Pearson attributes this to a "technology transfer", possibly indicating that Indian traders brought cloth-making to East Africa.
Although trade in these commodities probably had a long history by this date, it is signficant that slaves were being traded in Red Sea ports already in the12th century and in India in the 13th.
A significant wave of emigres from Hadramaut could be attributed to war, famine, or drought in their homeland.
This decline is attributed to an increase in competition from India, especially in textiles treated with dyes unavailable in East Africa.
Spanish discovery of gold in the Americas increased competition in the gold trade, lessening the demand for East African gold.
This shows that Kilwa no longer had control over the commercial activities of Sofala.
Civil wars in the African interior (around the Zambezi river) would have disrupted the gold trade upon which Kilwa's strength depended.
This is the beginning of the Shirazi period in East Africa in which Muslims of Persian origin held power in several ports.
Under bin Talut, Kilwa was transformed into a commercial center.
The Kingdom of Mutapa was centered around the Zambezi river and was important in gold and ivory trade from the interior.
Civil wars in the interior disrupted the gold trading routes to the coastline ports.