The earliest evidence for prehistoric warfare belongs to the Mesolithic cemetery Site 117, which has been determined to be approximately 14,000 years old. About forty-five percent of the skeletons there displayed signs of violent death. Since the rise of the state some 5,000 years ago, military activity has occurred over much of the globe. The advent of gunpowder and the acceleration of technological advances led to modern warfare. According to Conway W. Henderson, One source claims that 14,500 wars have taken place between 3500 BC and the late 20th century, costing 3.5 billion lives, leaving only 300 years of peace (Beer 1981: 20). An unfavorable review of this estimate mentions the following regarding one of the proponents of this estimate: In addition, perhaps feeling that the war casualties figure was improbably high, he changed approximately 3,640,000,000 human beings have been killed by war or the diseases produced by war to approximately 1,240,000,000 human beings...c. The lower figure is more plausible, but could also be on the high side, considering that the 100 deadliest acts of mass violence between 480 BC and 2002 AD (wars and other man-made disasters with at least 300,000 and up to 66 million victims) claimed about 455 million human lives in total. Primitive warfare is estimated to have accounted for 15.1 % of deaths and claimed 400 million victims. Added to the aforementioned (and perhaps too high) figure of 1,240 million between 3500 BC and the late 20th century, this would mean a total of 1,640,000,000 people killed by war (including deaths from famine and disease caused by war) throughout the history and pre-history of mankind. For comparison, an estimated 1,680,000,000 people died from infectious diseases in the 20th century. Nuclear warfare breaking out in August 1988, when nuclear arsenals were at peak level, and the aftermath thereof, could have reduced human population from 5,150,000,000 by 1,850,000,000 to 3,300,000,000 within a period of about one year, according to a projection that did not consider the most severe predictions concerning nuclear winter. This would have been a proportional reduction of the worlds population exceeding the reduction caused in the 14th century by the Black Death, and comparable in proportional terms with the plagues impact on Europes population in 1346–53.In War Before Civilization, Lawrence H. Keeley, a professor at the University of Illinois, says approximately 90–95% of known societies throughout history engaged in at least occasional warfare, and many fought constantly.Keeley describes several styles of primitive combat such as small raids, large raids, and s. All of these forms of warfare were used by primitive societies, a finding supported by other researchers. Keeley explains that early war raids were not well organized, as the participants did not have any formal training. Scarcity of resources meant defensive works were not a cost-effective way to protect the society against enemy raids.William Rubinstein wrote Pre-literate societies, even those organised in a relatively advanced way, were renowned for their studied cruelty...archaeology yields evidence of prehistoric s more severe than any recounted in ethnography .