Reading The Archives Of The Seabed

AAlmost everything the public knows about archaeology beneath the sea concerns ships, and the assumption buried inside that familiarity is seldom examined: that a site worth investigating is a discrete object which sank on a datable afternoon and can, in principle, be lifted. Museums reinforce the impression, since a hull raised from the mud photographs well and a drowned field does not. Yet the arithmetic of the continental shelves points elsewhere. When the sea rose after the last glaciation, an expanse of habitable land larger than several modern states passed below the waves, and everything that had happened upon it, from hearths and middens to the graves of people who never saw a ship, went down with it. Figures prepared for the Coastal Prehistory Panel in 1996 put the drowned area of north-western Europe at 480,000 square kilometres, against which the entire recorded inventory of wrecks looks slight. The difficulty is not that anyone denies this. It is that a drowned landscape offers nothing to photograph, and the methods developed for hulls do not work on a buried soil horizon.

BThe most sustained attempt to make such landscapes legible belongs to Ingrid Falk, a geoarchaeologist at the Rondane Institute for Coastal Prehistory, who maintains that the seabed ought to be read as a layered archive rather than searched as a scatter of objects. Her group works from cores: a steel tube is driven into the shelf sediment, and the column recovered is sampled centimetre by centimetre for pollen, insect remains and fragments of DNA shed by creatures that once moved across a surface now buried. Between 2013 and 2019 the team lifted 42 cores from the Vestland Shelf, and 19 of them yielded sequences belonging to species that cannot live in salt water, grazing cattle among them, in layers dated to the sixth millennium BC. Falk's claim is not that such evidence replaces excavation, but that it locates it. A single core costs a fraction of a diving season and can be taken in weather that would cancel one; where cores point to a former land surface, a survey can afterwards be aimed rather than dispersed across open water.

CFalk concedes that the technique is bounded, and the boundaries are narrow ones. Ancient DNA survives only where the sediment has stayed cold, waterlogged and free of oxygen since burial, so a core drawn from a mobile sandbank returns almost nothing however promising the ground above it once was. In practice this confines useful sampling to fine-grained deposits sealed beneath later clay, which on the Vestland Shelf amount to perhaps a seventh of the mapped area. Nor does the method date anything by itself: the ages attached to Falk's layers come from radiocarbon measurements on plant matter lying in the same centimetre of core, and such matter survives only in a minority of samples. There is a second restriction, less often stated. The method establishes that a species was present in a landscape; it says nothing about how many animals there were, still less about what people did with them. Falk therefore describes her results as a map of possibility rather than a portrait of a society, and she has objected in print to press reports that convert her sequences into settlements. Within those limits, she insists, the archive is real, and it is being read for the first time.

DTomás Beltrán, a sedimentologist at the Cabo Vidal Marine Laboratory, is sceptical of the whole enterprise, though his objection is technical rather than philosophical. Sediment, he points out, moves. A layer that looks undisturbed at the scale of a core may have been reworked again and again by currents and burrowing animals, dragging molecules downward through a column whose apparent order is an illusion. In experiments published in 2020 his laboratory buried tagged DNA in tank sediment, agitated it for ninety days, and recovered a third of the marker at depths corresponding, on Falk's own chronology, to two thousand years of deposition. If displacement of that magnitude occurs at sea, dates inferred from position in a core cannot be trusted. Falk's reply is that tank sediment, stirred continuously and never consolidated, resembles nothing on a sealed shelf, and Beltrán accepts that his apparatus exaggerates mixing. What he will not accept is that anybody has yet shown by how much it exaggerates it.

EThe dispute has not been settled, and it is unlikely to be settled by argument alone, since the two researchers reason from evidence of incompatible kinds, one from a shelf that cannot be controlled and the other from a tank that cannot be trusted to resemble it. Neither researcher expects the funding that would settle it, since a controlled trial on the shelf itself would have to run for longer than a career. What has changed is the standing of the question. Offshore wind farms and cable routes now require seabed survey as a condition of consent, and those surveys generate cores in quantities no research budget could ever finance; between 2016 and 2022 developers in northern Europe deposited more than 11,000 core logs in public archives. The material exists whether or not archaeologists know how to read it. Beltrán regards this as a reason for restraint, arguing that a flood of ambiguous data will harden into a literature of unexamined claims. Falk draws the opposite conclusion, noting that cores taken today will be destroyed by the very foundations they were taken to justify, and that a method which is imperfect now is worth more than a method perfected once the archive has gone.