How the attempt to sequence “Bigfoot’s genome” went badly off track

When we first looked at the report of the bigfoot genome, it was an odd mixture of things: standard methods and reasonable looking data thrown in with unusual approaches and data that should have raised warning flags for any biologist. We just couldn't figure out the logic of why certain things were done or the reasoning behind some of the conclusions the authors reached. So, we spent some time working with the reported genome sequences themselves and talked with the woman who helped put the analysis together, Dr. Melba Ketchum. While it didn't answer all of our questions, it gave us a clearer picture of how the work came to be.

The biggest clarification made was what the team behind the results considered their scientific reasoning, which makes sense of how they ran past warning signs that they were badly off track. It provided an indication of what motivated them to push the results into a publication that they knew would cause them grief.

Melba Ketchum and the bigfoot genome

The public face of the bigfoot genome has been Melba Ketchum, a Texas-based forensic scientist. It was Ketchum who first announced that a genome was in the works, and she was the lead author of the paper that eventually described it. That paper became the one and only publication of the online journal De Novo; it's still the only one to appear there.

The paper itself is an odd mix of things. There's a variety of fairly standard molecular techniques mixed in with a bit of folklore and a link to a YouTube video that reportedly shows a sleeping Sasquatch. In some ways, the conclusions of the paper are even odder than the video. They suggest that bigfeet aren't actually an unidentified species of ape as you might have assumed. Instead, the paper claims that bigfeet are hybrids, the product of humans interbreeding with a still unknown species of hominin.

As evidence, it presents two genomes that purportedly came from bigfoot samples. The mitochondrial genome, a small loop of DNA that's inherited exclusively from mothers, is human. The nuclear genome, which they've only sequenced a small portion of, is a mix of human and other sequences. Some are closely related, others quite distant.

But my initial analysis suggested that the "genome sequence" was an artifact, the product of a combination of contamination, degradation, and poor assembly methods. And every other biologist I showed it to reached the same conclusion. Ketchum couldn't disagree more. "We've done everything in our power to make sure the paper was absolutely above-board and well done," she told Ars. "I don't know what else we could have done short of spending another few years working on the genome. But all we wanted to do was prove they existed, and I think we did that."

How do you get one group of people who looks at the evidence and sees contamination, while another decides "The data conclusively prove that the Sasquatch exists"? To find out, we went through the paper's data carefully, then talked to Ketchum to understand the reasoning behind the work.

Why they think it was genuine

Fundamentally, the scientific problems with the work seem to go back to the fact that some of the key steps—sample processing and preparation—were done by forensic scientists. As the name itself implies, forensic science is, like more general sciences, heavily focused on evidence, reproducibility, and other aspects shared with less applied sciences. But unlike genetics for example, forensic science is very goal-oriented. That seems to be what caused the problems here.

Over the decades that DNA has been used as forensic evidence, people in the field have come up with a variety of procedures that have been validated repeatedly. By following those procedures, they know the evidence they generate is likely to hold up in court. And, to an extent, it seems like the people behind the bigfoot genome wanted it to hold up in court.

“It's non-human hair—it's clearly non-human hair—it was washed and prepared forensically, and it gave a human mitochondrial DNA result. That just doesn't happen.”

Many of the samples they had were clumps of hair of various sizes. Hair is a common item in forensic analysis, where people have to identify whether the hair is human, whether it is a possible match for a suspect's, etc. In this case, the team was able to determine that the hair was not human. So far, so good.

In cases where the hair comes attached to its follicle, it's possible to extract DNA from its cells. And that is exactly what the bigfoot team did, using a standard forensic procedure that was meant to remove any other DNA that the hair had picked up in the interim. If everything worked as expected, the only DNA present should be from whatever organism the fur originated from.

And, in Ketchum's view, that's exactly what happened. They worked according to procedure, isolating DNA from the hair follicles and taking precautions to rule out contamination by DNA from anyone that was involved in the work. Because of this, Ketchum is confident that any DNA that came from the samples once belonged to whatever creature deposited the fur in the woods—no matter how confusing the results it produced were. "The mito [mitochondrial DNA results] should have done it," she argued. "It's non-human hair—it's clearly non-human hair—it was washed and prepared forensically, and it gave a human mitochondrial DNA result. That just doesn't happen."

Ketchum was completely adamant that contamination wasn't a possibility. "We had two different forensics labs extract these samples, and they all turned out non-contaminated, because forensics scientists are experts in contamination. We see it regularly, we know how to deal with mixtures, whether it's a mixture or a contaminated sample, and we certainly know how to find it. And these samples were clean."

But note the key phrase two paragraphs up: "if everything worked as expected." Anyone who's done much biology (or presumably, much science in general) knows that everything typically does not work as expected. In fact, things go badly wrong for all sorts of reasons. Sometimes it's obvious they went wrong, sometimes results look pretty reasonable but fall apart on careful examination.

In this case, there was no need for careful examination; the results the team got from the DNA was a mix of warning signs that things weren't right (internally inconsistent information) and things that simply didn't make any sense. But Ketchum believed so strongly in the rigor of the forensic procedures that she went with the results regardless of the problems. In fact, it seemed as if almost everything unusual about the samples was interpreted as a sign that there was something special about them.