Chew on this: Historic “gum” records DNA
July 10, 2019 | Microbiome

Chew on this: Historic “gum” records DNA from human ancestors in Scandinavia

When telling you to throw out your gum, neither you nor your grade-school teachers ever expected research like this. 

In the quest to find ancient DNA left by our ancestors, a group of researchers analyzed masticsfound at a Mesolithic site, Huseby Klev, in western Sweden. Mastics are chewing “gums” made from tree pitch or other natural substances chewed both recreationally and for use in tool making around the world.

The pieces of birch bark pitch in this study, more than 10,000 years old and collected during an archaeological dig in the 1990s, yielded sufficient nuclear material to identify individuals from their residual salivary DNA hidden inside. The paper, published in the May 15 issue of Communication Biology brought together a team of researchers from the University of Oslo, in Norway, Uppsala University, Uppsala, Sweden, Stockholm University, Sweden, and the Foundation War-Booty Site Finnestorp in Kungsbacka, Sweden.
 
Ph.D. student Natalijia Kashuba and the team outlined techniques they developed to help extract nuclear material from these time-hardened gums. Of eight mastics processed, three of them provided usable human DNA. They noted that with QIAGEN’s QIAamp PowerFecal DNA Kit (Now QIAamp PowerFecal Pro DNA Kit), they were able to determine kinship between individuals profiled. Additionally, they reported the library created using the QIAGEN kit contained 23% endogenous DNA, a 10-fold increase in available material.

Mastics like these often retain the impressions of the teeth that chewed them ages ago, and while chemical analyses are performed, until recently, few steps were taken to attempt to use them to unlock more information about the mouths that had chewed them. In most cases, DNA retrieved from Mesolithic sites are found in bones and teeth from remains found at the site, however in some areas like Huseby Klev, these materials are degraded, compromised or missing. Research like this opens new opportunities for discovery.

These findings not only prove that mastics can remain a viable source of material to study the genetic makeup of ancient human groups worldwide, but that kits like the QIAamp PowerFecal Pro DNA Kit, allow more genetic content to be separated from encapsulating, hard-to-remove material. 

We previously published an article offering ways to improve  DNA isolation from stool and other challenging samples. If you’re interested in improving your processes, once you’ve finished chewing over Kashuba, et al, we invite you to give it a read as well. 

 

Reference:  Kashuba N, Kirdök E, Damlien H, Manninen MA, Nordqvist B, Persson P, Götherström A. Ancient DNA from mastics solidifies connection between material culture and genetics of mesolithic hunter-gatherers in Scandinavia. Communication Biology. 2019 May 15;2:185.

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