Table S1.

Description and chronology of sites included in this study

Site name (code), locationSite chronologyDescription
Eastern Africa
 Panga ya Saidi (PYS), Kilifi coast, Kenya (3.678333° S, 39.736016° E)Later Stone Age to approximately 12th centuries CERock shelter within large limestone cave complex located in the coastal uplands. First investigated by Soper (64) in the 1960s and reexcavated by the Sealinks Project in 2010 (21) (trenches PYS10/1 and PYS10/2; both 1 × 2 m). Lower layers contain evidence of occupation by microlithic stone tool-using foraging groups, with diagnostic ETT (7th to 10th centuries CE) and later ceramics present in upper layers. The archaeobotanical samples analyzed in this study derive from these upper layers.
 Panga ya Mwandzumari (SC), Kilifi coast, Kenya (3.696583° S, 39.738383° E)Later Stone Age to approximately 12th centuries CESmall rock shelter within a limestone cave complex located in the coastal uplands. First investigated by Soper (64) in the 1960s and reexcavated by the Sealinks Project in 2010 (21) (trenches SC10/2 and SC10/3; both 1 × 2 m). Lower layers contain evidence of occupation by microlithic stone tool-using foraging groups, with ETT and later ceramics present in upper layers. The archaeobotanical samples analyzed in this study derive from these upper layers.
 Mgombani (MGB), Kilifi coast, Kenya (3.840783° S, 39.6785° E)7th to 10th centuries CESmall village located in the coastal uplands. First excavated by Helm (65) in the 1990s and reexcavated by the Sealinks Project in 2010 (21) (trenches MGB10/1 and MGB10/2; both 1 × 2m). Mainly local ETT ceramics but also a very small quantity of imported ceramics and glass beads.
 Pango la Kijiji (PK), northern Pemba Island (4.901505° S, 39.688707° E)7th to 9th centuries CELimestone rock shelter with ephemeral occupation during the Middle Iron Age. First excavated by Chami et al. (66) in 2009 and reexcavated by the Sealinks Project in 2012. The results presented here derive from trench PK12-04 (2 × 2 m). Small quantities of ETT ceramics were present in addition to a rich faunal assemblage.
 Tumbe (TMB), northern Pemba Island (4.943762° S, 39.790757° E)7th to 10th centuries CELarge preurban Indian Ocean trading port. Excavated by Fleisher and LaViolette (67) in the late 1990s and early 2000s. Very rich in Indian Ocean trade goods, including ceramics (mainly Middle Eastern, some South Asian, and Chinese) and glass and stone beads, as well as local ETT ceramics. Archaeobotanical data published by Walshaw (22) are included in this study.
 Kimimba (KMB), northern Pemba Island (4.982154° S, 39.796809° E)8th to 10th centuries CESmall coastal village excavated by LaViolette and Fleisher (67) in the 2000s (68). Mainly local ETT ceramics but also some imported ceramics and glass beads. Archaeobotanical data published by Walshaw (22) are included in this study.
 Fukuchani (FK), northwest coast, Zanzibar (5.821666° S, 39.290833° E)7th to approximately 10th centuries CEA large coastal village first excavated by Horton and Middleton (69) in the 1990s and reexcavated by the Sealinks Project in 2011 [trench FK10l (1 × 3 m) and its extension, FK12 (1 × 2 m)]. Mainly local ETT ceramics but also moderate quantities of imported ceramics and glass beads.
 Unguja Ukuu (UU), southwest coast, Zanzibar (6.318601° S, 39.373978° E)7th to mid-11th centuries CELarge preurban Indian Ocean trading port. Excavated by Horton and Middleton (69) and Juma (70) in the 1980s to 1990s and reexcavated by the Sealinks Project in 2011 and 2012, which targeted an area with known deep (>3 m) organic-rich midden layers close to the foreshore [trenches UU11 (2 × 2 m) and UU14 (3 × 3 m)] as well as occupational areas set back from the beach [UU10 (1 × 2 m) and UU15 (1 × 2 m)]. Very rich in trade goods, including ceramics (mainly Middle Eastern, some South Asian, and Chinese) and glass and stone beads, as well as local ETT ceramics. Although the site contains evidence of late fifth century CE occupation (70), the samples analyzed in the study are seventh century CE and later.
 Juani Primary School (JS), Mafia archipelago, Tanzania (7.989777° S, 39.782600° E)3rd to 12th centuries CESmall iron-working village located on Juani Island. First investigated by Chami (7173) between 1997 and 2001 and reexcavated by the Sealinks Project in 2012. Contains two main occupation phases: Early Iron Age (approximately 3rd to 4th century CE) and Middle to Later Iron Age (8th to 12th century CE), although all crop remains date to the second phase. Crop remains were associated with local ETT ceramics, and there were very small quantities of imported ceramics and glass beads. Results presented here derive from two trenches: JS12-04 and JS12-05 (each 2 × 2 m).
 Ukunju Cave (PU), Mafia archipelago, Tanzania (8.002411° S, 39.775768° E)Approximately 9th to 11th centuries CERock shelter located on Juani Island. First excavated by Chami (72, 73) in 2000 and reexcavated by the Sealinks Project in 2012 (74) [trench PU12-01 (0.6 × 0.9 m)]. Mainly local ETT ceramics but also a very small quantity of imported ceramics and glass beads. No direct radiocarbon dates on crops, but the plant remains are associated with diagnostic ETT ceramics and late first/early second millennium imports.
 Mikindani (MKD), southern coast, Tanzania (10.280335° S, 40.111972° E)4th to 11th centuries CECoastal settlement locality in the vicinity of the modern town. Archaeobotanical remains were analyzed as part of a broad program of excavations conducted at 16 sites in the area by Pawlowicz (75). Samples included in this study date were from approximately 300 to 1100 CE.
Comoros
 Nyamawi (NMW), Grand Comore (11.373833°S, 43.374777°E)Approximately 9th to 10th centuries CEA small coastal hamlet located on a wave-cut cliff at the northern end of Grande Comore. Samples from the lower occupational horizon of an exposed section were collected for archaeobotanical analysis by the Sealinks Project in 2013. Ceramics include only local wares.
 M’Bachile (MBC), Grande Comore (11.760643° S, 43.2415° E)9th to 10th centuries CEA large coastal village located on a protected beach on the west coast of Grande Comore. Ceramics include local wares and imports principally of Middle Eastern origin. Archaeobotanical data published by Wright et al. (19) from excavations in the 1980s are included in this study.
 Sima (SMA), Anjouan (12.20945° S, 44.268736° E)8th to 10th centuries CEA large coastal village located on a high ridge on the western peninsula of Anjouan. Ceramics include local wares (mainly decorated with shell impressions, red slip, or graphite) and imports principally of Middle Eastern origin. First excavated by Wright et al. (19) in the 1980s and reexcavated by the Sealinks Project in 2013. Our excavation (Sima IV) targeted the exposed section that was sampled earlier by Wright et al. (19) (Sima III) and known to have good archaeobotanical preservation. Archaeobotanical data published previously by Wright et al. (19) are also included in this study.
 Dembeni (DMB), Mayotte (12.842508° S, 45.184816° E)8th to 10th centuries CEA large coastal village adjacent to the great eastern lagoon of Mayotte. Ceramics include local wares (mainly decorated with shell impressions, red slip, or graphite) and imports principally of Middle Eastern origin. Archaeobotanical data published by Allibert et al. (18) and Wright et al. (19) from excavations in the 1980s and 1990s are included in this study.
Madagascar
 Lakaton’i Anja (ANJA), Andavakoera Gorge, northern Madagascar (12.331506° S, 49.349758° E)Approximately 2000 BCE to 14th centuries CEEarliest known archaeological site in Madagascar. Rock shelter occupied ephemerally by microlithic stone tool-using foraging groups, with local and imported ceramics and glass beads also in upper layers (11th to 14th centuries CE). Excavated by Dewar et al. (8) in the 1980s, 2011, and 2012. Archaeobotanical samples collected in 2011 and 2012 from four 1 ×1-m units (J and L–N) were analyzed in this study.
 Ampasimahavelona (AMV), Bay of Iharana, northeast coast (13.3725° S, 50.007222° E)8th to approximately 12th centuries CEOpen shell midden site with local ceramics and faunal remains (all wild taxa). The lowest cultural layers, radiocarbon dated to the eighth century CE (8), contain coarse oxidized ceramics belonging to the earliest defined ceramic tradition in Madagascar (61, 62). First excavated by Dewar et al. (8) in 2008 and 2009 and reexcavated by the Sealinks Project in 2013 [trench AMV16/21 (2 × 2 m)].
 Mahilaka (MHLK), Bay of Ampasindava, northwest coast (13.802832° S, 48.312885° E)9th to 13th centuries CELarge Indian Ocean trading port and earliest known urban site in Madagascar; rich in local ceramics and chlorite schist, and foreign trade goods. Water management systems suggest irrigated rice agriculture. Excavated by Vérin in the 1970s and Radimilahy (63) in the 1990s, it was then reexcavated by the Sealinks Project in 2013. Our excavation [trench MHLK20 (2 × 2 m)] targeted an area with known deep (>3 m), organic-rich midden deposits. The archaeobotanical samples analyzed in this study date from the 11th to 13th centuries CE.