Juliette Garczynski is trained as a philosopher and is a PhD candidate in philosophy of biology at the Institute of Global Health (ASU-GHI). She is affiliated with the doctoral school Complexity of Life (ED 515), the Laboratory of Computational, Quantitative, and Synthetic Biology (UMR 7238) at Sorbonne University, and the Institute for the History and Philosophy of Science and Technology (UMR 8590) at Paris 1 Panthéon-Sorbonne.

She completed her first master's thesis in the philosophy of physics, focusing on indeterminism and interpretations of quantum mechanics, under the supervision of Vincent Ardourel (2023–2024). She then turned her attention to the philosophy of biology, producing a research thesis on the modalities of death and ageing under the supervision of Philippe Huneman (2024–2025).

Under the supervision of philosopher Philippe Huneman and biologist Eric Bapteste, her doctoral research aims to construct and develop the concept of biosocial age within a transdisciplinary approach to the evolution of ageing, at the intersection of philosophy, biology and medicine. Her work involves combining conceptual analysis with the development of measures of age. Her philosophical analyses will, on the one hand, enable her to question the underlying assumptions that make it difficult to define the concept of age – notably the idea that ageing is a purely individual property. Her biological analyses, conducted alongside Yuping Dai, also a PhD student at the AIRE laboratory and the University of Sherbrooke, and her research supervisor Eric Bapteste, on the other hand, will use bioinformatics methods to make the concept of biosocial age a truly operational measure, through the modelling of profiles and the study of their evolution over time.

Juliette’s work aims to offer a new, epistemological perspective on the following question, which at first glance seems very simple: “How old are you?” .  This question actually conceals complex issues that biologists, doctors… and philosophers alike are seeking to resolve. Chronological age is, of course, straightforward: the passage of time is the same for everyone. However, it seems that we do not all age in the same way: some appear to age faster than others; some remain in better health. The initial question thus becomes a genuine problem, which this thesis will seek to clarify: “How old are we really, if we all age differently?”.  The difficulty in defining the concept of age would then lie in the heterogeneity of ageing trajectories, and it is the causes of this heterogeneity that this work aims to elucidate, by examining the epistemic benefits of the hypothesis that the individual necessarily ages within an environment that is itself socially structured. This thesis in the philosophy of biology aims to account for the fact that social position seems, even in pure biology, to imply differences in the course of ageing. 

Juliette therefore proposes to develop the concept of biosocial age and to implement a new biosocial measure of age. One of the challenges of this work is to identify singularities and biosocial invariants of ageing by analysing individuals’ exposomes – that is, the totality of exposures to which an individual is subjected throughout their life; for example, the effects of viral presence, levels of air pollution, or alcohol consumption.  The aim of this work is to determine how to quantify the role of the biosocial in the progression of ageing, and to identify the factors that alter its pace, accelerating or decelerating it. The objective will be to better account for the socio-environmental determinants at work in the progression of ageing. This PhD project will thus contribute to improving our understanding of the heterogeneity in individual ageing rates, thereby enabling better prediction of ageing trajectories. This work aims to propose the epistemological conditions necessary for the development of a measure, and potentially a biosocial and environmental clock of age, that is more comprehensive than other clocks.

To achieve this, the aim will be to develop a robust theoretical framework based on the fundamental issues surrounding age measurement; Juliette’s research will seek to develop more sophisticated bio-social profiles by incorporating extra-genetic data into the statistical analysis of gene co-expression networks. This dissertation will help to construct profiles by identifying potentially significant parameters, and subsequently model overall profiles of individuals ageing under specific socio-environmental conditions. Juliette will thus contribute to defining scientific concepts for studying ageing, as well as to the analysis of data using these concepts.

This dissertation would therefore provide a better understanding of the malleable – and perhaps modifiable – aspects of ageing. Fully in line with the objectives of the Institute of Global Health, Juliette’s research would contribute to better prevention of the factors – particularly structural ones – that accelerate ageing, and thus to a more informed promotion of those that slow it down. Behind the inter-individual differences in ageing lie health, socio-environmental and political inequalities, an understanding of which is necessary to move towards greater equity in healthy ageing. Furthermore, conceptualising biological age in a more comprehensive way, taking into account its determining factors and their threshold effects, would enable us to rethink how age is considered in biomedical diagnoses, making it an even more significant, informative and useful parameter.