This entry was written by Margot Schneider as part of a project done in BIAN 2133 ‘Human Reproductive Strategies’ at The Australian National University in 2019 Semester 2.
Introduction
The Meriam are a population of the Torres Strait, Australia, of Melanesian descent (Smith, 2004). The population is found on the island of Mer, in the north of the Great Barrier Reef, with a population of around 430 individuals. This population relies heavily on the ocean for food. Apart from a dugong every now and then, Green sea turtles are the largest prey the Meriam hunt, they are shared between households and eaten at feasts. While everyone in the community fishes year-round, collecting these turtles during the nesting season from the beach, only men hunt them in the open ocean, the only method to catch them outside of the nesting season. This is a dangerous task that doesn’t always result in success, with an evolutionary explanation: costly signalling theory (CST) (Darimont, et al., 2017). This short essay will outline the evidence for CST in the Meriam population, a high risk high reward evolutionary behaviour.
Main Text
Showing off and Costly Signalling Theory
CST tries to explain why animals, including humans participate in activities that are not energy efficient, and place the member at risk (Shaver & Sosis, 2018). A non-human example of this is stotting in gazelles. Where the individual will jump up and down in front of a predator, at first glance this seems inefficient: jumping up and down in-front of the predator would be better spent running away. However, the gazelles are communicating with their predator, letting them know that they are strong and would do better not to attack them. If these gazelles are then less likely to be killed, the energy spent is not wasted, and they are more likely to survive to pass on their genes. When we look at the human population, we think of men ‘showing off’, the immediate evolutionary explanation for this is not obvious. Trophy hunters kill large game which is not eaten, a form of pride, signalling to their audience that they are strong and healthy, in the modern world the audience could be considered social media (Darimont, et al., 2017).
High Risk High Reward
The Meriam are a classic example population for CST. While men, women, and sometimes children help to provide food for the household, Meriam women will always maximise energetic efficiency, low risk fishing harvests reflect the amount of time spent (Bird, 2007). Whereas Meriam men, are more likely to choose the higher risk higher reward form of fishing, irrespective of the area of the reef they are in. Whether this is large hook fishing, instead of small hook fishing, or spear fishing instead of reef flat collecting. Even though the fishing the men choose does not always lead to a higher yield, the individual catches they obtain are larger and more likely to be shared even if the total haul is smaller. Men have a social role of providing their household and the community, this has led to the most extreme form of food collection in the population: green sea turtle hunting.
Increased Reproductive Success
Green sea turtles weigh about 100-150kg, taking a high level of skill to locate and kill them in the open ocean (Smith, 2004). While turtles collected during the nesting season by men, women, and children are often shared between households for smaller gatherings, turtles hunted in the open ocean are reserved for feasts and ceremonies, usually requested for by families (Smith, et al., 2003). As the food is shared, the hunters do not get a larger portion of the food then the rest of the community, they are not paid, the task is costly, physically and financially, which makes us wonder what the hunters themselves gain. Studies on multiple populations, Ache, Hazda, Meriam etc. have shown that the better hunters have higher reproductive success (Smith, 2004). Only the green sea turtle hunters (not speer fisherman) are shown to gain this advantage in the Meriam population, with up to 65% more mates. This increase is significant and is thought to come from signalling strength, successful hunts award the individuals with prestige and higher social status (Darimont, et al., 2017). The Meriam turtle hunters have more mates, having their first child on average at a younger age compared to non-hunters (Smith, et al., 2003). Often having younger more hardworking wives, and more children. Hardworking wives are those that harvest consistently high yields (Bird, 2007). This is thought to be due to sexual selection being based on female choice, a man with high status is seen to be more attractive for potential suitors (Smith, et al., 2003). While women are rewarded for their overall harvest, men are rewarded for the difficulty of their catch, as it shows patience, strength, skill, and an access to resources (Smith, 2004). Costly signalling allows the honest transmission of information about oneself to the greater community. This is reflected in populations like the Meriam and even gazelles, reflecting one’s personal health and in the case of the human population how well connected an individual is.
Conclusion
CST exists to explain the seemingly altruistic behaviour of why men share resources, putting themselves at risk for what seems to be no personal gain. Men’s preference for the hunting and capturing of larger food sources even if the success is lower, comes from a social obligation to provide for the community and not just the household. Hunting large game allows for men to display to their suitors that they can provide, that their genes are good. This results in higher reproduce success, with more offspring at a younger age for the male. The Meriam population are an example population of how big game hunting has an evolutionary explanation of signalling fitness in men for female choice.
Literature Cited
Darimont, C., Codding, B. & hawkes, K. 2017. Why men trophy hunt. Biology Letters, 13, 1-3.
Shaver, J. & Sosis, R. 2018. Costly Signaling in Human Culture. The International Encyclopedia of Anthropology, 1-7.
Smith, E. A. 2004. Why Do hunters Have Higher Reproductive Success?. Human Nature, 15(4), 343-364.
Smith, E. A., Bird, R. B. & Bird, D. 2003. The benefits of costly signaling: Meriam turtle hunters. Behavioural Ecology, 14(1), 116-126.
Bird, R. B. 2007. Fishing and the Sexual Division of Labor among the Meriam. American Anthropologist, 109(3), 442-451.