Pumice Rafting To Crete (and Wallacea) with Homo Erectus

How did homo erectus get to remote islands like Crete or Flores without boats? Floating rock from local volcanoes may be the answer.

A recent article proposed a new theory regarding the origin of life on earth. Pumice, a rock formed by volcanic eruptions, can float on the surface of the sea due to its very low density, forming “rafts” ranging in size from small grains to large masses on which plants can grow and people can stand. The article suggested that floating pumice rafts could have accumulated the materials necessary for life in their travels, which were subjected to various natural phenomena such as lightning and solar UV rays, eventually combining into something approximating life. I don’t know the merits of this hypothesis, but it immediately made me think of another mystery uncovered last year in Crete. Tools of the Acheulean type, apparently produced by members of a homo erectus group 130,000 years ago were discovered on that island and, though erectus specimens are attested on the mainland at that time, there seemed to be no way their makers could have got there without some sort of oceangoing capabilities. Building boats, or even rafts, however, was considered beyond their abilities; their known repertoire comprised mainly generic flint tools for cutting, digging or butchering. It’s possible that they did more sophisticated work with organic materials that have not survived, but the dexterity and planning required for boatbuilding sounds rather out of their reach.

A similar conundrum concerns the so-called hobbits (homo floresiensis) of Flores Island in Indonesia. These are generally (though not universally) considered to be some type of homo erectus, stranded on the island and shrinking over time due to the limited resources available to them. But how did they get there? Other erectus remains in, for example, Java can be explained by the fact that those islands were connected to the mainland at the time. But Flores is across the Wallace Line, which divides the flora and fauna of Asia from the very different ones of Australasia, and was never in that period connected to anything west of it.

I think those pumice rafts may hold a clue. One thing the Indonesian archipelago and the Aegean Sea have in common is volcanoes, some of the most powerful in the world. The 1883 eruption of Krakatoa sent pumice rafts as far as Africa, and floating pumice is common today as a result of the frequent activity of the many volcanoes all through that area. In the eastern Mediterranean, the massive eruption on Thera in around 1600 BC wiped out the Minoan civilization and may have spawned the legend of Atlantis, and both it and a similar event on the island of Kos in about 160,000 BC produced masses of pumice over the sea which can still be identified today on the surrounding shorelines. The latter event seems to fit with the age of the Cretan tools. It has been suggested that the distinctive plants and animals across the Wallace Line were originally carried there at least partly by pumice rafts, and I suggest that the homones erecti in question may have been affected by such eruptions, perhaps washed or sucked out to sea, finding refuge on one of these rafts, and eventually ending up somewhere they logically had no place being. It makes more sense than building rafts to go someplace they had no reason to go.

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