What is Ancient DNA or aDNA?

Uwe Ebbinghaus

Editor in the features section.

  • Follow I follow

Philipp Stockhammer: Ancient or old DNA is the genetic make-up of people who lived hundreds or thousands of years ago.

The genetic material is in their bones, even if not in all of them and is often only preserved to a small extent.

Among other things, it depends on the ambient temperature: the cooler, the better the preservation.

We can extract the genetic material by drilling into bones.

What exactly can you take from the bone powder?

As much DNA as possible is extracted from the bone powder.

A lot comes together: human DNA as well as DNA from bacteria, fungi and other living things from the soil.

Now we use small hooks with which we pull out the human DNA separately.

We then put these into sequencing machines, which read out the fragments.

The result is a data set that can be correlated with other data sets.

How do you avoid contamination by new DNA, that has long been a criticism of DNA analysis in archeology?

The investigation of aDNA takes place in a clean room laboratory, in which only old, not modern DNA is analyzed.

The employees had previously passed shower locks with special clothing.

Many processes run through automated robots.

How do you deal with the fact that an old bone can easily contain newer human DNA?

Unfortunately, this cannot be prevented, but in our analyzes we can filter out the new DNA, e.g. that of museum curators or laboratory technicians.

There are markers, small chemical changes that only take place after a certain age.

Old DNA is fraying at the ends, so to speak.

The procedures just described did not exist until ten years ago.

But since then we have been able to detect contamination with a probability bordering on certainty and, in most cases, filter out contaminated data sets.

How long is the "antique" or "old" period?

The oldest DNA published so far is the 1.6 million year old mammoth. The oldest human DNA is around 430,000 years old - this is an early human form. With good preservation conditions, DNA can also be found in such old bone fragments. The molecular chains become shorter and shorter over the years, and at some point there are hardly any DNA base pairs left. One speaks of old DNA when examining a hundred-year-old burial ground, even with the bones of people who are no longer living today. However, with comparatively young DNA, our contamination filters no longer work well. The term “old” is relative, but the focus of the research is clearly on older periods.

The age of bones is not determined by DNA analysis.

How do you get this out?

At most, one can tell from the DNA whether it is the bones of someone who died recently or who died a long time ago.

We use radiocarbon dating, the C14 method, to determine the age.