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Dunbar then compared this prediction with observable group sizes for humans.  Beginning with the assumption that the current mean size of the human neocortex had developed about 250,000 years ago, during the Pleistocene, Dunbar searched the anthropological and ethnographical literature for census-like group size information for various hunter–gatherer societies, the closest existing approximations to how anthropology reconstructs the Pleistocene societies. Dunbar noted that the groups fell into three categories—small, medium and large, equivalent to bands, cultural lineage groups and tribes—with respective size ranges of 30–50, 100–200 and 500–2500 members each.

Dunbar then compared this prediction with observable group sizes for humans.  Beginning with the assumption that the current mean size of the human neocortex had developed about 250,000 years ago, during the Pleistocene, Dunbar searched the anthropological and ethnographical literature for census-like group size information for various hunter–gatherer societies, the closest existing approximations to how anthropology reconstructs the Pleistocene societies. Dunbar noted that the groups fell into three categories—small, medium and large, equivalent to bands, cultural lineage groups and tribes—with respective size ranges of 30–50, 100–200 and 500–2500 members each.

邓巴随后将这一预测与可观察到的人类群体大小进行了比较。首先假设人类新大脑皮层的平均大小是在大约25万年前的更新世时期形成的，邓巴在人类学和人种学文献中搜索了各种与狩猎采集社会类似的人口普查的群体规模信息，这是现存最接近人类学如何重建更新世社会的方式。邓巴指出，这些族群分为三类，即小型、中型和大型，相当于族群、文化宗族和部落，各自的人数范围分别为30-50人、100-200人和500-2500人。

邓巴随后将这一预测与可观察到的人类群体规模进行了比较。首先假设人类大脑新皮层的平均大小是在大约25万年前的更新世时期形成的，邓巴在人类学和人种学文献中搜索了各种狩猎采集社会的类似人口普查的群体规模信息，这是现存最接近人类学如何重建更新世社会的方式。邓巴指出，这些族群分为三类，即小型、中型和大型，相当于族群、文化宗族和部落，各自的规模分别为30-50人、100-200人和500-2500人。

Dunbar's surveys of village and tribe sizes also appeared to approximate this predicted value, including 150 as the estimated size of a Neolithic farming village; 150 as the splitting point of Hutterite settlements; 200 as the upper bound on the number of academics in a discipline's sub-specialisation; 150 as the basic unit size of professional armies in Roman antiquity and in modern times since the 16th century; and notions of appropriate company size.

Dunbar's surveys of village and tribe sizes also appeared to approximate this predicted value, including 150 as the estimated size of a Neolithic farming village; 150 as the splitting point of Hutterite settlements; 200 as the upper bound on the number of academics in a discipline's sub-specialisation; 150 as the basic unit size of professional armies in Roman antiquity and in modern times since the 16th century; and notions of appropriate company size.

Dunbar has argued that 150 would be the mean group size only for communities with a very high incentive to remain together. For a group of this size to remain cohesive, Dunbar speculated that as much as 42% of the group's time would have to be devoted to social grooming. Correspondingly, only groups under intense survival pressure, such as subsistence villages, nomadic tribes, and historical military groupings, have, on average, achieved the 150-member mark. Moreover, Dunbar noted that such groups are almost always physically close: "[...] we might expect the upper limit on group size to depend on the degree of social dispersal. In dispersed societies, individuals will meet less often and will thus be less familiar with each other, so group sizes should be smaller in consequence." Thus, the 150-member group would occur only because of absolute necessity—due to intense environmental and economic pressures.

Dunbar has argued that 150 would be the mean group size only for communities with a very high incentive to remain together. For a group of this size to remain cohesive, Dunbar speculated that as much as 42% of the group's time would have to be devoted to social grooming. Correspondingly, only groups under intense survival pressure, such as subsistence villages, nomadic tribes, and historical military groupings, have, on average, achieved the 150-member mark. Moreover, Dunbar noted that such groups are almost always physically close: "[...] we might expect the upper limit on group size to depend on the degree of social dispersal. In dispersed societies, individuals will meet less often and will thus be less familiar with each other, so group sizes should be smaller in consequence." Thus, the 150-member group would occur only because of absolute necessity—due to intense environmental and economic pressures.

Dunbar, in Grooming, Gossip, and the Evolution of Language, proposes furthermore that language may have arisen as a "cheap" means of social grooming, allowing early humans to maintain social cohesion efficiently. Without language, Dunbar speculates, humans would have to expend nearly half their time on social grooming, which would have made productive, cooperative effort nearly impossible. Language may have allowed societies to remain cohesive, while reducing the need for physical and social intimacy. This result is confirmed by the mathematical formulation of the social brain hypothesis, that showed that it is unlikely that increased brain size would have led to large groups without the kind of complex communication that only language allows.

Dunbar, in Grooming, Gossip, and the Evolution of Language, proposes furthermore that language may have arisen as a "cheap" means of social grooming, allowing early humans to maintain social cohesion efficiently. Without language, Dunbar speculates, humans would have to expend nearly half their time on social grooming, which would have made productive, cooperative effort nearly impossible. Language may have allowed societies to remain cohesive, while reducing the need for physical and social intimacy. This result is confirmed by the mathematical formulation of the social brain hypothesis, that showed that it is unlikely that increased brain size would have led to large groups without the kind of complex communication that only language allows.

邓巴在《梳毛、八卦及语言的进化 Grooming, Gossip, and the Evolution of Language》一书中进一步提出，语言可能作为社交梳理的“廉价”手段而出现，从而使早期人类能够有效地保持社交凝聚力。邓巴推测，如果没有语言，人类将不得不花费近一半的时间进行社交梳理，这将使富有成效的合作努力几乎成为不可能。语言可以使社会保持凝聚力，同时减少对身体和社会亲密感的需求。社会大脑假说的数学表述证实了这一结果，该理论表明，如果没有语言所允许的那种复杂交流，仅增加大脑的尺寸是不可能导致庞大的群体的形成。

邓巴在《梳毛、八卦及语言的进化 Grooming, Gossip, and the Evolution of Language》一书中进一步提出，语言可能是作为社会化理毛的“廉价”替代方式而出现的，使得早期人类能够有效地保持社交凝聚力。邓巴推测，如果没有语言，人类将不得不花费近一半的时间用于社会化理毛，这将使富有成效的合作努力几乎成为不可能。语言可以使社会保持凝聚力，同时减少对身体和社会亲密关系的需求。社会大脑假说的数学表述证实了这一结果，该理论表明，如果没有语言所允许的那种复杂交流，仅增加大脑的尺寸不可能导致大型群体的形成。

== Applications 应用 ==

== Applications 应用 ==