25 April 2014

Tooth Sleuths

Welcome back. As much as I admire and respect each and every dentist, I am convinced that the ADA (American Dental Association) is in cahoots with popcorn producers. I chipped another tooth on an unpopped kernel. Actually, it might be the same tooth I chipped when I described the ordeals of having teeth before fluoride, floss and present-day dentistry in Dental Check-Up Time.

Knowing this day would come, I’ve been saving accounts of dental-related research. I’ll highlight three studies to give you something to chew on while I’m at my dentist. All fall under the archaeological umbrella.

Modern man and Neanderthal skull props.
(www.bjwinslow.com/gallery/skulls)

I’ve been tuned into dental anthropology since I was a grad student with a neighbor who was finishing his doctorate in anthropology. His major professor and sometimes my neighbor traveled the world to perform assessments of teeth--sort of an ADA-produced version of the TV show, Bones. Stay alert and you may see why I chose these three studies.

Neanderthals and Toothpicks

I’ve written about the shocking Georgia Toothpick Theft, when 374,400 plastic toothpicks were stolen from a toothpick manufacturer, but this toothpick news didn’t make the front page.

Researchers from Spain’s Universitat Rovira i Virgili, Universitat Autònoma de Barcelona and two other institutions examined three, upper jaw, Neanderthal teeth found at the archaeological site of Cova Foradà in Valencia, Spain.

Grooves between the teeth showed signs of pulling a hard, narrow object, such as a toothpick, between adjacent teeth. Cool! I thought, but I was applauding a concert at the wrong moment. It turns out the use of toothpicks has been documented from the beginning of the genus Homo. Interproximal grooves on Neanderthal teeth are common.

Although the investigators’ morphological analyses found no evidence of dental caries or calculus (tartar), abscesses or bone perforation related to a cyst, there were indications of periodontal (gum) disease. They had documented the oldest case of using toothpicks to ease the pain caused by dental disease.

Strontium Measure of Migration

Not far from St. Louis, Missouri, is a UNESCO World Heritage site: the Cahokia Mounds State Historic Site, the largest and earliest pre-Columbian settlement north of Mexico. The site, over 6 square miles, dates from the Mississippian period (800-1350), has some 120 mounds, and is estimated to have had a peak population of 10,000 to 20,000.

Mound at Cahokia Mounds State Historic Site.
(townplannerstl.com/Attractions/place/cahokia-mounds-state-historic-site/)

To better understand the settlement’s regional and cultural interactions and population history and diversity, researchers from the University of Illinois analyzed strontium isotope ratios of teeth.

Different isotopes of the chemical element strontium are found in most rocks, and the ratio of two of those isotopes, strontium-87 to strontium-86, varies with the geology. By consuming plants and water, humans and animals absorb strontium, thus collecting a signature of the local rock.

Because the strontium ratios found in teeth and bones reflect absorption at different life stages--tooth enamel ratios from infancy and childhood and bone ratios from the most recent 7 to 10 years--the different ratios are often compared in archaeological investigations.

For the Cahokia investigation, however, the researchers measured ratios from the teeth of individuals buried at different locations within the settlement, and compared those to ratios from the teeth of small animals found at the site, the assumption being that the animals had never left the site.

The analysis estimates that at least one third of the Cahokia’s residents came to the settlement from multiple places outside of the area.

Plaque Window to the Past

The last study illustrates how your teeth can become the center of attention. Don’t care for them and don’t visit your friendly dental hygienist to remove plaque, the biofilm that sticks to your teeth and causes decay and periodontal disease. Let that soft plaque build and harden to dental calculus (tartar), mentioned above.

After, say, 1000 years, the calculus on any teeth left in your skeleton may be selected for analysis, such as that led by the University of Zurich, Switzerland, and Denmark’s University of Copenhagen.

Plaque is loaded with microorganisms; the fossilized dental calculus preserves the microbiome. The study’s large group of collaborators (over 25 from 21 institutions in 4 countries!) applied genetic and protein-assessing (proteonomic) technologies to determine the DNA and proteins in ancient dental calculus.

They characterized the microbiome in a diseased state, opportunistic pathogens, ancient antibiotic-resistance genes, a genome reconstruction of a periodontal pathogen, numerous bacterial and human proteins, and DNA sequences matching dietary sources.

The analysis and those to follow permit the investigation of pathogen activity, host immunity and diet, and thereby extend direct investigation of common diseases into the human evolutionary past.

Wrap Up

And there you have it. Three studies that employed different approaches: morphological analyses, strontium determinations, and the latest genetic and protein-assessing technologies. All sought to gain insight into our past and perhaps our future. Thanks for stopping by.

P.S.

-Toothpick paper in PLOS One:
www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0076852
-Article on toothpick paper on Science Daily website:
www.sciencedaily.com/releases/2013/10/131017080300.htm

-Cahokia Mounds paper in Journal of Archaeological Science:
www.sciencedirect.com/science/article/pii/S0305440314000302
- National Geographic article on Cahokia Mounds research:
news.nationalgeographic.com/news/2014/03/140307-cahokia-native-american-archaeology-mississippian/
-Cahokia Mounds State Historic Site website: cahokiamounds.org/
-World Heritage Site description of Cahokia Mounds site: whc.unesco.org/en/list/198
-Handbook of Environmental Isotope Geochemistry (Chap 35: Applications of Sr Isotopes in Archaeology):  www.springer.com/978-3-642-10636-1

-Plaque analysis paper in Nature Genetics, Feb 2014:
www.nature.com/ng/journal/vaop/ncurrent/full/ng.2906.html
-The Times of India article on plaque analysis paper:
timesofindia.indiatimes.com/home/science/1000-years-old-microbial-Pompeii-unlocked/articleshow/30957394.cms
-Video presentation (5:31 min) of plaque work by lead author at March 2012 TED: www.youtube.com/watch?v=4ZB29iq_Zd8#t=78

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