War is an intense armed conflict between states, governments, societies, or paramilitary groups such as mercenaries, insurgents, and militias. It is generally characterized by extreme violence, destruction, and mortality, using regular or irregular military forces. Warfare refers to the common activities and characteristics of types of war, or of wars in general. Total war is warfare that is not restricted to purely legitimate military targets, and can result in massive civilian or other non-combatant suffering and casualties. While some war studies scholars consider war a universal and ancestral aspect of human nature, others argue it is a result of specific socio-cultural, economic or ecological circumstances. Etymology The English word war derives from the 11th-century Old English words wyrre and werre, from Old French werre (also guerre as in modern French), in turn from the Frankish *werra, ultimately deriving from the Proto-Germanic *werzō 'mixture, confusion'. The word is related to the Old Saxon werran, Old High German werran, and the German verwirren, meaning "to confuse", "to perplex", and "to bring into confusion". History The earliest evidence of prehistoric warfare is a Mesolithic cemetery in Jebel Sahaba, 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. Estimates for total deaths due to war vary wildly. For the period 3000 BCE until now stated estimates range from 145 million to 2 billion In one estimate, primitive warfare prior to 3000 BCE has been thought to have claimed 400 million victims based on the assumption that it accounted for the 15.1% of all deaths. For comparison, an estimated 1,680,000,000 people died from infectious diseases in the 20th century. 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 massacres. 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