At http://phys.org/print339925008.html … we have a fascinating story, rock art that depicts people swimming (a sort of dog paddle) – in one of the dryest parts of the Sahara desert. Whether they are really swimming is a matter of opinion. They could equally be flying – almost floating in the sky.
The rock art is said to go back around 7000 years. Recently, a couple of NASA geologists on the look out for a Mars like landscape, joined an archaeological team in the desert of SW Egypt, and being geologists started having a look at the general area – outside the rock shelter. They discovered evidence of an ancient lake – quite substantial in size. This, they concluded, accounted for the number of wild animals drawn on rocks, representing a picture of a former Sahara landscape.
It is thought the former wet Sahara environment was due to the monsoon track shifting in tune with the orbital changes (Milankovitch) which means the hydrology should have gradually faded, the drying of the desert taking place at a uniformitarian rate. This has all been modelled – but again, reality may not be conforming to the models. However, the dates produced for the lake are firmly attached to the Early Holocene – when the Sahara as a whole was much wetter and humans and animals thrived. The NASA geologists now plan to return in order to study the dried up lake shore in more detail – presumably with a greater amount of equipment. So, are they swimmers – or floaters?