|by Stephen Oppenheimer
Much has been made recently of a 'beachcombing' lifestyle among the first modern Africans as a motive for spreading out of Africa and around the Indian Ocean. For most of their first 2 million years on Earth, humans were roaming the savannah as hunter-gatherers. Like the Kalahari of southern Africa, they exploited the rich nutritional value of group-hunted game, supplemented by salads of roots, fruit, and leaves. As the major glaciation of 130,000 - 190,000 years ago began to reduce their savannah range, someone had the idea of foraging and eating shellfish and other marine produce from the beach. It is always possible that beachcombing started even earlier, but since the beaches are now under water, we will never know. Such a diet, being rich in protein, is nutritious, good for the brain, and easier to obtain than game. Beach tucker has the added advantage of remaining available when the savannah dries up during an ice age.
Evidence for such beachcombing is unexpectedly easy to assess, since characteristic piles of split shells (shell middens) are left behind. There is, however, a problem in knowing just how long humans have been doing it. Shell middens are generally found just above the high-tide line, but for most of the past 200,000 years sea levels have been many metres below today's beaches. This means we would expect to miss most ancient middens except those laid down during the high sea levels of an interglacial, such as the one 125,000 years ago.
Neanderthals combed beaches in Spain and Italy 60,000 years ago, so it is possible that they brought the practice with them from Africa. Until recently, however, the earliest evidence for African beachcombing came from the Klasies River mouth in South Africa, dated to between 100,000 and 115,000 years ago. In 2000, however, new evidence was discovered for early beachcombing at Abdur on the Eritrean west coast of the Red Sea, just to the north of the Gate of Grief. Dated to 125,000 years ago, at the peak of the Eemian interglacial, the same beach site yielded butchered remains of large mammals, indicating a mixed diet. The implements, which included blades made from obsidian, a volcanic glass, are most likely to have been made by modern humans.
The great interest in this site on the Red Sea is twofold: it provides us with the oldest evidence for beachcombing anywhere and it is very close to the southern route out of Africa. Both aspects feed into an attractive model, which may be called the 'beach-buggy to Australia'. We get a compelling story of beachcombers multiplying until their patch of beach could support them no longer, then moving on to the next unexploited beach, and so on. By such rapid progression, once over the Red Sea the vanguard would just have followed the coast of the Indian Ocean, eating their way right down to Indonesia within 10,000 years. The low sea levels of the time would have allowed a dry walk from Aden to the tip of Java, and then easy island hops to Australia, where shell middens are found from the earliest traces of human habitation.
I am pretty sure that this model of the early colonization of Australia is correct, but the dates have to fit, not only for the archaeological evidence but also for the molecular clock on the gene tree for all the other Eurasian dispersals. If, on top of this beach buggy model, we impose only a single out-of-Africa exodus to colonize both Australia and the rest of the world, we can start to make strong predictions for the order and dates of colonization en route of India, Southeast Asia, and the parallel movement to New Guinea. These predictions should be the test of the theory.