Andreas Bloch/Wikimedia Commons
Murder was a family affair among Iceland’s Viking settlers. And the bigger the family, the more murderous it could be.
Vikings have a long tradition of writing down their family histories in epic stories. Called sagas, these tales told of war and long voyages. They included births, marriages, migrations and deaths. Researchers gathered data from three of these family histories. And when it came to murder, family size was key, they now report.
Viking killers in Iceland had nearly three times as many relatives as their victims did, says Robin Dunbar. An evolutionary psychologist, he works at the University of Oxford in England. Vikings who murdered five or more people came from the biggest families, his team found.
Iceland is an island nation in the North Atlantic Ocean. Its first settlers were Viking explorers who arrived from Europe in the late 800s. Dunbar’s team studied sagas written by three Icelandic families between 900 and 1100. Their tales described feuds and murders. They named 1,020 people, spanning six generations. For each named individual, the researchers mapped out a network of relatives. This included people they were related to by birth or through marriage.
The three sagas cited 153 killings. And the death toll was high: roughly one in every six men. Just six Vikings were involved in almost half of those deaths. Each of these killers took the lives of between 5 and 19 people. The most successful slayers came from large families. Their victims, in contrast, came from small families. A desire for more land may have been the motive for many of the killings.
Under Norse law, a murder entitled the victim’s relatives to either a revenge murder or money to compensate them for their loss. It appears that the murderers’ big families discouraged the smaller families from seeking revenge.
Most murders had been committed by men who killed just once. Here, the killers usually had only slightly bigger families than their victims. These murders were probably unplanned, Dunbar’s team says. They may have been triggered by an insult or some argument.
The researchers described their findings online September 20 in Evolution and Human Behavior.
Murder rates tend to go up when there are few or no authorities to enforce social order, Dunbar says. “The real issue is not that there were so many murders among Icelandic Vikings, but that murders were carefully calculated based on knowing whether one had a sufficient family advantage to take the risk.”
There is even a mathematical formula that addresses this. During World War I, a British engineer calculated the advantage that a larger group has over a smaller one in a fight. The bigger group’s advantage gets much larger as the size difference between the groups increased, he showed.
Dunbar’s team found that the same thing among the Icelandic Vikings. The bigger the difference in family size, the more likely someone was to get away with murder.
It’s rare to find research on how family size might encourage murder. It’s even rarer to find that kind of study on preindustrial groups like the Vikings, says Dominic Johnson. He’s a political scientist at Oxford who was not involved in the new research. Johnson has studied how group size affects whether an animal or human might attack.
Today, big families can mean extra protection on the playground or the school bus. Which means that perhaps the Vikings weren’t so different from us after all.
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Atlantic One of the world’s five oceans, it is second in size only to the Pacific. It separates Europe and Africa to the east from North and South America to the west.
behavior The way a person or other organism acts towards others, or conducts itself.
engineer A person who uses science to solve problems. As a verb, to engineer means to design a device, material or process that will solve some problem or unmet need.
evolution (v. to evolve) A process by which species undergo changes over time, usually through genetic variation and natural selection. These changes usually result in a new type of organism better suited for its environment than the earlier type. The newer type is not necessarily more “advanced,” just better adapted to the conditions in which it developed.
evolutionary An adjective that refers to changes that occur within a species over time as it adapts to its environment. Such evolutionary changes usually reflect genetic variation and natural selection, which leave a new type of organism better suited for its environment than its ancestors. The newer type is not necessarily more “advanced,” just better adapted to the conditions in which it developed.
family A taxonomic group consisting of at least one genus of organisms.
generation A group of individuals born about the same time or that are regarded as a single group. Your parents belong to one generation of your family, for example, and your grandparents to another. Similarly, you and everyone within a few years of your age across the planet are referred to as belonging to a particular generation of humans. The term also is sometimes extended to year classes or types of inanimate objects, such as electronics or automobiles.
Iceland A largely arctic nation in the North Atlantic, sitting between Greenland and the western edge of Northern Europe. Its volcanic island was settled between the late 800s and 1100 by immigrants from Norway and Celtic lands (ones governed by the Scots and Irish). It is currently home to roughly a third of a million people.
migration (v: to migrate) Movement from one region or habitat to another, especially regularly and according to the seasons. One that makes this move is known as a migrant.
network A group of interconnected people or things.
political science A social science that deals with the governing of people, largely by elected officials and governments.
preindustrial An adjective that refers to the period before societies had begun to industrialize, using machines and fossil fuels to build products, often with assembly lines or big teams of workers. In the United States, that period began in the mid- to late-1700s.
psychologist A scientist or mental-health professional who studies the human mind, especially in relation to actions and behavior.
social order The system of values, practices, institutions and rules that guide the behaviors of an integrated group of people or animals.
Vikings Seafaring explorers who came from Scandinavia. They traveled as traders and raiders from the late 700s to roughly 1100 A.D. Although Vikings have a reputation for warring, history suggests most started as farmers that took summer trips to trade and expand their territories.
World War I Also known as WWI and the Great War. This war began in 1914, as two alliances faced off against one another. On one side were the so-called Central Powers — Germany, Bulgaria and the Ottoman and Austro-Hungarian empires. On the other side were the Allies — France, Great Britain, Russia, Italy and, beginning in 1917, the United States.