Lands of Red and Gold #3: Yams of Red, Trees of Gold
Picture a time four and a half thousand years ago in a history that never was, then picture a place along the banks of the river that will now never be called the Murray. Along this river, in the region that will now never be called Swan Hill, live a people called the Gunnagal. Like many of their neighbours along this river, the Gunnagal have domesticated a plant called the red yam. An extremely valuable source of food, this crop has let the Gunnagal and other river peoples become hunter-gardeners. They establish seasonal settlements along the river to live of their yam harvest for up to nine months, then disperse for the remaining months to live off what they can hunt, fish, and gather from the earth.
Beyond their lives as hunters and gardeners, the Gunnagal people have developed new methods. Inspired by travellers’ stories of the distant Junditmara chiefdoms, the Gunnagal have turned their attention to expanding the natural lagoon into a system of wetlands from which they can harvest fish and water plants. So successful are the Gunnagal that they can live year-round in stone dwellings and enjoy an abundance of food. With their harvests of yam and fish, they have no need to wander seasonally.
From their first settlements, the Gunnagal begin to expand along the river, bringing their methods of yam and fish with them. They have food, they have numbers, they have prestige, and they displace and absorb many of their neighbouring river peoples. Along a length of the river of some eight hundred kilometres, the Gunnagal language becomes a lingua franca, and their culture becomes predominant. Not all of their neighbours have been expelled, but those who remain do so because they have taken up Gunnagal farming and fishing methods, and in time their speech and many of their beliefs.
Along the river, amidst the expanded country of the Gunnagal, people still gather wild plants to supplement their regular sources of food. They have knowledge of farming, now, and a sedentary lifestyle which inclines them to replant their most favoured wild foods rather than keep moving in search of new food supplies. Selective human gathering of favoured plants started even before the Gunnagal adopted a fully sedentary lifestyle, and in time this process leads to the domestication of other crops...
* * *
The early Australian agricultural package consists of several plants which are native to the Murray Valley, and which show good potential for domestication:
The red yam (Dioscorea chelidonius) is a vine with perennial rootstock and foliage which usually dies back over winter and regrows in spring, although the foliage sometimes remains year-round in warmer and wetter climates. Red yams produce an edible (and very tasty) tuber as a food store. The tubers are formed quite deep in the ground (up to a metre down), and so take a reasonable amount of digging to extract, but the tubers are large enough to justify the effort. In the wild state red yam tubers can grow up to 1 kg in weight (more in wet years); domesticated red yam tubers are often much larger. Domesticated red yams have been artificially selected both for larger tubers and for a sweeter taste [1].
Like many (but not all) Australian wild yam species, red yams can be eaten raw but are usually roasted or cooked in other ways. In culinary terms, the red yam can be cooked in a variety of ways similar to the potato or sweet potato. It is a staple crop which for most people forms over half of their daily calorie intake. Red yams are native to the central Murray Valley, but domesticated forms can be grown without too much difficulty in regions of adequate rainfall between latitudes of about 25 to 45 degrees. Cultivation of red yams at more tropical latitudes will need to await the development of cultivars more heat-tolerant and better adapted to tropical growing seasons, which will not be quick [2].
Wattles (Australian species of the genus Acacia) are a diverse group of shrubs and trees with nearly a thousand species across the continent. Wattles are fast-growing, can tolerate extended periods of drought, and grow even on poor soils. Indeed, they are legumes whose roots provide nitrates to revitalise the soil. They produce large numbers of protein- and vitamin-rich seeds which are a valuable source of food. Wattle seeds are pseudocereals; while not true cereals, their seeds can be used in a similar manner. Wattle seeds also remain viable for many years; over twenty years for some species.
The early Gunnagal peoples domesticate three main species of wattle, the mystery wattle (Acacia difformis), the bramble wattle (A. victoriae) and the golden wattle (A. pycnantha). Domesticated wattles are distinguished from wild varieties by having larger seeds, more regular yields from year to year, and also for flowering reliably at around the same time each year. While each individual wattle species has its own qualities [3], their main uses are similar. Wattle seeds are used similarly to cereal grains such as wheat or barley; the seeds are ground into flour for baking into flatbreads, cakes and similar products. They have a higher protein content than most cereal grains, which is particularly valuable in a society which does not have many domesticated animals. They are extremely important as a food reserve; the long life of wattle seeds means that they are ideal for storage until drought years.
Apart from their seeds, domesticated wattles have many other uses. They grow very quickly and can be used as a valuable source of timber. Wattle bark produces fibre which can be used for rope and clothing, and also contains tannins which can be used to tan animal leather. Their roots replenish the nitrate content of the soil, which means that they can be used in a system of crop rotation or companion planting alongside red yams and other crops. The empty seed pods and dead leaves of wattles can be used similarly as compost or mulch to maintain soil fertility; they are often mixed back in with the replaced soil after yam tubers have been dug out. Wattles produce a very useful gum, which is sweet and edible either immediately or dried as stored food, added to water to make a sweet drink, sometimes used as a kind of candy, but which also has many other uses, such as an adhesive or binding agent in paints [4]. Even the pests of wattles have their uses; the galls formed by wattle pests are edible, as are the witchetty grubs which burrow into wattle trunks and roots. In time, domesticated wattles become as important to the Murray civilization as the olive tree is for Mediterranean peoples, or the date palm is in Mesopotamia; the Gunnagal word for wattles, butitju, will also become the root of their words for “wealth” and “prosperity.”
Murnong or yam daisy (Microseris lanceolata) is a perennial flowering plant which produces an edible radish-shaped tuber. Like the red yam, murnongs have perennial rootstock but their above-ground foliage usually dies back every winter. Murnong tubers are much smaller than those of red yams, but murnongs can be grown much closer together, and their tubers are nearer to the surface and thus require less digging. For culinary purposes, murnong tubers are treated similarly to the red yam or more familiar crops such as potatoes. In most areas, domesticated murnongs are a secondary crop when compared to red yams; they do not produce as high a food yield per hectare, but they add different flavours to the diet, and it is customary to have some land under murnong cultivation in case disease or pests affect the main yam harvest. In the highland areas of south-eastern Australia, murnongs will become a more important crop since hybrids with the related alpine murnong (M. scapigera) are better suited to upland growing conditions than most red yam cultivars.
Purslane (Portulaca oleracea) is a succulent annual flowering plant which tolerates a wide variety of soil conditions, and is resistant to drought. The leaves, seeds, stems and flowers are all edible. Purslane is abundant throughout mainland Australia and much of the Old World. It has been independently domesticated on multiple occasions throughout the world. Amongst the Gunnagal, it is normally grown as a leaf vegetable; the leaves can be harvested all year round and are a useful source of some vitamins and essential dietary minerals. The seeds are also sometimes collected to be ground into flour and added to wattleseed flour.
Spiny-headed mat-rush (Lomandra longifolia) is a perennial sedge-like plant, with many stiff leaves that grow close together and are suitable for weaving. Mat-rush is a hardy plant which can tolerate a wide variety of soils and weather conditions. Domesticated mat-rush is grown primarily as a vegetable fibre to make baskets, nets and the like. Mat-rush is occasionally used as a source of food during lean times; its seeds and the base of its leaves are edible, and its flowers are a source of nectar, but its primary role is as a non-food fibre crop.
Scrub nettle (Urtica incisa) is a relative of the stinging nettle (U. dioica) of North America and Europe. It is a perennial plant which dies back to the ground every winter. As with its northern hemisphere relative, the leaves and flowers of scrub nettle are covered with hollow hairs loaded with formic acid, which produces a nasty stinging reaction if it comes into contact with the skin. The main use of domesticated scrub nettle is harvesting high-quality fibre from its stems, which is mostly used to make textiles, and ropes and other cordage. Scrub nettle is occasionally used as a vegetable, too; its leaves are tasty and quite nutritious, provided that they are cooked first to neutralise the formic acid.
Native flax (Linum marginale) is a close relative of common flax (L. usitatissimum). Native flax is a perennial plant which, like many Australian plants, often dies back during winter. The wild version has long been used by Aboriginal peoples as a source of fibre and for its edible seeds. Domesticated native flax, like common flax, is used as a source of fibre for textiles; the Gunnagal will rely on linen for most of their clothing and other weaving. The seeds are edible on their own or sometimes added to wattleseed flour; they can also be used to make linseed oil, but this is rare because of its short shelf life under Australian conditions.
* * *
The Australian agricultural package has quite a different range of characteristics from most other agricultural packages which have arisen from other independent origins of agriculture [5]. Perhaps the most noteworthy of those is that all of the staple crops, apart from the relatively minor purslane, are perennial plants, i.e. they are planted once and then produce a harvest each year for a number of years. This is in contrast to most of the staple crops grown around the globe today and historically, which are annual plants i.e. plant once and then harvest.
Annual plants are the basis of most modern agriculture. Staple crops such as wheat, barley, maize, rice, potatoes [6] are all harvested as annual plants. Annual plants have a variety of advantages which have made them easy to domesticate and then use. As annual plants, they have a fast generation time which enables selective breading to happen more rapidly. There are a wide variety of annual plants which are domesticable and offer good food yields. In particular, there are many annual cereal crops which produce grains which can be stored for several periods, which is vital for preventing famine during drought. Moreover, with an annual plant, if the harvest is lost due to disease, drought, flood, fire or warfare, then only a single year’s production has been lost, and it can be replanted next year.
However, annual plants also have a number of disadvantages. They have quite high labour requirements, since the soil needs to be plowed and plants resown every year. The type of soil cover used with annual plants – light roots, soil often exposed to the weather during planting – means that topsoil erosion and other environmental damage is quite likely. The soil loss is often severe enough that annual crops can no longer be reliably grown. For example, the Greek highlands were originally deforested to plant wheat and barley; it was only after the topsoil was mostly washed away that farmers switched to perennials such as grapes and olives. Similar processes caused desertification in much of what used to be the Fertile Crescent. Apart from these problems, many annual crops also have to retain a considerable part of each harvest as seed for next year; in classical harvests of barley, wheat and other small grains, up to half the harvest had to be kept as seed grain.
While annual plants have been the foundation of most agriculture, there is a potential alternative. Some perennial plants also offer rich sources of food. As crops, they have several advantages over annual plants. The labour requirements for collecting food are much lower, since there is no need to plow and replant each year. Perennial plants also have established root structures which allow them to take advantage of out-of-season rains or the standing water table, which is very useful in drought-prone areas such as Australia. The same established root structures, combined with much more limited plowing, and more frequent (often permanent) plant cover means that the soil takes much less damage. Since perennials do not need yearly planting, it also means that there is no need to retain large amounts of each year’s harvest for seed crops.
Nonetheless, perennial plants also have some significant disadvantages. There are not as many easily domesticable perennial crops; a problem which is compounded by the fact that the longer generation time of perennial plants means that it takes longer to selectively breed new strains. Many perennial crops produce food which is difficult to store long enough for the next harvest; fruits are tasty but hard to preserve, as are many root crops. Probably the biggest disadvantage is the longer growing time for most perennial plants. If an annual crop is lost, more can be replanted for next year’s harvest, and a society has lost only one year’s worth of food. If a perennial crop is lost through warfare, raids, or fires, it may take fifteen or twenty years for the trees to regrow. This may make it difficult for a perennial agricultural society to feed itself in the interim.
For these reasons, it seems that perennials are rarely used as staple crops, despite the considerable labour savings. There are a few perennial crops which have been used as staple crops, such as plantains and breadfruit, but these have usually had a limited distribution. Most agricultural societies have used annuals as their main staples, with perennial crops such as fruit trees taking on a supplementary role rather than providing the bulk of people’s daily calorie intake. There have been occasional societies which have used perennials as their main source of food, such as parts of Sardinia which used chestnuts, and lowland New Guinea and the Moluccas which used sago palms.
The perennials which are grown in Aboriginal agriculture have some traits which minimise many of the disadvantages of perennial crops elsewhere. These plants are relatively quick-growing. Red yams and murnongs can both be planted in one year to be harvested in the same year, then keep on producing a fresh tuber every year [7]. Wattles grow quickly enough that they start to yield useful harvests of seeds within two to four years. Wattle seeds are also excellent as a food reserve for long-term storage.
Australian perennials are also well-adapted for recovering from damage, thanks to evolving on a landscape regularly visited by flood and fire. Yams already die back during winter and regrow in spring, and they can recover from fire in the same way. Wattles have the ability to regrow from their roots after fire or other damage, which will mean that domesticated wattles can regrow if raids by neighbours means that the trees are burnt or cut down.
The nature of Australian perennials also means that their farming methods are quite different from early farming methods elsewhere around the globe. The overall labour requirements for Aboriginal farming are lower than for most agricultural systems with annual crops. As perennials, there is minimal need for plowing. Wattles and yams are harvested at different times of the year [8], which means that farmers can rotate their work between crops without too much difficulty, and there is not the same intensity required to have all available workers available to help during the harvest. Outside of harvest time, Australian crops still need some ongoing tending – pruning of trees, tapping of gum, replacing individual plants when they die, and the like – but this can be spaced out over most of the year.
Overall, the perennial nature of Aboriginal agriculture means that they have a much higher food yield per worker than with most annual crops. Living in a dry and uncertain climate as they do, they do not have a particularly high yield per hectare, but individual farmers are quite productive. This makes it easier for them to accumulate food surpluses for storage. In turn, this allows Aboriginal farming societies to sustain a much larger percentage of their population as urban dwellers than in most early agricultural societies. Most early agriculture needed ten or more rural farmers to support one non-farmer, be it a smith or a priest. Australian perennial agriculture means that only four or five farmers are needed to support non-farmers. This means that they can support more specialists, more division of labour, and, in time, much more besides...
* * *
[1] Selection for relatively sweeter varieties is common to a lot of domesticated varieties of plants. This has an additional benefit of providing a higher nutritional yield for the domesticated yams, since more of the tuber is formed from digestible starch rather than water or indigestible fibre. Domesticated varieties of red yams have a lower water content (which means that they store longer) and it also means that they provide a higher calorie intake per unit of weight.
[2] The red yam has evolved into a form which is well-suited to the periodic droughts and semi-arid conditions along the Middle Murray. The most important of these is that red yams have evolved a process called crassulacean acid metabolism (CAM), which allows plants to store atmospheric carbon dioxide in their leaves at night, and then photosynthesise during the day. This means that CAM plants keep the stomata in their leaves closed during the heat of the day, and lose much less water than non-CAM plants. This makes red yams well-suited for semi-arid conditions, and combined with their deep roots, makes them resistant even to long and persistent droughts. CAM photosynthesis comes at a price, however; CAM plants are less efficient at absorbing atmospheric carbon dioxide. This means that in areas which do have higher rainfall, the red yam is likely to be out-competed by non-CAM plants. Thus, the red yam does not grow naturally in the wetter areas of Australia’s eastern coast, although domesticated red yams can grow there provided that the soil is well-drained. (Red yams, like other yam species, do not tolerate waterlogged soils very well.)
[3] The first domesticated wattle, the mystery wattle (Acacia difformis), grows in the old Gunnagal homelands around Swan Hill. As the Gunnagal expand west along the Murray, they domesticate the tree variously known as bramble wattle, gundabluey or elegant wattle (A. victoriae). As they move east along the Murray, they domesticate the golden wattle (A. pycnantha). These three wattles form the early domesticated wattle species, although other wattles will be domesticated elsewhere in Australian when agriculture spreads.
Of the early domesticated species, bramble wattle is tolerant of a very wide range of soil and weather conditions, grows very quickly, and usually produces the overall largest yield of seeds even in drought years. Mystery wattle produces a sizable seed yield, with very large individual seeds which are easy to harvest from their pods, tolerates a range of harsh conditions, and produces large quantities of edible gum. Golden wattle produces a tolerable crop of seeds, but it is slower-growing, and when grown in close cultivation, is more vulnerable to pests, disease and death. Domesticated golden wattles are usually planted alongside the edges of yam fields rather across whole fields. Golden wattles are on the whole less reliable as a source of food, but they have the advantage of growing much taller than other domesticates wattles, which makes them a source of longer timber. The bark of golden wattles is also an extremely rich source of tannins for animal leather, and its bark is useful for fibre.
[4] Wattle gum is similar to gum arabic, although true gum arabic comes from related African Acacia species (A. senegal and A. seyal).
[5] Collectively, the Australian agricultural package is most-suited to latitudes between 25 to 45 degrees at low elevations, with long-term rainfall between 300 to 500 millimetres. Their nature as perennials means that rain does not need to fall in a particular season; the plants can cope with irregular rainfall. Established plants can tolerate drought reasonably well, although a prolonged drought is likely to mean that new plantings do not grow. Growing the full package of crops with long-term rainfall below 300 millimetres is marginal; the main crops will tolerate areas where the long-term rainfall is anything above about 250 millimetres, although the yields will be lower. Rainfall above 500 millimetres can be tolerated, and to a degree this will increase the yield, but soils need to be well-drained; waterlogged soils will cause problems for yams, in particular. The plants grow best at low altitudes, although they can be grown at higher elevations, particularly at latitudes between 25 and 30 degrees. Some of the domesticated plants can grow at lower latitudes, particularly the bramble wattle, but the early agricultural package as a whole does not grow well in tropical latitudes.
[6] Potatoes are actually perennial, but are usually grown as annuals.
[7] Red yams can in theory be planted fresh each year from cuttings or tubers, and then harvested the same year, turning them in effect into annual plants. Such agricultural practices could be expected to give higher yields in good years, since most yam species grow more quickly with such practices than if they are left to regrow from roots with most of their food storage (i.e. a tuber) harvested. This is how yams are used in much of the world today, although not everywhere. The erratic nature of Australian rainfall, however, means that newly-planted yams would have trouble growing during drought years, since they lack the established root structures needed to draw on the water table or out of season rains. For this reason, and in line with Aboriginal gathering practices before crops, I expect that red yams will be turned into a perennial crop where they are harvested each year but where the uppermost part of the tuber and their root system is left as undisturbed as possible so that it can regrow each year.
[8] Australian wattles as a group flower year-round; there is almost no time when there is not a wattle blooming somewhere on the continent. However, the domesticated wattles fall into two main divisions. Early-flowering wattles (such as mystery wattle) flower around August-September, and their seeds are harvested around October-November. Late-flowering wattles (such as bramble wattle) flower around November-December, and their seeds are harvested around January-February. Red yams and murnongs are harvested in late autumn, around April-May.
* * *
Thoughts?
P.S. As mentioned in the post above, all of these plants (apart from red yams) exist. For those who are curious, below are some links to more information about some of them. For those who aren’t curious, Lands of Red and Gold is now moving past the “necessary background information stage” and into the actual depiction of early Australian agricultural societies, which the next few posts will be showing.
Bramble wattle/elegant wattle:
http://www.flindersranges.com.au/2008/08/27/the-wonder-wattle/
http://www.aridzonetrees.com/AZT In... Index/Cut sheets/Acacia/Acacia victoriae.htm
Golden wattle:
http://en.wikipedia.org/wiki/Acacia_pycnantha
http://asgap.org.au/a-pyc.html
Some information on how wattles are being used as crops today (no thanks to Messr. Diamond and “no domesticable crops in Australia”):
http://www.worldwidewattle.com/infogallery/utilisation/sehel.php
Murnong:
http://en.wikipedia.org/wiki/Microseris_lanceolata
http://www.australianplantssa.asn.au/photo/gallery/m-lanc-gall.html
Purslane:
http://en.wikipedia.org/wiki/Portulaca_oleracea
http://asgap.org.au/p-ole.html
Spiny-headed mat-rush:
http://www.anbg.gov.au/gnp/interns-2007/lomandra-longifolia.html
http://www.wildseedtasmania.com.au/webgallery/pages/Lomandra longifolia.htm
Scrub nettle:
http://morwellnp.pangaean.net/cgi-bin/show_species.cgi?find_this=Urtica incisa
http://www.utas.edu.au/docs/plant_science/field_botany/species/dicots/urticsp/urtiinci.html
Native flax:
http://www.rbgsyd.nsw.gov.au/scienc...lain_Woodland/woodland_plants/linum_marginale
http://www.anbg.gov.au/apu/plants/linumarg.html