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Dynamical dark energy (DE) phenomenon emerges as a geometrical effectaccompanying the cosmological expansion of nonrelativistic fermionic matter.This occurs without the need for any fluid, like e.g. dynamical scalar field(quintessence, cosmon, etc.), and with conventional form of the Einsteinequations in contrast to other known geometrical DE models. The phenomenonresults from first principles in the framework of the two measures field theorywhere, in the Einstein frame, both fermion masses and the cosmological constant(CC) turn into functions of the cold fermion density n. This n dependencebecomes negligible in regular (laboratory) conditions but it may have animportant role in cosmology. In the 4D gravity model where the original actioninvolves only CC and massive fermions without selfinteraction, for different(but wide) regions in the parameter space we have found two possible classes ofscenarios for the late universe starting from the cold matter domination era.We argue that the fermions which drive the variable CC should be associatedwith cold neutrinos disposed in voids and supervoids. The cosmological dynamicsof the first class practically coincides with that of the LambdaCDM model,while the dynamics of the second class is of the phantom-like regime with apseudo-rip scenario. Crossing the phantom divide happens due to a new type ofthe neutrino DE effect where neutrinos pass through the state with zero massand with the vacuum-like EoS P_{\nu}=-\rho_{\nu}.

Neutrino generated dynamical dark energy with no dark energy field