What are some German genetic traits

The genetic make-up in a person's cells determines what they look like - at least to a large extent. Eye, skin, and hair colors are stored in genes, as are many other physical characteristics. The obvious idea is to use genetic traces in a hair or a drop of blood at the crime scene to construct a phantom image. The technology is not that far yet, but genes as silent witnesses can already tell investigators a lot about the appearance of a suspect.

"At the moment we can determine eye and hair color quite accurately from DNA," says Manfred Kayser, Professor of Forensic Molecular Biology at Erasmus University in Rotterdam. With the help of six genetic markers, it is possible to identify with high accuracy whether a person has brown or blue eyes. All other colors are not so precisely determinable. Forensic scientists can also read red and black hair quite reliably from the genes. "Blonde and brown is more difficult because some blondes get darker with age," says Kayser. "Then the genes often show blond, although humans actually have light brown hair in the meantime." When it comes to skin color, forensic scientists are not yet ready. "Overall, we know a lot more about the genetic basis of disease than we do about the genetics of our appearance."

Current methods can only very imprecisely localize a person's origin

The situation is hardly different with DNA analysis to determine biogeographical ancestry. A few dozen genetic markers can be used to distinguish whether the genetic make-up comes from Western Eurasia, East Asia or a country south of the Sahara or is a native American, says Kayser. Forensic doctor Peter Schneider from the University Clinic in Cologne gives the probability that a person's continental origin can typically be determined from their DNA traces at 99.9 percent. "In a specific case it can of course also be that no clear continental allocation is possible." With today's resources, it is only possible to resolve the huge geographical area of ​​Western Eurasia more precisely for some regions, such as the Indian subcontinent. To change that, more genetic information about residents of the various regions would be needed and more knowledge about the genetic markers that influence appearance. "The quality of the forecast is crucially dependent on the reference data," says Schneider.

So far, he and his colleagues have mainly been working with data from public research projects. "But they don't represent all geographical regions," says Veronika Lipphardt from the University College Freiburg. "In the Middle East in particular, there are large gaps. In addition, people with a mixed genetic background are difficult to classify in many cases." She considers the probability data for determining eye, hair and skin color often mentioned in the current debate to be incorrectly calculated and fears an unjustified concentration on minorities in investigations based on genetic analyzes.

Some research groups are already working on deducing facial features from the genes. Even if such complex properties are not yet well understood, Peter Schneider believes that a phantom image constructed from the genetic makeup is possible in the long term. However, characteristics such as body size will remain difficult to determine in the future. This is controlled by a few hundred genes, and environmental factors also have an influence on how tall a person grows.

Schneider himself thinks that the 99.9 percent probability is currently heavily overrated in the public debate. "It's a value that we typically get from people with no very mixed genetic backgrounds. In reality, the accuracy is sometimes above and often below the value." This statistical information is not a sound barrier.