We study the long-term evolution of party demographics and the associated changes in parliamentary speech patterns of various withinparty groups in Finland during 1907-2018. We find significant speech differences by gender and university education status, while other MP characteristics - age, white-collar job, first-term MP status, or urbanicity - do not predict speech patterns. We find that when female seat share began to rise in the late 1950s, there is a concurrent increase in speech differences by gender. As the representation of women increased, there was also a shift in speech topics female MPs specialized in. Additionally, we observe a sharp increase in speech differences by education when the seat share of university-educated increased in the 1960s. These results suggest that descriptive representation of these groups may play a role in changing speech patterns, and thus, in their substantive representation.