The reported destruction of two important manuscript collections by Islamist rebels as they fled Timbuktu is an offence to the whole of Africa and its universally important cultural heritage. Like their systematic destruction of 300 Sufi saints' shrines while they held Timbuktu at their mercy, it is an assault on world heritage comparable with the demolition of the Buddhas of Bamiyan by the Taliban in 2001.

The literary heritage of Timbuktu dates back to the 15th and 16th centuries when the gold-rich kingdoms of Mali and Songhai traded across the Sahara with the Mediterranean world. It took two months for merchant caravans to cross the desert, and while gold and slaves went north, books were going south.

In his Description of Africa, published in 1550, the traveller Leo Africanus marvels that in the bustling markets of Timbuktu, under the towers of its majestic mosques, the richest traders were booksellers.

They were selling manuscripts by Arab scholars on everything from astronomy and arithmetic to Islamic law, as well as mystical texts on Sufism, the otherworldly, saintly style of faith that the al-Qaida-affiliated Ansar Dine finds so offensive.

This legacy of Arab learning that goes back to the great scientists and mathematicians who preserved the classical Greek heritage in the early middle ages is richly represented in the manuscripts of Timbuktu – but not necessarily in its original form. For scribes copied and recopied books in this city that loved leaning, creating a legacy of works transcribed in the 18th and 19th centuries as well as earlier.

They also wrote down their own history and laws, chronicling the families of Timbuktu and preserving the poetry and stories of north Africa – at least, that is what seems to have lain in the many manuscripts of Timbuktu's lost legacy that were just starting to be properly conserved when this terrible religious vandalism plagued the city.

When European empires scrambled for Africa in the 19th century the continent was seen as illiterate and lacking in history, memory, or literature. Its art was seen as "primitive", partly because it lacked a written art history.

Timbuktu is a palimpsest in the sand that proves otherwise. Libraries like the Ahmed Baba institute were rescuing Africa's history from oblivion. Timbuktu is Africa's city of books and learning that disproved racist myths about the continent. That luminous inheritance is what the Islamists have destroyed.