Science Briefs: Ancient human dental plaque, NC Botanical Garden exposition honors Bartrams, invasive kudzu bad for atmosphere

Glad ancient humans didn’t brush, floss

An international team of researchers has found new evidence that ancient humans had a detailed understanding of plants long before the development of agriculture.

By extracting chemical compounds and microfossils from dental calculus (calcified dental plaque) from ancient teeth, the researchers were able to provide an entirely new perspective on our ancestors’ diets. Their research suggests that purple nut sedge formed an important part of the prehistoric diet.

The research, published in PLOS ONE and led by Spain’s Universitat Autònoma de Barcelona and Britain’s University of York, suggests that prehistoric people in central Sudan may have understood both the nutritional and medicinal qualities of this and other plants.

Lead author Karen Hardy, affiliated with both universities, said, “Purple nut sedge is today considered to be a scourge in tropical and sub-tropical regions. ... By extracting material from samples of ancient dental calculus we have found that rather than being a nuisance in the past, its value as a food, and possibly its abundant medicinal qualities were known. ...

“We also discovered that these people ate several other plants and we found traces of smoke, evidence for cooking, and for chewing plant fibers to prepare raw materials. These small biographical details add to the growing evidence that prehistoric people had a detailed understanding of plants long before the development of agriculture.”

2 events in run-up to botanical exhibit

Two well-known N.C.-based naturalists are offering talks in Chapel Hill in advance of the opening of a major exhibition at the N.C. Botanical Garden there.

The “Following in the Bartrams’ Footsteps” exhibit, Aug. 30-Nov. 2, examines the work of John and William Bartram, famed father-son American botanists of the 1700s.

Tom Earnhardt (host of UNC-TV’s “Exploring North Carolina”) will speak at NCBG at 2:30 p.m. Aug. 10 on the state’s natural landscape ($15); at 2:30 p.m. Aug. 24, Jim Costa, executive director of Highlands Biological Station, will speak on how the Bartrams’ explorations of the Southeast influenced poets and scientists (free; advance registration required).

Both events will be held at Reeves Auditorium. Details/registration: 919-962-0522; www.ncbg.unc/edu/calendar. Staff Reports

Kudzu can accelerate global warming

Clemson University scientists are shedding light on how invasion by exotic plant species affects the ability of soil to store greenhouse gases.

In a paper published in the journal New Phytologist, plant ecologist Nishanth Tharayil and graduate student Mioko Tamura show that invasive plants can accelerate the greenhouse effect by releasing carbon stored in soil into the atmosphere. Since soil stores more carbon than both the atmosphere and terrestrial vegetation combined, the repercussions for how we manage agricultural land and ecosystems to facilitate the storage of carbon could be dramatic.

In their study, Tamura and Tharayil examined the impact of encroachment of Japanese knotweed and kudzu, two of North America’s most widespread invasive plants, on the soil carbon storage in native ecosystems. They found that kudzu invasion released carbon that was stored in native soils, while the carbon amassed in soils invaded by knotweed is more prone to oxidation and is subsequently lost to the atmosphere.

Tharayil estimates that kudzu invasion results in the release of 4.8 metric tons of carbon annually, equal to the amount of carbon stored in 11.8 million acres of U.S. forest. This is the same amount of carbon emitted annually by consuming 540 million gallons of gasoline or burning 5.1 billion pounds of coal.