Often when visiting historic places there is a feeling or a "presence" that one may begin to sense. For some, this might represent a literal connection to the people who visited there long ago; others may liken it to simple reverence for the amount of time that has passed, and the number of individuals that might have come and gone there.
Whether one literally ascribes to the idea of "ghosts" or not, this feeling is hard to ignore, particularly at early human habitation sites, or looking even further back, at locations where earlier forms of life on earth once existed, which predates the arrival of humans.
However, new technologies may soon also play a role in shedding light on these "ghosts" of the ancient past.
"Sometimes paleontologists uncover ghosts," wrote Riley Black, in a recent article at Scientific American. What he referred to specifically had been trace fossils, among which are the "ghost tracks" of ancient life forms that are indiscernible to the naked eye, but with the help of modern science, are beginning to give up their long-held secrets.
Ichnofossils can be defined as "an expression of the alteration of the depositional fabric of in sedimentary rocks by living organisms." In other words, these are the footprints or other alterations to an environment that become fossilized and are thus preserved, even in the absence of any actual fossilized organisms.
Black refers to a set of tracks that made news in months past, located at White Sands National Monument in New Mexico which tell a very unique story of ancient American hunters in pursuit of a giant sloth, which they stealthily followed leading up to a presumed Pleistocene-era ambush.
A recent study published in the journal Nature expounds on the White Sands discovery, where the authors note that data has now been recovered from various locations which presents "evidence for the successful detection and 3-D imaging of such footprints via ground-penetrating radar (GPR), including co-associated mammoth and human prints."
In other words, ground-penetrating radar technology can now successfully uncover trace fossil footprints, even when they are not exposed at ground level.
According to the study's extract:
"Using GPR we have found that track density and faunal diversity may be much greater than realized by the unaided human eye. Our data further suggests that detectable subsurface consolidation below mammoth tracks correlates with typical plantar pressure patterns from extant elephants. This opens future potential for more sophisticated biomechanical studies on the footprints of other extinct land vertebrates. Our approach allows rapid detection and documentation of footprints while enhancing the data available from these fossil archives."
This is exciting, in part due to the fact that the ability to discover trace fossils below ground, or in areas that are otherwise inaccessible, may be useful not only in the discovery of unrecognized archaeological sites, but also in their preservation. Excavation is an intrusive process, and despite what it helps us to learn about the past, it requires the removal of layers of earth that may once have coincided with early human living spaces or other historically significant areas. Ground-penetrating radar, on the other hand, reveals these features of the past without ever having to dig.
Short of having a time machine, such technologies are the next best thing to being able to open a window in time, through which these "ghosts" of the past become available to the modern eye.