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Introduction to Dating Methods

An introductory overview of dating methods
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One of the key bits of information we need at every archaeological site is when things happened. For that, we need to use as many dating methods as possible. Because not every dating method is perfect. In fact, over time, dating methods have improved gradually. So we start off with something like radiocarbon dating on charcoal pieces or, if it’s young enough, bits of bone. Then you can try luminescence methods, which are good for dating sediments when they were last exposed to sunlight. You can also try uranium series methods, which can be applied to cave formations– speleothems– and they can also be applied to bones themselves– as can electron spin resonance, which can be applied to tooth enamel.
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All of these methods can be applied at Liang Bua– and have been. So too you can date the volcanic ash, using argon dating methods. All of these methods are on the improve because people are working hard to get them better and better. Humans have been evolving in the past, but so too have deposits. It’s strange to think of it that way, but a deposit doesn’t stay static. Once it’s deposited in a cave, things start to happen to it. Things start to weather and decay and migrate through the deposit. And some of that can force contamination onto a stone tool or into a bone.
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In fact, that’s how we date uranium series of bones– by looking at the uranium migrating into the bone. Some of those things help, and some of them don’t. DNA decays rapidly under humid conditions and when it’s hot. So DNA attempts have been made on hobbit bones, and it’s still going to be worth trying in the future as techniques get better. Even on the stone tools themselves we can try different methods to look at what’s actually attached to a stone tool and how much of that is contamination from the outside and how much of it is to do with what people were using that stone tool for. All of these are things that need to be taken into consideration.
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Contamination is around us all the time. So we just need to factor in how much of it’s contaminant and how much of it is real. And that’s why we’re using archaeological chemistry to investigate some of these questions. So this is part of what we’re now doing at Liang Bua. And let’s go through some of these methods now and how they’ve been applied to the deposits and to the fossil remains of the hobbit.

Dating methods help us answer the question “When did it happen?”

Dating methods and techniques continue to improve over time and shed light on mysteries buried deep in the past. Each method has its own strengths, but none is perfect. So, experts work together to extract chronological information through applying a diverse range of techniques.

Dating Methods and Examples

  • Radiocarbon dating for wood or charcoal pieces or bits of bone and shell (if they are less than 50, 000 years old)
  • Luminescence methods for dating sediments when heated to a high temperature or last exposed to sunlight
  • Uranium-series methods for dating cave formations (speleothems) and bones
  • Electron spin resonance for dating tooth enamel
  • Argon dating methods for minerals in volcanic ash

Contamination

“Contamination is around us all the time. So we just need to factor in how much of it’s contaminant and how much of it is real” (Prof. Bert Roberts).

Deposits don’t stay static — they change over time. For example, the weathering and decay of materials and their migration through deposits can result in contamination of artefacts and ecofacts. These variables must be considered when dating deposits, skeletal remains and artefacts. In some instances, such as uranium-series dating of bones, contamination in the form of uranium migration into a bone is used to identify the age of that bone.

Conversation starter

  • Why might DNA analysis of Hobbit bones be complex and how may advancing methods address this?
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