The link below is to an article that takes a look at Late Bronze Age ‘Must Farm’ in eastern England.
Tag Archives: Bronze Age
The link below is to an article that looks at the early Bronze Age in the Levant (in the Middle East) region.
To mark the International Year of the Periodic Table of Chemical Elements we’re taking a look at how researchers study some of the elements in their work.
Today’s it’s tin, a chemical that has little use by itself, but mix it with other elements and it takes on a whole new life.
Mention tin and most people would think of the typical tin can, used to preserve foods you store in your cupboards. Tin is used here to help protect the can against corrosion (although not all cans today contain tin).
But while the use of tin in canning only dates back to the early 1800s, the mixing of tin with other elements dates back many centuries.
Tin – chemical symbol Sn with an atomic number 50 on the periodic table – is soft and silvery in colour, with a melting point of only 232℃. At first sight it doesn’t seem to be a promising prospect for making anything.
Somehow, humans discovered that adding controlled amounts of tin to copper produced a splendid, golden-yellow alloy we call bronze.
I first became interested in bronze during my final year undergraduate research project in 1978. That interest continues today – I’m working with colleagues in Thailand to reverse-engineer the technologies used to make ancient Thai bronze bangles.
The first known tin bronzes seem to have appeared in the Caucasus region of Eurasia in about 5800 to 4600 BCE. That these very scarce early examples of tin bronze may have been accidentally made from rather rare ores that naturally contained both copper and tin simultaneously.
There is abundant evidence that by about 3000 BCE, tin bronzes were being made in the Aegean and Middle East (Turkey, Syria, Iraq, Iran) by deliberately alloying tin and copper, with the ores being obtained from separate sources.
Clearly, a series of somewhat unlikely events had to occur before this could be the norm.
An accidental melt would have to have been made from suitable minerals containing oxides of tin and copper. The resulting metal would have to be recognised to have desirable properties, such as hardness, colour and toughness, such that superior weapons or ornaments could be produced.
Craftspeople would then have had to be organised enough to be able to work out how to repeat this smelting process to create artefacts such as swords, axe heads, bowls and bangles.
Trading networks then had to be established to bring the comparatively rare tin from faraway places, such as Afghanistan or Cornwall in Britain’s southwest, to any foundry. The metallurgical craft would have to be passed on to other practitioners, probably by oral means.
The spread of bronze
The trick of deliberately adding tin to copper then spread throughout the Old World, reaching Western Europe by about 2800 BCE, Egypt by 2200 BCE, the populous North China Plain by 2200 BCE, China’s Yunnan province by about 1400 BCE, Thailand by about 1100 BCE, and southern India by 1000 BC (if not a century or two earlier).
This has led to some robust discussion among archaeometallurgists on whether the special knowledge of tin’s useful attributes spread from a single founding location in the Middle East, or whether it had been repeatedly independently developed by indigenous craftspeople.
In the case of Thailand and Cambodia, arguments have been raised for several scenarios: that the technology was independently developed, that it was brought south from China (or maybe the reverse, exported from northeast Thailand to China), or that it was imported from Bengal.
With China, some local scholars have favoured the view for independent local discovery of tin bronze, although it the balance of evidence suggests that the knowledge was transmitted by horseriding visitors from West Asia.
Tin was also mined in precolonial times in Southern Africa, and some bronze artefacts – such as pieces of metal sheet or ingots – have been recovered at old metalworking sites there.
The available evidence for this region suggests the technology for producing and working iron, copper and bronze appeared contemporaneously at locations in sub-Saharan Africa, beginning about 500 BCE in the north and reaching South Africa in about 300 CE.
How did the metallurgical knowledge get to Southern Africa? Was it an indigenous discovery of the Bantu of East Africa that was then carried with them on their migrations, or was the skill transmitted southwards from the Middle East, and if so by who and how?
As in the case of Asia, interpretation of these issues can be coloured by modern political sensibilities. The question of the source of the metalworking skills that produced the beautiful copper and gold ornaments of the ancient city of Mapungubwe in South Africa, for example, has still not been settled.
Bronze in the Americas
The ancient cultures of the Americas also developed sophisticated skills for processing precious metals, copper and tin.
They were able to manufacture bronze artefacts such as rings, pendants, body ornaments, ornamental tweezers, sheet metal breastplates, large discs, ornamental shields and especially bells, by casting, albeit only from about 1000 CE in South America and then soon afterwards in western Mexico.
In the case of Mesoamerica, the knowledge of bronze was believed to have been carried north from Peru and Ecuador to Mexico by maritime traders.
Clearly, the ancient world, both Old and New, was well connected by lengthy trade routes along which ideas (and in many cases tin) flowed.
The mix of tin
The transmission of the technology can also be followed by paying attention to specific aspects of the physical metallurgy involved.
When more than about 15% tin by mass is added to the copper, the resulting alloy becomes rather brittle in its cast form, even if it still has a wonderfully warm golden yellow colour.
Somebody, somewhere, made the remarkable discovery that if such a casting is rapidly quenched from red heat into water (or better, brine), it becomes softer and relatively more ductile and workable.
The quenching heat treatment leaves a very characteristic needle-like microstructure (known as martensite) in the artefact that can be detected by a microscope. This tells an archaeologist that the part has been manufactured by a comparatively complex process, rather than merely cast.
When the tin content is less than about 15%, no martensite forms and nothing remarkable happens on quenching.
The result obtained when heat-treating a high-tin bronze is counterintuitive because, when iron is treated this way, it becomes hard and brittle. The trick to make the bronze tough is so specific that it is most likely this knowledge was transmitted from person to person.
Its transfer across the Old World would have required knowledgeable individuals travelling significant distance to foreign climes. The appearance of these artefacts at far-flung locations across Eurasia and Africa is another sign of ancient globalisation.
An extra element
There is one more trick that appears in the ancient bronzes, although this one might have been independently discovered at more than one location.
Some time in the Late Bronze Age or Early Iron Age (around 500 BCE), craftspeople began to add lead to their tin bronze castings. This gives the molten metal extra fluidity, allowing it to flow into fine detail in a mould so that castings with fine details and embossed figures can be made.
As an element, lead is not as shiny or attractive as tin; it is much denser and is found in quite different ores such as galena (lead sulfide). The earliest known cast bronzes with significant controlled additions of lead appear to be from China (500 BCE to 200 CE). Once again, it was clearly a deliberate innovation, and once again it spread rapidly all over Eurasia.
As more sites such as the ones in eastern Thailand are excavated, and as the database of alloy compositions and dates increases, it will become possible to cast more light on ancient routes of trade, migration and tech transfer.
The presence and usage of tin at these sites will act as a kind of metallurgical DNA, an indicator for ancient cultural and human exchanges.
If you’re an academic researcher working with a particular element from the periodic table and have an interesting story to tell then why not get in touch.
Whenever mummies are mentioned, our imaginations stray to the dusty tombs and gilded relics of ancient Egyptian burial sites. With their eerily lifelike repose, the preserved bodies of ancient Pharaohs like Hatshepsut and Tutankhamen stir our imaginations and stoke our interest in people and cultures which have long since passed away.
But the Ancient Egyptians weren’t the only ones to mummify their dead. As it happens, mummies dating back to the Bronze Age – between 4,200 and 2,700 years ago – have also been discovered in Britain. But until recently, we knew very little about how mummification was practised by ancient British societies, or to what extent. I devoted my PhD to finding out how peat bogs and bacteria affect the body after death, and helped to unravel some of the mysteries surrounding Britain’s Bronze Age mummies.
I first learnt that mummification may have been practised in Britain back in 2008, while a student at the University of Sheffield. Mike Parker Pearson gave a lecture on the evidence for mummification, based on skeletons he’d excavated at the site of Cladh Hallan on South Uist in the Outer Hebrides.
Several lines of evidence came together to suggest, rather controversially, that these skeletons had once been purposefully mummified. The tightly-flexed positions of skeletons were like Peruvian mummy bundles, and two teeth, part of the wrist and the knee of one of the Cladh Hallan skeletons, had been removed long after they had died, which suggested that the bodies had been curated for an extended length of time.
The radiocarbon dates from one of the skeletons were older than the dates obtained from the sediments at the burial sites. This suggested that the bodies may have been buried centuries after they had died. A thorough physical examination, together with DNA analysis, showed that both skeletons had actually been constructed from the mummified parts of several individuals.
Of course, based on this evidence alone, it was possible that these mummies were outliers. Mummification could well have been a fringe practice, carried out by people living on the peripheries of Britain’s Bronze Age societies.
The problem is that the same evidence from Cladh Hallan might not necessarily be found at all sites where mummification was practised. Radiocarbon dates would not always have the precision needed to identify significant delays between a person’s death and their burial. And there was no guarantee that the extensive meddling with mummified body parts identified at Cladh Hallan was practised elsewhere.
So, it was my challenge to identify whether remains from other sites might once have been mummies, too. And I was going to have to get my hands dirty.
Microscopic death tunnels
After we die, our gut bacteria circulate around our body through our blood vessels and begin to decompose our soft tissues. These bacteria also get into our bones and begin to eat away at the proteins, producing microscopic tunnels. Most of the bones from bodies that have been buried in the ground soon after death are filled with these tunnels, because the skeleton is essentially trapped in an enclosed environment with destructive bacteria.
Little or no tunnelling was observed within the skeletons from Cladh Hallan, suggesting that their putrefaction had been interrupted. Methods of mummification usually involve killing or removing gut bacteria soon after a person dies, in order to prevent this process. So studying the extent of bacterial attack inside bones was potentially a new way of identifying skeletons which had previously been mummies.
To test this theory, I examined the bone microstructure of two bona fide mummies. Both skeletons showed little or no bacterial attack, confirming that this pattern was consistent with mummification.
I then looked at bacterial tunnelling in the bones of over 300 British archaeological skeletons dating to various periods. As expected, almost all bones from most periods were filled with bacterial tunnels. But around half of the samples that dated back to the Bronze Age showed little or no sign of bacterial tunnelling.
The Bronze Age skeletons which bore this signature came from sites located all over Britain, stretching from north-west Scotland to south-east England. This was the first evidence that mummification was practised all over Bronze Age Britain.
Burned or buried?
Some of these skeletons even hinted at the processes that Bronze Age people may have used to mummify their dead. The Cladh Hallan bones looked like they had been eroded by acid. Yet they were buried in alkaline shell sand. The nearest acidic environments to Cladh Hallan during the Bronze Age would have been a series of peat bogs – so, these bodies were probably preserved by being buried in a peat bog for a few months.
In contrast, Bronze Age mummies from Kent were discoloured in a way which suggested that they had been burnt. So they may have been preserved by being smoked over a fire.
It is impossible to say for sure exactly why Bronze Age Britons mummified some of their dead. The evidence suggests that Bronze Age people kept their mummies above ground for a number of years, or even decades: quite the opposite to the practices of Ancient Egypt, where mummified bodies were locked away in a tomb.
Both ancient and present societies which keep their mummified dead close tend to view them as being alive, in some sense. In some ancient cultures – like the Aztecs – the bodies were used to communicate with ancestors in the afterlife. Even today, human remains are innately powerful objects, which can be leveraged for political or social purposes – one modern example is Lenin’s mummified remains.
We might even reasonably guess that Bronze Age people used the mummies of their ancestors to exert rights over land, resources and power. The next step will be to examine whether mummification was practised even further afield – perhaps in mainland Europe.
The link below is to an article reporting on the discovery of 8 Bronze Age wooden boats from a quarry in Cambridgeshire near Peterborough.