What characteristics assured the success of one sapient hominid to survive and reproduce amidst a savage, predator-infested environment? Researchers are focused on ancient African river deltas searching for evidence that the earliest humans foraged for mollusks and the eggs of seabirds.
In four studies of carbon isotopes in fossilized tooth enamel from scores of human ancestors and baboons in Africa from 4 million to 10,000 years ago, researchers found a surprise increase in the consumption of grasses and sedges--plants that resemble grasses and rushes but have stems with triangular cross sections. [The National Science Foundation]These aquatic hominids were no longer reliant on knuckle-walking as the buoyancy of water enables upright wading. Usually, she waded just deep enough to hide from or repel marauding hyenas and just shallow enough to leap away from crocodilians while an infant clung to her, fingers entwined in ample head and body hair.
Shellfish-crushing molars had evolved to replace the canine teeth more prevalent in other primates (now sometimes disappearing in modern humans), because she learned to soften food, especially meat, with fire. Wading and diving into deeper water lead to the development of her voluntary breath control, a trait absent in other primates and a core requirement for the evolution of language.
Some have dubbed her Mitochondrial Eve.
Having adapted logs to aid her migration from deltas to islands to continents beyond her native Africa, Richard Dawkins says her 2.5 million year swim continues to this day.
Humans' genetic relationship to a history of riparian life runs deep.
This post has been updated: originally uploaded in March, 2010. Updated 2 January, 2014.