While the rest of us look at the paintings and drawings of Leonardo da Vinci in awe, trying to figure out a smile or find a hidden message explaining everything, scientists are digging deeper and finding … bacteria? A new study reveals that researchers analyzing seven drawings by the master are covered with an unexpected amount of bacteria, fungus and human DNA. Human DNA! Does Dan Brown know about this?
“Seven emblematic Leonardo da Vinci’s drawings were investigated through third generation sequencing technology (Nanopore). In addition, SEM analyses were carried out to acquire photographic documentation and to infer the nature of the micro-objects removed from the surface of the drawings. The Nanopore generated microbiomes can be used as a “bio-archive” of the drawings, offering a kind of fingerprint for current and future biological comparisons.”
“Results showed a relatively high contamination with human DNA and a surprising dominance of bacteria over fungi.”
The study, published this week in the journal “Frontiers in Microbiology” and summarized in a press release, was conducted by researchers from the University of Natural Resources and Life Science and the University of Applied Science of Wien in Austria, and the Central Institute for the Pathology of Archives and Books (ICPAL) in Italy on seven 500-year-old sketches by Da Vinci, including ‘Portrait of a Man in Chalk’ and ‘Uomo della Bitta’ (Man of the Bitta). Dr. Guadalupe Pinar of the University of Natural Resources and Life Sciences led the analysis of the drawings using an innovative new genomic approach called Nanopore to reveal their complete microbiome composition. Oxford Nanopore Technologies, creators of the tool, call it “the only technology that offers direct sequencing of native DNA/RNA, or sequencing amplified samples.” So, what did it find?
“Here, a high proportion of these bacteria are either typical of the human microbiome, certainly introduced by intensive handling of the drawings during restoration works, or correspond to insects microbiomes, which could have been introduced, a long time ago, through flies and their excrements.”
Bug poop! Most ancient documents of this age and older are covered primarily in fungus, which grows readily in the dark, damp environments they’re either found in or stored in. On the other hand, these Da Vinci sketches, befitting of the genius who drew them, have been handled and studied by untold numbers of humans, resulting in bacteria overcoming fungus to be their number two content (after the actual image). The insect excrement is there because, well, it’s everywhere.
How about the DNA? Does it belong to Da Vinci? Jesus? Mary? Mona Lisa? Dan Brown?
“Unfortunately, we cannot assume that this DNA comes from the master himself but it might rather have been introduced by the restoration workers over the years.”
After the first revelation, that was expected. These documents have obviously been handled a lot – and by people not wearing protective gloves in non-sterile environments. Nevertheless, Nanopore offers one feature that is crucial in determining the place of origin of ancient documents, helping determine if they’re real or forgeries.
“However, some similarities were observed that could be influenced by the geographical location of the drawings. Some taxa were only detected in the drawings stored in the Royal Library of Turin, while other taxa were only detected in the drawings stored in the Corsinian Library in Rome.”
In this case, it’s been long verified that the drawings were made by da Vinci. Their microbiomes instead help draw a map of where the sketches have been since Leonardo lifted the chalk after the last flourish. In other words, the kind of data that used to get art history majors all hot and bothered before colleges dropped art history as a degree program. That itself is sad, because this discovery of the invisible bacteria, fungi and human DNA on these drawing illustrates that art history is human history and we never have enough of that.
Your move, Dan Brown.