3,000-year-old teeth solve Pacific banana mystery

Humans began transporting and growing banana in Vanuatu 3000 years ago, a University of Otago scientist has discovered.

Skeletons found at a 3,000-year-old Teouma cemetery, just outside the capital of Port Vila in Vanuatu
[Credit: Frederique Valentin]

The discovery is the earliest evidence of humans taking and cultivating banana in to what was the last area of the planet to be colonised.

In an article published this week in Nature Human Behaviour, Dr Monica Tromp, Senior Laboratory Analyst at the University of Otago's Southern Pacific Archaeological Research (SPAR), found microscopic particles of banana and other plants trapped in calcified dental plaque of the first settlers of Vanuatu. The finds came from 3000-year-old skeletons at the Teouma site on Vanuatu's Efate Island.

Dr Tromp used microscopy to look for 'microparticles' in the plaque, also known as dental calculus, scraped from the teeth of the skeletons. That allowed her to discover some of the plants people were eating and using to make materials like fabric and rope in the area when it was first colonised.

Teouma is the oldest archaeological cemetery in Remote Oceania, a region that includes Vanuatu and all of the Pacific islands east and south, including Hawaii, Rapa Nui and Aotearoa. The Teouma cemetery is unique because it is uncommon to find such well-preserved archaeological burials in the Pacific. Bone generally does not preserve in hot and humid climates and the same is true for things made of plant materials and also food.

The first inhabitants of Vanuatu were people associated with the Lapita cultural complex who originated in Island South East Asia and sailed into the Pacific on canoes, reaching the previously uninhabited islands of Vanuatu around 3000 years ago.

The findings were made from 3,000-year-old skeletons at Teouma, the oldest archaeological cemetery in Remote Oceania,
a region that includes Vanuatu and all of the Pacific Islands east and South, including Hawaii, Rapa Nui
and Aotearoa [Credit: University of Otago]

There has been debate about how the earliest Lapita people survived when they first arrived to settle Vanuatu and other previously untouched islands in the Pacific. It is thought Lapita people brought domesticated plants and animals with them on canoes - a transported landscape. But direct evidence for these plants had not been found at Teouma until Dr Tromp's study.

"One of the big advantages of studying calcified plaque or dental calculus is that you can find out a lot about otherwise invisible parts of people's lives," Dr Tromp says. Plaque calcifies very quickly and can trap just about anything you put inside of your mouth - much like the infamous Jurassic Park mosquito in amber - but they are incredibly small things that you can only see with a microscope."

The study began as part of Dr Tromp's PhD research in the Department of Anatomy and involved collaboration with the Vanuatu Cultural Centre, Vanuatu National Herbarium and the community of Eratap village - the traditional landowners of the Teouma site.

Dr Tromp spent hundreds of hours in front of a microscope finding and identifying microparticles extracted from thirty-two of the Teouma individuals. The positive identification of banana (Musa sp.) is direct proof it was brought with the earliest Lapita populations to Vanuatu.

Palm species (Arecaceae) and non-diagnostic tree and shrub microparticles were also identified, indicating these plants were also important to the lives of this early population, possibly for use as food or food wrapping, fabric and rope making, or for medicinal purposes, Dr Tromp says.

"The wide, and often unexpected range of things you can find in calcified plaque makes what I do both incredibly exciting and frustrating at the same time."

Source: University of Otago [January 22, 2020]

Green in tooth and claw

Hard plant foods may have made up a larger part of early human ancestors' diet than currently presumed, according to a new experimental study of modern tooth enamel from Washington University in St. Louis.

Five skull replicas of human ancestors from left to right: A. africanus, A. afarensis, H. erectus,
H. neanderthalensis and H. sapiens sapiens [Credit: Shutterstock]

Scientists often look at microscopic damage to teeth to infer what an animal was eating. This new research -- using experiments looking at microscopic interactions between food particles and enamel -- demonstrates that even the hardest plant tissues scarcely wear down primate teeth. The results have implications for reconstructing diet, and potentially for our interpretation of the fossil record of human evolution, researchers said.

"We found that hard plant tissues such as the shells of nuts and seeds barely influence microwear textures on teeth," said Adam van Casteren, lecturer in biological anthropology in Arts & Sciences, the first author of the new study in Scientific Reports. David S. Strait, professor of physical anthropology, is a co-author.

Traditionally, eating hard foods is thought to damage teeth by producing microscopic pits. "But if teeth don't demonstrate elaborate pits and scars, this doesn't necessarily rule out the consumption of hard food items," van Casteren said.

Humans diverged from non-human apes about seven million years ago in Africa. The new study addresses an ongoing debate surrounding what some early human ancestors, the australopiths, were eating. These hominin species had very large teeth and jaws, and likely huge chewing muscles.

"All these morphological attributes seem to indicate they had the ability to produce large bite forces, and therefore likely chomped down on a diet of hard or bulky food items such as nuts, seeds or underground resources like tubers," van Casteren said.

But most fossil australopith teeth don't show the kind of microscopic wear that would be expected in this scenario.

The researchers decided to test it out.

Previous mechanical experiments had shown how grit -- literally, pieces of quartz rock -- produces deep scratches on flat tooth surfaces, using a device that mimicked the microscopic interactions of particles on teeth. But there was little to no experimental data on what happens to tooth enamel when it comes in contact with actual woody plant material.

For this study, the researchers attached tiny pieces of seed shells to a probe that they dragged across enamel from a Bornean orangutan molar tooth.

They made 16 "slides" representing contacts between the enamel and three different seed shells from woody plants that are part of modern primate diets. The researchers dragged the seeds against enamel at forces comparable to any chewing action.

The seed fragments made no large pits, scratches or fractures in the enamel, the researchers found. There were a few shallow grooves, but the scientists saw nothing that indicated that hard plant tissues could contribute meaningfully to dental microwear. The seed fragments themselves, however, showed signs of degradation from being rubbed against the enamel.

This information is useful for anthropologists who are left with only fossils to try to reconstruct ancient diets.

"Our approach is not to look for correlations between the types of microscopic marks on teeth and foods being eaten -- but instead to understand the underlying mechanics of how these scars on tooth surface are formed," van Casteren said. "If we can fathom these fundamental concepts, we can generate more accurate pictures of what fossil hominins were eating."

So those big australopith jaws could have been put to use chewing on large amounts of seeds -- without scarring teeth.

"And that makes perfect sense in terms of the shape of their teeth" said Peter Lucas, a co-author at the Smithsonian Tropical Research Institute, "because the blunt low-cusped form of their molars are ideal for that purpose."

"When consuming many very small hard seeds, large bite forces are likely to be required to mill all the grains," van Casteren said. "In the light of our new findings, it is plausible that small, hard objects like grass seeds or sedge nutlets were a dietary resource for early hominins."

Source: Washington University in St. Louis [January 17, 2020]