River-margin habitat of Ardipithecus ramidus at Aramis, Ethiopia 4.4 million years ago, Nature Communications 2, Article number: 602 doi:10.1038/ncomms1610
"Great rivers such as the Nile and Ganges have been very important in our history, and we now find that rivers might have also helped play a key role at the dawn of humanity," researcher Royhan Gani, a geologist at the University of New Orleans, told LiveScience.
Now, many humans on Earth simply turn on the tap, run the bath, reach for the bottle and there's the water. But 4 million years ago our ability to find and maintain contact with water required a different application of our senses.