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Are there fitness benefits to violence? The case of medieval Iceland

Dunbar, R. I.M. and Wallette, Anna LU (2024) In Evolution and Human Behavior 45(5).
Abstract

Males that behave violently to achieve social and reproductive objectives are a widespread phenomenon among mammals, as well as humans. Because this kind of behaviour can be socially very disruptive, its continued survival in human populations, in particular, remains a puzzle. We use historical data on the pedigrees of medieval Icelandic Vikings to test the hypothesis that males who killed had higher fitness than other males. Whereas most studies that examine the evolutionary benefits of behaviour focus on the numbers of offspring sired, in this paper we measure fitness more directly in terms of the number of grandchildren produced both directly and indirectly via collateral relatives, as well as determining the costs of pursuing... (More)

Males that behave violently to achieve social and reproductive objectives are a widespread phenomenon among mammals, as well as humans. Because this kind of behaviour can be socially very disruptive, its continued survival in human populations, in particular, remains a puzzle. We use historical data on the pedigrees of medieval Icelandic Vikings to test the hypothesis that males who killed had higher fitness than other males. Whereas most studies that examine the evolutionary benefits of behaviour focus on the numbers of offspring sired, in this paper we measure fitness more directly in terms of the number of grandchildren produced both directly and indirectly via collateral relatives, as well as determining the costs of pursuing alternative strategies in terms of experienced mortality rates. We show that, on average, killers gain a very significant fitness advantage despite the often high costs they pay and, more importantly, that they had a dramatic effect on the fitness of their male kin. We suggest that such behaviour represents a phenotypic, rather than genetic, response to opportunities provided by local circumstances.

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publishing date
type
Contribution to journal
publication status
published
subject
keywords
Berserkers, Fitness, Murder, Vikings, Violence
in
Evolution and Human Behavior
volume
45
issue
5
article number
106614
publisher
Elsevier
external identifiers
  • scopus:85200976062
ISSN
1090-5138
DOI
10.1016/j.evolhumbehav.2024.106614
language
English
LU publication?
yes
id
7a400cfc-e0ab-4799-a7f4-dd22ad72685e
date added to LUP
2024-09-05 14:57:02
date last changed
2024-09-05 14:57:46
@article{7a400cfc-e0ab-4799-a7f4-dd22ad72685e,
  abstract     = {{<p>Males that behave violently to achieve social and reproductive objectives are a widespread phenomenon among mammals, as well as humans. Because this kind of behaviour can be socially very disruptive, its continued survival in human populations, in particular, remains a puzzle. We use historical data on the pedigrees of medieval Icelandic Vikings to test the hypothesis that males who killed had higher fitness than other males. Whereas most studies that examine the evolutionary benefits of behaviour focus on the numbers of offspring sired, in this paper we measure fitness more directly in terms of the number of grandchildren produced both directly and indirectly via collateral relatives, as well as determining the costs of pursuing alternative strategies in terms of experienced mortality rates. We show that, on average, killers gain a very significant fitness advantage despite the often high costs they pay and, more importantly, that they had a dramatic effect on the fitness of their male kin. We suggest that such behaviour represents a phenotypic, rather than genetic, response to opportunities provided by local circumstances.</p>}},
  author       = {{Dunbar, R. I.M. and Wallette, Anna}},
  issn         = {{1090-5138}},
  keywords     = {{Berserkers; Fitness; Murder; Vikings; Violence}},
  language     = {{eng}},
  number       = {{5}},
  publisher    = {{Elsevier}},
  series       = {{Evolution and Human Behavior}},
  title        = {{Are there fitness benefits to violence? The case of medieval Iceland}},
  url          = {{http://dx.doi.org/10.1016/j.evolhumbehav.2024.106614}},
  doi          = {{10.1016/j.evolhumbehav.2024.106614}},
  volume       = {{45}},
  year         = {{2024}},
}