This story is a tale of research woes. We like to pretend everything goes to plan in our studies, but sometimes the archaeology doesn’t want to play along…
Lead is a really important element in human history. Very early on we realised that it was a useful metal for us, it was nice and soft and could be made into lots of things. It didn’t seem to rust, it could be used to make bright white paints and cosmetics, it even tasted sweet – so you could use it to make your food better, or to quietly poison people. Later in our history we realised that if we added lead to petrol it stopped the ‘knocking’ of car engines. A wonder metal indeed!
People realised pretty early on that lead might be a little bit poisonous (**spoilers, lead is actually a lot poisonous**). People working with it tended to get quite sick, losing motor control, their sight, and often their teeth. They developed anaemia, infertility, memory loss. Sometimes they died from their symptoms. Still, lead was a useful metal and generally it wasn’t the rich people or the factory owners getting sick. So there wasn’t much effort put into making working with lead safe, and it continued to be used despite the health issues it caused.
In Industrial Revolution period Britain lead was everywhere. Water flowed into houses via lead pipes, white lead was used in paints, cooking pots and drinking vessels were made out of pewter (a lead alloy), lead glaze was common on pottery. People were exposed to lead in their water, their food and the air that they breathed. Children were particularly at risk of high exposure from gnawing the lead paint on their cribs.
All this means that lead is quite a useful element for working out who (in our NZ cemetery samples) might have come from Britain, or other industrialised countries, and who was born in NZ. Although European settlers brought some lead objects with them to NZ, lead was not mined here and we weren’t a heavily industrialised country. Because of this we’d expect our European settlers to have high levels of British lead in their teeth, while people born in NZ shouldn’t have had as much lead exposure. A foolproof method for pinpointing our first settlers…
… or so we thought. Unfortunately in Milton this cunning plan doesn’t work at all because once we tested our Milton settlers we found that EVERYONE (even the children born in Milton) had lead levels in their teeth far higher than they could have been exposed to in life. Something in our burial environment was introducing lead into the teeth after they had died.
And after a lot of testing we found our culprit – those beautiful coffin strips we have talked about before. It turns out they’re made of thinly pressed pewter, a lead-tin alloy. As the coffin strips have broken down in the ground, they’ve released lead into the burials. That lead has been taken up into the teeth of everyone on site.
So Victorian funerary decorations may have been pretty… but they’re also pretty annoying for people like me trying to look at where the people of Milton came from!
Although this particular method hasn’t worked for us, don’t worry, we have other ways of looking at where people came from, and we’ll report on those results later!
Charlotte King, January 2020
King, CL, P Petchey, HR Buckley, E Girvan, R Kinaston, and GM Nowell. 2020 . Lead Astray: The Potentials and Pitfalls of Lead Isotopes in a New Zealand Colonial Burial Context. Journal of Archaeological Science: Reports, 30.