investigating some of the chemical reactions and methods employed by First Nations Australians to convert toxic plants into edible food products
Content description
Connecting the elaboration and content description
This elaboration provides a context for students to learn about decomposition reactions and factors affecting reaction rates. Students study the methods employed by First Nations Australians in the detoxification of poisonous endemic plants, such as cycads in Queensland, into edible food products.
Detail
The development of complex detoxification processes by the rainforest Aboriginal peoples of North Queensland was undoubtedly driven by the food needs of the society at the time. The recognition of patterns in data, gathered from experiments that attempted to remove toxins, allowed this cultural group to modify and perfect the detoxification processes. Since Europeans survived a near-fatal experience after consuming under-processed cycad kernels on the first voyage to Australia by Cook and his party in 1770, many of the detoxification processes of poisonous plant foods employed by Aboriginal peoples throughout Australia have been documented. These detoxification processes provide evidence of Australia's First Nations peoples’ extensive scientific knowledge of chemical and physical processes, and an acute ability to draw conclusions that are consistent with evidence.
Students can explore a great variety of methods to remove toxins from poisonous foods as used by many of Australia’s First Nations’ peoples. A particularly suitable example for student investigation may be the method to detoxify cycad seeds employed by the rainforest Aboriginal people of North Queensland.
Cycads are a rich source of carbohydrates, but they contain a toxic substance called cycasin, which causes not only a range of acute symptoms, such as vomiting, nausea and abdominal pains, but also long-term damage to the nervous system and liver. Cycasin has been linked to various types of cancer. It consists of an innocuous sugar part (glucose) that is chemically bound to the active toxic substance methylazoxymethanol (MMA). In a chemical reaction with water (called hydrolysis), cycasin is broken up into these two parts, thus facilitating the removal of the toxic (and water soluble) MMA. However, this is a slow reaction under normal conditions, which made it necessary for the rainforest Aboriginal peoples of North Queensland to discover and employ a range of measures to speed up the reaction, including increasing both the contact surface with water and the temperature. In contrast, if the untreated cycad kernels are consumed, the same reaction happens at a much greater rate in the body due to the presence of a catalyst (an enzyme called β-glucosidase), thus leading to the rapid onset of acute symptoms.
By investigating the detoxification of cycads, students are given opportunities to gain a deeper understanding of the factors that govern the rate of chemical reactions, as well as to learn about and appreciate the highly developed science inquiry skills, ingenuity, and scientific knowledge of the rainforest Aboriginal peoples of North Queensland.