African camels and rodents migrated to Iberia, and European rabbits and rats migrated to North Africa at the same time before isolation of the Mediterranean Sea during the Messinian.
A new date of 6.23 million years ago for the Venta del Moro fossil site (Spain) can be regarded as the first appearance datum for the African migrants Paraethomys and Paracamelus in Europe.
At the same time (6.21 million years ago), the North African site of Afoud-1 (Morocco) shows the first Messinian European migrants (e.g. Prolagus, Apodemus). This indicates that 0.25 million years before the onset of the Messinian Salinity Crisis (MSC), a mammal exchange occurred between Europe and Africa through an ephemeral land-bridge.
Intensification of the last Miocene glaciations 6.26 million years ago and associated glacioeustatic sea level falls facilitated this corridor allowing a limited exchange of immigrants and serving as a prelude of a new Afro-Iberian dispersal that would follow during the desiccation of the Mediterranean Sea (5.5 million years ago) during the MSC. At 5.33 million years ago, the Zanclean flood refilled the Mediterranean basin and originated the strait of Gibraltar, a marine barrier that impeded additional dispersals during the remainder of the Neogene.
Luís Gibert et al., Departament de Geoquímica, Petrologia i Prospecció Geològica, Universitat de Barcelona, C/Martí i Franqués s/n, 08028 Barcelona, Spain. DOI:10.1130/G34164.1