First
By 6 million years we already have very good evidence of upright walking bipedal hominins in Ororin of Kenya.
6-Million-Year-Old Human Ancestor 1st to Walk Upright?
To figure out if the species was bipedal, Richmond and co-author William Jungers of Stony Brook University in New York measured telltale indicators of bipedalism, such as joint size and thighbone shaft strength, and compared them to other early hominin fossils, living apes, and bones from about 130 modern humans from around the world.
O. tugenensis's thighbone, or femur, was different from that of modern humans and living apes but surprisingly similar to species that lived three to four million years later.
"It really closely resembles the thighbone structure of early hominids like
Australopithecus, the species that [the well-known female specimen] 'Lucy' belongs to," Richmond said.
Donald Johanson, director of the Institute of Human Origins at Arizona State University and Lucy's discoverer, agreed.
"I had occasion to see the material about five years ago in Nairobi, and I was struck by the similarities—particularly between the femur and Lucy's femur," said Johanson, who was unaffiliated with the research.
Second
Sahelanthropus fossil shows that multiple hominin species existed and had a wide distribution. They were not only limited in the East African Rift Valley but ranged through much of Central and North Africa.
Toumai is a 6-7 Million Year Old Ancient Hominoid Ancestor
Third
Between 6-5 million years Northern Africa was completely contiguous with Southern Europe. What is now Sahara was then savannah, and there was no Mediterranean Sea. The basin was dry land filled with lakes and marshes.
Messinian salinity crisis - Wikipedia
The
Messinian Salinity Crisis(
MSC), also referred to as the
Messinian Event, and in its latest stage as the
Lago Mareevent, was a geological event during which the
Mediterranean Sea went into a cycle of partly or nearly complete
desiccationthroughout the latter part of the
Messinian age of the
Miocene epoch, from 5.96 to 5.33
Ma (million years ago). It ended with the
Zanclean flood, when the Atlantic reclaimed the basin.
[2][1]
This massive desiccation left a deep and dry basin, reaching a depth of 3 to 5 km (1.9 to 3.1 mi) below normal sea level, with a few
hypersalinepockets similar to today's
Dead Sea. Then, around 5.5 Ma, less dry climatic conditions resulted in the basin receiving more freshwater from rivers, progressively filling and diluting the hypersaline lakes into larger pockets of
brackish water (much like today's
Caspian sea). The Messinian Salinity Crisis ended with the Strait of Gibraltar finally reopening 5.33 Ma, when the Atlantic rapidly filled up the Mediterranean basin in what is known as the
Zanclean flood.
[4]
Conclusion
Given the above facts, there is no reason to be surprised that several hominin species had extended their ranges into well watered and forested Mediterranean basin and Southern Europe during this 5-6 million year period.