The first humans who left Africa to populate the world headed south along the coast of the Indian Ocean, Science magazine reports.
Scientists had always thought the exodus from Africa around 70,000 years ago took place along a northern route into Europe and Asia.
But according to a genetic study, early modern humans followed the beach, possibly lured by a seafood diet.
They quickly reached Australia but took much longer to settle in Europe.
Dr Martin Richards of the University of Leeds, who took part in the study, says the first humans may have moved south in search of better fishing grounds when stocks in the Red Sea dwindled due to climate change.
“That might have been the push that set them off,” he told the BBC News website.
When the first modern humans evolved in Africa, they lived mainly on meat hunted from animals. But by 70,000 years ago, they had switched to a marine diet, largely shellfish.
The new research suggests they moved along the coasts of the Arabian peninsula into India, Indonesia and Australia about 65,000 years ago. An offshoot later led to the settlement of the Middle East and Asia about 30 to 40,000 years ago.
The data comes from studies by two teams of scientists on the DNA of native people living in Malaysia and on the Andaman and Nicobar Islands between India and Burma.
Scientists can estimate how closely related we are by studying the DNA of the energy producing parts of the cell, our mitochondria.