Using computer-aided methods, the largest available databases were used to examine the extent to which the global genetic diversity of humans is reflected in the structure and form, the so-called morphology, of different skeletal elements. The team achieved the best results when comparing specific elements in the dentition and skull, but with different weightings. The new results can be used in archaeological and forensic investigations when DNA analysis is not possible. The study was published in the journal PNAS Nexus.
Features with different weighting
The morphology of the human skeleton is highly variable and differs both between individuals and between populations worldwide. This diversity evolved as a result of complex interactions of various evolutionary forces over a long period of time. “Evolutionary biologists divide these forces into two distinct processes. A neutral process describes the process by which mutations produce new diversity that offers no direct advantages or disadvantages to the affected individuals. This new diversity increases or disappears randomly as a result of what is known as genetic drift within a population,” explains Hannes Rathmann. “On the other hand, there are non-neutral processes that describe, for example, the process by which mutations affect the fitness of an individual. The affected individuals can then either adapt better or worse to environmental factors.« In order to draw detailed conclusions about family relationships, according to the scientist, only skeletal elements that developed through neutral processes should be used.
In the study, the team focused on the dentition and skull, the structures of which are considered to be predominantly developed by neutral processes. “Contrary to previous assumptions, not all features in the teeth and skull reliably reflect the underlying genetic code, some are much better suited than others,” reports Rathmann. Smaller morphological features on the teeth, such as groove patterns in the crowns, the number and size of the cusps, the shape of the roots and the presence or absence of wisdom teeth proved to be particularly suitable. “However, we achieved the best results, almost identical to a classic genetic relationship analysis, when we included all features of the skull and dentition in an integrated form,” he reports.
Non-destructive alternative
Katerina Harvati, senior author of the study, adds: “The results advance our understanding of the origins of human skeletal diversity. They are also promising for use in archaeological and forensic investigations.” Genetic analysis is often only possible to a very limited extent if the DNA is poorly preserved. This is often the case with very old bones or those that have been exposed to a warm climate. The bones would also have to be damaged for DNA analysis, which is often out of the question in the case of brittle material or rare finds. “In such cases, the non-destructive examination of the skull and dentition is a valuable alternative, for example to reconstruct past population history or human ancestry in archaeological contexts or to create family profiles in forensics.”