Terry Brown (The University of Manchester, Manchester)

Ian Barnes (Royal Holloway, University of London, Surrey)

What can we learn from genetics?

Palaeoegenetics is the study of ancient DNA which is preserved within ancient specimens. We can use this DNA to investigate how organisms have adapted in response to environmental change. DNA is one of several biomolecules that are preserved once a living organism reaches the end of its life. Other biomolecules include:

  • Lipids
  • Proteins
  • Carbohydrates
  • DNA

We can extract DNA from a number of sources, including:

  • Hair – particularly good preservation potential.
  • Preserved soft tissue – not widely used.
  • Coprolites (fossilised dung)– very good preservation potential.
  • Plant remains – good preservation potential.
  • Sedimentary DNA – DNA within lakes, ice cores etc. – problematic as preservation is poor.
What have been the major developments in the use of genetics?

In 1984, Russell Higuchi was the first to extract ancient DNA from a 160 year old museum specimen of a quagga (a now extinct sub-species of the plains zebra, from South Africa). In 1989, ancient DNA was extracted from bone for the first time by Hagelberg et al. (1989) and Hanni et al. (1990). Many early studies claimed to have identified ancient DNA from millions of years ago – in leaves, of dinosaur remains, for example. However, it has since been recognised that ancient DNA does not last longer than around 1 million years (Ma) in the archaeological record due to decay. So, previous claims of older DNA are thought to be due to contamination. After this time, the majority of researched focused on minimising sample contamination. This culminated in a paper by Alan Cooper and Hendrik Poinar, published in Science in 2000, entitled ‘Ancient DNA: Do It Right or Not at All’. At present, the oldest DNA that we have been able to extract and reconstruct is from a 700,000 year-old horse genome.

What are the major challenges?

Ancient DNA research is focused not only on finding and extracting uncontaminated DNA, but also on handling the data effectively. As technology continues to develop, it is important for the research field, and its analytical techniques, as a whole to progress alongside these changes. Ancient DNA studies are often hindered by DNA damage, contamination, and complications in the purification of the DNA. We need to use technological developments to help us overcome these issues.

Another major issue in the study of ancient DNA is that we often assume that the individuals in the assemblage (group of fossilised remains) are members of a population that existed at the same time and could breed. This is not necessarily the case. We can use statistics (such as Bayesian methods) to try and explore the links between members of a population in terms of their contemporaneity. This will allow us to use ancient DNA to explore the ways in which species have adapted and behaved in response to Quaternary environmental change.