Crocs and fish the key to human evolution

Almost two million years ago, early humans began eating food such as crocodiles, turtles and fish — a diet that could have played an important role in the evolution of human brains and our footsteps out of Africa, according to new research.

In what is the first evidence of consistent amounts of aquatic foods in the human diet, an international team of researchers has discovered early stone tools and cut marked animal remains in northern Kenya. The work has just been published in the Proceedings of the National Academy of Sciences (PNAS).

“This site in Africa is the first evidence that early humans were eating an extremely broad diet,” says Dr Andy Herries from the University of New South Wales (UNSW), the only researcher from Australia to have worked with the team. The project represents a collaborative effort with the National Museums of Kenya and is led by David Braun of the University of Cape Town in South Africa and Jack Harris of Rutgers University in the US.

The researchers found evidence of the early humans eating both freshwater fish and land animals at the site in the northern Rift Valley of Kenya. It is thought that small bodied early Homo would have scavenged the remains of these creatures, rather than hunting for them.

“This find is important because fish in particular has been associated with brain development and it is after this period that we see smaller-brained hominin species evolving into larger-brained Homo species- Homo erectus – the first hominin to leave Africa,” says Dr Herries, of the School of Medical Sciences.

“A broader diet as suggested by the site’s archaeology may have been the catalyst for brain development and humanity’s first footsteps out of Africa.”

Dr Herries dated the archeological remains using palaeomagnetism, a technique that identifies the fossilised direction of the Earth’s magnetic field in sediments.