Sharks are older than trees by a wide margin. The oldest shark-like fossils date to the Late Ordovician period, roughly 450 million years ago, while the earliest known trees appear in the fossil record around 385 million years ago in the Middle Devonian. That gap of about 65 million years means sharks had been swimming in ancient oceans for tens of millions of years before the first forests took root on land. But the story behind those dates is far more interesting than the headline comparison suggests, because neither “shark” nor “tree” meant then what it means now.
When Sharks Entered the Fossil Record
For a long time, the oldest recognized shark fossils came from the early Silurian period, around 420 to 430 million years ago. That changed when researchers described shark-like scales preserved in the Harding Sandstone of Colorado, a formation dating to the Late Ordovician. That discovery pushed the shark fossil record back by about 25 million years, placing early shark relatives in the oceans around 450 million years ago.1Nature. Scales of thelodont and shark-like fishes from the Ordovician of Colorado These weren’t the torpedo-shaped predators you’d picture today. The evidence consists of tiny mineralized scales, similar in structure to what we see on modern sharks but belonging to animals whose overall body shape remains mostly unknown.
This is one of the recurring frustrations of shark paleontology. Sharks have skeletons made of cartilage rather than bone, and cartilage rarely fossilizes well.2PubMed Central. Digital removal of dermal denticle layer using geometric AI from 3D CT scans of shark craniofacial structures enhances anatomical precision What does survive are teeth, scales (called dermal denticles), and fin spines. So the deep history of sharks is pieced together from scattered hard parts rather than complete skeletons. A shark from the Late Devonian Gogo Formation in Western Australia, for instance, preserves mineralized tessellated cartilage with a structure recognizably similar to modern shark cartilage, but specimens like that are exceptional.3PLOS ONE. First Shark from the Late Devonian (Frasnian) Gogo Formation, Western Australia Sheds New Light on the Development of Tessellated Calcified Cartilage For most of their early history, we’re reading the story of sharks through fragments.
When Trees First Appeared
The earliest known forest is the famous Gilboa site in New York State, where fossil tree stumps were discovered in the 1870s, still rooted in their original life positions. For more than a century, nobody knew what the tops of those stumps looked like. That mystery was resolved when spectacular specimens from nearby Schoharie County revealed that the trees belonged to a group called cladoxylopsids, specifically a plant named Wattieza. These were tall, tree-fern-like organisms, at least eight meters high, with trunks bearing large branches arranged in ranks.4PubMed. Giant cladoxylopsid trees resolve the enigma of the Earth’s earliest forest stumps at Gilboa They date to the Late Middle Devonian, roughly 385 million years ago.
If that sounds like a specific and slightly narrow definition of “tree,” it is. Land plants had been colonizing terrestrial environments since at least the Silurian period, more than 420 million years ago, but those early plants were small. They lacked the structural innovations needed to grow tall. The Gilboa trees represent the earliest clear evidence of the tree body plan, a tall central trunk supporting a crown of branches, which is a very particular engineering achievement for a plant.
Shortly after Wattieza, a different group called progymnosperms produced Archaeopteris, which looked more like what we’d recognize as a tree today. Fossil wood from Archaeopteris, dating to about 375 million years ago, shows evidence of the same hormone-driven growth patterns that modern woody plants use to lay down new wood.5American Journal of Botany. Evidence of polar auxin flow in 375 million-year-old fossil wood Archaeopteris had true wood, true leaves, and grew into large forest-forming trees. It’s the earliest organism that most people would look at and call a tree without hesitation.
The Tree Body Plan Keeps Reinventing Itself
One of the more striking findings in plant evolution is that trees aren’t a single lineage. The tree form, a tall plant with a trunk and a crown, has evolved independently many times across different groups of plants. Modern oaks, palms, and tree ferns all qualify as trees by any reasonable definition, but they achieve their height through fundamentally different developmental strategies. An oak grows outward by adding rings of wood each year. A palm grows by expanding a single terminal bud at its tip without ever thickening its trunk. A tree fern supports itself with a trunk made of densely packed root tissue rather than wood.6PubMed. Evolution of arborescence at hydraulic, structural, and developmental limits
The Devonian cladoxylopsids at Gilboa were yet another independent solution. They weren’t closely related to modern trees and didn’t use wood in the same way seed plants do. They were more like oversized ferns that figured out how to stand tall. This repeated, parallel evolution suggests that the ecological advantages of being tall, primarily access to light and the ability to spread spores or seeds over a wider area, are so powerful that natural selection has driven plants toward the tree form again and again across hundreds of millions of years.7Current Biology. Are Trees Older Than Sharks? An Evolutionary History
Sharks, by contrast, are a single evolutionary lineage. All living sharks belong to the group Selachimorpha within the broader class Chondrichthyes, which also includes rays and chimaeras. Molecular clock estimates place the split between sharks and rays somewhere around 300 million years ago, in the late Carboniferous, though the range of uncertainty stretches from about 250 to nearly 390 million years ago depending on the method and calibration used.8PLoS ONE. Revealing Less Derived Nature of Cartilaginous Fish Genomes with Their Evolutionary Time Scale Inferred with Nuclear Genes The point is that while “tree” is a body plan that many unrelated plant lineages have converged on, “shark” refers to a genuine clade with a shared common ancestor.
How the First Forests Changed the Planet
The rise of trees didn’t just fill up the landscape. It fundamentally altered Earth’s atmosphere and climate in ways that affected ocean life, including sharks. As forests spread during the Devonian, their roots broke apart rock, dramatically accelerating a process called silicate weathering. That process pulls carbon dioxide out of the atmosphere and locks it up in sediments. Modeling work suggests this plant-driven weathering caused a massive decline in atmospheric CO2, from several thousand parts per million down to roughly 500 ppm over the course of about 30 million years.9Nature Communications. Low atmospheric CO2 levels before the rise of forested ecosystems
Other models put the starting CO2 even higher, simulating a drop from over 6,000 ppm to around 2,100 ppm between the Early and Late Devonian. Interestingly, those same models found that the CO2 drop didn’t necessarily cool the planet as much as you’d expect. The spread of dark-colored plant cover reduced Earth’s surface reflectivity, and this warming effect partially offset the cooling from lower CO2.10Earth and Planetary Science Letters. The climate change caused by the land plant invasion in the Devonian So early forests may have simultaneously scrubbed greenhouse gases from the air and warmed the planet through a completely different mechanism.
The transformation of soils during this period is visible in the fossil record itself. Devonian paleosols, ancient preserved soils, show increasing clay content and deeper chemical weathering profiles as root systems grew more extensive. This trend actually began in the Silurian, before trees existed, driven by smaller vascular plants with primitive root-like structures. But trees accelerated it enormously.11PubMed. Early Forest Soils and Their Role in Devonian Global Change The drawdown of atmospheric CO2 started well before the appearance of large logs and diverse terrestrial ecosystems, but once full-sized forests arrived, the process intensified.
For marine life, these atmospheric changes had far-reaching consequences. Falling CO2 and shifting ocean chemistry contributed to a series of extinction events in the Late Devonian that reshaped ocean ecosystems. The connection between the greening of the land and the dying of the seas is one of the more counterintuitive stories in Earth history.
Surviving Mass Extinctions
Both trees and sharks have survived multiple mass extinction events, but the way each group weathered those crises looks quite different. The Late Devonian extinctions, particularly the Hangenberg event around 359 million years ago, hit marine vertebrates hard. Many of the armored fish that had dominated Devonian seas went extinct entirely. But sharks, along with the ancestors of modern bony fish, not only survived but diversified in the aftermath.12PubMed Central. End-Devonian extinction and a bottleneck in the early evolution of modern jawed vertebrates Before the Late Devonian, sharks were relatively minor players. After it, they became one of the dominant groups in the oceans.
The pattern of shark recovery after the Hangenberg event is revealing. Not all shark lineages fared equally well. A group called acanthodians, spiny shark-like fish now understood to be early members of the broader shark lineage, had thrived in the Early Devonian but declined from the Middle Devonian onward. They barely survived the Hangenberg extinction and never recovered. Meanwhile, other shark groups, particularly the ancestors of modern chimaeras, underwent a major diversification that peaked throughout the Carboniferous period.13Paleobiology. Rise and diversification of chondrichthyans in the Paleozoic The post-Devonian world was a new ocean, and the sharks that populated it were largely new kinds of sharks.
Trees faced their own crises. The Permian-Triassic extinction, the worst mass extinction in Earth’s history at about 252 million years ago, devastated land plant communities. In the Southern Hemisphere, vast forests dominated by glossopterid seed plants collapsed. These glossopterid forests had been one of the most extensive and long-lived biomes on the planet, and their disappearance marked a profound ecological rupture. The immediate aftermath was characterized by a surge of opportunistic fungi, algae, and ferns rather than new forests.14GSA Bulletin. Refined Permian–Triassic floristic timeline reveals early collapse and delayed recovery of south polar terrestrial ecosystems Forest recovery took millions of years.
A broader analysis of plant extinction events across Earth’s history identifies strong evidence for terrestrial ecosystem collapse in the Late Devonian, mid-late Pennsylvanian, end-Permian, end-Triassic, and end-Cretaceous. In four of those five events, the ecosystem that eventually recovered was fundamentally different from what came before, transitioning to a novel arrangement rather than simply restoring the old one.15Research Square. The geological history of plant mass extinction and terrestrial ecosystem collapse Trees kept existing through each of these crises, but the types of trees, and the ecosystems they formed, changed profoundly each time.
Sharks at the End of the Dinosaur Age
The asteroid impact that ended the Cretaceous period about 66 million years ago provides a useful case study in how sharks handle catastrophe. Analysis of shark tooth shapes across that boundary shows that most shark groups maintained remarkably stable levels of dental diversity. Their overall range of tooth forms didn’t shrink much.16PubMed Central. Tooth morphology elucidates shark evolution across the end-Cretaceous mass extinction The exceptions were telling: apex predators with large, triangular, blade-like teeth took the hardest hit, particularly a group of lamniform sharks called anacoracids that had been dominant marine predators during the Cretaceous.
What happened next mirrors the pattern seen after the Devonian extinctions. As lamniform sharks lost their grip on certain ecological niches, carcharhiniform sharks, the group that today includes reef sharks, hammerheads, and tiger sharks, expanded into the vacated territory. Detailed analysis of tooth shape distributions shows that areas of tooth morphology occupied by lamniforms in the late Cretaceous were immediately exploited by carcharhiniforms in the early Paleocene.17Current Biology. Dental Morphometrics and Disparity of Lamniform and Carcharhiniform Sharks across the Cretaceous–Paleogene Boundary The group as a whole persisted; the composition within it shifted. Sharks have been extraordinarily resilient not because individual species are indestructible, but because the lineage keeps producing new forms to fill whatever ecological opportunities emerge.
Why the Fossil Record Can Be Misleading
Comparing the antiquity of trees and sharks requires some caution about what the fossil record actually preserves. Shark teeth and scales are among the most common vertebrate fossils in marine sediments, but complete shark skeletons are vanishingly rare because cartilage decomposes before it can mineralize. Trees, on the other hand, can leave behind wood, root impressions, leaf compressions, spores, and pollen, but the preservation of these depends heavily on local conditions. Taphonomic studies of marine vertebrate fossils show that differential preservation between different types of organisms is strongly correlated with physical processes like sediment transport and sedimentation rate.18PubMed Central. Comparative taphonomy, taphofacies, and bonebeds of the Mio-Pliocene Purisima Formation, central California
What this means in practice is that both lineages almost certainly originated earlier than their oldest known fossils indicate. The Ordovician shark-like scales from Colorado are the current record-holders, but they may represent animals whose ancestors stretched back even further. Similarly, the Gilboa trees are the oldest known forests, but smaller tree-like plants might have existed earlier without leaving a trace we’ve found yet. Every “oldest known” date in paleontology is a provisional minimum, not an absolute origin point. New discoveries regularly push these dates back, as the Colorado shark scales themselves demonstrated when they extended the shark record by 25 million years from its previous benchmark.
Two Survivors on Different Trajectories Today
After hundreds of millions of years of survival, both trees and sharks face a threat neither lineage has encountered before: rapid human-driven environmental change. Forests cover roughly 30 percent of Earth’s land area and remain the planet’s dominant terrestrial ecosystem, though deforestation continues to reduce that coverage. Trees as a group are not at risk of disappearing, though individual species face pressure from habitat loss, disease, and climate shifts.
Sharks are in a more precarious position. A global assessment found that about one-quarter of all shark and ray species are threatened with extinction, and their overall extinction risk is substantially higher than for most other vertebrate groups. Only about one-third of species are considered safe.19PubMed Central. Extinction risk and conservation of the world’s sharks and rays The most vulnerable tend to be large-bodied species living in shallow waters, precisely the kinds of sharks most likely to encounter fishing gear and coastal habitat degradation. A lineage that survived every mass extinction event in the past 450 million years is now losing species faster than at almost any point in its evolutionary history, driven not by asteroid impacts or volcanic eruptions but by overfishing and bycatch. The irony is difficult to overstate: the older of these two ancient lineages is now the one closer to serious trouble.