Long before we built cities or roads, life was intertwined with branches, under the canopy of the forest. Our ancestors ate mangosteen and black juniper, ate nuts, and dug up tubers and roots. One fateful day, one of them slipped and fell to his death from the same 40-foot-high canopy that had sustained him.
Three million years later, remarkably complete fossil remains from what is now Ethiopia inspired the world’s interest in human origins. By 2016, Lucy, the bipedal hominin, had become an icon, her story pieced together by scientists who re-imagined how she might have lived and died among the trees.
British biochemist and dendroscience consultant Harriet Rix writes in her 2025 book, The Genius of Trees (2025; Vintage Digital), “Our ability to leap along vertical branches, our desire to build nests and smell pine wood – all adaptations of primates – are adaptations to trees.”
Most impressive are our rough fingers, which have pads filled with fat and fluid that expel air like a tire for greater friction, and fingerprints that evolved to repel films of water or moss for better grip. Thick shoulders also evolved to help us move faster as we swung along the branches. Trees are planetary engineers, ubiquitous witnesses and a living record of climate history and human evolution. How did they shape the world? And how has the world shaped them?
root awakening
It began with a delicate act of survival about 500 million years ago. At first, colonies of green, sheet-like algae were exposed to harsh UV light and washed ashore on barren land. They learned to adapt, developing stronger vascular systems to cope with this infection.
Along with ankle-length plants, huge towers emerged that constitute a distinct branch of life today. They were branchless, up to 26 feet tall, smooth-skinned, dark, resembling wooden logs called prototaxites.
Within the next 100 million years, trees spread across the planet, storing so much carbon that they completely changed the atmosphere. During this period, certain bacteria or fungi may break down lignin, the compound that gives trees their strong structure. When trees died they did not decay. Swamp forests would store carbon, which would lead to increased photosynthesis, which would change the world.
Oxygen levels increased from 15% to 35%, and soon the Earth became home to giants. Dragonflies as large as birds flew in the sky, giant cockroaches stalked the ground, while predators like early tetrapods or crocodiles dominated the swamps.
And rather ironically, all the readily available oxygen made wildfires unstoppable, destroying large numbers of trees. “Repeatedly in deep history, millions of years ago, trees have destroyed themselves by producing so much oxygen that they alter the climate and often burn themselves to death,” Ricks told Wknd.
New types of trees evolved from the ashes of Carboniferous forests. The first modern or true tree, the now extinct Archaeopteris, with fern-like leaves, emerged in the same period, about 380–360 million years ago.
As volcanic eruptions caused the climate to become drier and warmer and Pangea split into Gondwana and Laurasia, ancient gymnosperms (seed-bearing, non-flowering vascular plants) such as conifers, ginkgos, and cycads appeared. These plants developed waxy needles and hard cones to survive in harsh conditions.
About 66 million years ago, gymnosperms gave way to angiosperms, or flowering trees, but it was only after Chicxulub (an asteroid that collided with Earth) that they spread rapidly, covering more than 90% of the globe.
Fire again became an important ecological force around 20 million years ago. Trees developed thick bark and fire-resistant properties, while some clever pines learned to use this heat to their advantage. The heat helped the cones burst and release their seeds.
Most of the modern tree species we know today evolved during this period.
sticking together
When modern humans evolved about 40,000 years ago, there were already an estimated 6 trillion trees on the planet. Ricks says they have already discovered surprising changes not only in leaf shape and size but also in bark texture, stem structure, pollination and dispersal methods.
Relic trees from earlier geological ages that survive in the Mediterranean, south of the Caspian Sea in Iran, and in China and Japan, have evolved in several “warm and wet” cycles. Yet three million years ago, when the world became colder and drier, many species became extinct.
Later humans also came forward to help.
For example, ginkgo was reportedly saved from near extinction by domestication and cultivation by Buddhist monks in 11th-century China and later in Japan and Korea. “The liquidamber trees that survive in a small part of Turkey’s humid southern coast probably survive because of the sweet-smelling sap, which was once highly prized for perfume,” says Ricks.
It was our ancestors’ ability to sleep safely in nests high in the trees that improved sleep quality and aided brain development, as well as, of course, the fat-packed fruit of the trees that fueled this rapid progress.
Ricks explains, “The need to find that fruit and keep moving forward to find more of it added a “discovery” element to our psyche.
Romantic as they are, trees have also left destruction behind. Eucalyptus can draw so much water from the groundwater level that its neighbors die of thirst. Pine trees are notorious for starting a fire cycle that destroys everything about every 20 years. Allelopathic trees release toxic biochemicals into the soil to eliminate their competitors for local resources.
Walnuts are resistant to fire, partly because they poison the plants around their roots, which die and act as ladder fuel, preventing flames from reaching the top.
to expand
Interestingly, India is still home to descendants of ancient Archaeopteris. Queen sago or Cycas circinalis, which resembles a palm tree and is a frequent centerpiece in garden landscapes across India, traces its lineage back to a region of erstwhile Gondwana. Today, it is found in dry areas of peninsular India, extending to the interior Deccan Plateau, says TR Shankar Raman, a scientist and ecologist with the Nature Conservation Foundation.
The ornamental plant is slow-growing and naturally resistant to drought and fire, but is currently in danger of being over-harvested. He added, “Their prehistoric appeal makes it popular with collectors for the plant trade.”
According to the FAO Global Forest Resources Assessment 2025, the country ranks ninth in total forest area with an estimated 72.7 million hectares, which is about 2% of the world’s total cover. Our forests contain a fascinating diversity of trees that have adapted dramatically: deep-rooted banyans, water-conserving and fire-resistant crocodile-bark trees, expanses of salt-tolerant mangroves, and high-altitude species such as deodar cedar, chestnut, and pine pines.
Among the oldest are junipers (Juniperus genus), dating back 56 to 33 million years, including the oldest at 2,032 years in the Lahaul-Spiti Valley, sustained by resin glands, self-pruning abilities, and a double root system that can spread more than 100 feet. During drought, this cuts off the flow of water to some branches, giving them their crooked, twisted shape.
Most notably, trees also block parts of the country’s 11,000-km coastline. The ancient mangroves – whose ancestors appeared about 75 million years ago – use aerial roots to survive in anaerobic, tidal soils and cover vast stretches such as the 140,000-hectare Sundarbans, the world’s largest continuous mangrove forest.
weather heights
The big story is one of perseverance. “When times are tough, trees conserve their energy and put it into their roots, saving for the good times and surviving the bad,” says Valerie Trouet, a dendroclimatologist at the University of Arizona’s Tree-Ring Research Laboratory. Unlike animal cells, which can limit how long they can divide – protecting against cancer – tree cells do not have a uniform lifespan.
“This means that most trees die only because of external factors such as pests, disease, drought or flooding.”
Although humans cannot wipe them out in a single attack like the Chicxulub, our actions are by no means merciful. We are still reducing the space for them to survive.
“After a large prehistoric extinction event, the trees that survived changed dramatically, but the survivors had room to radiate into the desert,” says Ricks.
According to the Global Forest Resources Assessment 2025 of the Food and Agriculture Organization of the United Nations, the total forest area today is 4.14 billion hectares, which is 31-32% of the total land area of the Earth. 10.9 million hectares of land were deforested annually between 2015 and 2025.
Today 38% of the world’s trees are in danger of extinction. Of the 73,000 known tree species, only 25 can live for 1,000 years.
At this rate, the ancient giants won’t be around much longer to impart their centuries of wisdom.
We evolved in a world where trees stabilized everything around us – air, rain, soil – and we immediately began destroying those stabilizers. “We must learn that if we don’t work with and give space to other components of the natural world, we will have to do all we can to stabilize ourselves, and we don’t know how to do that,” says Ricks.
