Dr Caroline Smith for The Conversation and Radio New Zealand on Ötzi the Iceman

In The Conversation article Dr Smith discussed how reliable these DNA predictions about appearance can be. Because Otzi was frozen in permafrost almost immediately upon his death, the quality of samples that can be taken from his body is high, and researchers have been able to sequence his entire genome. Human genomes consist of billions of DNA bases: chemical building blocks containing adenine, thymine, cytosine and guanine arranged in different sequences. Some regions are extremely variable and forensic scientists evaluate these regions to match them to crime scene samples, suspects, victims or relatives.

Dr Smith said: “Much of the genome’s DNA sequence is common to all humans, but there are places where a change from one base to another results in changes to our physical appearance.” 

Dr Smith argues that while some aspects of appearance can be accurately predicted, such as red hair, our understanding of these gene variants, particularly in regard to face shape, are incomplete. She said: “Many of the identikit pictures built from DNA analysis alone bear a resemblance to actual images of the individuals. But when DNA is the only evidence available to build a portrait, the prediction of facial appearance can be skewed by body composition which is significantly affected by diet and lifestyle.” 

While things like eye colour and hair colour can be more accurately predicted by DNA, much of human appearance is affected by environmental factors, stress, diet and disease. DNA bases can also change through someone’s life depending on lifestyle and environment. As scientists continue to gather DNA data from around the world, it will be easier for forensic scientists to predict ancestry and appearance with more accuracy.

Speaking on Radio New Zealand, Dr Smith told the host what scientists had found out about the appearance of Otzi. She said: “There are a lot of background studies of Europeans so because they were able to compare the DNA from Otzi with different background populations, they were able to work out that Otzi had probably come from a Mediterranean, southern European ancestry. Consistent with that ancestry, they found that Otzi had quite dark skin and quite dark hair.”

Read her article New research reveals that Ötzi the iceman was bald and probably from a farming family – what else can DNA uncover? on The Conversation website. This article was also republished in The New European.  

Listen to the full radio interview on Radio New Zealand.