The glass beads found at archaeological sites up and down the eastern coast of Africa between the 7th and 17th centuries ce bear witness to the trade that connected communities from all reaches of the Indian Ocean and beyond. Glass beads are small, relatively inexpensive to produce, and easy to transport as well as being colorful, often beautiful, and very durable. They were thus ideal trade items, especially when glass was a rare commodity that was produced in a limited number of places. Careful study of the glass beads traded into eastern Africa illuminate trade connections and patterns in the Western Indian Ocean that are not seen through a study of ceramics or glass vessels. In the earliest period, from the 7th to the mid-10th century, the East Coast (Kenya and Tanzania) first received beads made from a mineral soda glass from Sri Lanka (or possibly South India). The next to arrive were all made of a type of plant-ash glass that was probably produced in Iraq, but, because raw glass was widely traded, the beads were made in different places: perhaps the Persian Gulf/Iraq/Iran and even Thailand. In southern Africa in this period all beads were made of this same plant-ash glass but the beads—cut from drawn tubes—may have been finished locally. Similar beads of this glass have been found around the Old World including South and Southeast Asia, both East and West Africa, the Mediterranean, and as far north as Scandinavia—all date from the 8th into the mid-10th century. From the mid-10th to mid-13th century mineral soda beads from India were found in both the southern and northern regions of Africa’s east coast, but many of them appear to be from different areas of India and would likely have arrived by different routes. In the mid-13th to mid-15th century period, during which the gold trade out of southern Africa was at its peak, southern Africa turned away from Indian beads and accepted only ones from a region that has yet to be identified, while East Africa continued mainly with ones from South Asia. However, early in the 15th century a small number of Chinese beads appeared on the East Coast that might have arrived on ships from the fleet of the Chinese general Zheng He. The final period, the mid-15th to late 17th century, saw the two ends of the coast receiving the same beads for the first time, reflecting the growing dominance of European traders in the Indian Ocean. Although from their first arrival Europeans had attempted to trade their own beads in eastern Africa, populations there refused to accept them, forcing the outsiders to purchase beads in India, for which they were obliged to pay—often in silver.
The Indian Ocean and its adjoining seas, from the Middle East and East Africa to Southeast Asia, have been witness to the nautical ventures of most, if not all, major sea powers of world history. Progress in nautical archaeology in the past few decades has brought about a much better understanding of shipbuilding traditions of the Indian Ocean, until then limited to textual and ethnographic sources. Only a few shipwreck sites and terrestrial sites with ship remains have been studied so far along the shores of the Red Sea, the Persian Gulf, or the Indian Ocean proper. Many more were found in recent excavations in the Southeast Asian seas, which were built along Southeast Asian or Indian Ocean shipbuilding traditions. Two main technical traditions can now be clearly identified for pre-modern times: the Arabo-Indian sewn-plank ships of the western Indian Ocean, which survived into our times, and the Southeast Asian vessels that evolved from a distinctive sewn-plank technology to fully doweled assemblages, as could still be observed in Indonesian vessels of the late 20th century. The still limited number of shipwrecks brought to light in the Indian Ocean as well as the considerable imbalance in archaeological research between the Indian Ocean proper and the Southeast Asian seas have hindered the advancement of the discipline. Considerable difficulties and interpretation problems have moreover been generated by biased commercial excavations and subsequent incomplete excavation records, not to speak of the ethical problems raised in the process. Such deficiencies still prevent solid conclusions being drawn on the development of regional shipbuilding traditions, and on the historical role of the ships and people who sailed along the essential Indian Ocean maritime networks.