In the heart of Bolivia, an Amazonian society is losing its traditional knowledge of the medicinal value of local plants, to the detriment of its children’s health. The Tsimane’ are a small seven thousand-strong population living in a lowland region of Bolivia, who possess tremendous knowledge about the plants they share their forest with.

Their botanical know-how trickles down through the generations and allows them to use the local plant-life for construction, tool-making, medicine and food. These plants account for over half of their household consumption of goods, while those purchased from the outside world make up a meagre three per cent at most.

But globalisation is changing all that. The Tsimane’ are now starting to integrate into societies that place no value on their indigenous knowledge. They are promised alternatives in the form of Western medicine without necessarily having access to it. Their culture is disappearing.

But unlike many other societies, it is only beginning to do so. And that gives scientists like Thomas McDade and William Leonard from Northwestern University a chance to work out what impact the loss of traditional knowledge might have on the Tsimane’s future.

To do this, they assessed the health of 330 Tsimane’ children, aged 2-10, and tested their mothers and fathers on both their knowledge about local plants and their skills at using them.Their results were striking. Children with plant-savvy parents – mothers in particular – were much healthier than their peers, irrespective of other factors such as education or integration into other societies.

On the other hand, those with more ignorant parents had higher levels of an immune system chemical called C-reactive protein, which accumulates in the presence of frequent infections. They had smaller fat reserves to draw on for growth or fighting off disease. And they were more likely to have stunted growth, a sign of infections or malnutrition.

Westerners often look down on traditional knowledge as mere folk tales or cultural curios. But for the Tsimane’, they are clearly more – they are a vital ingredient for the society’s good health. Knowledgeable mothers can pick out the most nutritious plants to give their children the healthiest and most balanced diets (and all without Jamie Oliver’s assistance).

But various forest plants also have medicinal value. In an environment rife with disease and with little access to modern medicines, the Tsimane’s knowledge acts as a buffer against infections, helping their children to recover faster. And since parents begin passing their tips and tricks down at an early age, children of well-versed parents can start self-medicating or helping their younger friends.

The cultural transmission of knowledge is a key part of the human species’ adaptive power. And as globalisation continues for better or worse, we would do well to remember that such enlightenment also exists at a small and intimate scale. Education, modern medicine and economic security can certainly boost global prosperity. But as the Tsimane’ show, they can also do harm at a local level by replacing vital cultural expertise while offering little in its place.

On the other hand, it would be foolish to assume that all ‘traditional knowledge’ is golden. The strength of Western medicine lies in it scientific foundations and its own transmission of knowledge through journals and conferences. Groups like the Tsimane’ arrive at their local knowledge of plants through remarkably parallel means, using similar processed of inductive reasoning.

But there, the impetus is survival. Their knowledge of local plants is put to constant use and there is great value in getting things right. Using the wrong plant in the wrong circumstances could make things much worse, and there is a strong incentive for weeding out incorrect strategies. Superstition doesn’t get a look in.

When the stakes are lowered, the door is open to quackery. A herb salesman on a busy high street, for example, may claim that their prescriptions may claim to be based on centuries-old knowledge but face no direct repercussions if their products don’t work. Without the immediacy of need that the Tsimane’ face, knowledge handed down over generations can be diluted to the point of inaccuracy.

Reference: McDade, Reyes-Garcia, Blackinton, Tanner, Huanca & Leonard. 2006. Ethnobotanical knowledge is associated with indices of child health in the Bolivian Amazon. PNAS 104: 6134-6139.

November 1st, 2008 by Ed Yong in Art and Culture, Medicine & health | 4 comments | RSS feed | Trackback >