Workshop – London 2014

Workshop summary (London 17-19 June 2014)

On 17-19 June 2014, a workshop was held at the Institute of Archaeology, University College London. The goal of this workshop was to bring together experts in human and environmental change in Africa, and through a series of presentations and discussion stimulate interdisciplinary communication and better understand the current state of knowledge and approaches to addressing the issues of human-environment interaction in Africa.

Tuesday 17 June

To get things started, Jed Kaplan introduced the ACACIA project and the goals of the workshop. The ACACIA project tackles the problem of the co-evolution of society and environment during the transition to the Iron Age in Africa. The group studies the importance of environmental changes, both exogenous and endogenous, on the potential for human modification of the landscape. In order to study these factors the team will develop and apply integrated human-environment models.

Dorian Fuller presented on the current state of archaeobotany across the greater Bantu region, citing the level of work and the number of publications completed in each country to illustrate the data gaps and emphasize the limits imposed on any synthesis study by the data available. He also provided information about the various indigenous African grains, their domestication, and spread.

Andrea Kay introduced the methodological approach of the ACACIA project in developing a categorization of African subsistence strategies, which will form a portion of her PhD research. This research covers the period from 1000 BC to 1500 AD and examines the various degrees of land use intensity employed by different groups at different times, e.g. wild-forage, herding, vegetable or cereal crops, and pottery or metallurgy. This broad data synthesis will inform the development of ACACIA’s human-environment models.

Michael Petraglia gave a presentation about the SEALINKS project in East Africa. The SEALINKS project has been working to collect environmental and archaeological datasets from sites along the East African coast, Madagascar, and nearby islands. The project seeks to clarify the role of Indian Ocean trade in the local economies and the introduction of certain crop species. SEALINKS employs methods and gathers data related to archaeology, genetics, linguistics, and palaeoenvironmental studies.

Basil Davis presented his understanding of the current state and potential applications of the African Pollen Database. He described other pollen databases around the world and showed examples of how this data has been applied from previous work in Europe. This talk placed a large emphasis on data availability and the inconsistencies between the data that is publicly available online and the data that has appeared in recent publications.

Christelle Hély presented her research on the Holocene West African vegetation response to climate change. Her research uses pollen records and model simulations to examine the effects of water availability on vegetation, and to investigate the issue of the changing latitudes, spatial extent and intensity of the African monsoons during and through the end of the African Humid Period. She also discussed the abrupt climatic shifts that occurred around 4.5 cal ka BP (the end of the monsoon intensification and a shift from Guineo–Congolian to Sudanian and Sahelian species South of 15 N) and 3.2 cal ka BP (the opening of the Dahomey gap).

Matthew Davies showed examples from his work and other sources to highlight the potentials, problems and challenges of researching demography in Africa’s Later Iron Age as well as earlier periods. Of particular note were the examples from Binford of hunter-gatherer sites that showed a large amount of variability both seasonally (due to the seasonal migration of people) and functionally (due to craft specialization or local resource availability); and the site of Engaruka in Tanzania, where numerous studies have attempted population estimates and produced significantly different results.

Wednesday 18 June

Paul Lane covered a variety of topics in his talk titled: Domesticating African Landscapes – Developing New Theoretical Frameworks for Studying the History of Food Production in Sub-Saharan Africa. He cautioned that many of the terms being discussed, particularly ‘Iron Age’ carried some semantic baggage and should be used carefully. He also discussed the conceptual issues surrounding the domestication of both plants and animals, and how food production can occur using ‘wild’ cultivars; and that some cultures herd ‘wild’ species, such as reindeer. He described specific species and pottery types associated with the Bantu expansion. Finally, he talked about his work with cycles of site abandonment and landscape reclamation; the pioneer species present at sites can indicate the length of time since abandonment but also attract grazers who’s activities keep the area open, and maintain natural glades.

Rob Marchant gave a presentation on the past, present and future ecosystem dynamics in East Africa. His work looks at the recent past in the area of the Kenya/Tanzania border: estimating carbon storage in different biomes and how it relates to socioeconomic factors. He showed an example of the relationship between land ownership and kinship in a valley where, as families grew, they leapfrogged one another, creating a mosaic of associated kinship ties as opposed to larger territories.

Louis Champion presented some preliminary archaeobotanical results from his PhD research in northeastern Benin on the Crossroads of Empire project. He also showed photos from his community outreach efforts and a video explaining the basic process of gathering archaeobotanical materials.

Carsten Lemmen explained his work on prognostic modeling of the spread of agriculture in Europe and suggested that a similar approach could be applied to the African context. He showed a video from the model output of what happened when he tried the unaltered European model on the African landscape. The result was a close resemblance to the known domestication centers, with the exception of a model-predicted far SE African domestication center, that has no known real-world occurrence. He also talked about population modeling.

Roger Blench described the use of historical linguistics and the spread of Bantu languages to explain archaeological distributions, and cautioned against the assumption that a farming “package” accompanied the spread of the Bantu languages. He also described the idea that the opening and closing of forest corridors (due to environmental factors) likely “trapped” small populations of animals in clearings in the forest, and a similar mechanism may have affected human populations. This theory sees migration as pulsing phenomenon dependent on climate fluctuation and subsistence decisions. He also gave his insights into a few African crops such as Sorghum and Hausa potato (a tuber from mint family).

Katie Manning presented her work on the demographic response to Holocene climate change in the Sahara. This work looks at the prevalence of radiocarbon dates throughout the region and various time periods, groups them into cultural/or regional assemblages, and examines how each grouping varies in size or distribution through time in response to climate change. Population estimates indicate a stepped rather than gradual change and that this occurs in different regions at different times. It was not clear if and how this type of work could be applied to sub-Saharan Africa.

Ulrich Salzmann presented on the need to disentangle late Holocene human impact and climate change in West African pollen records. He discussed the same 4.5 cal ka BP (end of AHP) and 3.2 cal ka BP (opening of Dahomey gap) climate events mentioned by Christelle Hély. He suggested (rather provocatively) that while archaeologists have interpreted the related pollen records as showing proof of human impact (for the 3.2 cal ka BP event), the same ecological conditions might have been produced by a higher degree of seasonality. He suggests that more robust evidence is needed to prove that human activity was indeed the cause.

Dirk Verschuren also discussed the relative robustness of various paleo-indicators of past human activity in an African context. He discussed examples from his lake coring work in east Africa. The cores from Lake Victoria (which has a massive watershed) show little change in lake chemistry and eutrophication until the last 50 years, when there is a very large change. This differs from examples from smaller lakes nearby, which show only small changes when the large changes happen in Lake Victoria. He also highlighted the relevance of shifting ecotones and the importance of climate variability for changing ecotones.

Thursday 19 June

The last day of the workshop consisted of discussion, workshop synthesis, a review of lessons learned, and suggestions for ways forward and potential future collaborations. A few of the biggest lessons learned were the importance of the abrupt environmental changes at 4.5 cal ka BP (end of green Sahara) and 3.2 cal ka BP (opening of Dahomey gap) in relation to a human cultural response; and that in Africa, in contrast to Europe, a mosaic of land use types existing in complement to each other in similar time and space. This can be accounted for in the model by distributing various subsistence types throughout niches in the landscape.

A recurring theme in the discussions was the issue raised by Basil Davis about the data available from the APD and the inconsistencies between the data that is publicly available online and the data that has appeared in recent publications. The online version of the APD has not been updated since early 2007. Due to numerous email inquiries from participants to Anne-Marie Lezine (who manages the database), it seems there will now be renewed data collation activity and expansion of the APD. Should these activities result in our access to a more complete dataset (including surface samples) then a more complete paleo-vegetation reconstruction can be produced and integrated into ACACIA’s models of human-environment interaction.

A major conclusion that came out of this workshop was the decision to initially focus data synthesis and modeling efforts on two case study areas: a West African case study (Ghana-Cameroon), and an East African case study (Great lakes, Kenya-Zambia). These two areas were chosen due to data availability and variety, and the relevance of a modeling approach to the pertinent regional questions, e.g. opening and closing of migration corridors, or human vs. environmental factors contributing to the opening and maintenance of the Dahomey gap. These case study areas would then be used to inform and calibrate a larger pan-African model of human-environment interaction.

In addition to contributions to the direction of the ACAICA project, numerous collaboration ideas were proposed. Initially this would involve data collection and synthesis, georeferencing sites, and collecting archaeobotanical data from Dorian including specific percentage information as opposed to presence absence. The first major product of this effort will be a review paper for West Africa presenting time slice maps with synthesized data. In addition to the article, a meeting with Rob Marchant’s post-doc modeler (Colin) has been arranged at the beginning of September to discuss the effects of fire use on landscape degradation in East Africa, as well as charcoal and pollen records.

Finally, plans were discussed to have a follow-up meeting after one year to continue the interdisciplinary cooperation and research begun here. Ideally this meeting would be held somewhere in Africa and incorporate a community outreach element.