Hidden Threads
We have neglected to investigate the hidden spaces, where deep connections often lie
This article is the first in a three-part series on the surprising, often overlooked phenomena that help explain how the natural world works. The series brings together an array of recent discoveries across the animal and plant kingdoms, showing how deeply, and unexpectedly, life is intertwined.
They were always there; we just never noticed them. They surrounded us in the natural world, in the forests and the jungles. In some cases, they were literally right beneath our feet. They were in our bodies, binding and sustaining us, without our ever knowing it. They are the strange and critical connections, the hidden ties that link us all. And we have only just begun to discover and comprehend them. So why did we overlook them for so long? It’s not because we lacked the tools; it’s that our attention has been focused elsewhere. We failed to plumb the negative spaces—the less obvious realms where deep connections often lie.
Silent Rumbles
Something was wrong with the elephants. They were agitated, frantic, disturbed. Some seemed to flee in terror. The humans had no idea why. Soon it would be painfully clear. On Dec. 26, 2004, the second-most-powerful earthquake in recorded history erupted off the northern coast of Sumatra, triggering a tsunami that killed more than 227,000 people. Yet surprisingly few animals lost their lives.
Before the waves came crashing in, dogs refused to go to the beach. Flamingos flew off for higher ground. Zoo animals rushed inside their shelters. At least, that is what many people reported. Scientists did not all agree that the animals had sensed it coming. The reports of animals’ behavior were anecdotal, some of them after the fact. It was difficult to gather concrete, measurable data. Still, the case of the elephants was especially odd. How had they sensed the impending disaster?
For millennia, humans have interacted with elephants without noticing their communications with each other. In 218 B.C., Hannibal famously led an army over the Alps with elephants in its ranks. South Asians have long harnessed them for labor. In 1883, P.T. Barnum marched them across the Brooklyn Bridge. And as Jacob Shell details in his book “Giants of the Monsoon Forest,” the Japanese Army enlisted them to help build the “Railway of Death” in World War II.
Although scientists have studied them in the wild, no one managed to observe the signals they were sending. That’s partly because while elephants communicate over vast distances by emitting low-pitched rumbles, these rumbles exist below the range of human hearing.
Nonetheless, it was still possible to glean clues about their connections through simple observation. It took Caitlin O’Connell, a postdoctoral researcher who lived among elephants, to see what no one else had: They were hearing through their feet.
O’Connell did not come to the study of elephants directly. Her initial research dealt with insects. The shift in scale was as immense as the change in environment. To observe elephants for her fieldwork, she traveled from California to the jungles of Namibia in southwest Africa. Often camped out in a makeshift bunker, surrounded by hyenas, lions and hippos at the watering hole, not to mention the ever-present malaria-bearing mosquitos, O’Connell placed herself in the front row of a wild kingdom. Sometimes, curious elephants would slide their trunks into her shelter, sniffing to determine what kind of creature she might be.
From such long and close-up cohabitation, she noticed that elephants possessed an amazing ability to, in essence, tiptoe. Once, she watched a herd, startled by a sound of approaching predators, simultaneously turn and race into the forest, while barely making a sound. They appeared to be elevated on their toes. She also noticed that elephants often stood motionless, leaning forward and digging their toenails into the ground. O’Connell wondered if they might be doing something similar to the insects she had previously studied: detecting seismic signals—sound waves transmitted through the earth. In the elephants’ case, the vibrations might be picked up via bone conduction.
O’Connell’s hunch took years of elaborate experiments to explore. Eventually, she and her research team were able to produce seismic signals of their own and observe how the elephants responded. As she details in her 2018 book, “The Elephant’s Secret Sense: The Hidden Life of the Wild Herds of Africa,” her initial hypothesis proved correct. Today, we recognize that elephants hear through their feet using bone conduction, as well as through their ears. They can hear each other’s trumpet calls from roughly two miles away, but they can detect each other’s rumbles through the earth at up to twice that distance.
If herds of elephants have always been communicating with each other over kilometers, why did it take us so long to notice? The signals were always there for us to feel. We heard their trumpet calls; we could not have missed those if we tried. But then we stopped wondering what else might connect them. We accepted what was right in front of us, and we failed to imagine anything more.
The Wood Wide Web
We have to ask the same question about the forests: What took us so long to spot their extensive connections? Only very recently have we learned that plants, too, are emitting sounds below the range of human hearing. As a team of scientists at Tel Aviv University led by Itzhak Khait recently showed, plants produce what appear to be distress calls when dehydrating or when being cut, and those calls are distinct from each other. They also differ by plant type: tomato versus tobacco plants, for example. The sounds are measurable and within the range of hearing of certain insects, including moths, up to several meters from the source. These sounds may be detectable by other plants, though the research on this is just beginning. Like the elephants, plants have always been connected and communicating in ways we previously never realized. And those connections extend below the surface.
Forests maintain an underground system of fibrous tentacles extending from the roots of each tree, intertwined with those of mycelia (fungi), forming a vast labyrinthian communications network. In 1988, E. I. Newman published a paper on this underground network, officially known as mycorrhiza, positing that the connections he had found among a set of trees might exist far beyond that of his small sample. If it did, he knew that the implications would be dramatic. It is remarkable that modern science had not noticed this network previously, given that mycorrhizal systems have existed for roughly 450 million years. We just needed to dig and observe. The problem is that we as a species had been digging plenty; we just never thought to look at all the interwoven strands within our grasp. Our attention was elsewhere.
Ecologists continued to build on Newman’s work without fanfare for decades, until 2021, when Suzanne Simard published her best-selling book, “Finding the Mother Tree: Discovering the Wisdom of the Forest.” In it, she suggests that her research proved an altruistic relationship among trees and seedlings. The notion that trees recognized each other, nurtured their young and defended each other by raising alarms against invading pests enthralled the public. Her TED talks have been viewed more than 10 million times. The mycorrhizal network has been dubbed the wood wide web, or sometimes, the forest internet. It all sounds so fantastically human. Not surprisingly, there soon came a backlash. Three scientists challenged Simard’s findings as anthropomorphic and overstated, sparking a contentious debate.
The mother tree debate is really a subset of a much larger argument that has been slowly working its way across scholarly fields. It involves the nature of evolution: Is it primarily competitive or cooperative? The groundbreaking work of Charles Darwin and Alfred Russel Wallace have led many to a view of nature as competitive, an endless struggle over finite resources, allowing only for the survival of the fittest to pass along their selfish genes. But more recently, this perspective is being challenged by those who see it as one-sided, omitting the tremendous role that cooperation also plays in nature. Simard’s depiction of trees as altruistic is just one more salvo in the battle.
Another example involves evolutionary biologists, who have long thought that the chimpanzee was our closest cousin among the primates. Chimps, being aggressive, warlike and known to commit murder, served to foster the idea that humans are warlike by design. Then we found the bonobo, a primate just as closely related to humans genetically as the chimp, but a creature with an entirely opposite lifestyle. Rather than being constantly aggressive, bonobos stand out for their prodigious sex lives. Bonobos are the free-love hippies of the primate world. Matriarchal and peaceful, they offer a mirror image to the chimp-centric thesis. If humans are just as close genetically to bonobos as to chimps, then couldn’t people be pacific by nature instead of warlike? And isn’t it possible that cooperation, not competition, is what has led to human advancement?
Historian Yuval Harari is one of the most recent and popular writers to advance this view in his best-selling history of humanity, “Sapiens,” but the idea certainly precedes him. Elements of the debate underlie the 19th- and 20th-century arguments between capitalism and communism. Peter Kropotkin, the Russian anarchist, scientist and philosopher, reflected this divide in his late 19th- and early 20th-century writings. He maintained that laborers working collectively outproduce the sum product of individual efforts. Ultimately, these debates are reductive. Both competition and cooperation are always at play in nature, and both help explain survival. Those who cooperate, however, appear much happier in the process. The bonobos sure seem to be enjoying themselves.
The mother tree dispute has distracted from the remarkable fact on which scientists agree: The wood wide web is real, though its functions and purpose are still being explored. Mycorrhizal fungi connect the same and different species of plants, while mycelia can spread like a web across vast distances. A subterranean network actually does link trees within a forest. And those links extend even deeper and more unexpectedly than we thought. Lately, science has been showing us comparable connections among and within all manner of complex systems, including the human body itself.
I’ll explain what I mean in the second part of this series, but to do so, I’ll need to introduce you to the people who have seen shocking connections not just within ecosystems, but even within the systems that let our bodies function. Their insights have been overturning our notions about the ties that bind us all.
Zachary Shore is professor of history at the Naval Postgraduate School, Senior Fellow at UC Berkeley’s Institute of European Studies and a National Security Visiting Fellow at Stanford’s Hoover Institution. He is the author of “This Is Not Who We Are: America’s Struggle Between Vengeance and Virtue” (Cambridge University Press, 2023). The views expressed are those of the author alone and do not represent those of the Naval Postgraduate School, the Department of Defense or the U.S. government.