Illuminating the Hidden Forest, Chapter 29: Trees and the art of aging
To read the previous chapters of ‘Illuminating the Hidden Forest,’ click here.
Jan. 16, 2020
Scientists have recently discovered ginkgo trees more than 600 years old in China. This is very old for a tree, even for a tree whose forebears have been around for 2,000 years. They asked, “What kept this tree alive for so long, and could it possibly live forever?”
What the biologists discovered is that the trees’ cambium, the active vascular layer beneath the bark, can continue making new cells indefinitely. The cambium of these ancient trees look as youthful and healthy as trees say, 560 years younger.
This is not to say that trees don’t die. Forest floors are littered with dead and decaying trees, downed by wind, lightning, bugs, fire, arboreal disease and other falling trees, not to mention overlogging. But it does suggest that in the absence of human and natural threats to arboreal life, trees don’t necessarily decline with age. The cambium can maintain the vital forces of life even as the body of the tree decays around it.
In my walks in the woods, I sometimes come across large and venerable trees with cracked and hollowed trunks that, in season, carry leafy canopies above. In such a tree behind my house, in pensive moments, I stand inside the trunk with my ear to the cambium and listen — for what I don’t know, but I seem to find serenity inside that ancient mother tree, who continues to generate life and growth despite age and injury.
We humans and other creatures of the animal and insect world, it seems, are programmed to decline in age. But is our decline inevitable? In some ways we share characteristics with trees. A vascular system carries moisture and nutrients through our bodies. A skin that protects our insides from the outside world surrounds us. Of course, we’re also different in countless ways, but as with the tree’s cambium, we have one organ that drives the work of our human body. Curiously, that organ shares a name with the tree.
The outside layer of our brains, cortex, is Latin for bark. Cerebral cortex is the bark of the brain. Rather than insulate the brain from the outside world as bark does for the tree, however, our cortex is the largest site of neural integration in the central nervous system, functionally more akin to a tree’s cambium than to its enveloping bark.
Remarkably, the likeness to a tree’s cambium doesn’t end there. The cortex and other parts of the brain continue to generate new cells and connections throughout life, even into our 80s and 90s. A 78-year-old (like me!) can have as many young neurons as a 20-year-old. In addition, he or she has a wealth of memories to draw from (perhaps helping to explain a longer retrieval time) and of life experiences to understand and interpret what life has to offer. In other words, older people cannot only stay smart, they can become wiser. Mental decline in a healthy nonagenarian is not a given. Yet even if the mind’s decline isn’t inevitable, it needs to be fed. Reading, thinking, debating, hearing new songs, savoring new tastes and meeting new people in new places can all feed the neuronal generation that helps keep our brains young and healthy.
As I reflect from my niche inside the ancient tree behind my house, the tree seems to be hugging me. I feel a spiritual connection not only with this patient and enduring soul, but also with the forest and, as well, with the universe of living things beyond. We all grow old. Someday we shall all die, even the gingkoes persisting through the centuries.
Yet while we are here, we can cherish the intelligence and endurance that keeps life pulsing on. We must protect the resources to feed, sustain and develop the life the ginkgoes and we are privileged to enjoy. That means not only taking care of our bodies, but also taking care of the planet that sustains us all, from the forests to the oceans, from the rivers to the plains, from the mountains to the valleys and to all their inhabitants.
To read more about the gingkoes and our regenerating brains, here are some references:
Multifeature analyses of vascular cambial cells reveal longevity mechanisms in old Ginkgo biloba trees, Li Wang, et al., Proc Natl Acad Sci USA, Jan. 13, 2020.
Daniel Levitin, Everyone Knows Memory Fails as You Age. But Everyone is Wrong, NYTimes, Jan. 10, 2020, https://nyti.ms/2scpG4J