Transition to Darwinian evolution - towards the origin of the very first species

The concept of Darwinian evolution relies on vertical gene transfer from one generation to the next. Such evolution brings about ever more species that originated from a universal common ancestor, the very first species. In contrast, it is hypothesized that in the era just before that species existed, life was fundamentally collective with genetic material freely shared through massive horizontal gene transfer (HGT). How did the era of collective evolution come to an end and start the Darwinian era we live in today? Here we propose a stochastic model dynamics that offers a fundamental mechanism for such a way out of collective evolution. The model suggests that HGT-dominated dynamics may have been intermittently interrupted by selection-driven processes during which genotypes became fitter and decreased their inclination towards HGT. Stochastic switching in the population dynamics with three-point (hypernetwork) interactions may have destabilized the HGT-dominated collective state and essentially contributed to the emergence of vertical descent and the first well-defined species in early evolution. A systematic nonlinear analysis of the stochastic model dynamics supports this view. Our findings thus suggest a viable direction out of early collective evolution, potentially enabling the start of individuality and vertical Darwinian evolution.