A skull found in 1929 in Aitape, northern Papua New Guinea, has been identified as coming from a tsunami victim, the oldest example we know of.
When geologist Paul Hossfeld found the Aitape skull, it aroused interest because it was at first thought to have belonged to Homo erectus, but has since been identified as being from a modern human who lived approximately 6,000 years ago. Palaeontologists have continued to study it as one of the earliest examples of human remains from the region.
Dr Mark Golitko of the University of Notre Dame considered the skull sufficiently important to lead a team to Aitape to examine the place where it was found, seeking evidence of what killed its unfortunate owner. "We don't know exactly where Hossfeld found the skull, but I think we were within 100 meters of the original location based on his description,” Golitko said in a statement.
Analysis technology has improved a lot in 88 years, allowing Golitko and his collaborators to study the sand on the beach and the shells deposited there. The sediments from which the skull was extracted were rich in diatom shells – single-celled marine organisms whose shells provide a wealth of information about the temperature and salinity of where they grew. These shells have been broken in a way that can only happen in very high energy water.
Along with the size of the sediment grains and the local chemistry, all this pointed to a tsunami sweeping the diatoms onto land and pulverizing them in the process. Papua New Guinea has suffered several devastating tsunamis in recent decades, including one in Aitape itself that killed 2,000 people in 1998, so this indicates the area was similarly seismically volatile at the time.
Indeed the similarity between the sediments in which the skull was found, and those deposited in 1998, increased the team's confidence in their findings. In PLOS ONE they argue the skull belonged to someone who was killed and buried in the tsunami, or had died previously and been buried nearby, with the tsunami disturbing the grave site so the skull became mixed with sediments.
The skull dates back to one of the few periods in the last few million years when sea levels, at least locally, were higher than they are today. Consequently, even though the skull was found quite a way inland from the ocean, the tsunami occurred at a time when the location would have been more vulnerable to threats from the seas.