Genomics help scientists estimate the population size of the first Samoans


The earliest population of Samoans measured between 700 and 3,000 individuals, according to a new study. Photo by Charles S. Greene/Talofa, Samoa: A Summer Sail to an Enchanted Isle/Wikimedia Commons
April 15 (UPI) -- New genomic analysis has allowed scientists to estimate the population size of the first Samoans to arrive on the Pacific island some 3,000 years ago.

From approximately 3,000 to 1,000 years ago, between 700 and 3,400 people lived on the island of Samoa. Roughly 1,000 years ago, the island's population exploded from a few thousand to 10,000 individuals.

By analyzing the genomes of 1,197 individuals living in Samoa, scientists were able to gain new insights into one of the last major migrations of humans into previously uninhabited territories.

The results of the genomic analysis -- published this week in the journal PNAS -- could also help researchers explore links between early human history in Samoa and the modern health problems, including obesity, hypertension and Type 2 diabetes, that currently plague the island nation.

"These findings are relevant for our ongoing public health research in Samoan populations because they highlight the importance of population history and size in influencing our ability to identify the effect of novel genetic variations, and their interactions with 21st century environments on population health," study co-author Stephen McGarvey, professor of epidemiology and of anthropology at Brown University, said in a news release.

The prevalence of obesity in Samoa has led to record rates of related problems, including diabetes, cardiovascular disease, kidney disease and cancer, according to McGarvey, who has been studying the island's health issues for many years.

"Smaller populations and the evolutionary mechanisms resulting from them, including genetic drift from bottlenecks and natural selection from novel challenging environments such as experienced by the first settlers of Samoa, make it easier to detect new gene variants and different frequencies of known variants that affect cardiometabolic disease risk factors now in the 21th century," McGarvey said.

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The latest genomic data showed modern Samoans get most of their genetic heritage from from Austronesian lineages. Samoans are the descendants of the aboriginal peoples of Taiwan, the islands of Southeast Asia, coastal New Guinea and other Oceanic islands.

The analysis also showed modern Samoans only derive 24 percent of their genome from the people of Papua New Guinea. Most other Polynesian groups share most larger portions of their ancestry with Papuans.

In addition to revealing the ancestry of modern Samoans, the latest data revealed evidence of the population decline that followed the arrival of the earliest European visitors. Hundreds of Samoans died from diseases brought by the first Europeans. Around 150 years ago, the island's population stabilized and began to grow once more.

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"These findings indicate that the modern Samoan population is a result of these demographic dynamics from the earliest times 3,000 years ago to the very recent colonial period in the 19th century," McGarvey said. "Any questions about putative genetic influences and their interactions with modern ways of life must be asked in the context of population history."
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