How long does DNA evidence last?

Tamsin O'Connell and Alan Cook discuss how long DNA evidence remains recoverable...

After how many years can you still find DNA evidence? Does it break down quite quickly?

Alan - Yes. When we're actually recovering things from crime scenes care and prevention of cross contamination is a big issue, but so is care of the exhibits once we've actually got them. We need to get them into fridges and freezers as quickly as possible so that scientists can go on and look at them.

Chris - In what ways does DNA get damaged or deteriorate with time?

Tamsin - For archaeologists, water is a real problem because it helps to break down the bonds within the DNA and eventually washes it away. Preservation of protein and the whole sample is also a problem, so we have to look for well preserved samples. These include things like mammoths found in the natural freezer, or permafrost, in Russia. Things in the desert are an absolute disaster because of seasonal rain and the fact that it's very dry. This helps the DNA break down easily as well.

Chris - How far back would we need to go to find the first humans?

Tamsin - To find modern Homo sapiens, you'd probably have to go back about 100 000 years to find the first Homo sapiens, which is not very far back in terms of human evolution. We split apart from the great apes about 6 million years ago, and there are various other hominin species in between them and modern Homo sapiens sapiens.

Chris - In the past 100 000 years or so we've had us, plus those hobbit people in Flores, and there are deposits of Neanderthal man until as recently as 20 000 years ago.

Kat - I think some of them are still hanging around in London actually!