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Yalewa vuku: The Prestigious Elderly Women of Fiji that Hold the Secret to Human Cultural Adaptation

Article by

Andoni Sergiou, MSc.

A warm breeze sweeps over you from across the horizon, and the continuous sound of the ocean lapping at the beach is occasionally interrupted by the thudding of the odd falling coconut or too. You are feeling satisfied after a meal of cassava, yams, and reef fish, and sit cross legged upon the sand talking with some friends. This is what an evening may feel like on a good day at Yasawa island; an archipelago situated North West off of the island of Fiji. But all is not as it would seem in the garden of Eden. The very marine food chain that sustains you, your family, and community, is also the perfect natural system for the accumulation of deadly marine toxins.

This article is about why this decision won’t only save your life, but enable your descendants to prosper for generations to come within tropical marine environments. Think of it as an episode of Lost, anthro-style!

Well, what are you going to do about it? You are the descendant of a lineage of tropical primates that have evolved to be especially dependent upon culturally transmitted knowledge for your survival. As such, you have not genetically evolved adaptations that filter out these dangerous toxins. In fact, out of all the extant primate species, yours lacks an innately acute sense of smell for detecting toxins (like a lemur), and your gut enzymes and morphology cannot deal with toxic foods on a daily basis (like gorillas and some New World monkeys). Biologically, you are a hairless mammal with no claws, blunt teeth, and a simple gut, but a large metabolically expensive brain that would really appreciate some oily marine foods right now to keep your mind ticking over – an evolutionary catch-22 if ever there was one. You know what I would do? Copy what everyone else in the village is doing, and that is chatting to the village elders, especially the Yalewa vuku (the prestigious elderly women of the Yasawan villages). This article is about why this decision won’t only save your life, but enable your descendants to prosper for generations to come within tropical marine environments. Think of it as an episode of Lost, anthro-style!

First things first. Where are these marine toxins coming from, and how will they affect your health? Ciguatera fish poisoning is a threat faced by many marine subsistence communities situated across the tropics. The ciguatera poison is initially secreted in small amounts by certain species of photosynthetic sea algae that spend their lives attached to coral reefs. As these algae are consumed by herbivorous reef fish, and as those fish are consumed in turn, the concentration of ciguatera becomes increasingly concentrated and potent within the organs of fish as you move up the food chain. In short, Mufasa may need to revise his ‘Circle of Life’ philosophy! This news is particularly disheartening if you are a Yasawan fisherman that spends several hours a day spear fishing for prey that typically come from the upper ends of the food chain. Depending upon where your particular catch falls within this food chain, you may be subjecting your kin and wider community to various and potentially fatal health problems. These symptoms of Ciguatera poisoning can vary from simple long-term diarrhoea, to permanent neurological and heart dysfunctions. Most at risk are pregnant and breastfeeding mothers with their infants, as the toxins are even more harmful during the development of an infant’s nervous system and can be transmitted via the umbilical cord and breast milk.

So at this point you may be thinking (well, at least if you are a European or American scientist anyway) “right, no problem… I have a brain that is three times larger than a chimpanzee… I’ve got a degree… and I even learned how to cook pasta last week… blah blah blah, I’ll just watch who gets sick and figure out through trial and error what I can eat”. This sounds like a solid plan, right up until you really find out how difficult it is to solve this problem alone within a single human life time.

First, you need to have detailed ecological knowledge, not only of all the marine species around your reefs, but also of their diets. You and your aunt both eat eels that are roughly the same size, shape and colour, but you get very sick and she is absolutely fine. Then some fish (eels and reef sharks) eat the same resources, but do so in different quantities which means some are more deadly to eat than others, and you have to follow sharks watching everything they do all day to find out – yikes! And then you have to come up with some causal explanations as to why eating certain fish at certain times makes you sick. Is it because they contain ciguatoxin or maitotoxin chemicals? Am I not preparing or cooking my food properly? Are the ancestors angry with me? Was it actually that dodgy latte I had this morning? It’s not like your family can survive on cassava and yams in the mean time either, there are essential vitamins coming from your marine fish diet that you can’t get from local vegetables. In fact, a ready supply of vitamin A from fish oils prevents your children from going blind!

The problem is, many species look alike. At this point, it’s looking like you have all this human brain power, and yet it is a mystery as to what all that cognitive fire power actually does to help you survive. Studying the Yalewa vuku of Yasawa is beginning to teach us that the individual human brain is but one sophisticated and powerful link in a population-level multi-generational super computer, which builds up cultural adaptations over generational time. Instead of inherent genius, our big brains may have evolved for acquiring cultural knowledge, and doing so from the best sources. That is, if you need to know adaptive information about a complex environment, it can be less costly if you learn from other people in your social milieu, and then sharpen that knowledge up with some discoveries of your own. Things get even better if you can use cues of another person’s life-long success to get the most adaptive information. From an evolutionary perspective, if you strategically choose to learn from someone that is elderly, it is more likely that they have accumulated knowledge and discoveries that have helped them attain their great age (at least in ancestral human environments).

Studying the Yalewa vuku of Yasawa is beginning to teach us that the individual human brain is but one sophisticated and powerful link in a population-level multi-generational super computer...

Furthermore, within the context of something inherently dangerous for breastfeeding, like ciguatera poisoning, choosing elderly women who are locally known to be prestigious community leaders helps you to further filter that knowledge for applications in successful child rearing. When you iterate this cycle of strategic social learning and innovation across multiple generations, you get a build up increasingly adaptive beliefs, institutions, tools, and development plans for really specific problems, like avoiding ciguatera poisoning. What we may be looking at on Yasawa island then, is a community of sophisticated brains that form cultural ‘collective brains’, which in turn solve problems that are too complex for any individual to solve alone, and the Yalewa vuku (and elderly women in similar societies) may be one of the many essential engines that drive this collective brain mechanism.

Advocates of the above preproposal are professors like Natalie and Joseph Henrich, a wife and husband team of evolutionary anthropologists from Harvard university (#lifegoals!). Together with other ethnographers, marine biologists, and health care scientists, they have helped to set up a long-term research and development centre on Yasawa island. Their research has shown that Yasawan tabu (symbolic taboos and rules involving the will of spirits and ancestors) acts as an adaptive repertoire of dos and don’ts that helps people focus on only those fish that are low in ciguatera toxins. For one particular tabu that applies to women during pregnancy, abstaining from eating Murray eels has been shown to reduce the chances of mothers contracting ciguatera poisoning by up to 30% during pregnancy, and up to 60% during lactation. Furthermore, and in line with cultural evolutionary predictions, when asking locals about where they obtained their tabu knowledge from, individuals overwhelmingly cited their village Yalewa vuku. The Henrichs have also observed this pattern in other societies, where traditional food spicing combinations have been shown to combat regionally-specific kinds of foodborne pathogens.

So, if you and your colleagues get parachuted into the middle of the Amazon rainforest, don’t expect your big brains to fire up and reproduce your society with all it’s technological perks overnight – or even after multiple generations. What you need to find instead is someone with an accumulated body of local cultural adaptations… you need to find a Yalewa vuku!


Short bio: Andoni is an alumnus from the University of Kent specialising in Collective Brain theory. He uses computer simulations and artificial intelligence to study how human social networks process cultural information over multiple generations in order to produce cultural adaptations, technological innovations, and socioecological development.


For more info on Andoni's current projects see below:

Fractal Anthropology Research Programme - F.A.R:

The images contained in this article come from Dr. Joseph Henrich’s pulbic research site:

The research cited comes from the following journal article: “The evolution of cultural adaptations: Fijian food taboos protect against dangerous marine toxins”

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