New research paper about cooperation in groups of Saami reindeer herders

People rely on one another in fundamental ways, but cooperation in groups can be fragile. Every day, we face tensions between acting in a socially responsible manner and following our own self-interest. These situations are called social dilemmas and they come in varying shades of subtlety, from littering and eBay to overpopulation and climate change. Overcoming these dilemmas can make all the difference, especially for marginalised groups such as pastoralists – people who make their living from herding animals.

Pastoralists use about a quarter of the world’s land for grazing their herds. Nowadays, all over the world, governments are privatising many of their pastures, and so herders must work together in increasingly fragmented places.

We wanted to learn how groups of Saami reindeer herders living in Norway’s Arctic Circle worked together. Our study, just published in the journal Human Ecology, found that cooperation pivoted around the ‘siida’: a group of herders—often family members—sharing pastures and migration routes. Smaller siidas were more cooperative, but the presence of closer family members did not affect cooperation.

While interviewing the reindeer herders, we gave them vouchers for five litres of petrol and asked how much of it they wanted to contribute to their siida. The amount they’d receive in return depended not only on how much they chose to give but also on how much everyone else in their group gave.

This economic situation is known as a public goods game. A public good is any resource (or ‘good’) that’s open for anyone to access without diminishing through use. This blog post, for example, is a public good. Your enjoyment (or otherwise) of it doesn’t stop anyone else from reading.

In a public goods game, a group of people choose how much of their money to share with everybody else. The experimenters increase whatever was donated to the group’s pot (we multiplied donations by 50 percent) and then distribute the final amount equally among all players, regardless of how much each person contributed.

This kind of experiment is very much a caricature of real-life dilemmas about how best to make decisions given how other people are behaving, but caricatures are helpful shortcuts to understanding cooperation – especially in places like Norway where everything costs a lot of money and learning how reindeer herders work together out in the pastures would require decades of observation (and a hardiness to the despair of winter that I probably can’t muster).

In theory, people make their donation decisions based on how much they expect to get back. In economic parlance, this is the ‘marginal per-capita return rate’. Groups with fewer members tend to have higher return rates and so they should donate more. This is what we found:

Petrol donations by marginal per-capita return rate

Smaller groups could expect to receive more in return for every litre they donated and this corresponded with larger donations in our experiments.

We also asked people about how often they took part in a set of activities – tasks like herding, slaughtering and making handcrafts (duodji, in the Northern Saami language). Herders directed most help towards their own siida, though helping people in other siidas wasn’t unknown. This makes sense, since siidas might rely on one another to repair shared fences or to separate reindeer when their herds mix.

Cooperation, as reported by the herders we interviewed

The study is available to read for free here:

For the overtly nerdy, we’ve also released our data and analysis code here:


I’ve been quiet lately because I had to write my thesis then defend it. Now I’m being quiet because I’ve gone to bimble around Hanoi for a while in an attempt to decompress from PhD life.

We’re trying to publish some of my chapters so the actual thesis itself is embargoed at the moment (one chapter was published last year). But in case you are interested, here’s a summary written using only the ten hundred most common English words:

We think we know what people are like from how they act in rooms where brain-people in white jackets make them do things. But I want to check how people act in real life. I looked at how people work together in two places – one where they keep animals in the cold land at the top of the world and another place where they grow food around a body of water in a big big land. The people helped their friends, family and other close people. They liked good people and didn’t help bad people.

And here’s the official summary:

Humans live in cooperative groups of varying scales and composition, from families to nations and international communities. Segregating into groups can provide benefits by alleviating individual costs. However, individuals also face a dilemma between following their own interests and those of the group, which can lead to a breakdown in cooperation. The evolutionary benefits and costs of cooperation are well-understood theoretically, but the real-world dynamics of cooperative behaviour remain unclear. This thesis investigates cooperation in two populations, employing field experiments and social network methods grounded in a human behavioural ecology framework. Part I centres on Saami reindeer pastoralists, an indigenous minority who live and work in cooperative herding groups around northern Norway. I collected survey and experimental data, using gift games to test whether herders acted cooperatively towards genetic relatives or to their herding group, or both. I also played public goods games to understand how herders respond to and solve social dilemmas. Cooperative behaviours were biased towards the herding group, although kinship also had a positive effect on gift-giving. Smaller groups were more cooperative, although this pattern was not driven by relatedness. Part II analyses demographic and experimental data collected by others from a population of Mosuo farmers living in rural southwest China. The Mosuo are a minority whose social system traditionally revolved around matrilineal households but which is changing in response to increased tourism. The results show how affinal relationships encourage a real-word measure of cooperation: labouring on farms. Some Mosuo people were considered witches. I test whether witchcraft accusations act as a form of costless punishment, allowing people to withhold help from witches. Witches were somewhat isolated within their villages but clustered together and did not suffer significantly lowered reproductive success. These results underline the importance of studying cooperation in real-world groups in addition to laboratories.

New research paper about Saami reindeer herders and gift-giving

I’m enormously pleased to say that I have a new bit of research published. The paper is about gift-giving in a group of reindeer herders living in Norway. It’s the culmination of nearly two and a half years’ worth of work – from our initial planning, though some months of hanging out in the (surprisingly warm) arctic, to endless rounds of statistics and writing and revising and statistics and *facepalming* and statistics and *headdesking* and statistics and revising.

The paper itself is published in a journal called Behavioral Ecology but because of funding constraints we weren’t able to make it open access – to my great chagrin (but you can download a PDF for free here or read it online here, or feel free to email me if you want a copy).
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The evolution of cooperation isn’t so puzzling

There’s a bit of a vibe in evolutionary anthropology/biology/theory that the evolution of cooperation is puzzling. A recent book — The Moral Brain — says “cooperation between unrelated individuals poses a puzzle from both the perspective of natural selection and that of rational self-interest”. Still there are loads (and I mean *loads*) of theoretical models showing a variety of ways for cooperation to evolve. In a moment of heightened procrastination, I decided to delve into the literature and find out just how puzzling scientists find cooperation (warning: this is not even remotely a scholarly piece of work).
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A tool to visualise the scientific literature

I spent an enjoyable couple of days last week in the beautiful Wellcome Trust taking part in a data/text mining workshop run by The Content Mine.

The idea behind their project is to develop tools that help scientists and other interested sorts pull data from published articles, potentially on a large scale. If you want to learn more, all their presentations are online, as are the materials from the Wellcome workshop.

The second day was a hackday. For this, my team wanted to build on the ContentMine tools to create something that helps you explore the scientific literature and find connections between papers you might not otherwise have found. We thought it would work something like this:
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New paper about how sibling competition and mortality risks affect birth intervals

My very first contribution to the collected sum of human knowledge has just been published in the Journal of Evolutionary Biology. The paper is called: “A Dynamic Framework for the Study of Optimal Birth Intervals Reveals the Importance of Sibling Competition and Mortality Risks” and you can read it online or download a PDF. I’ll talk about the main results in this post.

paper header 2
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My review of the Crick Lecture 2014 – ‘Genetic control and the mammalian radiation’

I reviewed last November’s Crick Lecture at the Royal Society on behalf of BioNews. Dr Duncan Odom spoke about mammals, genes, a branch of biology called ‘comparative functional genomics’ and how we all owe everything to tiny shrews. I also took the opportunity to have a moan about simplistic sloganeering and the rights of marginalised forest-dwelling people. Have a read.