It wasn’t until 2015 that the Defense Department finally granted the lab approval to exhume all the unknown graves of the Oklahoma.
“We were ready to go,” said LeGarde.
But the forensic obstacles had only just begun to emerge.
It was soon apparent that mitochondrial DNA, the type that is inherited from the maternal line, wasn’t enough to tell many of the sailors apart. Mitochondrial DNA is relatively easy to collect because it is so abundant but it also means relatives who are possible donors for a match are limited to those only within unbroken maternal lineage.
Unlike Jesus Garcia, who was one of the few non-Caucasian crew members (in a still-segregated Navy, he was limited to jobs serving the ship’s officers), the vast majority of the Oklahoma crew was white. They were about the same age (most of them between 18 and 25) and mostly the same height (the average between five-foot-seven and five-foot-nine).
It wasn’t simply that bone length and size were so similar. There were numerous cases of overlapping genetic markers; in other words, the heritage of the sailors was so similar that even though they were not related their ancestors were.
McMahon explained it this way: “You have John Smith and Tim McMahon. Both their ancestors are from England, and they have the same mother’s line basically, or the same sequence.”
One of those DNA sequences, for instance, matched the remains of 25 individuals, all of them Caucasian. “So, 25 people all have that same mitochondrial DNA and many of those were about the same height and age,” explained LeGarde. “So, the anthropologists were kind of stuck again. What do we do next?”
Investigators knew they had to gather DNA samples from the crew members’ paternal line. This material is less plentiful in each cell and therefore harder to collect. But it’s also more precise, giving investigators a greater potential pool of relatives for samples to compare to the unidentified remains. That meant collecting more DNA samples from relatives.
“If we didn’t have that DNA,” LeGarde explained, “we wouldn’t be able to do what we have done.”