The Genographic Project Explores the Ancient History of Guam

Latte stone pillars, unique to the Marianas Islands. Photo by Miguel Vilar.

The name Micronesia, meaning small islands, describes the region well since most of these are small atolls, less than 80 square miles. I’m among the beautiful Marianas islands of western Micronesia, more specifically in Guam to meet the Chamorro people, and to see if together we could unlock some of the mysteries hidden in their DNA.

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Nearly half of Guam’s 160,000 people are Chamorro. Chamorros, the ethnic group of the Marianas, are thought to be descendants from the earliest settlers of Remote Oceania, and they likely reached the archipelago from the islands of Southeast Asia more than 3,500 years ago. Today, nearly all Chamorros speak English as well as their native Chamorro, which itself is a linguistic isolate among Pacific Island and East Asian languages, while also a relic of a distant connection between Guam and the islands of Southeast Asia.

But language is only one of the attributes that make Chamorros unique. Archaeologically the Marianas are home to massive stone pillars, some as tall as 5 meters, known as latte. These stones are often found standing in parallel lines, suggesting they may have functioned as large stilts that at one time held up buildings. Latte stones are found nowhere in the world except the Marianas.

Chamorros are also genetically unique. Our recent manuscript on mitochondrial DNA (mtDNA) diversity in the Marianas showed that Chamorros were distinctive from not only their Micronesian neighbors, but even across each island of the archipelago. However, that study was limited in scope since it looked strictly at maternally-inherited mtDNA. That brings me to one of the main purposes of my trip to Guam, we would like to analyze the paternally-inherited Y Chromosome DNA and the bi-parentally inherited autosomal DNA of Chamorros.

Chamorro man participating in the Genographic Project in Guam
Chamorro man participating in the Genographic Project in Guam. Photo by Miguel Vilar.

Over the course of two days of fieldwork, and on opposite coasts of Guam, I enrolled 85 participants in the Genographic Project. Participants joined after giving informed consent, providing demographic and genealogical information, and rubbing the inside of their cheek for 20 seconds with a swab designed to capture cheek cells. Each participant gave two swab samples, which were stored individually in buffer-filled test tubes and taken to the University of Pennsylvania for DNA extraction, amplification and sequencing.

What we will find in the DNA still remains a mystery, since we know Chamorros experienced hundreds of years of Spanish occupation, followed by American and Japanese occupation in the 20th century. And the proximity and historic connection to the Philippines will undoubtedly have played a role in the make-up of the Chamorro gene pool.

The Genographic Project, now in its eighth year, has enabled scientists around the world to fill in the blanks on mankind’s genetic maps of the world. These maps are enhanced every time we work with unique populations such as the Chamorros, and in many cases what we learn becomes incorporated into the history of a people.

Professors at the University of Guam are already using the mtDNA results we published in late 2012 in their history and anthropology courses, and they are enthusiastic about collaborating with National Geographic and helping us produce new results that will enhance what we collectively know about Guam and Chamorro history.

But the Genographic Project is foremost a collaboration between participants and scientists, and what we learn from analyzing the DNA is always made available and explained to participants. That is why upon leaving Guam, I promised the Chamorros that I would return to the Marianas next year, present the results, and enroll new participants in this exciting project. And next time I will bring my family. I promised them, too.

Members of the public can participate in the Genographic Project by visiting

By Miguel Vilar, Scientific Manager, Genographic Project 

Miguel standing alongside latte stones. Photo by Miguel Vilar.
Miguel standing alongside latte stones. Photo by Miguel Vilar.
Participant swabs his cheek in Mangilao, Guam
Participant swabs his cheek in Mangilao, Guam. Photo by Miguel Vilar.

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Meet the Author
Dr. Miguel Vilar is the Science Manager for National Geographic's Genographic Project. Miguel is also a molecular anthropologist and a science writer. His fieldwork has taken him to remote places throughout the South Pacific, East Africa, Mesoamerica, and the Caribbean. In the laboratory he researches the modern genetic diversity of human populations from Melanesia, Micronesia, North and Central America, and the Caribbean. Miguel has published in several anthropology and genetics journals, as well as popular science magazines.