If it all sounds a bit like environmental determinism gone mad, think again. Researchers can now read markers left on ancient DNA by climate, famine and disease in the long-distant past.
For the first time, researchers have proved that it’s possible to read details about changes in the ancient environment within a person’s lifetime from DNA samples going back 4,500 years. But how does the environment affect someone’s genes?
The science behind the theory
To understand the principle behind this, a quick lesson in epigenetics might be useful! Epigenetics is the study of traits that are not caused by changes to the underlying DNA, but sort of on or around DNA. In short, researchers look at how environmental factors like diet, disease and climate influence gene expression (whether it is turned on, off or read differently) during someone’s life. Mechanisms that can do this include DNA methylation, where a methyl group attaches itself to a bit of DNA, changing how it is read, but still without changing the underlying DNA itself. Epigenetic changes like this can be permanent, others more temporary, while some can also prove to be hereditary. In simple terms, this means that everything right down to the weather can potentially alter who we are!
These kinds of epigenetic changes be detected in fresh DNA, but researchers from the University of Texas are the first to successfully detect an unprecedented number of epigenetic markers in a sample of 29 ancient human remains.
They did this using a technique known as bisulfite sequencing, which was previously thought too impractical for use on ancient samples due to the destructive nature of the method.
But researchers have proved that it can be successfully used on remains with better preservation, opening the door for new studies looking at the effects of environmental factors, such as disease, on ancient populations.
What does it mean for archaeology?
Previous studies have looked at epigenetic changes in people who experienced famine during WW2 and found that markers could remain present in following generations.
By studying epigenetic markers in historical samples, scientists can track which genes are expressed in response to particular environmental stresses, and how this in turn shaped physical traits and health across the generations to come.
This opens the door to a much better understanding of how past populations responded to disease, climate change or other environmental stresses, but also to a clearer picture of past environments themselves.
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