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Genes tell old story

Ancient cells hold evidence of a massive die-off of Native Americans

dna

When European settlers arrived in North America, they brought their diseases with them. Shortly thereafter, large numbers of Native Americans began dying from smallpox infection. Five-hundred-year-old documents record this tale, but now scientists say they’ve found additional evidence buried deep inside human cells.

In a new study, Brendan O’Fallon and Lars Fehren-Schmitz report evidence found in genes that the Native American population dropped by half after the arrival of Europeans. O’Fallon studies genes at ARUP Laboratories in Salt Lake City. Fehren-Schmitz is an anthropologist, a scientist who studies humankind, at the University of Göttingen in Germany.

Cells make up every part of the body. Deep inside almost every cell is a long, coiled molecule called DNA. Genes are chunks of DNA that play important roles in determining one’s life. Genes help determine a person’s appearance, such as skin color and height, and also play a role in many things you can’t see, like the chance of getting a disease.

Genes change over time, and by tracking these changes scientists can learn about a person’s ancestors. O’Fallon and Fehren-Schmitz looked at genes in the mitochondria of cells. (Mitochondria are like factories that help cells use energy from food.) The scientists compared DNA from

the remains of ancient Native Americans with DNA from living people descended from Native Americans.

The scientists studied patterns in the genes from the two groups and identified ways the patterns changed over time. Using statistics, which includes useful mathematical tools for analyzing large amounts of data, the researchers were able to estimate the size of the Native American population before and after the Europeans’ arrival. The comparison showed the number of native people plummeted after the colonists’ landed in the New World.

Earlier genetic studies didn’t turn up evidence of the Native American die-off. Scientists involved with the new study say that there’s now more data from ancient remains, so researchers can get a better idea of what happened.

Some scientists question the findings. “These new results confirm what’s known from historic sources, but the quality of ancient DNA data raises potential concerns,” Phillip Endicott told Science News. Endicott is a scientist at the Musée de l’Homme in Paris who looks for clues to history in DNA changes. He points out that the DNA from ancient Native Americans may have been damaged, from contamination in the ground or from scientists handling the remains.

POWER WORDS (from the New Oxford American Dictionary)

DNA, or deoxyribonucleic acid. A long molecule in nearly all living organisms that carries genetic information. Each molecule of DNA consists of two strands coiled around each other to form a double helix, a structure like a twisted ladder.

mitochondria An organelle found in large numbers in most cells. Where energy production occurs.

cell The smallest structural and functional unit of an organism, typically microscopic.

gene The basic unit of hereditary information.

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