely were largely egalitarian, beyond distinctions based on age and gender, virtually all people had equivalent rights, status, and access to resources.

Archaeologist Donald Henry suggests that the combination of a rich habitat and sedentism (permanent, year-round settlement) led to a dramatic increase in human population. In his view, nomadic, simple foragers have relatively tow levels of fertility. Their high-protein, low-carbohydrate diets result in low body-fat levels, which are commonly associated with low fertility in women. High levels of physical activity and long periods of nursing, which are common among modern simple foragers, probably also contributed to low levels of female fertility if they were likewise common among ancient foragers.

In Henry's view, the adoption of a more settled existence in areas with abundant food resources would have contributed to higher fertility levels among the sedentary foragers. A diet higher in wild cereals produces proportionally more body fat, leading to higher fertility among women. Cereals, which are easy to digest, would have supplemented and then replaced mother's milk as the primary food for older infants. Since women are less fertile when they are breast-feeding, substituting cereals for mother s milk would have resulted in closer spacing of births and the potential for a greater number of live births for each woman. A more sedentary existence may also have lowered infant mortality and perhaps increased longevity among the aged. These more vulnerable members of society could safely stay in a fixed village rather than be forced regularly to move great distances as part of a nomadic existence, with its greater risk of accidents and trauma.

All of these factors may have resulted in a trend of increasing size among some local human populations in the Holocene (since 9600 B C E ). Given sufficient time, even in very rich habitats, human population size can reach carrying capacity, the maximum population an area can sustain within the context of a given subsistence system. And human population growth is like a runaway tram once it picks up speed, it is difficult to control. So even after reaching an area’s carrying capacity, Holocene human populations probably continued to grow in food-rich regions, overshooting the ability of the territory to feed the population, again within the context of the same subsistence strategy. In some areas, small changes in climate or minor changes in plant characteristics may have further destabilized local economies.

One possible response to surpassing the carrying capacity of a region is for a group to exploit adjoining land. However, good land may itself be limited—for example, within the confines of a river valley where neighbors are in the same position, having filled up the whole of the desirable habitat available in their home territories, expansion is also problematic. Impinging on the neighbors' territory can lead to conflict, especially when they too are up against the capacity of the land to provide enough food.

Another option is to stay in the same area but to shift and intensify the food quest there. The impulse to produce more food to feed a growing population was satisfied in some areas by the development of more-complex subsistence strategies involving intensive labor and requiring more cooperation and greater coordination among the increasing numbers of people. This development resulted in a change in the social and economic equations that defined those societies. Hierarchies that did not exist in earlier foraging groups but that were helpful in structuring cooperative labor and in organizing more-complex technologies probably became established, even before domestication and agriculture, as pre-Neolithic societies (before the tenth millennium B C E) reacted to the population increase.

在人类历史的大多数时间里，我们是通过搜寻活动（捕猎、捕鱼，以及采集野生植物）来获得食物的。小的游牧群体可以很容易地为自己家人获得生存下去的必需品。每个人之需要自己必须的量，给他们提供超出需要的食物也没有什么意义。这种社会的组织可以是很简单的，它围绕着年龄和性别运作。这样的社会很大可能是奉行平等主义的，超越了年龄和性别的差异，在它里面实际上所有的人拥有平等的权利、地位和对资源的获取权。 人类学家Donald Henry认为，物产富饶的居住地和定居主义（即永久的、全年的定居生活）的结合导致人类人口出现了爆发式的增长。他认为，游牧生活、简单的采集食物的生产方式相对来说只能使人口维持在较低水平。游牧民族的高蛋白、低碳水的饮食导致他们体脂率低，这就导致了女人的生育率低。如果古代游牧民族与现代游牧民族相像的话，那么在靠简单采集食物的方式为生的游牧民族里，高强度的体力活动和长时间的养育儿童可能也同样导致了女性的低生育率。 Henry认为，在食物丰富的地区，人们对于更加固定的生存方式的采用导致了更高的生育率。野生谷物占比更高的食谱导致人们体内的体脂更高，女人的生育率也就更高了。更容易消化的谷物会促进哺乳期女性产奶，并且可以替代母乳成为稍微大一点的婴儿的食物。因为女性在母乳喂养孩子的时候生育率会变低，谷物代替母乳就导致了每个女人生育间隔的缩短和更高的婴儿成活率。更稳定的生活方式可能同时也降低了婴儿的死亡率并且增加了老人的长寿率。像老人婴儿这种社会里最易受伤害的群体可以安全地待在定居的村庄里，而不是像在游牧生活中需要经常在东奔西跑长途迁徙中受到伤害。 上述所有因素导致了全新世的一些当地居民人口的增长趋势（从公元前9600年开始）。只要时间充足，即使是在非常富饶的定居地，人类的人口数量终究会到达生态最大可承载量，也就是一个地区在现有的生活系统下可以维持的最大人口数。并且，人口数量的增长就像是一辆有轨电车，一旦加速起来，就控制不住了。所以即使一个地方的人口数已经达到了最大可承载量，全新世的人类人口数在物产富饶的地区继续增长，超过了在这种生活系统中，这片土地可以养活的数量。在一些地区，气候或者植被特征的微小特征可能会进一步使得他们变得不稳定。 应对人口过多的办法之一就是去开发相邻的土地。然而，好的土地毕竟稀少——比如，在河谷里，临河的肥沃土地总是有限的。当人们聚集在一个地方，并且把所有的好的栖息地都占据了以后，人口的扩张就成了一个问题。去侵入临近民族的土地会导致冲突，尤其是对方同样也到达了人口可承载极限、现有的土地再也不能提供足够的食物之后。 另一种解决办法是仍旧待在旧地方，但是改变和加强这片土地的食物供应量。依靠着更复杂的生产技术的发展，加上劳动力的密集化，还有人与人之间更好的协调合作，养活不断增长的人口所需要的食物量可以被满足。这种发展导致了定义这些社会的社会和经济法则的变化。在早期的社会中不存在的等级制度开始形成，它促进了劳动力协调合作组织结构的形成，也促进了更复杂的技术的形成。作为旧石器时代（在公元前万年）应对人口增长的解决方法，甚至早于饲养家畜和农业的产生。