Scientists have greeted with skepticism (and in some cases derision) the claim that Jack the Ripper has been identified from DNA as an immigrant Polish barber named Aaron Kosminski. It was reassuring to see, for a change, that a good deal of the media coverage reflected that.
Is it possible that defense attorneys on TV have taught people — including reporters — to look at claims for evidence more dispassionately?
Jack the Ripper, of course, is the near-mythical late-19th Century London serial killer, never firmly identified. He is believed to have brutally murdered and mutilated at least five women in 1888, perhaps as many as 11 all told. I say “he” because that seems most likely — the mutilation featured removing bits of a uterus and vagina — even though one of the many candidates endorsed by amateur detectives over the years was a woman.
At the heart of the skepticism is provenance. When judging the worth of a piece of information, consider from whence it came.
First, consider the provenance of the announcement of the new theory. Even though purportedly based on DNA, the hypothesis did not appear in, say, The Lancet or the British Medical Journal. Instead it was published in the Daily Mail, first among those classic London rags that purvey (and sometimes invent) gossip: gossip about the royal family, gossip about movie stars, gossip about politicians — the more salacious the better. Appearance in the Daily Mail is immediate cause for skepticism.
Next, consider the site where the DNA evidence was found: A bloodstained shawl that maybe perhaps belonged to one of the victims. Also, the tale of its recovery is, um, remarkable: the scarf is supposed to have been given to one of the policemen working on the Ripper case more than 125 years ago, which is certainly odd, and then given by him as a gift to his wife, which is even odder.
Was ever a husband so clueless — or hostile? The wife, said to have been quite reasonably horror-struck, stuck the bloody thing away. It remained in storage for more than a century before being auctioned off by one of the happy couple’s descendants.
Price undisclosed, but the purchaser was self-described armchair detective and Ripper tour operator Russell Edwards. Who just happens to be the author of the forthcoming Naming Jack the Ripper, the book that—surprise!—was excerpted by the Daily Mail. Edwards says he was inspired by the 2001 Johnny Depp movie From Hell (although Depp actually played detective Frederick Abberline, not the Ripper.)
The search for mitochondrial DNA
Edwards turned the scarf over to Jari Louhelainen, who lectures on molecular biology at Liverpool John Moores University and is said to freelance as a genetic investigator on cold cases. Louhelainen found blood, presumably the victim’s, but also a stain that looked like semen.
The hunt was on for mitochondrial DNA, usually called the cell’s powerhouse because, as Wikipedia tells us, it can “convert chemical energy from food into a form that cells can use.”
There are hundreds of mitochondria in nearly every body cell, sometimes thousands. So in a search for old degraded DNA, finding mtDNA is more likely than finding DNA from the cell’s nucleus. DNA in the nucleus is usually what we mean when we say “the genome,” but there’s only one copy in each cell.
While mtDNA is more likely to be found because there are so many copies of it, it is also useful only for tracing relationships through maternal lines because it is passed on only from mothers to all their offspring. Edwards found a great-great-great grandaughter of the Ripper victim associated with the shawl, Catherine Eddowes, and Louhelainen said her mtDNA was a match for mtDNA recovered from blood on the shawl. If the data hold up (for example, if other forensic geneticists also found a match), that would be pretty good evidence that the blood on the shawl belonged to the victim Catherine Eddowes.
Is the semen the Ripper’s?
The apparent semen stains were another story. It would be next to impossible to trace them to Jack or any other man. Only mothers pass mtDNA on to all their children, daughters and sons. Fathers do not. The egg contains mtDNA, but sperm hardly ever do. Sperm contain nuclear DNA, because that’s how fathers pass their genes on, but getting nuclear DNA from that century-old stain was next to impossible too.
However they did find, Louhelainen says in a sidebar to the Daily Mail piece, epithelial cells that might have sloughed off the Ripper’s urethra during ejaculation. From them they recovered mtDNA that purportedly matches the mtDNA of one of Kosminski’s living relatives.
Louhelainen claims that the mtDNA haplotype is T1a1 and says it is common in Russian Jews. Kosminski was Jewish, an immigrant from Poland. I couldn’t find T1a1 in a quick search of Jewish mtDNA haplotypes, a topic I’ve been writing about recently. So that’s puzzling. It is a possible Ashkenazi Jewish mtDNA haplotype, but if so it does not appear to be a common one.
Also puzzling is the fact that Louhelainen says he was able to determine that the provider of the epithelial cells had dark hair. Hair color is determined by genes in the nucleus. It has nothing to do with mtDNA.
I don’t know what to make of Louhelainen’s assertions, except to say that they are definitely confusing. They also underscore the need for this genetic research to be repeated by sources with no connections to Louhelainen or Edwards—or media circuses.
It’s quite possible that Edwards’s claim is correct. Aaron Kosminski was one of the chief suspects at the time of the murders, and he ended his days in an insane asylum. The violence and personal sexual nature of the slaughters certainly imply a misogynist madman. But the evidence Edwards presents will be unconvincing until it’s confirmed.
I have a suggestion: Send the scarf to Svante Pääbo’s lab at the Max Planck Institute for Evolutionary Anthropology in Leipzig, the source of all wisdom on ancient DNA. The investigators there would be appalled when they learned that the scarf has been handled frequently over the years, and may contain DNA from scores of people. But perhaps they would welcome the challenge.
Tabitha M. Powledge is a long-time science journalist and a contributing columnist for the Genetic Literacy Project. She also writes On Science Blogs for the PLOS Blogs Network. Follow her @tamfecit.