http://en.wikipedia.org/wiki/Messinian_Salinity_Crisis
“...But the Strait of Gibraltar is 320 m deep, and global sea levels during the most recent Ice Age are believed to have lowered sea levels by only about 100 m, so the basin was not dry during the Ice Age. That there had been an extreme drying event in the region earlier, was to be discovered forty years later.”
It is my understanding that the Mediterranean Basin was composed of two large lakes in times past. I also have read that the ocean has been as much as 400 feet lower during various ice ages. If during one of the previous ice age mixima in the past million years there was mostly dry land with only a relatively small passage of water from ocean to Mediterranean I am sure it would have been possible for hominids to swim or raft across. Furthermore, how do we know that the current channel depth was not caused by erosion from rising ocean levels rushing in to fill the entire M basin? Perhaps it was much less deep in times past.