Pick your poison study examines the use of plant poison on prehistoric weaponry

Archaeologists have long believed that our ancestors used poisons extracted from plants such as foxgloves and hemlock to make their weapons more lethal and kill their prey more swiftly. By dipping an arrow head into a poisonous paste, the hunter could ensure that an animal would receive a dose of toxic chemicals - alkaloids or cardenolides - that would either kill it immediately or slow it down.

Until very recently it has been very difficult to demonstrate that poisons extracted from plants were used by early societies. Dr Huw Barton from the School of Archaeology and Ancient History has advised research conducted by Dr Valentina Borgia from the University of Cambridge - based on his expertise in the analysis of organic residues - that suggests our ancestors may have used poisons on weaponry as far back as 30,000 years ago.

Dr Barton explained: “Valentina is undertaking a very interesting and difficult study of the history of toxins and their use in prehistory. My work with Valentina, at this stage has mostly been advisory and we have discussed methods that could be employed to detect toxic compounds persisting on the surface of stone and bone tools.

“Broadly this study can be termed ‘residue analysis’ - something that I have been engaged in for many years. Prehistoric stone and bone tools sometimes retain very small traces of organic compounds that they have come into contact with. This might be hafting resin, gut or plant bindings, or the materials that the tool has worked, such as meat, bone, plant tissues, bark, wood and so on. Valentina is focused on the recovery of toxic compounds that people have added to tools to aid them in hunting animals. Currently, we don’t know when humans first discovered toxins and applied their properties. This is what we hope to find out.”

In collaboration with colleagues working at the Niah Caves in Borneo (2007-2010), Dr Barton has helped to recover pieces of highly poisonous yams dating to at least 20,000 years ago. Today this yam is detoxified and eaten, though rare cases of poisoning are not unheard of. Early work at the cave also recovered several burnt nut fragments of a plant that is still widely eaten in Southeast Asia, but one that is also highly toxic and capable of killing a person if not properly treated, that date to around 40,000 years ago.

Dr Barton added: “If people knew how to detoxify poisonous plants 40,000 years ago, were they aware of how to apply their properties for other purposes? We don’t know, but Valentina’s work could find the answers. I hope to work on some of the plant residues discovered and try and identify the plant source through the application of starch granule analysis.”

Starch granule analysis is a technique in plant residue analysis that Dr Barton has helped pioneer at the University of Leicester and is currently being used by Dr Barton to examine the prehistory of plant use in Borneo and southern China.