Introduction

Leather is the chemically stabilised form of, principally, mammal skins. The original chemicals were natural plant tannins, natural fats and proteins and, more recently, certain chemical salts and synthetic compounds e.g. glutaraldehyde. Well-tanned leather is chemically remarkably inert and leather goods in a fine state of preservation have been recovered from such diverse sites as palaeolithic hunter-gatherer’s burial sites in central Asia, the wreck of the Titanic, medieval sewers, inside Tudor chimneys and Roman rubbish pits. In spite of this long technological history, the basic technique seems to have changed very little and some of the most ancient archaeological leather material e.g. from the palaeolithic gatherer-hunter groups of central Russia, dating from about twenty-three thousand years ago, appear to show identical processes to those in use well into the 20th century.

Is it possible to speculate to any advantage the possible steps by which early peoples made this technical advance and, thereby, with this new and flexible adaptable product, were able to penetrate into a whole range of new habitats?

The Historical Perspective

Let us here accept the general thesis that early Homo sapiens emerged out of Africa and slowly migrated into the Indo-European zone. Written records of these events are rare but the early chapters of the Bible may give us the occasional clue. Under tropical conditions the apocryphal fig-leaf might have sufficed and, as Genesis 3:7 tells us ‘... they sewed fig leaves together, and made themselves aprons...’

But these garments would have been less than adequate as the palaeolithic tribes spread out firstly into to sub-tropical and then into the temperate zone.

Genesis is describing, in powerful analogy, many of the seminal events of the transition of the human race from the late palaeolithic through the mesolithic and into the neolithic period. The conflicts of the hunter-gatherers and the new farmers are graphically described, as are the devastating effects of the floods of the glacial retreat. Genesis also hints at the difficulties presented to the spreading population and restrictions of territory as, possibly, a steadily rising population, forced the first diaspora. The Garden of Eden was to be replaced by the harsher conditions of the temperate forest and then those of the boreal zone. By verse 21 times are obviously getting harder, ‘Unto Adam also and to his wife did the Lord God make coats of skins, and clothed them.’

The stimulus

It would have been natural for nomadic peoples, skilled in hunting and gathering, to have considered the utilitarian possibilities of the skins of the animals they had killed. Nevertheless, they would have been well aware that the skin, fresh stripped from the flesh, would rapidly putrefy if kept moist but harden to the stiffness of horn if kept perfectly dry. Neither condition served much purpose. In the latter case, very long slow hand lubrication with natural fats would have impregnated the leather, brain proteins were used for the same process by the Mongols and the Amerindians of north America and these processes would have produced the thin soft leather of the moccasin type. Moreover, this technique, which forces the triglyceride fats and a mixture of phospholipids and lipoproteins into the collagen fibres, is relatively quick and highly suited to a nomadic people. But brain protein does not render leather totally immune to putrefaction if kept constantly wet. Brains, too, were in limited supply and were nutritionally valuable. The Inuit peoples evolved the technique of gently chewing seal skin through the long winter nights. This technique was effective but with the same limitations as brain protein conversion and was, even by palaeolithic standards, somewhat labour intensive. But protein/ fat preserved leather is very limited in its applications; its production has virtually died out in modem times.

What we can, term ‘nomad’ leather was a technological cul-de-sac. The prize in social development was to go to the group of peoples who evolved a passive method of high quality leather production adaptable to a range of skin types. These techniques were to produce a diversity of leathers and a tolerance to a range of climates. They were not to require the consumption either of long hours of manual labour or of a very valuable food source or both.

But what possible accident or series of accidents, combined with human memory and the power to reason could possibly have evolved that exquisite product, namely fine oak-tanned leather? True leather requires the interaction of tannins, plant products, from constantly renewed fresh sources, with animal skins in a certain state, not just for months but perhaps for years. The by-word of the tanner is that good leather takes a year and a day.

The breakthrough

As early nomadic peoples moved away from the tropical zone into the sub-tropics and then to temperate climates they would have evolved temporary night shelters. New age travellers in our society would have called them ‘benders’

The first bedding within these benders would probably have been bracken and gathered leaves. But, as the colder zones were penetrated and the grip of the northern autumn closed in it would have been natural to have put down, fur-side uppermost, animal skins. Such skins would have offered a modicum of warmth and, at least temporarily, resisted the penetration of damp. But on wet soil the skins would have rotted; on dry soil they would have hardened to useless brittleness. A natural progression would have been to gather leaves under the thin skin layer.

As the palaeolithic peoples penetrated to the colder north or higher altitudes, the most obvious readily available autumn leaves would have been those of deciduous oaks (Quercus spp). The stiff evergreen oak leaves of the Mediterranean region would not have been so attractive. Deciduous oak leaves were readily available, curly and resistant to rot.

But there was labour involved in collecting afresh at each camp site; enter thus the second phase of technology the invention of the palliasse (or paillasse (Fig.4)). Again the most obvious stuffing would principally have been oak leaves (Fig.4b). Unlike grass they had no other value. Oak leaves were easy to collect and not allergenic. Simple stitching (Fig.4a) had, from archaeological evidence, already evolved by 23,000 BC.

Hydrolysable tannins, in which oak leaves are rich, (Hemingway & Laks, 1991) are best isolated at slightly acid pH, and temperatures up to 35°C (Slabbert, 1991). The normal activities of the night would have raised the temperature inside the sack significantly and steadily crushed and broken the individual leaves inside; skin secretions would have lowered the pH. Regular augmentation would have been required (Fig. 4b). Tannins would, steadily, have begun to leach out of the filling.

Throughout what is now Israel and Lebanon there is a good candidate for a tannin source, namely Quercus ithaburensis, (Fig.3). Q. ithaburensis was widespread until the end of the Ottoman empire and its tannin-rich leaves still stain the stoneware of the patios of Israeli villas where they fall. There would have been plenty of other deciduous oak species in the middle-east, but Q. ithaburensis is a useful candidate for our speculation since it grows on Mount Carmel, an area of very early human settlement and archaeological evidence suggests that the leather industry, in the sense that we understand it here, began somewhere in the middle-east (Haslam, 1989).

The early migrants in the sub-tropical zone would have emptied each palliasse as they moved to a new site to reduce the bulk, but the labour invested in the double-skinned empty palliasse (Fig.4a) would have made it likely that it would be carried on to the next location to be followed by more fresh filling, for months and months, perhaps from one season to the next. Oak trees, moreover, tend to retain their lower leaves through the winter and drop them in the early spring (Otto & Nilsson. 1981) so that fresh supplies would have been available until summer came again.

Oak leaves would not. obviously, have been the only filling used; pine needles would, in comfort terms have been a perfectly adequate substitute, but gymnosperms do not readily yield significant quantities of tannins (Hemingway & Laks, 1991: Slabbert. 1991). Grasses would also have served, but in the absence of steel edge-tools been more difficult to collect. Other tannin-rich angiosperms e.g. the leaves of the Mediterranean sumach (Rhus coriaria), would have yielded large quantities of hydrolysable tannins but are highly allergenic and would have been avoided for bedding purposes. The continual, day-by-day observation of travelling people would soon have closed the equation:

stitched palliasses of any sort of skin or mixed skins + oak leaves + constant bed use over many years + travelling and occasional wetting = permanent leather.

The process might have taken months or even years, but speed was not of the essence. The palaeolithic period lasted for very long time. The concept would have been reinforced by the very occasional discovery of naturally tanned dead animals in the deep, persistent leaf litter of the oak forests.

It requires no great stretch of the imagination to move from oak leaves to oak bark. Leather tanners using such vegetable tannins were, by long practice and much observation, able through the manipulation of the various stages of the process to produce a whole range of leathers from hard, naileable sole leathers to the delicate stretchy material of the glovers (Thomson, 1991.). It was to be a very long time before even the most basic features of the chemistry of this process were understood (Haslam, 1989), but the practical, empirical industry seems to have been well established long before the Christian era.

The prize

Vegetable tanned leather is a product of infinite variability. A diversity of animal sources and a developing technological skill in the preparation of the skins, the cutting of those skins, the length and intensity of the tanning processes (Bickley, 1991) and the intermediate processing of the developing leather produced a dazzling variety of products (Haines, 1991, & Thomson. 1991). Such a diversity was not available to lipid/ protein derived or ‘nomads’ leather. The tannin technology gave its chosen people more than clothing, bedding and shoes. Before long there would have emerged that devastating weapon of hunting and war, the sling. For an early opinion - ask Goliath. There would soon have been wrist guards and finger stalls for more potent archery, naileable boots for fast-marching soldiers, saddles and harness, tents for Roman armies. The grim efficiency of the legion was based in no small part on the sophistication of the Latin tanning industry. Soon there came bottles and jugs (the waterproof tanned goatskin was the ‘jerrycan’ of desert peoples), parchment and vellum for scribes, sails for early boats and above all armour - embracing shield, helmet and body wear (Waterer, 1981). It is sometimes overlooked that the late mesolithic/ bronze-age hunter found frozen five thousand years ago in the ice in the Italian Alps had seven different, life-supporting items of leather, but just one of metal.

The magic of complex plant phenols, plus the collagen of animal hide, thrust forward the development of human society just as powerfully as the discovery of bronze, iron and steel.

References

• Bickley, J C, 1991 Vegetable tannins, in C Calnan and B Haines 1991, 16 -23
• Calnan, C, and Haines, B, (eds), 1991 Leather: Its Composition and Changes with Time; Proceedings of the First Conference of the Leather Conservation Centre, August 1986, Northampton, The Leather Conservation Centre, Northampton. ISBN 0-94607204-3.
• Haines, B M, 1991 Skin structure and leather properties, in C Calnan and B Haines 1991, 1-4
• Haslam. E, 1989 Plant Polvphenols - Vegetable Tannins Revisited, Cambridge University Press, ISBN 0-521-321891
• Hemingway, R W, and Laks, P E, (eds.), 1992 Plant Polvphenols: Svnthesis, Properties, Significance Plenum Press, New York and London, ISBN 0-30644252-3
• Otto, C, and Nilsson, L M, 1981 Why do beech and oak leaves retain leaves until spring?, Oikos, 37, 387-90
• Scalbert, A. 1992 Tannins in woods and their contribution to microbial decay prevention, in R W Hemingway and P E Laks (eds) 1991,935-47
• Slabbert, N P, 1992 Wattle tanning, in R W Hemingway and P E Laks (eds) 1992, 120-31
• Thomson. R S, 1986 A history of leather processing from the medieval to the present time, in C Calnan and B Haines (eds) 1986, 12-5
• Waterer, J W, 1981 Leather and the Warrior, ed. Joyce T Meade, pub, Museum of Leathercraft, Northampton, ISBN 0-950-418218.