The second question has to do with the relation between this notion of
timescales and more familiar CHAT schemes (micro-, meso-, onto-, socio-,
phylo-genesis) and the notion of heterochrony realized through semiotic
mediation. The question is to what extent either timescales or levels of
genesis simply index time and to what extent they also point to particular
media in which, in Hutchins' sense, structure is being embedded.
Ontogenesis seems to me to be about not only periods of 60-100 years but
also about the particular ways that humans function as material-semiotic
artifacts. Likewise, mesogenesis seems to index not only intermediate time
scales, but also a certain level of social organization, the development of
a locally situated activity system. I'm thinking here too of Scribner's
suggestions on the history of psychological systems, like memory, where it
seems that it is the psychological system as well as the time scale that
was at issue.