cannot marry. In the top 20 countries in the 2017 Fragile States Index, polygyny is widely practiced. In West Africa, more than one-third of women are married to a man who has more than one wife, and a study of 240,000 children in 29 African countries has also shown that, after controlling for other factors, children in polygynous families were more likely to die young. A 2019 study of 800 rural African ethnic groups published in the Journal of Conflict Resolution found that "young men who belong to polygynous groups feel that they are treated more unequally and are readier to use violence in comparison to those belonging to monogamous groups." In a 2011 doctoral thesis, anthropologist Kyle R. Gibson reviewed three studies documenting 1,208 suicide attacks from 1981 to 2007 and found that countries with higher polygyny rates correlated with greater production of suicide terrorists. Political scientist Robert Pape has found that among Islamic suicide terrorists, 97 percent were unmarried and 84 percent were male (or if excluding the Kurdistan Workers' Party, 91 percent male), while a study conducted by the U.S. military in Iraq in 2008 found that suicide bombers were almost always single men without children aged 18 to 30 (with a mean age of 22), and were typically students or employed in blue-collar occupations. In addition to noting that countries where polygyny is widely practiced tend to have higher homicide rates and rates of rape, political scientists Valerie M. Hudson and Bradley Thayer have argued that because Islam is the only major religious tradition where polygyny is still largely condoned, the higher degrees of marital inequality in Islamic countries than most of the world causes them to have larger populations susceptible to suicide terrorism, and that promises of harems of virgins for martyrdom serves as a mechanism to mitigate in-group conflict within Islamic countries between alpha and non-alpha males by bringing esteem to the latter's families and redirecting their violence towards out-groups. Along with his research on the Tamil Tigers, anthropologist Scott Atran found that Palestinian terrorist groups (such as Hamas) provide monthly stipends, lump-sum payments, and massive prestige to the families of suicide terrorists. Citing Atran and other anthropological research showing that 99 percent of Palestinian suicide terrorists are male, that 86 percent are unmarried, and that 81 percent have at least six siblings (larger than the average Palestinian family size), cognitive scientist Steven Pinker