Literacy is a fundamental aspect of development and a step towards freedom and liberation from socio-economic constraints, because it enables all citizens to realise their basic right to learning. However, the global efforts which -- according to a 2017 estimate of the United Nations Educational, Scientific and Cultural Organization (UNESCO) -- resulted in an increase in literacy from 55.7% in 1950 to 86.2% in 2015 at the world level (an average of 5% for each decade) did not significantly affect the actual number of people with low (or no) literacy skills. Due to rapid population growth, the number of people unable to read or write was higher in 2015 (745 million) than it was in 1950 (700 million), with some world regions being more affected than others. After reflecting on global historical trends in adult literacy education, this article focuses on the African continent, and on Tanzania in particular. The authors offer a few recommendations for developing countries to progress towards ensuring that all youth and a substantial proportion of adults, both men and women, achieve literacy and numeracy by 2030.