George Washington’s family secrets revealed by DNA sampling of 19th-century marked graves.

(CNN) — Genetic analysis sheds light on a long-standing mystery surrounding the fate of President George Washington’s younger brother Samuel and his relatives. Samuel and two of his mother’s descendants were recently identified from skeletal remains found in an anonymous burial in the 1880s. The research also provided the first patrilineal DNA map of the first US president, who had no children.

The researchers identified key details of ancestry through a variety of DNA analyses, including a new technique that analyzes thousands of genomic data points called single nucleotide polymorphisms, or SNPs, which are variations in the genetic sequence that affect a single nucleotide, the building block . No DNA.

Another key component was the DNA of a living descendant of Samuel Washington. By comparing a descendant’s pristine DNA with centuries-old degraded DNA in bone fragments, scientists discovered long-lost links to identity and connections in the Washington family, researchers reported Thursday in the journal iScience.

“This set of methods allowed us to reveal relationships between unidentified human remains from the mid-19th century and living descendants many generations removed from their ancestors,” said Charla Marshall, molecular anthropologist and deputy director of the study’s lead author. DNA operations from the US Department of Defense, in an email.

The techniques could also help identify unidentified remains of people who served in the World War II-era military, according to the study.

Buried in marked graves

Samuel Washington, more than two years younger than George, died in 1781 and was buried in the cemetery of his Harewood estate near Charles Town, West Virginia. Records show Harewood Cemetery was home to 20 members of the Washington family, “including Samuel Washington and his two wives, their children, grandchildren and great-grandchildren, among others,” said the study’s lead author, Courtney L. Cavagnino said. Scientist at the US Armed Forces DNA Identification Laboratory.

But unlike George Washington, who is buried in a lavish marble tomb in Mount Vernon, Virginia, Samuel’s grave is unmarked, likely to protect it from grave robbers, Cavagnino told CNN in an email. Other graves also lacked headstones, leaving modern historians unsure of who was buried where.

Researchers excavated five unmarked graves in the cemetery in 1999 in an attempt to locate Samuel Washington’s resting place. They recovered small bones and teeth from three burials, but DNA testing was inconclusive at the time, as the samples were heavily degraded and contaminated with bacteria.

Fortunately for the authors of the new study, “DNA analysis has come a long way since the early 2000s,” Cavagnino said. They combined techniques that optimized short strands of damaged DNA from residues, allowing them to extract the genetic material they needed. Maternal relationships were determined by sequencing mitochondrial DNA, while paternal relationships were found by looking at Y chromosomes. More details came from 95,000 SNPs, a large amount of data targeting autosomal DNA (DNA that is not linked to the sex chromosome).

Genetic information first established that the remains were of a woman and her two children; The records further specify that the woman was Lucinda “Lucy” Payne and the men were Samuel’s grandsons (and George’s great-grandsons): George Steptoe Washington Jr. and Dr. Samuel Walter Washington. DNA of the living descendant Dr. Samuel had the same DNA as Walter Washington.

Scientists said the data not only established that the dead doctor was the living Washington’s great-grandfather, but also showed which remains belonged to which brother, which would otherwise have been impossible to establish with certainty.

Recovered identity

In 1882, the remains of many were disinterred from Harewood and moved to a tomb at Zion Episcopal Church in Charles Town. Among them were Lucy Penn and her children. But some of his bones were left behind; When they were recovered in a 1999 excavation, it was unclear who they belonged to. Now, almost 150 years later, those remains have finally been identified.

“The combination of dead and living relatives made this study a wonderful puzzle, where you had to work hard to solve it, but it had all the necessary pieces,” Connie J. said Mulligan, a professor in the Department of Anthropology and coordinator of the institute. Graduate Program in Genetics and Genomics from the University of Florida. Mulligan, who studies genetic variations to understand how DNA shapes health and disease, was not involved in the research.

A living descendant, Samuel Walter Washington, the current owner of the Harewood property, turns out to have more DNA in common with the two deceased brothers than researchers expected. Washington attributes this to multiple cross-cousin marriages in the family tree (when marriages between relatives shorten the number of ancestors) to genealogical collapse.

“Cross-cousin marriages only affected the kinship of the siblings and not their mothers, who married into the family,” Mulligan told CNN. “I know of no other study that has a data set as interesting as this one, able to use empirical data with pedigree complexity to test how inbreeding has changed relatedness estimates.” The study, he added, “was a combination of sophisticated science and great detective work!”

The researchers’ analysis also produced the first Y-chromosomal DNA profile of George Washington, as the male subjects (living and deceased) in the study “were all direct paternal descendants of George Washington’s father, Augustine Washington,” Marshall said. . The profile can clarify genealogical relationships among people who have inherited the Washington surname but are unsure of their family connections “to determine who has a paternal relationship to George Washington himself,” the study authors wrote.

But while the discoveries provide many new insights, the question that started the 1999 dig remains: Where is George’s brother buried? According to Marshall, Samuel’s grave has not yet been found, nor have his remains been identified. At this point, he added, his whereabouts could be lost forever.

“The search for Samuel Washington’s grave is no longer ongoing,” Marshall said. “His grave may have been exhumed long ago and may never be found again.”

— Mindy Weisberger is a science writer and media producer whose work has appeared in Live Science, Scientific American, and How It Works magazines.