Culture and deforestation in the Pacific: A phylogenetic perspective


My colleagues and I conducted a comparative study of pre-European deforestation and reforestation (referred to hereafter as ‘forest outcomes’) on 70 Pacific islands (Atkinson et al 2016). Our aim was to see if any cultural, especially agriculture and land ownership norms, or geographic aspects of locations on those islands were associated with forest outcomes.

We published the results of the study in PLoS ONE, an open-access journal published by the Public Library of Science.

Atkinson QD, Coomber T, Passmore S, Greenhill SJ, Kushnick G (2016) Cultural and Environmental Predictors of Pre-European Deforestation on Pacific Islands. PLoS ONE 11(5): e0156340.  Link   PDF

Using comparative methods one can test hypotheses about functional relationships (i.e., about cause and effect). It is like choosing 100 kids that vary in candy consumption and testing the hypothesis that, if sugar causes cavities, you should see more cavities in the kids that eat more candy.

Of course, without conducting a controlled experiment, it’s hard to say anything definitively about causation. Poor health habits, for instance, may lead to eating tons of candy and never brushing your teeth. In those 100 candy eaters, was the higher incidence of cavities due to candy or poor dental hygiene?

The same goes in comparative cross-cultural studies like the one we’ve conducted. There are inter-dependencies in the data for a number of reasons, including shared environments and cultural history (for example, is there really a causal relationship between mountainous environment and prevalence of polyandry, or is there just a cluster of Himalayan societies that all live in the mountains and that all engage in this practice because their ancestors did?)

To control for cultural history and shared environments, we used phylogenetic methods — yes, the ones used more commonly in evolutionary biology to look at evolutionary relationships amongst species.

We found that geographic and cultural factors are associated with forest outcomes, but there was little phylogenetic signal. This suggests “that forest outcomes were not tightly constrained by colonists’ cultural ancestry, but instead reflect a combination of ecological constraints and short-term responses of each culture in the face of those constraints” (Atkinson et al 2016).

What was my role in the study?

I was enlisted by the lead author of this study to help provide data on land tenure for the societies on the focal islands. This required many hours of work reading dusty, early 20th century tomes on Pacific ethnography — which I loved of course. I also provided feedback on the analyses and helped to write the paper.

My previous work on the evolution of land tenure norms in societies of SE Asia and the Pacific was published in 2014. Click here to download that paper.


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Steve Pinker demolishes John Horgan’s view of war

Why Evolution Is True

As you may recall, Science Contrarian John Horgan’s notorious “admonition to skeptics” blog post at Scientific American criticized the entire skeptical community for its supposed failure to campaign against war. That “hard target”, said Horgan, should take precedence over our attempts to attack “soft targets” like homeopathy, global warming denialism, and opposition to vaccination and GMO foods.  But he also criticized those who propounded what he called the “deep-roots theory of war”.  Let me refresh you on what he said (note that every single one of his “references” goes to a Horgan blog post!):


The biological theory that really drives me nuts is the deep-roots theory of war. According to the theory, lethal group violence is in our genes. Its roots reach back millions of years, all the way to our common ancestor with chimpanzees.

The deep-roots theory is promoted by scientific heavy hitters like Harvard’s Steven Pinker, Richard Wrangham and Edward…

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What do we know about the ecology of pairbond stability?

What features of the environments that people live in, whether in small-scale foraging societies like the !Kung or in industrialized societies like my own, lead to changes in the stability of marriage?

Late in 2015, I was asked to provide a brief review of science’s progress toward answering that question. I was invited to contribute a chapter on the “Ecology of Pairbond Stability” to the upcoming Encyclopedia of Evolutionary Psychological Science edited by Shackelford and Weekes-Shackelford and due to be published in print in 2018.

Update (13 Nov 16):

My chapter has been accepted and is now published! The published version is behind a paywall. Springer allows some degree of open access, though, by permitting me to make the accepted mansuscript available on my website.

  • Kushnick G, 2016. Ecology of pairbond stability. In Shackelford T & Weekes-Shackelford V (eds.), Encyclopedia of Evolutionary Psychological Science (pp.1-7). NY: Springer, doi: 10.1007/978-3-319-16999-6_111-1.

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PLOS Funding for Conference Presentation

Public Library of Science (PLOS) is offering grants for conference travel. They are small purses ($500) and the requirements are stringent — must be a grad student or graduated a PhD in past 5 years, must have published in PLOS journal, must be presenting during a narrow range of dates — but they still might be worth applying.

More information here:

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Cross-cultural study shows how industrialization drove the evolution of maternal care-taking norms

Kushnick G, Hanowell B, Kim J, Lanstieh B, Magnano V, Oláh K (2015) Experimental evidence for convergent evolution of maternal care heuristics in industrialized and small-scale societies. Royal Society Open Science, 2, 140518 (doi: 10.1098/rsos.140518).  PDF  Link


Mother and child in a Karo village, Indonesia

Parental investment theory predicts that mothers will vary their care-giving behavior in ways that maximize fitness. Meaning that maternal decision making should be a tradeoff between the survival of her current offspring and her ability to produce future offspring.

In my new paper, which was written in collaboration with a group of international scholars (the PIVP Project) and published today in the new open-access journal Royal Society Open Science, we found that maternal care heuristics differed markedly between industrialized and small-scale societies. The differences can be thought of as adaptive strategies that arose to deal with the very different care-taking environments found in these societies. This idea is supported by gradients in the order and magnitude of the society-by-society heuristics and various national-level measures, such as total fertility rate, infant mortality rate, expenditures on health, and oil consumption.

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Bad is Bad, But How Bad Depends

moral intent

Our study found no support for the strong version of the Moral Intent Hypothesis.

Striking another person with intent to harm is wrong, we’d almost all certainly agree. But, if it was done in self-defense, we might reconsider that judgment. We might think that it was necessary and, thus, not quite as bad as a blindsided sucker punch thrown for no apparent reason. But, we might also consider that person a hero for standing up to a bully.

In the US, where I grew up, it’s pretty standard to take into account mitigating factors and intent when judging whether something’s wrong . In fact, its codified into law throughout the US and is thus considered by judges and juries when sentencing those who have perpetrated such behavior.

The role of mitigating factors and intent in shaping moral judgments has been called a universal feature of human moral psychology. Meaning that our brain just works this way and thus we should see similar moral reasoning in all people, in all societies from the simplest to the most complex. (1)

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Survival of the Aggressive?

They say love is worth fighting for, and it appears men in some small-scale societies have to do exactly that to play the mating game. Tara-Lyn Carter, a master’s student in biological anthropology at The Australian National University, and I conducted a study of behaviour and beliefs related to male aggression in 78 societies from around the world.

COLLECTIE_TROPENMUSEUM_Studioportret_van_een_krijger_uit_Nias_in_vol_ornaat_TMnr_60039092We found support for our hypothesis that, if these aspects of male aggression have been shaped by sexual selection—that they arise and stick around in societies because they offer an advantage in competing for mates—they will be more prevalent in societies where the intensity of mating competition is higher.

We were able to rule out alternative hypotheses, such as the notion that these behaviours and beliefs are simply due to socialization to a warlike society, or that shared environments and shared cultural histories may account for the associations.

We’ve deposited the paper at PeerJ Preprints, and intend to submit for publication in a peer-reviewed journal. You can read and provide feedback at:


Photo Source:

Photograph of warrior from Nias (North Sumatra, Indonesia)
Creative Commons Attribution-Share Alike 3.0 Unported licence
Attribution: Tropenmuseum, part of the National Museum of World Cultures

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