Galen Brokaw's A History of the Khipu endeavors to outline the known history of the khipu through an interdisciplinary approach. Such an approach is necessary given the fact that there is so much to the khipu that is unknown or poorly understood. By drawing from various disciplines like anthropology, history, literacy studies, media studies, theories of Quechua ontology of numbers, and archaeology, one can surmise certain features of the khipu. Indeed, by viewing khipu as a medium with different genre conventions across time and place, Brokaw's review of the history of this particular non-alphabetic medium can emphasize its semiotic heterogeneity over the longue durée. This encompasses all that is known of pre-Hispanic Andean khipu as well as the survival and transformation of khipu in the colonial and independence eras.
Perhaps most important for our interests is the emphasis on growing sophistication of khipu for recording different types of information in the Wari and Inca empires. Earlier forms of Andean semiosis through Wari architectural, Moche inscribed beans, yupana counting boards and textile patterns of the Wari civilization are all significant, but with the rise of larger, imperial political systems in the Andean region, the need for different types of khipu to record information necessary for the bureaucracy became paramount. While the Wari khipu are not the same as that of the Inca, who may have developed even more genre conventions such as imperial khipu historiographical "texts" and more refined census, tribute, and calendrical khipu, there does appear to be a correlation between more developed khipu literacies and state formation and administrative needs. This is not to deny the earlier forms of semiosis through features like inscribed beans analyzed by Brokaw in the early chapter on the Moche.
After the Spanish conquest, khipu use persisted. However, with the demise of the Inca political system, certain genres, like historiographical khipu used for recounting the past of the Inca rulers, gradually disappeared. Khipu genres used for census purposes or recording tribute, however, were used by the Spanish colonial system. These genres provided necessary information for the system of encomiendas and the visitas across various regions of the Andes. Of course, the khipu had to be adapted since the Spanish tribute system was not the same as that of the Inca one. Moreover, despite past scholarship's emphasis on the Third Lima Council's alleged "ban" on khipu, Brokaw cites numerous sources (Jesuit and other) on the use of confessional khipu or khipu use promoted by the Church to further evangelize the Indians. This suggests that khipu was never banned outright, despite some discomfort or hesitation about "idolatrous khipu" used for the worship of huacas or unease about the prominence of indigenous community leaders in carrying out Church functions. Nonetheless, it becomes quite clear that khipu use continued throughout the colonial period.
After 1650, clear references to the khipu in the colonial archive become rare. Brokaw elucidates this pattern quite well, demonstrating that it was due to the colonial state relying less on the types of information supplied by the khipu, the growth of alphabetic literacy among indigenous communities, and the dissolution of indigenous community organizations based on indigenous principles. Brokaw additionally explains why the way pastoral khipu are used today in parts of the Andes may differ from the khipu of the Inca era. In short, many scholars ignore the diversity in genre of khipu, and the role of a large state system in codifying certain types of khipu genres for its purposes. Once the Inca state disappeared, these types of khipu records gradually dissolved with it, leaving behind local khipu records of the genre used by indigenous communities for keeping track of camelid herds or recording tribute obligations.
Finally, Brokaw seems less confident about the possibility of fully cracking the "code" of khipu. Given the diversity of genres and how perhaps the most complex narrative khipu seem to have disappeared by the 1600s, the "code" for cracking one genre of khipu may not be useful for "reading" other genres. Each genre followed its own conventions, and historians and archaeologists will have to uncover more khipu artifacts, colonial-era transcriptions, or other types of evidence to fully understand this highly complex medium.