Lightning Strikes Carve a Deadly Signature Deep In The Bones, Scientists Discover

There is an idea in the popular imagination that being struck by lightning is an extremely rare path. Statistically speaking, there is some truth to that.

However, deadly lightning, rare or not, continues to be an unbridled source of human misery every year. It is known that at least 4,500 people are killed by lightning each year, although according to some estimates the figure could extend to the tens of thousands.

The thing is, we don’t really have good data on death by natural electrocution. With many strikes taking place in remote places, evidence of such a death is not always easy to gather.

When a body is struck by lightning, many different things happen. For those who do not survive the suffering, on their bodies remain a range of physical evidence that can identify the cause of death: damage to the skin, including sometimes burn marks, as well as trauma to various organs.

But what if all the tissue breaks down? From the point of view of forensic scientists, who may only have bones to work with, does lightning leave any visible trace on a skeleton?

According to a new study, yes yes.

(Nicholas Bacci & Hugh Hunt, Wits University)

Above: a sample of bone before, during and after (from left to right) current was applied to it, during the arrangement of the experiment.

“Our work is the first research that identifies unique signs of lightning damage deep in the human skeleton and allows us to recognize lightning when only dry bone survives,” says forensic anthropologist Nicholas Bacci of Wits University in South Africa.

In previous experiments, Bacci and fellow researchers identified these unique signs in animal bones, noting “extensive microfracture and fragmentation of the bone matrix” in pig bones subjected to high impulse current, simulating the electrical shock of lightning.

In that study, the same kind of micro-fracture was also seen in the bones of a wild giraffe that was killed by a lightning strike, but it remained unclear whether human skeletons exposed to lightning levels of flow will reveal the same horrible signature.

With the help of corpses donated to science, we now have our answer, with the researchers observing similar patterns of micro-fracture in human bone subjected to the current application, and of a kind that is different from solely thermally induced changes to bone (e.g. bones burned in fire).

“[The lightning damage] takes the form of cracks that radiate from the center of bone cells, or that jump irregularly between clusters of cells, “says forensic anthropologist Patrick Randolph-Quinney of Northumbria University in the United Kingdom.

“The pattern of trauma is identical although the microstructure of human bone differs from animal bone.”

(Patrick Randolph-Quinney, Northumbria University / Tanya Augustine & Nicholas Bacci, Wits University)

Above: Patterns of micro-trauma and micro-fractures in human bone and in giraffe bone.

While the patterns are the same, their intensity depends on the source, and the wild giraffe killed by real lightning showed a “markedly higher chance of micro-fracture and more irregular micro-fractures overall” than the human bones, the team explains in its paper.

Another expected differentiator affecting micro-fracture spread in human skeletons is bone density, which decreases with age after humans reach about 40 years, and which may be sensitive to larger amounts of lightning-induced fracture due to bones being more fragile.

According to the researchers, a double mechanism explains why microfractures in bones form as they do.

“First, the current itself produces a high-pressure shock wave as it travels through the bone,” members of the research team explain in an article written for The Conversation.

“Lightning specialists call this trauma: the passage of electrical energy literally blows up bone cells.”

The second mechanism is an example of the piezoelectric effect, influencing how bone behaves when it is in an electric field.

“Collagen, the organic part of a bone, is arranged like fibers or fibrils,” the researchers explain.

“These fibrils rearrange themselves when flow is applied, causing stress to build up in the mineralized and crystallized component of bone, in turn leading to deformation and cracking.”

For forensic pathologists, the discovery of the micro-fracture patterns could indeed be a “smoking gun,” indicating the likely cause of death in mysterious deaths where no other evidence remains.

For the rest, if we ourselves want to avoid these microscopic cracks, it is best to stay indoors whenever the weather seems like it could become fatal.

Indeed even if lightning (almost) never strikes twice, it is often needed only once.

The findings are reported in Forensic Science International: Synergy.

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