With violent conflicts happening across the world right now, war feels like a permanent condition. But have humans ever lived without war?The answer depends on how you define "war." If war means a fight between two governments, then yes, there have been peaceful periods "because for nearly 99% of human history, there were no governments," said Ian Morris, a historian at Stanford University and author of "War! What Is It Good For? Conflict and the Progress of Civilization from Primates to Robots" (Farrar, Straus and Giroux, 2014). Violence, on the other hand, has always been with us. If the question becomes "Have people ever lived without violence?" then "the answer is pretty clearly no people have always fought and killed each other," Morris told Live Science in an email.The theory of a peaceful prehistoryAccording to a review of studies published in 2022, war was rare or nonexistent in early human history when people lived as nomadic hunter gatherers. Peter Stearns, a professor emeritus of history at George Mason University and author of "Peace in World History" (Routledge, 2014), agrees with this idea. There was "little or no war in hunting and gathering [cultures] before the rise of agriculture," he told Live Science in an email. Sign up for our newsletter(Image credit: Marilyn Perkins / Future)Sign up for our weekly Life's Little Mysteries newsletter to get the latest mysteries before they appear online.This idea is based on archaeological records. Researchers examining ancient human bones from around the world have looked for skeletal evidence of war injuries, for instance of multiple individuals with unhealed wounds from stabbing, slicing and blunt force trauma who were buried in mass graves. However, they found little evidence of war injuries before 8000 B.C. After that, when humans began transitioning from nomadic life to permanent settlements, such injuries appeared widely.This doesn't mean that lethal violence was absent in prehistoric societies. Researchers in Kenya found 27 skeletons dating to 10,000 years ago at the archaeological site of Nataruk; these skeletons show signs of violent death, which some anthropologists interpret as evidence of intergroup violence among early hunter-gatherers. And at Jebel Sahaba, a prehistoric cemetery in Sudan, archaeologists unearthed 13,000-year-old remains bearing signs of intergroup attacks.But these cases of interpersonal violence don't count as war, because of how researchers usually define it. "Researchers who focus on war as a specific category of violence usually define it by saying it has to be violence organized by a government or else collective violence that kills more than a certain number of people," Morris said. "Prehistoric societies rarely had formal governments and hunter-gatherer bands rarely had more than a few dozen members, so if you define war as a conflict run by a government or one that kills >100 people, then by definition there can't have been wars in [early] prehistory."David Christian, a historian and professor emeritus in the Department of History and Archaeology at Macquarie University in Australia, echoed this idea. "For much of human history communities were so small that it is not clear if we can equate violence with war," he told Live Science in an email. "I guess we can say that humans have always been capable of violence and as communities got larger that violence began to take on forms that we might want to describe as 'war.'"War killed about 231 million people in the 20th century, which includes the roughly 80,000 Soviet soldiers who died at the Battle of Berlin in World War II and who are honored at the Soviet War Memorial in Treptower Park (pictured above) in Germany. (Image credit: Oliver Strewe via Getty Images)Peace between rival powersOnce large kingdoms and empires appeared, war became very common. A doctoral thesis written by Jared Morgan McKinney, now an assistant professor of international security studies at Air War College in Alabama, focused on periods of peace between major powers. He concluded that war was basically the norm throughout history and that famous "peaceful" eras, like the Pax Romana (Roman Peace), usually just meant one powerful group had beaten everyone else into submission.But there were exceptions. "Wars are expensive and risky," said Peter Frankopan, a professor of global history at the University of Oxford. "So in many periods in history, stability and peace have been achieved by rivals, adversaries and neighbors being able to match each other's capabilities." McKinney's thesis identified several periods when rival powers managed to avoid war.From around 1400 to 1200 B.C., the big powers of the ancient Middle East mainly Egypt and the Hittite Empire, an ancient civilization in modern-day Turkey went through two unusually long stretches without major wars. Peace was possible because the "Great Kings" recognized one another as equals and settled their territorial and political differences through formal treaties rather than war.The Tomb of the Unknown Soldier at Arlington National Cemetery in Virginia, just outside of Washington, D.C. It's the burial site of a World War I soldier whose identity was unknown. (Image credit: Judd Brotman via Getty Images)For most of their history, Rome and Persia were at war. Then, from roughly A.D. 387 to around 501, the two superpowers mostly stopped fighting. Historians call this the "Long Fifth Century" and have put forward many explanations for this period of peace, including that both sides faced serious outside threats that made fighting less affordable and that the two sides developed a language of "brotherhood" that acknowledged each other as equals rather than enemies, McKinney wrote in his thesis. Between roughly A.D. 1000 and 1200, the rich Song dynasty in China secured peace with its militant northern neighbors the Liao and the Jin by paying them regularly to keep the peace. Although these monetary gifts (or bribes) looked like weakness, the payments were tiny compared with what China was earning through trade, according to McKinney.Another example, according to Morris, is the "long peace" between China, Korea and Japan between about 1600 and 1850. While European states spent those centuries competing for power and territory through war, the East Asian states lived in relative peace. "In Europe, we've tended to be a lot more aggressive and competitive which gives the impression that war is a 'natural state' of being," Frankopan said.Related mysteriesWhat happened to Rome after the empire fell?Were the Vikings really that violent?When did the Brits and Yanks become allies again after the Revolutionary War?A notable period of relative peace in North America was the Long Peace among the Iroquois nations, McKinney told Live Science in an email. For roughly three centuries, from about 1450 to 1777, five (and later six) Native American nations who had previously engaged in violent and costly conflict forged a peaceful relationship known as the "Haudenosaunee Confederacy" or "League of Five Nations."In South America, McKinney pointed to the South American Long Peace. This refers to the absence of major interstate wars between sovereign nations in South America ever since 1935."War is 'normal' in history," McKinney said. But, as these examples show, "patterns have exceptions."Can you identify these historical objects of war? Test your smarts with our weapons of the world quiz.