Neurogenesis is the production and integration of new neurons into neural networks in the brain. Along with synaptic plasticity, it determines the ability of the brain to recover from damage. There is some controversy over the degree to which it occurs in adult humans; the consensus is that it does, but the vast majority of research on this topic has been carried out in mice, not humans. If there is little or no natural neurogenesis in the adult human brain, a situation quite different from that of mice, then the prospects diminish for the development of therapies to hold back aging that work by increasing neurogenesis. This is an important topic in the field of regenenerative research.
The open access paper noted here offers an interesting hypothesis: that humans and a range of other larger-brained mammals exhibit lesser (or possibly absent) adult neurogenesis because they have lost olfactory function over evolutionary time. We should consider adult neurogenesis to be a co-evolved feature of large and capable olfactory systems in the brain, and we do not have a large and capable olfactory system. Mice do. This is a tenuous hypothesis, in need of considerable support,