Could be, but I'm not aware that the mediterranean sea was that low during the last 12 million years.
I'd guess that Sardinians are mostly from paleolithic european stock plus neolithic invaders, but they populated the island later.
the peak of the last ice age, about 18,000 years ago
http://www.ngdc.noaa.gov/mgg/topo/pictures/GLOBALsealeveldrop110m.jpg
http://www.ngdc.noaa.gov/mgg/topo/globega2.html