The total number of known cave art sites worldwide is well under one thousand, while the number of open rock art sites is likely to be up to one million, and they often present vastly greater numbers of motifs than the cave sites. Yet, in comparison to European cave art, their study has been relatively neglected. For instance, no publication about Chinese rock art had appeared in English until 1984, although the earliest literary mention of rock art is from China. The philosopher Han Fei (280-233 BC) provided the first known reference to rock art, while the geographer Li Daoyuan (AD 386-434) described numerous rock art sites in China and even mentioned occurrences in India. In South America, Captain De Carvalho found rock art in 1598 in what is now Brazil, and published his recordings in 1618, while in Europe, the first known recordings, made by Peder Alfsscin in Denmark in 1627, were not published until 1784. More determined scholarly efforts commenced during the nineteenth century, focusing initially on Russia, Scandinavia, and northern Africa, later on southern Africa, parts of South America, Australia, and eventually India.
With the beginning of the twentieth century, after archaeology finally accepted the authenticity of Franco-Cantabrian cave art, the study of rock art became nominally integrated into mainstream archaeology. However, this merely promoted the proliferation of simplistic stylistic constructs and the development of various unproductive methods. For instance, some archaeologists considered that taxonomic constructs and statistical analyses of stylistic or morphological matrices of motif types would provide empirical interpretations, in the same way other artifacts were classified and interpreted statistically. However, rock art has no archaeologically perceptible time depth, and most major rock art sites are cumulative assemblages deriving from different eras. Lumping these different traditions together and treating them as a ‘style’ because they happened to occur at the same place served no useful purpose, and this is even before the complex issues of selective survival (taphonomy) are considered. Thus, the greatest barrier to integrating rock art successfully into archaeology was the intractability of its dating. Worldwide, there have been only about 20 instances of reasonably convincing minimum dating by finding rock art under supposedly datable sediments.
Archaeological age estimations, generally by considerations of style and ‘content’, have varied greatly for specific corpora. For example, there is a distinctive tradition of shelter paintings in eastern Spain, the Levantine genre. Over the course of the second half of the twentieth century, it has been attributed to every single archaeologically perceived cultural period from the Perigordian to the Iron Age (i. e., to every age from about 35 000 to 2500 years ago), yet its true age, now thought to be Neolithic or later, remains still unknown. Much the same applies throughout Eurasia. In Portugal and western Spain, a corpus of engravings known to be no more than a couple of centuries old was consistently described as being from 20 000 to 30 000 years old. The ‘oldest known rock art site of Central Asia’, at Zaraut-Kamar shelter (Uzbekistan), is now thought to have been painted in the nineteenth century, as is a series of ‘Palaeolithic’ cave paintings in Mladec: Cave (Czech Republic). These and hundreds of similar examples suggest that age determination of rock art by stylistic or archaeological means is tenuous at best.
The paradox is that, without some idea of its age, rock art has little archaeological relevance, and it is difficult to separate components of different traditions at sites. Some archaeologists have suggested that the study of rock art should best be left to ‘specialists’; others have vigorously opposed this view. The last few decades of the twentieth century witnessed the emergence of rock art research organizations in many parts of the world, beginning in North America, Australia, and Western Europe. In 1988 these bodies formed the International Federation of Rock Art Organizations (IFRAO), which currently has over 40 affiliated member associations, covering in effect most of the world. One of their principal aims is to introduce scientific methods, grounded in such diverse disciplines as geology, semiotics, or cognitive science. This trend is currently replacing interpretative endeavors with contextual studies, and concerns with meaning are giving way to epistemological rigor (see Oceania: Australia).