A large number of authors recently highlight the need to include various forms of non-genetic inheritance alongside genetic (sequence) inheritance. Here, we address whether it is necessary to develop a new synthetic theory of evolution to replace the current mainstream Modern Synthesis, or whether the latter can accommodate the recent discoveries about the ubiquity and diversity of non-genetic inheritance pathways without any significant change (Danchin 2023).

 For this purpose, we compare the modern synthesis (MS, focusing only on the transmission of DNA sequence information) with an inclusive evolutionary synthesis (IES) gathering inheritance components as varied as genetics, epigenetics, organism, behaviour and environment. We develop two evolutionary models one representing the MS and one representing the IES to qualitatively compare the resulting evolutionary dynamics from one generation to the next. We use these two innovative possibilistic models (into the so-called EDEN framework) to compute all possible evolutions according to these two conceptions of inheritance (Gaucherel and Pommereau 2019, Gaucherel et al. 2024). EDEN models, still unknown in evolution biology but already applied in environmental sciences, compute all possible pathways (i.e., successive states and transitions) from a chosen initial state according to a set of documented inheritance processes.

 We found that the computed MS dynamics is almost entirely contained within the IES evolutionary dynamics, as expected. Furthermore, the IES dynamics appears far better at capturing the complexity of life than the Modern Synthesis, showing a set of possible pathways already witnessed by many observations in evolutionary biology (Gaucherel and Danchin 2024). In particular, our possibilistic IES model highlights three possible deadlocks (i.e., dead-ends of evolved systems), one of which being clearly separated from the two others by a structuring role of Behaviour, from the two other deadlock in which genetics, epigenetics, and environment play dominant roles. Here, we will illustrate the IES evolutionary dynamics onto a specific species.

 Overall, our theoretical, qualitative and possibilistic IES model reveals highly differentiated evolutionary pathways organised along a gradient of degrees of inclusivity, from the MS model, which gives only a role to sequencic information in inheritance, to potential dynamics that give more and more weight to non-genetic inheritance (Gaucherel and Danchin 2024). Our results therefore confirm that we likely need to have the Modern Synthesis evolve towards a more inclusive evolutionary synthesis.