text: Although it’s unclear whether genetics or other factors are responsible, new study suggests that lethal violence is part of our evolutionary history 
   
   Humans are predisposed to murder each other, new research suggests, although it remains unclear if it’s down to genetics or other factors. 
   
   Researchers from Spain have found that a tendency to bump off members of the same species is particularly common among primates, and have estimated that around 2% of human deaths at the origin of our species were down to such lethal spats. 
   
   
   
   “What it is saying, in the broadest terms, is that humans have evolved strategies for solving problems with violence,” said Mark Pagel, professor of evolutionary biology at the University of Reading, who was not involved in the research. 
   
   But, the authors add, the impact of society can greatly modify how aggressive humans are, with the proportion of human deaths due to people fighting between themselves fluctuating over mankind’s history. 
   
   “Lethal violence is part of our evolutionary history but not carved in stone in ‘our genes’,” said José María Gómez, first author of the study from the Estación Experimental de Zonas Áridas (EEZA) in Spain. “At least to some extent, the way humans organise in societies influences our levels of lethal violence.” 
   
   The question of human violence has puzzled thinkers for centuries, from Thomas Hobbes in the 17th century, to contemporary psychologists such as Jared Diamond and Steven Pinker, the Johnstone professor of psychology at Harvard University and author of The Better Angels of Our Nature. 
   
   Pinker has previously argued that humans engage in lethal violence as a “natural condition,” but that deaths from such violence have decreased with the rise of modern societies with sophisticated institutions and laws. But the idea has proved controversial. 
   
   
   
   The new research is likely to add further fuel to the debate. 
   
   Writing in the journal Nature, the team of researchers from four Spanish institutions sought to unpick the evolutionary contribution to lethal human violence by looking at how commonly a range of different mammals kill members of the same species. 
   
   To do so, they examined the evolutionary family tree of mammals, looking at data from more than 1,020 species, as well as 600 human populations stretching as far back in time as the Stone Age, drawing on evidence from human remains found in archaeological excavations. 
   
   For each species of mammal, the team looked at the proportion of deaths that were down to violence between members of the same species. The findings showed that such lethal violence is more common in some mammals, such as primates, than in others, such as bats or whales, and is more common among mammals that exhibit social and territorial behaviour that those that go it alone. 
   
   Using statistical models, the researchers then estimated the likely levels of such lethal violence for evolutionary ancestors at various points in the family tree of mammals. 
   
   The results revealed that for the ancestor of all mammals, around 1 in every 300 deaths was down to lethal violence between members of the same species. But, the authors note, for evolutionary ancestors of the primates and apes, the figures were higher. 
   
   Around 1.8% of deaths are thought to have been down to lethal violence for the ancestor of the great apes, and around 2% for the first humans - a figure more than six times higher than at the origin of mammals. 
   
   “We cannot tell that 2% of violence is due to genetic factors,” said Gómez. “Not only genes are inherited from ancestors, also environmental conditions and ecological constraints. Those are also probably influencing the human lethal violence in our evolutionary past.” 
   
   But Pagel believes it is important to emphasise that genetic adaptations could be at play. “Humans emerged from a very long lineage of species - great apes and before them the primates - that all expressed relatively high levels of lethal violence,” he said. “When you immerse an animal in a particular environment, it evolves genetic-based strategies for dealing with that environment. There is good reason to believe this reflects a real genetic or innate tendency to solve problems with violence.” 
   
   The research also shows that, according to observed evidence, levels of lethal violence among humans have fluctuated over time. While the figure was around 2% for prehistoric man, matching the expected level from the calculations, the proportion of deaths down to such violence rose during other eras such as the iron age and the post-classic period (around 800-500 years ago), falling in contemporary times to below 2%. 
   
   “From the empirical figure of 2% of deaths by lethal violence in primitive hunter-gatherers, different historical times have had different levels of lethal violence,” said Gómez. 
   
   Pinker told the Guardian the new research is impressive and supports his views that humans have a natural tendency to engage in lethal violence, that rates of such violence were high in prehistoric societies and are higher in tribes and chiefdoms than hunter-gatherer bands, and that such impulses are dampened in modern societies. “Though I made all these points in The Better Angels of Our Nature in 2011, [the authors] have demonstrated them with much greater precision, rigour, and depth,” he said. 
   
   But Douglas Fry of the University of Alabama at Birmingham in the US, disagreed, saying that: “Gómez and colleagues demonstrate that recent assertions by Steven Pinker and others that violent death in the Paleolithic was shockingly high are greatly exaggerated. To the contrary, the findings show that social organization is critically important in affecting human violence.” 
   
   Gómez says the research highlights the control humans have over their situation in life and death. “The main message of our study is that no matter how violent or pacific we were in the origin, we can modulate the level of interpersonal violence by changing our social environment,”he said. “We can build a more pacific society if we wish.” ||||| FILE - In this Sept. 21, 2016 file photo, the sister, nieces and nephews of slain Rev. Jose Alfredo Suarez de la Cruz grieve as they watch his casket lower into the floor inside Our Lady of Asuncion Church... (Associated Press) 
   
   FILE - In this Sept. 21, 2016 file photo, the sister, nieces and nephews of slain Rev. Jose Alfredo Suarez de la Cruz grieve as they watch his casket lower into the floor inside Our Lady of Asuncion Church in Paso Blanco, Veracruz state, Mexico. Mourners packed the church for the funeral Mass in memory... (Associated Press) 
   
   WASHINGTON (AP) — Evolution and genetics seem to have baked a certain amount of murder into humans as a species, but civilization has tamed some of the savage beast in us, according to a new study. 
   
   Scientists calculated the rate at which more than 1,000 mammal species kill their own kind, and noticed how closely related species have similar rates of lethal violence. They essentially found that where a species is on evolutionary tree of life tells a lot about how violent the species is to its own kind. And we're in a rough neighborhood. 
   
   Humans are "in a position within a particularly violent mammalian clade, in which violence seems to have been ancestrally present," the study in the journal Nature says. That means that based on other rather murderous species closely related to us, humans have "inherited their propensity for violence." 
   
   As a group, mammals average a lethal violence rate against their own of about three killings of their own species in 1,000 deaths. The "root" violence rate of early humans and many of our closer primate cousins is about 20 in 1,000, said study lead author Jose Maria Gomez at the University of Granada in Spain. But in the medieval period, between 700 and 1500 A.D., that deadly rate shot up to about 120 per 1000. 
   
   But we've gotten less murderous. 
   
   On average, modern humans now kill each on a rate of 13 in 1000, Gomez said, basing his calculations on World Health Organization data. But he says the exact numbers are rough and depend on many technical variables, so what is more accurate is to say "violence has decreased significantly in the contemporary age." 
   
   "It seems that we are in the present time less violent than we were in the past," Gomez said in an email interview. 
   
   While humans are killing each other less than we once did, we are not nearly as peaceful as the killer whale — which despite the name, has a rate of interpersonal violence of pretty much zero (though Gomez notes that only a small sample of killer whales was examined). Many whale species, bats and anteaters are particularly peaceful to their own kind, the study finds. 
   
   But humans are far less violent than the cougar, certain baboons, lemurs and chinchillas that have murder rates of well over 100 per 1,000. 
   
   The study looks at violence through the lens of phylogenetics — the study of evolutionary relationships, or how closely related species seem to share common traits. 
   
   "We found that closely related mammal species tend to have similar levels of violence," Gomez said. The more closely related species are, the more similar are their violence levels. 
   
   Gomez and colleagues used 1,044 studies that looked at 1,024 different mammal species, with the causes of death determined for more than 4 million individual mammals. Then for each species, the researchers counted the number of deaths due to a member of the species killing another. They didn't use studies where they couldn't find causes of death. And because of the study's historical nature, Gomez could only examine killings, not wounding. 
   
   Moving up in evolutionary complexity often seems a walk on the wild side, especially in the branches of the tree of life where humans come from. 
   
   If mammals have a three in 1,000 violence rate, a superorder of species called Euarchontogilires that includes our ancestors, hares, and rodents has a violence rate of about 11 in 1000. Further on, the large grouping called Euarchonta that includes us, other primates, tree shrews and flying lemurs has a rate of about 23 per 1,000. It drops to about 18 for great apes. 
   
   It was hard to calculate lethal violence rates for early humans; Gomez examined several thousand prehistoric people's deaths across the globe in archaeological sites. 
   
   Culture, government and other factors tamp down the inherited violence, Gomez and colleagues conclude. 
   
   "Our study suggests that the level of lethal violence is reversible and can increase or decrease as a consequence of some ecological, social or cultural factors," Gomez said. 
   
   These conclusions are similar to what Harvard psychologist Steven Pinker found in his book "The Better Angels of Our Nature." He charted long-term reductions in war, murder, rape and bigotry. 
   
   Pinker praised the Gomez study as creative and thorough. 
   
   "Based on three biological facts — we are apes, we are social and we are territorial — one would predict that humans should engage in lethal violence in our natural conditions," Pinker wrote in an email. "Modern societies have developed, especially the rule of law, that have reduced rates of lethal violence below what would expect for a mammal with our ancestry and ecology." 
   
   Harvard biological anthropologist Richard Wrangham, who studies the roots of violence, praised the breadth Gomez study, but said there some issues remain. He's especially concerned about too closely linking primates killing their own, which is more the murdering of infants, to humans whose killing their own mostly involves adults. 
   
   Few species beyond humans and some social territorial carnivores like wolves and lions are part of the "adult-killing club" of their own species, Wrangham said. "Humans really are exceptional." 
   
   ___ 
   
   Online: 
   
   Nature: http://www.nature.com/nature 
   
   ___ 
   
   Follow Seth Borenstein at http://twitter.com/borenbears and his work can be found at http://bigstory.ap.org/content/seth-borenstein
target: – Violence comes naturally to humans, but we are far less murderous than we used to be, a new study shows. Scientists in Spain who examined the tendency among more than 1,000 mammal species to kill their own found that humans have been "particularly violent" throughout our history, reports the AP. Early humans killed each other at a rate of about 20 in 1,000, but got more violent during the Middle Ages when the rate shot up to 120 in 1,000. After studying 600 human populations from the Stone Age to the present day, the researchers concluded that "lethal violence is part of our evolutionary history but not carved in stone in ‘our genes,’” lead author Jose Maria Gomez tells the Guardian. Levels of violence are influenced by societal pressures and have "decreased significantly in the contemporary age," says Gomez. Still, the study published in the journal Nature found modern humans to be pretty dangerous, killing each other at a rate of about 13 in 1,000. At least we're not the worst. That title goes to, surprise, the meerkat. "Almost one in five meerkats, mostly youngsters, lose their lives at the paws and jaws of their peers," Ed Yong writes in the Atlantic. The meerkats were followed by two types of monkeys and assorted lemurs. The New Zealand sea lion, long-tailed marmot, lion, branded mongoose, and grey wolf round out the top 11. Not surprisingly, violence was more common among mammals who share territory than among loners like bats and whales. "Our study suggests that the level of lethal violence is reversible and can increase or decrease as a consequence of some ecological, social, or cultural factors," says Gomez. (A study found early humans may have killed off real-life hobbits.)