The evolutionary significance of hippocampal neurogenesis.

Hippocampal neurogenesis (HN) has been implicated in a variety of hippocampus-dependent behaviors in the laboratory but its evolutionary significance is still debated. Some authors have argued that HN is an adaptation while others argued it is an atavism. However, recent analyses lead to the conclusion that HN likely evolved concurrently with the dentate gyrus itself, both being dependent on a migration of neural stem and progenitor cells out of the periventricular zone that occurs during development. This may render the previous debates obsolete, as selective pressure was likely acting upon the mammalian dentate gyrus itself, with neurogenesis being a mere spandrel in dentate gyrus' evolution.