  Where do the most popular online cultural artifacts such as image memes
originate? Media narratives suggest that cultural innovations often originate
in peripheral communities and then diffuse to the mainstream core; behavioral
science suggests that intermediate network positions that bridge between the
periphery and the core are especially likely to originate many influential
cultural innovations. Research has yet to fully adjudicate between these
predictions because prior work focuses on individual platforms such as Twitter;
however, any single platform is only a small, incomplete part of the larger
online cultural ecosystem. In this paper, we perform the first analysis of the
origins and diffusion of image memes at web scale, via a one-month crawl of all
indexible online communities that principally share meme images with English
text overlays. Our results suggest that communities at the core of the network
originate the most highly diffused image memes: the top 10% of communities by
network centrality originate the memes that generate 62% of the image meme
diffusion events on the web. A zero-inflated negative binomial regression
confirms that memes from core communities are more likely to diffuse than those
from peripheral communities even when controlling for community size and
activity level. However, a replication analysis that follows the traditional
approach of testing the same question only within a single large community,
Reddit, finds the regression coefficients reversed -- underscoring the
importance of engaging in web-scale, cross-community analyses. The
ecosystem-level viewpoint of this work positions the web as a highly
centralized generator of cultural artifacts such as image memes.
