Secondary products revolution
In 1981 Andrew Sherratt proposed that a ‘secondary products revolution' had taken place in European prehistory that coincided with the introduction of copper and bronze metallurgy, and contributed significantly to the rise of more complex societies.[278] He argued that Neolithic animal exploitation had focused on the use of animals for meat, but by the Chalcolithic (Copper Age) and early Bronze Age there were major shifts occurring in the patterns of animal husbandry, which saw widespread dairying as well as increased use of animal labour for transport and ploughing.
This massive intensification of the animal side of mixed farming helped underpin increases in population, changes in patterns of wealth and power, and a movement towards significantly more complex societies. The geographic focus for this revolution was the eastern Mediterranean and Near East, where the economy was strongly based upon mixed farming, but the Chalcolithic/Bronze Age also sees the expansion of significant pastoralist cultures in the eastern European plain and Central Asian steppes in the general absence of cereal agriculture.[279] [280] Sherratt was not explicitly arguing that practices such as milking, use of wool, or animal traction were first invented at the same time as copper metallurgy, but more that at that same time the emphasis of economies shifted strongly towards intensive exploitation of secondary products. In order for us to understand the development of prehistoric pastoralism, it is necessary to ask when practices such as milking first developed, and whether the timing of Sherratt's secondary products revolution holds true for all regions and environments within Eurasia.The 1970s and 1980s saw significant advances in Zooarchaeological methods by scholars such as Sebastian Payne and Tony Legge.16 This body of research established methods for identifying the age and sex ratios of slaughtered animals from the study of animal bones in the archaeological record.
Such work allows past herd structures and slaughter patterns to be reconstructed and compared against a number of different husbandry models. When animals are kept for different purposes, it makes economic sense to maintain herds with different sex and age ratios. The following zooarchaeo- logical models were developed through ethnographic observation of traditional farming practices. When keeping animals primarily for dairying, it makes sense to slaughter most males soon after birth, to avoid wasting fodder on them and to prevent them from using up their mother's milk. Only enough males to maintain a breeding population need to be kept. For meat exploitation it is logical to slaughter most males when they reach full size, when they will produce the maximum amount of meat; killing any later will simply result in wasting fodder to no economic advantage. A small number of males are kept for breeding with the females of the herd. For maximizing wool exploitation, all animals can be kept alive while still productive. These are all extreme models, and mixed use can also be identified. It is quite common to see many males slaughtered just before their first winter in order to exploit some meat, but also avoid the need for extra winter fodder. This leaves a selective slaughter pattern that lies somewhere between meat and milk models.Analyses of faunal assemblages using such methods generally supported Sherratt's view of a secondary products revolution at the start of the Bronze Age, particularly in southeastern Europe, Anatolia, and the Near East. However, the Zooarchaeological record also hinted at the possible presence of significant Neolithic dairying in some regions of Europe with a less Mediterranean climate. Early Neolithic Britain was one such region, with cattle dominating faunal assemblages at a number of causewayed enclosure sites. The majority of these cattle bones appear to have derived from adult females.[281] The evidence for the very early slaughter of male calves is absent, but so is evidence for the consumption of meat from juvenile males that have just reached full size.
The consumption of mature females suggests the use of dairy cows for meat at the end of their productive lives. Elsewhere, such as the Alpine foreland, patterns of caprine exploitation were more suggestive of a mixed strategy of milk and meat exploitation, rather than meat production alone.1[282] Much more recent Zooarchaeological analyses, that incorporate methodological advances and consideration of a wider range of herd structures (including significant milking), however, are beginning to suggest that human groups in many regions extensively exploited dairy products during the Neolithic.[283]A step-change in the study of pastoral economies has been made possible over the last fifteen years or so, as a result of the development of new techniques for identifying chemical residues in archaeological pottery. It is now possible to identify both lipid (fat) and protein residues derived from the milk of ruminant animals.[284] Lipid residue techniques, developed by Richard Evershed's team, have been most useful in the study of early dairying because fats survive very well when absorbed into the fabric of ancient, unglazed pottery. Residues can be commonly found in large proportions of pottery sherds from many thousands of years ago, and it is possible to distinguish the fats of ruminant animals from other species such as pig or horse, and to establish if the ruminant fats derive from meat or milk. Early applications of this method focused upon dairying evidence in Britain, and found that milk residues dominated during the early Neolithic, demonstrating that those mature cows from causewayed enclosures probably were from dairy herds.[285] While species proportions fluctuate throughout British prehistory, the lipid residues indicate that milk was a key component of the economy from the earliest farming onwards. More recent studies of Neolithic ceramics from southeastern Europe, Anatolia, and the Near East show that milk residues are present in small proportions in all those regions.
However, in northwestern Anatolia, where the environment is more suited to cattle husbandry, a very high proportion of Neolithic pots appear to contain milk residues.[286] The most recent data on the subject suggest that early Neolithic dairying might well be most associated with areas where cattle were most likely to thrive.The notion of a secondary products revolution remains reasonably valid for some regions, notably Greece and some areas of the Near East, but it is clear that in other environmental zones, particularly more temperate ones, dairying was an important feature of early animal husbandry in the Neolithic. This is important, as it suggests that the innovation of dairying did not require such a long lead-in time, and the problems associated with the intensive exploitation of animals for milk could be overcome more easily than previously suspected. This means that the theoretical ability for people to live principally from milch pastoralism existed much earlier than the obvious establishment of such cultures on the plains and steppes of Eurasia. As a result, we can no longer view the secondary products revolution of the Bronze Age as being an essential prerequisite for such cultures, and we must look elsewhere for explanations for their genesis.
This is not to say that there are not significant barriers to the successful, intensive exploitation of herds for dairy products. It is worth discussing two of these potential barriers: sustaining milk let-down in primitive breeds, and human lactose intolerance. Naturally, animals produce milk for their young, not for us. As such, lactation is designed to stop after their young have been weaned. Millennia of selective breeding have resulted in modern dairy cattle producing much higher yields and prolonged milk let-down in the absence of a calf to feed. Early breeds produce much less milk and tend to stop producing it without stimulus from a calf.[287] On the other hand, if the calf is present, it is consuming much of the milk, rather than us.
One way of dealing with this problem is to keep at least one calf alive to stimulate milk let-down, while controlling its consumption to an extent to ensure that enough surplus milk can be harvested for human consumption. Such a method may result in a peak of slaughter of calves shortly after weaning, and before overwintering. Recent Zooarchaeological analyses of Neolithic sites in France have indicated that such a practice may well have been in place among early dairy herds in that region. Other sites in France, Italy, and the Balkans, however, display classic milk herd patterns of slaughtering many male calves very young indeed.[288] Without so many calves there is more milk for human use, but how is milk let-down encouraged? First, female calves are unlikely to be slaughtered, but second, ethnography tells us about a number of tricks that can be used to induce milk let-down in primitive cattle breeds. Such practices include tricking the cow with the use of a calf skin, or the stimulus of the cow's vulva by blowing strongly into it, sometimes with the aid of a pipe.[289] It is clear that with a combination of trickery and careful herd management, this problem could be readily overcome prior to significant breed improvement.As infants, all mammals should be able to digest milk, because they produce an enzyme called lactase which is designed to help break down lactose, the sugar found in milk. However, after weaning, lactase is no longer produced and it becomes difficult to digest milk thereafter. This state is known as lactose intolerance, and, rather than being an unusual condition, it is the default for adult mammals. Lactose intolerance would also have been the normal state for human populations prior to the domestication of animals and the regular exploitation of their milk. Over time, human groups that consume dairy products must have been put under considerable selective pressure to tolerate that foodstuff.
Those who could would have a genetic advantage, and the result is the high prevalence of the lactase persistence gene among modern humans. There are, however, a number of racial groups who, no doubt related to their forebears' subsistence economies, have not developed this genetic trait.[290] So, how did dairying become so popular in the first place - when most people were lactose intolerant - and to an extent significant enough to pose selective pressure towards lactase persistence?There are a few key facts we need to know about lactose intolerance in order to answer this. First, it is not an allergy that can have potentially fatal consequences. Instead, it is an intolerance that leads to digestive discomfort, and even with that discomfort, however unpleasant, it is still possible to extract nutritional value from milk. Second, milk can be made more digestible through the consumption of processed dairy products rather than raw milk. The biotic and chemical processes involved in the production of fermented drinks, yoghurt, butter, and cheeses all tend to result in the partial breakdown of lactose prior to consumption. As such, it is possible to conceive of a largely lactose intolerant population still deriving much nutrient value from dairy products, while those naturally possessing lactase persistence would be afforded a selective advantage.
With our much increased capability to understand the human genome and extract ancient DNA (aDNA), it has become possible to study the issue of lactase persistence directly. Work in this area is still in its infancy, but the most recent models suggest that the lactase persistence gene may well date back to about 7,500 years ago somewhere in the central European or Balkan region.[291] While this date relates to the earliest animal herding in these regions, studies of aDNA in central and eastern Europe do not indicate that the gene was widespread at this time,[292] and it may not have become prevalent for another thousand years among groups that were particularly dependent upon dairying. This work is still based upon quite small sample sizes, and many regions and periods are yet to be analysed using this aDNA technique. It is becoming clear, however, that while there was a period of milk exploitation by largely lactose intolerant individuals, perhaps aided by use of processed dairy products, the evolution to lactose tolerance was still relatively quick. It is also likely that lactose tolerance was established among mixed farmers in Europe, prior to the expansion of pure pastoralism in the plains and steppes further east. No similar aDNA work has been performed in those regions, so it is still open for us to debate whether pastoralism was an adaptation of local indigenous populations of the steppes, or whether already lactose tolerant groups moved into the area with their domestic herds.
The establishment of African pastoralism and dairying is an even more complex issue. Modern-day Africa is home to many pastoralist groups who are dependent upon secondary products.[293] Some of the most notable are the Bedouin and Berbers of North Africa, the Tuareg of the north-central Sahara, the Afar of the Horn of Africa, the Fula people of the Sahel, and a number of cultures in central East Africa, including the well-known Maasai. It is clear that cattle pastoralism was present in Africa well before the development of cereal agriculture.[294] Domestic cattle appear in North Africa every bit as early as in the Near East, but in Africa the cattle come first, while in the Near East sheep and, particularly, goats are arguably the earliest animals to be domesticated.[295] While there is still much room for debate, current genetic studies of African cattle provide some support for a long-held archaeological view that cattle were independently domesticated in North Africa to fill a very particular economic niche in an unpredictable arid environment, where mobile herds could respond better to localized drought than an economy based upon the planting of immovable crops.[296] Later, increased aridity may well have encouraged expansion of this form of economy further south.[297] Human genetic studies also support a separate origin for dairying in Africa, because sub-Saharan Africans appear not to share the same lactase persistence gene as Eurasians, yet they are lactose tolerant.[298] While the genetic basis for lactose tolerance in these populations is yet to be determined, this difference is likely to indicate the indigenous development of dairying rather than an influx of lactose tolerant pastoralists from the Near East. One exception to this are the Berbers, who share the Eurasian gene, perhaps showing a more integrated development of pastoralism and dairying between people in the far north of Africa and Eurasia, or at least later population movement into North Africa.[299]
Other important secondary products, such as wool, have not received quite the same level of recent scientific attention, and as a result we know little more about that topic now than we did thirty years ago. Wild sheep are not particularly woolly, but instead have a more hairy coat made up of coarse 'kemps'. Below the kemp is a soft, warm underwool that is rather short. Over perhaps thousands of years, domestic sheep were selectively bred to reduce the kemp and increase the amount and length of the underwool. Further breed improvements resulted in higher yields and white rather than brown wool, and prevented unwanted moulting prior to harvesting with shears.[300] Given the current lack of genetic evidence for the geography and timing of such developments in sheep and other wool-bearing animals, we have to rely upon the Zooarchaeological identification of wool production herd structures, alongside evidence from the portrayal of animals in art and the rare survival of ancient fabrics. The vast majority of this evidence still supports Sherratt's original suggestion that this secondary product became more important from the Chalcolithic and Bronze Age onwards.[301] This still suggests that woolly sheep were potentially available to the early pastoralists of the Eurasian steppes, and neither caprines nor wool were the focus of early African pastoralism.