Petro Pesonen

Archaeological Radiocarbon Dates for Studying the Population History in Eastern Fennoscandia

In this work, archaeological radiocarbon data gathered from eastern Fennoscandia have been scrutinized to discuss their suitability for studies of population history. The temporal distribution of the archaeological 14C dates has been analyzed against possible research priorities and sample material deterioration. An outstanding ?Stone Age? maximum has been observed in practically all the displayed temporal date distributions. The pattern remains the same throughout the history of 14C dating in Finland. Due to sample material differences, equal taphonomic corrections based on 14C-dated volcanic deposits cannot account for all the sample degradation effects; therefore, material-dependent correction procedures are suggested.

Event reconstruction through Bayesian chronology: Massive mid-Holocene lake-burst triggered large-scale ecological and cultural change

Precise timing of natural and cultural events provides a foundation for understanding how past natural phenomena have driven changes in population and culture. In this study, we used high-resolution Bayesian chronology to describe an event sequence of a massive and abrupt water level decline of a large lake and the contemporaneous cultural changes that occurred in eastern Fennoscandia during the mid-Holocene. The study provides the first transdisciplinary analysis of the causes and effects of the events by using a combination of archaeological, geological and ecological data. Nearly 6000 years ago, ancient Lake Saimaa, estimated to cover nearly 9000 km2at the time, was abruptly discharged through a new outlet. The event created thousands of square kilometres of new residual wetlands. The archaeological record shows a profound cultural replacement and a subsequent sharp human population maximum in the area during the decades after the decline in water level. During the population maximum, the proportion of Alces alces (moose) in the diet rapidly increased and became prominent as a dietary resource. The eventual population decline in the area coincided with ecological development towards old boreal conifer forests, along with the colonization of a new species of tree Picea abies (Norway spruce). The new ecosystem was less suitable for moose to forage in, and this attenuated the dietary role of moose and thus contributed towards the eventual population and cultural decline. The methodological approach described in this paper allowed the reconstruction of past natural and cultural events and demonstrated how they can be causally intertwined.

Archaeology, Genetics and a Population Bottleneck in Prehistoric Finland

The long-term history of prehistoric populations is a challenging but important subject that can now be addressed through combined use of archaeological and genetic evidence. In this study a multidisciplinary team uses these approaches to document the existence of a major population bottleneck in Finland during the Late Neolithic period, the effects of which are still detectable in the genetic profile of the Finnish population today. The postglacial recolonisation of Finland was tracked through space and time using radiocarbon dates and stone artefact distributions to provide a robust framework of evidence against which the genetic simulations could be compared.

The role of climate, forest fires and human population size in Holocene vegetation dynamics in Fennoscandia

Questions: We investigated the changing role of climate, forest fires and human population size in the broad-scale compositional changes in Holocene vegetation dynamics before and after the onset of farming in Sweden (at 6,000 cal yr BP) and in Finland (at 4,000 cal yr BP). Location: Southern and central Sweden, SW and SE Finland. Methods: Holocene regional plant abundances were reconstructed using the REVEALS model on selected fossil pollen records from lakes. The relative importance of climate, fires and human population size on changes in vegetation composition was assessed using variation partitioning. Past climate variable was derived from the LOVECLIM climate model. Fire variable was reconstructed from sedimentary charcoal records. Estimated trend in human population size was based on the temporal distribution of archaeological radiocarbon dates. Results: Climate explains the highest proportion of variation in vegetation composition during the whole study period in Sweden (10,000-4,000 cal yr BP) and in Finland (10,000-1,000 cal yr BP), and during the pre-agricultural period. In general, fires explain a relatively low proportion of variation. Human population size has significant effect on vegetation dynamics after the onset of farming and explains the highest variation in vegetation in S Sweden and SW Finland. Conclusions: Mesolithic hunter-gatherer populations did not significantly affect vegetation composition in Fennoscandia, and climate was the main driver of changes at that time. Agricultural communities, however, had greater effect on vegetation dynamics, and the role of human population size became a more important factor during the late Holocene. Our results demonstrate that climate can be considered the main driver of long-term vegetation dynamics in Fennoscandia. However, in some regions the influence of human population size on Holocene vegetation changes exceeded that of climate and has a longevity dating to the early Neolithic. (Less)