Artifacts and isotopes

Since the 1960s the whole approach to the human past has got more scientific," says Professor Martin Jones of the Department of Archaeology at the University of Cambridge. "As archaeologists started to apply new techniques from other areas of science to their field, they realised that as well as the artifacts and skeletons accessible to the naked eye, there was a whole range of other material available to investigation."

The emphasis also shifted towards putting the human past in a more rounded context by looking at how people interacted with the world around them. "Archaeologists became interested in how humans worked as part of a larger ecosystem," explains Professor Jones, who also chairs the Wellcome Trust’s Bioarchaeology Panel. "They wanted to know what diseases people had, what they ate and how they changed the environment."

During the last decade, terms such as ‘bioarchaeology’ or ‘science-based archaeology’ began to be coined to cover an emerging discipline that uses cutting-edge biomedical technology to shed light on the archaeological past. Several organisations have supported such research, including the Wellcome Trust through its Bioarchaeology Programme (see box below).

From molecules…

"Lipids – fats, oils and waxes which are insoluble in water – found in archaeological deposits are incredibly durable markers," says Professor Jones. "If you find a lipid on the surface of a pot, you can get an ‘isotopic signature’ from it and find out what was once cooked in the pot. You can do the same for cholesterol in bone or tissue."

At the University of Oxford, Professor Robert Hedges, Director of the Radiocarbon Accelerator Unit, is also looking at isotopes to answer dietary questions. "Isotopes are more likely to be found in pristine form than molecules," he explains. "It’s like having a very small but clear window into the past. In fact, isotopes make it possible to survey whole populations, and give an idea of generality and trends."

For example, nitrogen isotopes in ancient bone collagen indicate what kinds of proteins were eaten. "The isotopic ratio tells you where in the trophic level in the general ecosystem the dietary object was, whether it was a plant or animal," says Professor Hedges. "So you can put together a better picture not only of the past, but of the economy of the past." Isotopes indicate which foods people chose to eat out of the ecological range available to them, which in turn depended on their methods of hunting and cultivation.

"Isotopic studies also tell you a lot about lactation and weaning," says Professor Hedges. "That tells us something about social practice and feeds back into questions about population growth and demography because of the connection between weaning and further pregnancies."

Radiocarbon dating is another area that has grown out of the integration of molecular methods into other fields. "The technique originated in nuclear physics, studying the instability of the radiocarbon nucleus but nowadays it’s especially involved in biological systems," explains Professor Hedges. "It can take you back 50 000 years.

The amount of radiocarbon left in the remains of a once-living organism tells you for how long radiocarbon nuclei have been decaying, and therefore when it died." Carbon isotopes can also be used to trace what happens to the planet and atmospheric sphere when fuel is burnt. "Carbon isotope tracers show how carbon gets assimilated from the atmosphere into the ocean, plants and soil, so you can use them to look at whole earth systems."

During the last decade, the polymerase chain reaction has made it possible to amplify small fragments of ancient DNA. This research area has helped to shed light on a number of important questions, not least the migration of human populations. In addition, genetic information from Neanderthal bodies has clarified the relationship between humans and other primates. "Although Neanderthal and human skeletons appear very similar, Neanderthal DNA has shown there is a significant difference, indicating that they do not really belong to the same species as us," explains Professor Jones. "As a result, we now know we did not evolve from Neanderthals: they’re our cousins, not our ancestors."

Molecular evidence of tuberculosis, leprosy and plague has helped pinpoint the emergence of these and other diseases with greater accuracy. While it is evident that increasing population densities increase the possibility of epidemics, molecular studies can indicate whether disease outbreaks appeared at the time of the Industrial Revolution or much further back in time, at the beginning of the Neolithic period when the first settlements grew up.

For example, lipids called mycolic acids that are specific to the coat of the TB bacterium can be found in bones. There are closely related strains of TB in humans and cattle, and one argument claimed that TB jumped from cattle to humans when agriculture started. However, molecular evidence revealed that TB affected Native Americans before the influx of Europeans, indicating that the disease was around in the human population long before cattle farming began.

"Bioarchaeology gives a broad-brush picture of the long-term time dynamics of disease," explains Professor Jones. "While we can historically document diseases like TB, leprosy and syphilis over a few hundred years, the archaeological evidence lets us look across tens of thousands of years."

… to global systems

"The other area of bioarchaeology that’s really moving forwards is the issue of climate change," says Professor Jones. "Palaeoclimatologists are now working at far greater levels of precision, seeing human action as an important factor in climate change, and in that sense their field is converging with archaeology."

Since humans have evolved, the earth has experienced massive extremes of hot and cold, and modern evidence is showing that this temperature curve is vital in understanding human colonisation of the world. "Neanderthals and humans co-existed at one point, yet the Neanderthals died out whilst modern humans colonised the globe," says Professor Jones. "We still don’t know why or how that happened." A suite of methods for environmental modelling and climatic tracking are converging to address this and many other unanswered questions.

"This more precise plotting of the climate has made everybody far more aware of how rapidly the climate can fluctuate," says Professor Jones. "Current research is showing that many parts of the whole system, like the ozone layer or the amount of ice in the sea, are balanced on a knife’s edge. It’s also showing that prediction is a limited concept when it comes to climate and weather. There’s more weather in the climate than we thought."

In providing new insights in these areas and many others, bioarchaeology is becoming an important tool in the quest to understand how our ancient ancestors lived and died. Studies of both the historic and prehistoric past shed light on the ways in which people have interacted with the world, what diseases they encountered and how they coped with them. These interactions have led inexorably to our modern world, tying us inextricably to our distant forebears. Thus, while new techniques are giving us an ever clearer picture of the past, the insight they bring could conceivably have important implications for modern humans too.

See also

• Bioarchaeology Programme: Scheme details
• They were what they ate: Article describing bioarchaeology research on reconstructing ancient diet
• Bone idol: Article describing bioarchaeology research on ‘fossil’ cells embedded in living animals

External links

• Department of Archaeology, University of Cambridge: Research interests of Martin Jones
• Research Laboratory for Archaeology and the History of Art, University of Oxford: Research interests of Robert Hedges