would have led to large groups without the kind of complex communication that only language allows. Applications Dunbar's number has become of interest in anthropology, evolutionary psychology, statistics, and business management. For example, developers of social software are interested in it, as they need to know the size of social networks their software needs to take into account; and in the modern military, operational psychologists seek such data to support or refute policies related to maintaining or improving unit cohesion and morale. A recent study has suggested that Dunbar's number is applicable to online social networks and communication networks (mobile phone). Participants of the European career-oriented online social network XING who have about 157 contacts reported the highest level of job offer success, which also supports Dunbar's number of about 150. There are discussions in articles and books, of the possible application of using Dunbar's number for analyzing distributed, dynamic terrorist networks, cybercrime networks, or networks preaching criminal ideology. Reactions Alternative numbers Anthropologist H. Russell Bernard, Peter Killworth and associates have done a variety of field studies in the United States that came up with an estimated mean number of ties, 290, which is roughly double Dunbar's estimate. The Bernard–Killworth median of 231 is lower, because of an upward skew in the distribution, but still appreciably larger than Dunbar's estimate. The Bernard–Killworth estimate of the maximum likelihood of the size of a person's social network is based on a number of field studies using different methods in various populations. It is not an average of study averages but a repeated finding. Nevertheless, the Bernard–Killworth number has not been popularized as widely as Dunbar's. Criticism A replication of Dunbar's analysis on updated complementary datasets using different comparative phylogenetic methods yielded wildly different numbers. Bayesian and generalized least-squares phylogenetic methods generated approximations of average group sizes between 69–109 and 16–42, respectively. However, enormous 95% confidence intervals (4–520 and 2–336, respectively) implied that specifying any one number is futile. The researchers drew the conclusion that a cognitive limit on human group size cannot be derived in this manner. The researchers also criticised the theory behind Dunbar's number because other primates' brains do not handle information exactly as human brains do, because primate sociality is primarily explained by other factors than the brain, such as what they eat and who their predators are, and because humans have a large variation in the size of