The emergence of novel forms in evolution can be viewed as the exploration of new regions in evolutionary space. This study investigates exploratory dynamics in evolutionary spaces through the empirical analysis of a social tagging system, which considers tags as an evolving entity and the tag set space as an evolutionary space. Dimensionality reduction showed distribution of a tag set in high dimensional tag set space embedded in 2-dimensional space and suggested that the new use of common tags was explored around common use, while new use of an uncommon tag was explored multi-regionally. Exploratory paths of evolution in tag set space were visualized as directed networks, and they exhibited structures called “branch” and “bunch.” The former suggests exploration deep into the space and the latter indicates wide exploration. These two modes of exploration imply exploration dynamics in evolutionary space in a mining-like manner in which prospects deposit novel tag sets by digging deep and excavating a wide area of strata with deposits.

Social network services (SNSs) are examples of non-living systems that evolve in response to internal and external events and have many similar characteristics assumed in biological evolution. In the present study, we analyzed the evolution of hashtag use on an SNS called RoomClip. Using a biological evolution analogy, we viewed each post (photo submission) as a species and each set of associated hashtags with a photo as genome. Further, we virtually defined parent–offspring relationships among posts based on their hashtag use and observed the resulting family tree of posts. Our analysis revealed that there was weak selection on hashtag usages relative to the Yule–Simon processes with strong feedback, and hashtag use quickly diverged. The evolution of novel hashtag combinations was observed, which is more salient than an evolution of individual novel hashtags.