Palaeogenetics and Population History
Until recently, most of our knowledge on prehistoric man came from archaeological evidence alone. The palaeogenetic analysis of archaeological skeletons helps to reconstruct biological processes of the past. Even from a single genome we can learn a lot about the populations that shaped it.
European Hunter-gatherers and The Neolithic Transition
One of the most interesting questions in prehistory is that of the origins of European peoples following the introduction of settled farming life to the continent during the Neolithic period some 8,000 years ago.
The term ‘Neolithic’ refers to a novel human way of life centered on crop and animal domestication and the construction of permanent settlements with special-use buildings. The transition from mobile foraging to sedentary farming first occurred around 11,000 years ago in the Near East with the cultivation of several edible grasses and legumes and the domestication of cattle, sheep, goats and pigs, and spread throughout southwest Asia, reaching Europe 8,500 years ago. The manner in which farming spread to Europe remains one of the most hotly debated topics in European prehistory.
In 2005, our group was the first one that sequenced DNA from Neolithic skeletons (Haak et al. Science 2005). Four years later, we were able to show that European hunter-gatherers were not the ancestors of the early Neolithic farmers (Bramanti et al. Science 2009) but admixed later (Lazaridis et al. Nature 2014) or co-existed separately for many centuries (Bollongino et al. Science 2014). With genomic studies from 2016, we could show that there is a genetic link between Mediterranean and Central European early farmers and those of Greece and Anatolia, extending the European Neolithic migratory chain all the way back to southwest Asia (Hofmanová, Kreutzer et al. PNAS 2016) but not as far as the eastern Fertile Crescent (Broushaki et al. 2016, Science).
We examine “natural selection” from the perspective of evolutionary neutralists, in other words, we prefer to adopt a critical stance to overhasty selection hypotheses. But in some cases, the signals for recent selection in humans are very strong, such as in the case of lactase persistence and variants associated with pigmentation or susceptibility to inflammatory diseases.
An early study of lactase persistence already provided convincing evidence for the selection hypotheses with ancient DNA (Burger et al PNAS 2007). The work of Itan et al. 2009 (PLoS Computational Biology) by our colleagues from UCL, presented a spatially explicit modeling of the spread of the allele associated with lactase persistence in conjunction with Approximate Bayesian Computation (ABC).
In 2014, together with our colleagues from UCL, we were using a forward simulation of allele frequencies that integrates genetic drift and positive selection in a larger dataset in order to identify the positive selection of pigmentation genes (Wilde et al. PNAS 2014). The idea here was to gather statistical evidence to indicate whether changes in allele frequencies between a prehistoric sample and a modern population can be explained by the normal process of genetic drift or whether positive selection must be used as an explanatory factor.
The domestication of plants and animals is a comparably recent, still ongoing, and path-breaking process that massively altered human subsistence and lifestyle. The earliest signs for the management and breeding of sheep, goats, pigs and cattle date back to the Neolithic period in southwest Asia more than 10,000 years ago and landmark the increasing impact that humans have on the biosphere until today. Like goats and sheep, European domesticated pigs have Near Eastern roots, but experienced several episodes of introgression from wild boar (Ottoni et al. 2013). In domestic European cattle, the degree of admixture with wild forms (aurochs; Ur) is much smaller (Bollongino et al. 2006, Edwards et al. 2007, Scheu et al. 2008). Cattle were domesticated from a relatively small herd in the Near East (Bollongino et al. 2012) and with the help of ancient DNA data we can even describe some demographic details of their migrations from this region via Western Anatolia and the Balkans to Central and Northern Europe (Scheu et al 2015).
Dogs were the earliest domestic species. A genomic study from 2017 revealed that a 7,000 year old dog from Germany was already very similar to modern dog breeds (Botigué et al. 2017).
Late Romans and The Early Medieval Period in Central Europe
The time between the 4th and the 8th century AD plays an important role for the self-image of today’s European nations. Against this background, our research aims to analyze the genetic diversity of populations of that time and infers the population genetic parameters involved in the formation of populations that are described as Romans, Celts and Germans.