Dear Gerhard,

Burke and Wills were introduced to eating nardoo sporocarps by the Yandruwandha Aborigines at Cooper Creek, and nardoo became their sole source of food towards the end of their lives. It has been suggested that the Thiaminase contained in the nardoo sporocarps fatally poisoned Burke and Wills. However, there are two different proposals as to how the nardoo affected the explorers, both of which contradict each other, and consequently there are some questions over the validity of these claims.

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What is nardoo?

Nardoo is an aquatic fern, resembling a four-leaf clover, and there are 65 different species in the Marsileaceae family. The nardoo that Burke and Wills ate was Marsilea drummondii. The spores of the plant are contained in a small, hard sporocarp, which is the part eaten by Aborigines (not the leaves). The sporocarp is ground to a flour and then mixed with a little water to form dough which is then cooked in the ashes, or it is mixed with a larger quantity of water and drunk as a thin porridge or gruel. Yandruwandha elder, Benny Kerwin explained to Gavan Breen how the nardoo was prepared;

Ngardu ngala, parndringa ngandra, nga pinakanga nhulu pitjili. Ngapala ngapa kurrari nga thayinga ngapali. Kathi thukali ngala thayi-rnangatji marna-ngadikinitji mandri-rnanga. Kathi thukali, walya kalpurru thalpali or walya darlamurruli, ngarru kathi thukali mandri-rnanga.

Then there is the nardoo. They crush it and then rock it in a coolamon. Then they pour the water on it and eat it with the water…They eat it by spooning it into their mouths with a mussel [shell], not with a coolabah leaf or with bark, only with a mussel. (Kerwin, 1986).



Nardoo seeds

Dried seeds and portion of Nardoo plant brought back from Cooper's Creek by John King of the Burke and Wills Expedition, [ca. 1861], [Realia] H5180, State Library of Victoria.

When did Burke and Wills eat nardoo?

When Burke, Wills and King returned to the Dig Tree on 21 April 1861, they found the food that Brahe had buried there. As they considered it sufficient to get them to Mount Hopeless, they were not initially concerned with supplementing their diet with indigenous foodstuffs.

Their first experience of nardoo was on 7 May when they met a group of Yandruwandha near Maramilya Waterhole on Cooper Creek. Burke and Wills were given 'lumps of bread, which they call nardu'. They had nardoo again on the following day, and when Burke and Wills returned to their own camp on the 9 May, Wills considered they could supplement their dwindling stores with nardoo. However they thought the nardoo was the seed of a tree, and consequently could not find any sporocarps to collect. King recalled that

Burke and Wills went in search of the natives, to endeavour to find out how the nardoo grew; having found their camp they obtained as much nardoo cake and fish as they could eat, but could not explain that they wished to be shown how to find the seed themselves.

This is not surprising, as preparing nardoo was women's work, and as neither Burke nor Wills were initiated, or had a totem group or skin name, the Yandruwandha would have treated them as guests and given them prepared nardoo to eat, but would not have shown them the intricacies of how the women gathered or prepared the sporocarps.

On 17 May King finally discovered some nardoo sporocarps on the ground at the foot of a sandhill near Marra-tale. Wills stated 'this discovery caused somewhat of a revolution in our feelings for we considered that with the knowledge of this plant we were in a position to support ourselves even if we were destined to remain on the creek; & wait for assistance from Town.' Nardoo then became a significant part of their diet, although initially they had no way to grind the sporocarps into flour, so they boiled them and ate them whole.

On 24 May they found a grinding stone at a gunyah, and began to pound the nardoo as they had seen the Yandruwandha women do. They found it a difficult and time-consuming process, and so they mixed the ground nardoo with an equal amount of their dwindling supplies of flour. Nardoo was clearly becoming their most important food source as Wills referred to it as 'the staff of life.'

On 27 May Wills again met a group of Yandruwandha near Marrpu Waterhole, and they gave him nardoo and fish (this is the first time Wills had seen any Aborigines since 9 May). Wills visited their camp again a week later on 3 June, when he was given nardoo 'cake' as well as nardoo ‘porridge,’ which he described as 'a large bowl of the raw Nardu flour mixed to a thin paste a most insinuating article and one that they appear to esteem a great delicacy.' Wills stayed at the Yandruwandha camp for two days before they moved off upstream, indicating that Wills had better leave and go downstream. The 6 June was the last time Burke and Wills saw Aborigines before they died.

After 6 June nardoo became their sole source of food. Wills and King collected around 2kg of sporocarps a day and Burke cleaned the stalks from the sporocarps and ground them into flour. By 10 June Wills was too weak to collect nardoo, and he took over the responsibility of grinding while Burke and King harvested the sporocarps. Four days later, Burke became too weak to go out to harvest, and the task of feeding the three men fell on King.

By the 20 June Wills wrote, 'I cannot understand this Nardu at all it certainly will not agree with me in any form. We are now reduced to it alone and we manage to get from four to five pounds per day between us. The stools it causes are enormous and seem greatly to exceed the quantity of bread consumed and is very slightly altered in appearance from what it was when eaten.' Nevertheless Wills thought 'starvation on nardu is by no means very unpleasant, but for the weakness one feels and the utter inability to move oneself, for as far as appetite is concerned, it gives me the greatest satisfaction.'

Burke and Wills died during the last few days of June or the first few days of July 1861. Although the Victorian government held a Commission of Enquiry into the deaths of Burke and Wills, they reported on the circumstances that led to the explorers running out of food, rather that enquiring into the medical causes that resulted in their deaths. The Commission thought 'Mr Burke was forced into the necessity of overtaxing the powers of his party, whose continuous and unremitting exertions resulted in the destruction of his animals, and the prostration of himself and his companions from fatigue and severe privation.' As they died outside of the colony, there was no coronial inquest, and the public assumed that the explorers had died of starvation, exhaustion and dysentery or scurvy caused by the privations consequent with their exertions.

Nardoo grinding stones used by Burke, Wills and King at Cooper's Creek, 1861.

[Realia] H5103; LTRE 16, State Library of Victoria.

Would nardoo have poisoned Burke and Wills?

In 1982 Dr Tom Bergin posited that in addition to scurvy, the explorers suffered from beri-beri; a disease caused by a lack of vitamin B1 (thiamine). He demonstrated that the explorer's diet was deficient in vitamin B1, but he also suggested there were similarities between Burke and Wills' symptoms and those seen in a 1974 mass-poisoning of sheep and ovine polio-encephalomalacia, caused when one of the enzymes in nardoo, Thiaminase, destroys thiamine in the body. Bergin thought the explorers failed to prepare nardoo in the traditional indigenous manner, and as a result, had not removed the Thiaminase and had therefore poisoned themselves. Bergin suggests the correct way to remove Thiaminase was to mix the nardoo flour into dough and cook it in the coals, where the heat would destroy the toxic enzyme. Bergin did not think there was any evidence to suggest the explorers cooked nardoo bread, but merely mixed it with water and drank it as porridge. He argued that the Yandruwandha only consumed nardoo as bread and had never given the explorers nardoo porridge. They had presented Wills with porridge, but Bergin supposed this was made from the seeds of Portulaca oleracea, which Wills had mistaken for nardoo. Wills subsequently used the porridge method to prepare the nardoo, and because they did not subject the Thiaminase to heat during cooking, the toxin remained in the porridge. He concluded the both Burke and Wills died of beri-beri.

In 1994 Dr John Earl and Dr Barry McCleary also suggested that the explorers died as a result of beri-beri brought on by the consumption of toxic Thiaminase in incorrectly prepared nardoo sporocarps. Earl and McCleary made no reference to having read Bergin’s thesis, so they may have arrived at this conclusion independently as they had previously worked on the 1974 mass-poisoning of sheep and ovine polio-encephalomalacia. However they concluded that heat had little effect on Thiaminase as nardoo is well adapted to extreme summer temperatures. They thought the correct way to prepare the nardoo was to dilute it with water to reduce the effect of the Thiaminase enzyme. They suggested that although the Yandruwandha had shown Wills the nardoo porridge, the explorers prepared the sporocarps in the traditional way that Europeans prepared grain, and ground the nardoo into flour, mixed it into dough and cooked it in the coals. As they did not dilute the Thiaminase with sufficient water, it remained toxic. Earl and McCleary also concluded that Burke and Wills died of beri-beri.

Inconsistencies and further questions...

The papers by Bergin and Earl and McCleary both agree that Burke and Wills died of beri-beri which was exacerbated by the consumption of toxic Thiaminase.

Bergin argues that the correct method of preparation of nardoo to remove Thiaminase as practiced by the Yandruwandha was to subject it to heat during cooking. Earl and McCleary contradict this and suggest that the correct method of preparation as used by the Yandruwandha was to dilute the flour in water. It appears Bergin and Earl and McCleary have different and opposing ideas on how the Yandruwandha prepared nardoo, even though Wills’ journal clearly indicates he observed the Yandruwandha using both methods.

Bergin overemphasises the toxicity of nardoo. He mentions nardoo has been found to contain up to 100 times the level of Thiaminase found in other toxic plants like bracken. However he fails to mention that these high levels of toxicity occur in the leaves of the plant, which were not consumed. The sporocarps are nowhere near as toxic and only contain two to three times the Thiaminase concentrations found in bracken. In addition Bergin states that Thiaminase levels are highest in plants which have been the subject of intensive grazing, and as Brahe’s Depot Party had been at the Dig Tree for six months with six camels and twelve horses, they would have grazed the nardoo thereby increasing its toxicity. However Burke and Wills were more than 50 kilometres downstream of the Dig Tree and did not collect any nardoo from the areas where Brahe’s animals grazed. Bergin also states that nardoo is most toxic between February and May; however he fails to mention whether these dates are relevant to nardoo growth at Cooper Creek, or whether the reference was for the Gwydir Valley, where mass sheep poisonings occurred during these months. Bergin claims Burke and Wills ate the nardoo in April and May, during the times of highest toxicity, yet the explorer’s diaries show they did not begin preparing nardoo until 20 May, and most of their consumption of the plant was in the less toxic time of June.

Bergin also claims that the nardoo porridge Wills was given was actually made from the ground seeds of Portulaca oleracea. Bergin does not believe the Yandruwandha would have bothered to use the extra process of baking the nardoo flour had it been readily available as a non-toxic porridge. However Kirwan indicated the Yandruwandha did eat nardoo as porridge. Bergin also does not elaborate or explain how Wills would have mistaken the dark grey fragrant flour from portulaca seeds with the bitter yellow nardoo flour.

The chronology of Wills’ description of consuming nardoo does not fit with Bergin's hypothesis either. The first time Wills was introduced to nardoo it was in the form of bread. Wills does not mention nardoo porridge until four weeks later, by which time he has already begun harvesting and preparing nardoo himself in both bread and porridge forms.

Earl and McCleary claim Burke and Wills did not mix the nardoo into porridge, but Wills describes having a breakfast of ‘nardu porridge’ in late May, several days before he first describes been shown this method of preparation by the Yandruwandha.

Earl and McCleary also claim that Kirwan's description of not allowing the ground nardoo paste to come into contact with coolibah leaves or bark was a way of minimising contact with organic matter that would act as an endogenous cosubstrate for the Thiaminase. However they do not explain why the Yandruwandha stored the nardoo paste in wooden pitjili (coolamon bowls), and whether they would have acted as a cosubstrate.

Nardoo plants with sporocarps on a grinding stone, Cooper Creek.

Image © Dave Phoenix 2008.

Conclusion

Burke and Wills were almost certainly suffering from beri-beri during the later stages of their lives. However there is sufficient doubt to question whether this was the cause of their deaths. There are symptoms of the disease which were not present in Burke and Wills prior to their deaths. Beri-beri causes mental confusion and disorientation and Wills meticulous journal is maintained without error until shortly before his death. In addition beri-beri is associated with a rapid and shallow pulse, whereas Wills described a pulse of 48 shortly before his death.

It is also doubtful that the way the explorers prepared nardoo caused them to ingest Thiaminase, and therefore the hypothesis that they fatally poisoned themselves is questionable. Neither Bergin nor Earl and McCleary successfully demonstrate the Yandruwandha restricted their nardoo intake to ground sporocarps that had either been heated or diluted in water, and Wills’ diary indicates the Yandruwandha consumed both varieties. Wills’ diary also indicates that from 24 May 1861, they too alternated between the two methods, and the three explorers ate nardoo bread and nardoo porridge.

The argument that Burke and Wills did not observe the correct indigenous preparation of nardoo relies on the Yandruwandha preparing nardoo in just one particular fashion, and Burke and Wills using an alternative method to prepare their own food. However, it is clear from Wills’ diary that he observed the Yandruwandha using both methods of preparation, and the explorers used both methods of preparation in their own camp.

Because Burke and Wills were so exhausted, emaciated and most likely suffering from scurvy, the onset of beri-beri would have accelerated their deaths, but was probably not the sole cause for their demise. Additional factors such as malnourishment from a lack of calories provided by the nardoo they consumed combined with hypothermia, which is significant factor but has previously been overlooked, would also have played a significant role in their deaths.

This article is © Dave Phoenix, 2011. All rights reserved.

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References.

* Bergin, Thomas John. Courage and Corruption: An Analysis of the Burke and Wills Expedition and the Subsequent Royal Commission of Enquiry. MA Thesis, University of New England, 1982.

* Earl, John W. "A Fatal Recipe for Burke and Wills." Australian Geographic, Issue: 43, 1996: pp. 28-29.

* Earl, John W, and Barry V McCleary. 'Mystery of the Poisoned Expedition,' Nature, 368, 1994.

* Kerwin, Benny (transcribed by Gavan Breen), This is what happened: Historical narratives by Aborigines. (Eds: Luise Hercus, P Sutton). Australian Institute of Aboriginal Studies: Melbourne, 1986.

* King, John. Narrative: September 1861, Alfred Howitt's diary, Notebook #255110, Box FB33, MS 13071, State Library of Victoria.

* King, John. Narrative: September 1861, Edwin Welch's Field book No 1, Box 2087/7a, MS 13071, State Library of Victoria.

* Victoria: Parliament. Burke and Wills Commission. Melbourne: John Ferres Government Printer, 1862.

* Wills, William John. Journal of trip from Cooper Creek towards Adelaide: 1861, MS 30/7, National Library of Australia.

Nardoo, Marsilea drummondii, growing at Cooper Creek.

Image © Dave Phoenix 2008.

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