Every moment of every day, whether you’re at school, at home or in the woods hiking, you are surrounded by creatures that are just waiting to consume you.
Most of them are microscopic in size and thus we live our days unaware of their presence, but, like a flock of vultures, they wait for the moment something drops dead.
This seemingly ubiquitous community of microbes that eat the deceased has been called the necrobiome.
They live just about everywhere but are quite rare until a fresh corpse falls on them.
When that happens, their populations bloom like wildflowers after a desert rain as they consume the nutrient rich bodies of the dead.
Various species of anaerobic bacteria are the first to bloom as they thrive in the oxygen-free environment inside a corpse.
As these bacteria break down the fat, protein and other nutrients inside the body, they produce gases which eventually rupture the corpse.
This introduces oxygen so aerobic bacteria can bloom.
Eventually, microscopic worms find their way to the party and feast on the bacteria that have spread like wildfire.
This process of a living community responding to habitat change with a predictable succession of species changes is known as an ecological succession.
It’s the same process that happens in a forest after a burn, when larger species of plants replace the smaller ones that colonize the burn first, until the trees return and the forest goes back to normal.
The progression of the necrobiome occurs much faster than a forest’s, and it occurs in a consistent clock-like fashion.
This has led some researchers to believe that they could use the necrobiome to predict the time of death in criminal investigations.
A team of researchers led by Jessica Metcalf at the University of Colorado at Boulder has set out to do just that.
Her team has conducted experiments to figure out how predictable the post-mortem microbial succession is.
The researchers placed dead mice outside in different environments and monitored the microbial community using genetic-sequencing techniques as time progressed.
After 25 days outside, the researchers were able to predict the mouse’s time of death to within two to four days.
They also found the environment had little effect on the microbial community — the same communities were present on mice left in multiple types of soil.
They have also been conducting macabre experiments at a place, darkly known as a body farm, where cadavers are left outside so forensic scientists can study the process of human decomposition.
The results from cadavers were consistent with those from mice: the necrobiome succession happens in a predictable fashion, and the researchers could predict the time of death to within two to three days.
For its next study, the team will place cadavers at three different body farms in all four seasons. This helps the researchers better understand the impacts of the environment on the necrobiome and allow them to fine tune their post-mortem clocks.
Death is just another opportunity for life, and now we can use that fact to catch criminals.
jaykgold@indiana.edu
@JayKeche
