Ancient seafarers may have hunted whales around the world

Ancient seafarers may have hunted whales around the world
Elizabeth Pennisi, Michael PriceJul. 10, 2018 http://www.sciencemag.org/news/2018/07/ancient-seafarers-may-have-hunted...

According to myth, the Maori people arrived in New Zealand riding the back of a whale; today, whales figure prominently in Maori art and stories. Now it appears that Maori ancestors may also have systematically hunted the animals.

Archaeological sites in New Zealand hold few recognizable whale bones, but a new technique for detecting species from short snippets of DNA in bone scraps has enabled researchers to identify the remains of five whale species in early New Zealand settlements, including smaller or slow-moving species, the likely targets for hunters. The same “DNA meta-barcode” method showed that the early New Zealanders may also have decimated populations of a native parrot. And on the opposite side of the world, a team used a simpler barcode method to suggest that the Romans hunted whales too, potentially pushing the first known commercial whaling industry back by about a thousand years.

By revealing species from once-meaningless bone fragments, barcodes are “opening new windows into historical ecosystems” says Ana Rodrigues, an ecologist at the University of Montpellier in France. And the new data are changing views. “For a long time, we thought that ancient cultures were technologically not advanced enough to significantly influence animal populations, but more and more evidence is accumulating that they actually did,” says evolutionary biologist Michael Hofreiter of the University of Potsdam in Germany.

At Curtin University in Perth, Australia, DNA researcher Michael Bunce, graduate student Frederik Seersholm, and colleagues have been assessing the impact of human arrival in New Zealand in about 750 B.C.E. They developed a way to cheaply and easily determine the DNA barcodes of hundreds of bones by high throughput sequencing of blends of ground-up bones. Barcodes, named after the ubiquitous labels on items in stores, are short stretches of DNA that uniquely identify a species. Bunce’s team applied their method to 5000 bone fragments from 38 sites in New Zealand spanning the past 20,000 years. “It’s bones that never would have been identified,” says Rodrigues, who was not part of this study.

Seersholm pinpointed 110 near-perfect matches to known species, as the group reported this week in the Proceedings of the National Academy of Sciences. Until now, archaeologists usually assumed that whale bones at sites in New Zealand were from pilot whales that had been scavenged after they beached. But the DNA barcodes identified orca, true dolphins, Cuvier’s beaked whales, fin whales, and southern right whales. “We think they were hunting the smaller whales,” driving the mammals into shallow water with boats and then harpooning them, Seersholm says.

The barcodes also suggested the early New Zealanders hunted fur seals, sea lions, and elephant seals. And the method identified several terrestrial species including the kākāpō, a now-endangered ground-dwelling New Zealand parrot. Further analysis of kākāpō DNA showed that its genetic diversity plunged once New Zealand was settled. “It really shows that high impact humans had on the biodiversity,” Seersholm says.

In the Gibraltar region by the Mediterranean Sea, Rodrigues and colleagues took a focused approach, analyzing 11 putative whale bones from five sites. There, the Romans fished tuna from villages dating to between 400 B.C.E. and 425 C.E. Cryptic texts referring to “sea monsters” or “ram fishes,” plus large bones suspected to be whale (and often shaped into tools), suggested the Romans also hunted coast-hugging gray and right whales. But these behemoths don’t ply those waters today.

Rodrigues’s team combined tried-and-true barcoding with collagen fingerprinting, a technique that matches amino acids in samples’ connective tissue to known animal families. They found that 10 of the 11 bones belonged to whales—three gray, three right, one fin, one pilot, one sperm, and one dolphin. The preponderance of gray and right whales, which are reliably found close to shore and thus could have been hunted, raises the possibility of a forgotten 2000-year-old Roman whaling industry, the researchers suggest this week in the Proceedings of the Royal Society B. That’s about 1000 years before Basque whalers, long considered the first commercial whalers, emerged.

If the Romans did hunt gray and right whales from Gibraltar, the authors note, they may have played a role in the species’ disappearance from the eastern North Atlantic. But other scholars say it’s more likely that the Romans scavenged beached whales.

The identification of the 11th presumed whale bone threw the researchers for a loop: It belonged to an elephant. That’s “why it’s good to use these methods,” Rodrigues says. “Who knows how many other bones out there have been misidentified?”

Barcoding has limitations. It can’t identify a species if its sequence isn’t included in the barcode database, which is rapidly expanding but still incomplete. And barcodes can’t yet show how abundant a species was—only that it was present.

But Rodrigues, for one, is in awe of barcoding’s power. “It’s like a miracle,” she says. “You send them a little bit of dust and they send you back results.”