 Volcanic eruptions happen more often nowadays.

 The diatom shells alone suggest that a tsunami occurred in 1998.

 A combination of factors suggests that a tsunami occurred when the skull was underground.

 The scientists did not focus on details such as sediment grain size and composition.

By Charles Choi | October 25, 2017 1:00 pm

Paragraph 1 Tsunamis have claimed hundreds of
 thousands of lives in the past two decades.
 Now a new study finds that a 6,000-year-old
 skull may come from the earliest known
 victim of these killer waves.

Paragraph 2 The partial human skull was discovered in
 1929 buried in a mangrove swamp outside
 the small town of Aitape Papua New Guinea,
 about 500 miles north of Australia.
 Scientists originally thought it belonged to an
 ancient extinct human species, Homo 
 erectus. However, subsequent research
 dated it to about 5,000 or 6,000 years in age,
 suggesting that it instead belonged to a
 modern human.

 A Rare Specimen
Paragraph 3 The skull is one of just two examples of
 ancient human remains found in Papua New
 Guinea after more than a century of work
 there. As such, archaeologists wanted to
 learn more about this skull to elucidate how
 people settled this region.

Paragraph 4 The scientists went back to where this skull
 was found and sampled the soil in which it
 was discovered. They focused on details
 such as sediment grain size and
 composition.

Paragraph 5 In the sediment, the researchers discovered
 a range of microscopic organisms from the
 ocean known as diatoms. These were similar
 to ones found in the soil after a 1998 tsunami
 killed more than 2,000 people in Papua New
 Guinea — for instance, their shells of silica
 were broken, likely by extremely powerful
 forces.

Paragraph 6 These diatom shells, combined with the
 chemical compositions and the size ranges
 of the grains, all suggest that a tsunami
 occurred when the skull was buried. The
 researchers suggested the catastrophe
 either directly killed the person or ripped
 open their grave.

Paragraph 7 Tsunamis, which are giant waves caused by
 earthquakes, volcanic eruptions or
 underwater landslides, are some of the
 deadliest natural disasters known. The 2004
 tsunami in the Indian Ocean killed more than
 230,000 people, a higher death toll than any
 fire or hurricane.
 Paragraph 8 The site where the skull was found is
 currently about 7.5 miles away from the
 coast. Still, the researchers noted that back 
 when whoever the skull belonged to was
 alive, sea levels were higher, and the area
 would have been just behind the shoreline.

Paragraph 9 The waves of the tsunami that hit Papua
 New Guinea in 1998 reached more than 50
 feet high and penetrated up to three miles
 inland. “If the event we have identified
 resulted from a similar process, it could have
 also resulted in extremely high waves,” study
 co-lead author Mark Golitko, an
 archaeologist at the University of Notre
 Dame in Indiana and the Field Museum in
 Chicago.

Paragraph 10 These results show “that coastal populations
 have been vulnerable to such events for
 thousands of years,” Golitko said. “People
 have managed to live with such
 unpredictable and destructive occurrences,
 but it highlights how vulnerable people living
 near the sea can be. Given the far larger
 populations that live along coastlines today,
 the potential impacts are far more severe
 now.”

Paragraph 11 Golitko plans to return to the area over the
 next few years “to further study the
 frequency of such events, how the
 environment changed over time, and how
 people have coped with the environmental
 challenges of living in that environment.” He
 and his colleagues detailed their findings
 Wednesday in the journal PLOS O.

 The scientists sampled the soil before the skull was found.

 The scientists sampled the soil after the skull was found.

 The scientists will sample the soil in which the skull was discovered.

 The scientists have been sampling the soil in which the skull was discovered since it was found.

 The approximate location of the finding of the skull.

 The details about the method that the scientists used to unearth the skull.

 The fact that scientists originally thought it belonged to an extinct human species.

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