Family trees have become so fundamental to the way we think about evolution that we barely notice them; we seem intuitively to understand when the history of life on Earth is discussed in terms of “roots” and “branches,” or when ramified “tree” diagrams are drawn to represent the evolutionary histories of species and languages, populations and DNA. It appears that family trees have become so embedded in our language – in everyday discourse as in specialized, scientific vocabularies, in both words and visual representations – that most people tend to accept the entangled genealogical-arboreal imagery as rational, intuitive, or even natural.

Whereas family trees have been key resources in the production, organization, and interpretation of scientific data on life since the late nineteenth century, they in fact entered the sciences at an earlier date, independently of the evolutionary perspectives they were later made to illustrate. They once served markedly different ends in knowledge production.

To investigate what family trees meant, before they came to mean evolution, and to address the consequences of their early incorporation into the modern sciences, I look to France at around the turn of the nineteenth century. Tentatively in the second half of the eighteenth century, and then more emphatically in the early years of the nineteenth, the conventional shape of genealogical representation was seized upon by scientists and scholars, who applied it in their various fields of knowledge production. This appropriation was not fully unprecedented, yet the scope of application quickly expanded as family trees were brought into fields where they had not previously been employed, including natural history, language studies, and music theory.

Given that genealogy had long been thoroughly entangled with the social stratification of Europe’s dynastic monarchies, where it had served to distribute wealth and privileges, it is remarkable that this development took place at around the time of the French Revolution, perhaps the most sustained revolt against dynastic principles and hereditary privileges to date. Right at the historical moment when genealogy was eclipsed as the organizing principle of social order, the conventional format of genealogical representation – the family tree – reappeared as an organizing principle in the sciences.