Archaeological science, globalisation, and local agency: gold in Great Zimbabwe

Great Zimbabwe (CE1000-1600) is world famous for outstanding cultural innovations and localised and globalised entanglement with trans-Africa and trans-Indian Ocean exchange. New excavations yielded fragments of over a hundred gold processing vessels comprising reused pottery and purpose-made crucibles from stratified contexts in the Eastern Ridge Ruins and adjacent areas. Selected samples were studied using archaeological, microscopic, and compositional (SEM-EDS) techniques. All ceramics were made of alumina-rich clays and contain minerals common to granite-derived lithologies typical of the area, although it is possible that particularly refractory clays were selected to make crucibles locally. These technical ceramics were used for refining and collecting gold at high temperature, most likely producing not only relatively standardised ingots but also finished objects. The composition of the gold prills set in crucible slag is consistent with that of natural, unalloyed gold, while the variability in silver levels and minor impurities point to heterogeneous sources of the gold. Considering these finds in their multiple site and regional contexts, and together with complementary threads of information from early reports of antiquarians and looters, we argue that local agency and gold consumption were much more significant than generally assumed. The conclusion to the paper is that Great Zimbabwe's famous participation in local and global exchanges was backed by internally driven but improvisation laden production and consumption occurring in homesteads located throughout its various settlements. We end by raising a word of caution about oversimplified narratives of globalisation and their archaeological expressions (see Supplementary Material S0 for the abstract in Shona).

Supplementary Information

The online version contains supplementary material available at 10.1007/s12520-023-01811-7.

Reconstructing the geological provenance and long-distance movement of rectangular, fishtail, and croisette copper ingots in Iron Age Zambia and Zimbabwe

The southern third of Africa is unusually rich in copper ore deposits. These were exploited by precolonial populations to manufacture wound-wire bangles, other forms of jewelry, and large copper ingots that were used as stores of copper or as forms of prestige. Rectangular, fishtail, and croisette ingots dating between the 5th and 20th centuries CE have been found in many locations in the Democratic Republic of the Congo (DRC), Zambia, and Zimbabwe, with isolated finds in Malawi and Mozambique. Molds for casting these ingots have been found mostly in the Central African Copperbelt, but also around the Magondi Belt copper deposits in northern Zimbabwe. For years, scholars have debated whether these ingots were exclusively made in the Copperbelt or if the molds found in Zimbabwe indicate that local copies were produced from Magondi Belt copper ore (Garlake 1970; Bisson 1976). Before the recent application of lead isotopic and chemical methods to provenance copper in central and southern Africa, there was no way to discern between these hypotheses. Rademakers et al. (2019) and Stephens et al. (2020) showed that copper artifacts from southern DRC (mostly from Upemba) and from northwestern Botswana (Tsodilo Hills) match the lead isotope ratios of ores from the Copperbelt. Building upon these previous studies, we present here the first results from a copper provenance project across the southern third of Africa, from the Copperbelt to northern South Africa. We apply lead isotopic analysis (LIA) and chemical analyses to establish the provenance of 29 croisette ingots recovered in Zimbabwe, 2 fishtail and 1 rectangular ingot recovered from sites in Zambia, and an "X" shaped ingot smelted in an experiment in Zambia in the 1970's. Our chemistry and lead isotopic results indicate that 16 of these objects were smelted with copper from the Copperbelt, 16 objects source more specifically to the Kipushi deposit within this geological district, and only one HXR ingot sources to the Magondi Belt in Zimbabwe. Taken together, we clearly illustrate that croisette ingots were traveling significant distances to reach their eventual sites of deposition, and that there was also local production of these objects in Zimbabwe.

Sourcing Elephant Ivory from a Sixteenth-Century Portuguese Shipwreck

The oldest known shipwreck in southern Africa was found in Namibia in 2008.^1-4 Forty tons of cargo, including gold and silver coins, helped identify the ship as the Bom Jesus, a Portuguese nau (trading vessel) lost in 1533 while headed to India.^4-6 The cargo included >100 elephant tusks,⁷ which we examined using paleogenomic and stable isotope analyses. Nuclear DNA identified the ivory source as African forest (Loxodonta cyclotis) rather than savanna (Loxodonta africana) elephants. Mitochondrial sequences traced them to West and not Central Africa and from ≥17 herds with distinct haplotypes. Four of the haplotypes are known from modern populations; others were potentially lost to subsequent hunting of elephants for ivory. Stable isotope analyses (δ¹³C and δ¹⁵N) indicated that the elephants were not from deep rainforests but from savanna and mixed habitats. Such habitats surround the Guinean forest block of West Africa⁸ and accord with the locations of major historic Portuguese trading ports.^9,10 West African forest elephants currently range into savanna habitats;^11-13 our findings suggest that this was not consequent to regional decimation of savanna elephants for their ivory in the 19^th and 20^th centuries. During the time of the Bom Jesus, ivory was a central driver in the formation of maritime trading systems connecting Europe, Africa, and Asia. Our integration of paleogenomic, archeological, and historical methods to analyze the Bom Jesus ivory provides a framework for examining vast collections of archaeological ivories around the world, in shipwrecks and other contexts.

COVID-19 Pandemic and Africa: From the Situation in Zimbabwe to a Case for Precision Herbal Medicine

This opinion commentary on the coronavirus disease 2019 (COVID-19) pandemic brings together observations from Zimbabwe specifically, and Africa broadly, drawing from the fields of pharmacogenomics, precision herbal medicine, and responsible innovation so as to respond to the pandemic in ways that are efficient, critically informed, principled, and responsive to needs in rural and urban communities across Africa. With new findings suggesting that COVID-19 is a systemic disease, impacting the respiratory system and beyond in some individuals, we need new molecular targets for therapeutics innovation more than ever. We argue that the current pandemic will likely strip the limited resources from other diseases such as malaria, human immunodeficiency virus (HIV) infection, and among others affecting the African continent. Hence, we need to address not only COVID-19 but also its broader health care and societal impacts in Africa. Extensive diagnostic testing to trace and isolate the COVID-19 cases as well as basic income and economic support for those who are unable to work will be needed. A critically informed and democratic governance that builds on transparency and trust for the elected leaders is crucial. Finally, the pandemic offers a silver lining for Africa: the prospects to integrate omics research with long-standing expertise in herbal medicine in Africa, thus accelerating the advances toward novel molecular therapeutic targets for COVID-19 and precision herbal medicine worldwide.

Bush mint (Hyptis suaveolens) and spreading hogweed (Boerhavia diffusa) medicinal plant extracts differentially affect activities of CYP1A2, CYP2D6 and CYP3A4 enzymes

ETHNO-PHARMACOLOGICAL RELEVANCE

Hyptis suaveolens (L) Poit and Boerhavia diffusa Linn are medicinal herbal plants commonly found in the tropics and sub-tropics. They are used to treat various conditions among them boils, dyslipidaemia, eczema, malaria, jaundice and gonorrhoea. Thus, the herbal medicinal extracts are now found as part of some commercial herbal formulations. There has not been adequate characterization of these medicinal herbs on their effects on drug metabolising enzymes.

AIM OF THE STUDY

To investigate the effects of extracts of Hyptis suaveolens (HS) and Boerhavia diffusa (BD) on activity of drug metabolising enzymes, CYP1A2, CYP2D6 and CYP3A4, as well predict their potential for herb-drug interaction. A secondary aim was to identify constituent compounds such as polyphenolics, in the crude extract preparations of Hyptis suaveolens and Boerhavia diffusa and measure them for activity.

MATERIALS AND METHODS

CYP450 inhibition assays using recombinant CYP450 (rCYP) and fluorescence screening employing individual isozymes (CYP1A2, CYP2D6 and CYP3A4) were used to determine reversible- and time-dependent inhibition (TDI) profiles of extracts of Hyptis suaveolens and Boerhavia diffusa. Inhibition kinetic parameters, K_i and K_inact were also estimated. UPLC-MS employing a Synapt G2 (ESI negative) coupled to a PDA detector was used to identify polyphenolic compounds in crude extracts of Hyptis suaveolens and Boerhavia diffusa.

RESULTS

The inhibitory potency of Hyptis suaveolens and Boerhavia diffusa extracts varied among the different enzymes, with CYP1A2 (3.68 ± 0.10µg/mL) being the least inhibited by HS compared to CYP2D6 (1.39 ± 0.01µg/mL) and CYP3A4 (2.36 ± 0.57µg/mL). BD was most potent on CYP3A4 (7.36 ± 0.94µg/mL) compared to both CYP2D6 (17.79 ± 1.02µg/mL) and CYP1A2 (9.48 ± 0.78µg/mL). Extracts of Hyptis suaveolens and Boerhavia diffusa exhibited TDIs on all CYPs. The most prominent phenolic candidates identified in both medicinal herbs using UPLC-MS analysis included caffeic acid, rutin, quercetin, citric acid, ferulic acid and gluconic acid. These phenolic compounds are thought to potentially give HS and BD their therapeutic effects and inhibitory characteristics affecting CYP450 activities. In vivo predictions showed the potential for HS and BD extracts to cause significant interactions if co-administered with other medications.

CONCLUSIONS

The study reveals that crude aqueous extracts of HS and BD potentially inhibit drug metabolising isozymes CYP1A2, CYP2D6 and CYP3A4 in a reversible and time-dependent manner. Thus care should be taken when these extracts are co-administered with drugs that are substrates of CYP1A2, CYP2D6 and CYP3A4.

What was the population of Great Zimbabwe (CE1000 - 1800)?

The World Heritage Site of Great Zimbabwe is one of the most iconic and largest archaeological settlements in Africa. It was the hub of direct and indirect trade which internally connected various areas of southern Africa, and externally linked them with East Africa and the Near and Far East. Archaeologists believe that at its peak, Great Zimbabwe had a fully urban population of 20,000 people concentrated in approximately 2.9 square kilometres (40 percent of 720 ha). This translates to a population density of 6,897, which is comparable with that of some of the most populous regions of the world in the 21^st century. Here, we combine archaeological, ethnographic and historical evidence with ecological and statistical modelling to demonstrate that the total population estimate for the site’s nearly 800-year occupational duration (CE1000–1800), after factoring in generational succession, is unlikely to have exceeded 10,000 people. This conclusion is strongly firmed up by the absence of megamiddens at the site, the chronological differences between several key areas of the settlement traditionally assumed to be coeval, and the historically documented low populations recorded for the sub-continent between CE1600 and 1950.

H3Africa and the African life sciences ecosystem: building sustainable innovation

Interest in genomics research in African populations is experiencing exponential growth. This enthusiasm stems in part from the recognition that the genomic diversity of African populations is a window of opportunity for innovations in postgenomics medicine, ecology, and evolutionary biology. The recently launched H3Africa initiative, for example, captures the energy and momentum of this interest. This interdisciplinary socio-technical analysis highlights the challenges that have beset previous genomics research activities in Africa, and looking ahead, suggests constructive ways H3Africa and similar large scale science efforts could usefully chart a new era of genomics and life sciences research in Africa that is locally productive and globally competitive. As independent African scholars and social scientists, we propose that any serious global omics science effort, including H3Africa, aiming to build genomics research capacity and capability in Africa, needs to fund the establishment of biobanks and the genomic analyses platforms within Africa. Equally they need to prioritize community engagement and bioinformatics capability and the training of African scientists on these platforms. Historically, the financial, technological, and skills imbalance between Africa and developed countries has created exploitative frameworks of collaboration where African researchers have become merely facilitators of Western funded and conceived research agendas involving offshore expatriation of samples. Not surprisingly, very little funding was allocated to infrastructure and human capital development in the past. Moving forward, capacity building should materialize throughout the entire knowledge co-production trajectory: idea generation (e.g., brainstorming workshops for innovative hypotheses development by African scientists), data generation (e.g., genome sequencing), and high-throughput data analysis and contextualization. Additionally, building skills for political science scholarship that questions the unchecked assumptions of the innovation performers be they funders, scientists, and social scientists, would enable collective innovation that is truly sustainable, ethical, and robust.

Zimbabwe culture before Mapungubwe: new evidence from Mapela Hill, South-Western Zimbabwe

Across the globe, the emergence of complex societies excites intense academic debate in archaeology and allied disciplines. Not surprisingly, in southern Africa the traditional assumption that the evolution of socio-political complexity began with ideological transformations from K2 to Mapungubwe between CE1200 and 1220 is clouded in controversy. It is believed that the K2−Mapungubwe transitions crystallised class distinction and sacred leadership, thought to be the key elements of the Zimbabwe culture on Mapungubwe Hill long before they emerged anywhere else. From Mapungubwe (CE1220–1290), the Zimbabwe culture was expressed at Great Zimbabwe (CE1300–1450) and eventually Khami (CE1450–1820). However, new fieldwork at Mapela Hill, when coupled with a Bayesian chronology, offers tremendous fresh insights which refute this orthodoxy. Firstly, Mapela possesses enormous prestige stone-walled terraces whose initial construction date from the 11^th century CE, almost two hundred years earlier than Mapungubwe. Secondly, the basal levels of the Mapela terraces and hilltop contain élite solid dhaka (adobe) floors associated with K2 pottery and glass beads. Thirdly, with a hilltop and flat area occupation since the 11^th century CE, Mapela exhibits evidence of class distinction and sacred leadership earlier than K2 and Mapungubwe, the supposed propagators of the Zimbabwe culture. Fourthly, Mapungubwe material culture only appeared later in the Mapela sequence and therefore post-dates the earliest appearance of stone walling and dhaka floors at the site. Since stone walls, dhaka floors and class distinction are the essence of the Zimbabwe culture, their earlier appearance at Mapela suggests that Mapungubwe can no longer be regarded as the sole cradle of the Zimbabwe culture. This demands not just fresh ways of accounting for the rise of socio-political complexity in southern Africa, but also significant adjustments to existing models.