Miikka Tallavaara

Did the mid-Holocene environmental changes cause the boom and bust of hunter-gatherer population size in eastern Fennoscandia?

Prehistoric hunter-gatherer population size is often assumed to follow climatic and other environmental forcings that affect environmental productivity and the availability of food for human foragers. We tested this assumption by studying the co-variation of archaeological and palaeoenvironmental records during the Holocene in eastern Fennoscandia. The reconstruction of population history is based on the summed probability distribution of archaeological radiocarbon dates, and environmental changes are tracked with locally available, high-resolution biological and physical proxies that are relevant in terms of hunter-gatherer food availability and population dynamics. The results show major population growth during the period of high summer temperature and high productivity of the terrestrial, lacustrine and marine ecosystems that occurred during 7500–5700 cal. yr BP. The growth was followed by an abrupt decline during 5500–4000 cal. yr BP correlating with the onset of late-Holocene cooling and a major forest ecosystem change brought about by the expansion of Norway spruce and the associated change from species-rich mixed forests to a conifer-dominated boreal ecosystem. Forest ecosystem changes likely enforced the negative effects of decreasing productivity on hunter-gatherer food availability. The link between population and environmental proxies breaks down along with the intensification of agriculture after 3500 cal. yr BP, which indicates that agriculture weakened the environmental forcing on long-term human population dynamics.

Human population dynamics in Europe over the Last Glacial Maximum

Significance Despite its importance for understanding genetic, cultural, and linguistic evolution, prehistoric human population history has remained difficult to reconstruct. We show that the dynamics of the human population in Europe from 30,000 to 13,000 y ago can be simulated using ethnographic and paleoclimate data within the climate envelope modeling approach. Correspondence between the population simulation and archaeological data suggests that population dynamics were indeed driven by major climate fluctuations, with population size varying between 130,000 and 410,000 people. Although climate has been an important determinant of human population dynamics, the climatic conditions during the last glacial were not as harsh as is often presented, because even during the coldest phases, the climatically suitable area for humans covered 36% of Europe. The severe cooling and the expansion of the ice sheets during the Last Glacial Maximum (LGM), 27,000–19,000 y ago (27–19 ky ago) had a major impact on plant and animal populations, including humans. Changes in human population size and range have affected our genetic evolution, and recent modeling efforts have reaffirmed the importance of population dynamics in cultural and linguistic evolution, as well. However, in the absence of historical records, estimating past population levels has remained difficult. Here we show that it is possible to model spatially explicit human population dynamics from the pre-LGM at 30 ky ago through the LGM to the Late Glacial in Europe by using climate envelope modeling tools and modern ethnographic datasets to construct a population calibration model. The simulated range and size of the human population correspond significantly with spatiotemporal patterns in the archaeological data, suggesting that climate was a major driver of population dynamics 30–13 ky ago. The simulated population size declined from about 330,000 people at 30 ky ago to a minimum of 130,000 people at 23 ky ago. The Late Glacial population growth was fastest during Greenland interstadial 1, and by 13 ky ago, there were almost 410,000 people in Europe. Even during the coldest part of the LGM, the climatically suitable area for human habitation remained unfragmented and covered 36% of Europe.

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.

Productivity, biodiversity, and pathogens influence the global hunter-gatherer population density

Significance Because of complex cumulative culture, human populations are often considered to be divorced from the environment and not be under the same ecological forcing as other species. However, this study shows that key environmental parameters net primary productivity, biodiversity, and environmental pathogen stress have strong influence on the global pattern of hunter-gatherer population density. Productivity and biodiversity exert the strongest influence in high and midlatitudes, whereas pathogens become more important in tropics. The most suitable conditions for preagricultural humans are found in temperate and subtropical biomes. Our results show that cultural evolution has not freed human hunter-gatherers from strong biotic and abiotic forcing. The environmental drivers of species distributions and abundances are at the core of ecological research. However, the effects of these drivers on human abundance are not well-known. Here, we report how net primary productivity, biodiversity, and pathogen stress affect human population density using global ethnographic hunter-gatherer data. Our results show that productivity has significant effects on population density globally. The most important direct drivers, however, depend on environmental conditions: biodiversity influences population density exclusively in low-productivity regions, whereas pathogen stress does so in high-productivity regions. Our results also indicate that subtropical and temperate forest biomes provide the highest carrying capacity for hunter-gatherer populations. These findings document that environmental factors play a key role in shaping global population density patterns of preagricultural humans.

The advance of cultivation at its northern European limit: Process or event?

Dates for early cultivation in Finland obtained from pollen analysis and remains from archaeological sites are compared with the changes in population size derived from the summed calendar-year probability distributions. The results from these two independent proxies correlate strongly with one another indicating that population size and the advance of farming were closely linked to each other. Moreover, the results show that the adaptation and development of farming in this area was a complex process comprising several stages and with major differences between regions The most intensive expansion having occurred in and after the Iron Age. It is therefore more accurate to describe the introduction of farming into the area as a long-lasting process, rather than an event.

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)