The evolution of altruism in human societies has been intensively investigated in social and natural sciences. A widely acknowledged recent idea is the “parochial altruism model,” which suggests that inter- group hostility and intragroup altruism can coevolve through lethal intergroup conflicts. The current article critically examines this idea by reviewing research relevant to intergroup conflicts in human evolutionary history from evolutionary biology, psychology, cultural anthropology, and archaeology. After a brief intro- duction, section 2 illustrates the mathematical model of parochial altruism (...) and some critiques of the model and its interpretation, primarily from an evolutionary biology point of view. Section 3 delves into the archaeological evidence of prehistoric intergroup conflicts in the Japanese archipelago’s Jomon and Yayoi periods, Europe’s Mesolithic period, and North America’s Pacific period as counter examples of the paro- chial altruism model. In section 4, the ethnographies of intergroup relationships and conflicts reveal that intergroup relationships in many ethnic groups are not as simple as the assumption in the mathematical model of parochial altruism. In section 5, we outline psychological research on intergroup conflicts which suggest that intergroup hostility and ingroup altruism are not necessarily correlated. In conclusion, we argue that the assumption and parameter settings of the parochial altruism model are inconsistent with empirical data. (shrink)

The causes of prehistoric inter-group violence have been a subject of long-standing debate in archaeology, an- thropology, and other disciplines. Although population pressure has been considered as a major factor, due to the lack of available prehistoric data, few studies have directly examined its effect so far. In the present study, we used data on skeletal remains from the middle Yayoi period of the Japanese archipelago, where archaeologists argued that an increase of inter-group violence in this period could be explained (...) by a population-pressure hy- pothesis. We quantitatively examine the effect of population pressure on the frequency of inter-group violence by compiling an exhaustive data set. We collected demographic information based on burial jars (kamekan) and the frequency of violence based on the ratio of injured individuals. The results are consistent with the hypothesis, i. e., high population density can promote inter-group violence. (shrink)

Whether man is predisposed to lethal violence, ranging from homicide to warfare, and how that may have impacted human evolution, are among the most controversial topics of debate on human evolution. Although recent studies on the evolution of warfare have been based on various archaeological and ethnographic data, they have reported mixed results: it is unclear whether or not warfare among prehistoric hunter – gatherers was common enough to be a component of human nature and a selective pressure for the (...) evolution of human behaviour. This paper reports the mortality attributable to violence, and the spatio-temporal pattern of violence thus shown among ancient hunter–gatherers using skeletal evidence in prehistoric Japan (the Jomon period: 13000 cal BC–800 cal BC). Our results suggest that the mortality due to violence was low and spatio-temporally highly restricted in the Jomon period, which implies that violence including warfare in prehistoric Japan was not common. (shrink)

Whether man is predisposed to lethal violence, ranging from homicide to warfare, and how that may have impacted human evolution, are among the most controversial topics of debate on human evolution. Although recent studies on the evolution of warfare have been based on various archaeological and ethnographic data, they have reported mixed results: it is unclear whether or notwarfare among prehistoric hunter–gathererswas common enough to be a component of human nature and a selective pressure for the evolution of human behaviour. (...) This paper reports the mortality attributable to violence, and the spatio-temporal pattern of violence thus shown among ancient hunter–gatherers using skeletal evidence in prehistoric Japan (the Jomon period: 13 000 cal BC–800 cal BC). Our results suggest that the mortality due to violence was low and spatio-temporally highly restricted in the Jomon period, which implies that violence including warfare in prehistoric Japan was not common. (shrink)

The origins and consequences of warfare or largescale intergroup violence have been subject of long debate. Based on exhaustive surveys of skeletal remains for prehistoric hunter-gatherers and agriculturists in Japan, the present study examines levels of inferred violence and their implications for two different evolutionary models, i.e., parochial altruism model and subsistence model. The former assumes that frequent warfare played an important role in the evolution of altruism and the latter sees warfare as promoted by social changes induced by agriculture. (...) Our results are inconsistent with the parochial altruism model but consistent with the subsistence model, although the mortality values attributable to violence between hunter-gatherers and agriculturists were comparable. (shrink)

It has been commonly claimed that prehistoric warfare in Japan began in the Yayoi period. Population increases due to the introduction of agriculture from the Korean Peninsula to Japan resulted in the lack of land for cultivation and resources for the population, eventually triggering competition over land. This hypothesis has been supported by the demographic data inferred from historical changes in Kamekan, a burial system used especially in the Kyushu area in the Yayoi period. The present study aims to examine (...) the previous claim by using an expanded dataset of human skeletal remains and Kamekan. First, in order to quantify the intensity of warfare, we developed a database of injured individuals found in the middle phase of the Yayoi period in two large populations in the northern Kyushu area, the Fukuoka plain and the upperand middle-stream of the Homan River. Second, we collected Kamekan data from site reports published after 1990 and constructed a comprehensive database to infer the demography in these areas. Finally, we compared the frequency of injured individuals and the inferred demography. The results suggest that the frequency of injured individuals and the population increase tended to be higher at the upper- and middle-stream of the Homan River than on the Fukuoka plain. Different assumptions of the lifetime of each type of Kamekan can produce mixed results on the relationship between demography and the frequency of injured individuals. They were positively correlated under the traditional assumption of constant time intervals, while there was no correlation using time intervals based on carbon dating by the National Museum of Japanese History. Thus, our results are partially consistent with the previous claim that the population increase and the lack of land and resources due to the introduction of agriculture were causes of warfare in the northern Kyushu area in the middle phase of the Yayoi period. (shrink)

The present study collected a larger set of three-dimensional data on human crania from the Kofun period (as well as from previous periods, i.e., the Jomon and Yayoi periods) in the Japanese archipelago (AD 250 to around 700) than previous studies. Three-dimensional geometric morphometrics were employed to investigate human migration patterns in finer-grained phases. These results are consistent with those of previous studies, although some new patterns were discovered. These patterns were interpreted in terms of demic diffusion, archaeological findings, and (...) historical evidence. In particular, the present results suggest the presence of a gradual geological cline throughout the Kofun period, although the middle period did not display such a cline. This discrepancy might reflect social changes in the middle Kofun period, such as the construction of keyhole-shaped mounds in the peripheral regions. The present study implies that a broader investigation with a larger sample of human crania is essential to elucidating macro-level cultural evolutionary processes. (shrink)

The present study examines the 3-dimensional data of human crania from the Yayoi period (800 BC to AD 250) of the Japanese archipelago by geometric morphometrics to investigate demic diffusion patterns. This is the first study on the Yayoi crania using their 3D data and geometric morphometrics with a much larger number of skeletal remains outside of the Kyushu regions than previous studies. The comparative results between the Jōmon and Yayoi samples show that the Yayoi people not only in the (...) eastern parts but also in the western parts of the archipelago are significantly different from the final Jōmon people and the Yayoi people were not strongly affected by the Jōmon people. A relatively gradual geological cline is also found among the Yayoi population, suggesting that the immigrants from the continental East Asia moved from the western parts to the eastern parts of the archipelago though the causes of the morphological changes are unclear. (shrink)