The Earth’s ancient past holds many surprising secrets about the evolution of life. When considering which life forms emerged first, many might imagine a certain order. However, our planet’s deep history often reveals timelines that defy common expectations. A fascinating question arises when comparing two seemingly disparate life forms: sharks and trees. Both are incredibly successful and ancient, but their evolutionary journeys began at different points, and the answer to which appeared first might be quite unexpected.
The Dawn of Sharks
The lineage leading to modern sharks stretches back hundreds of millions of years into the oceans of the Paleozoic Era. The earliest indications of shark-like ancestors appear in the fossil record during the Late Ordovician period, approximately 455 million years ago, evidenced by fossilized scales and dermal denticles that resemble those of present-day cartilaginous fish. More definitive fossil evidence of shark-grade cartilaginous fishes, known as acanthodians or “spiny sharks,” dates to the Early Silurian period, around 439 million years ago. These early forms were not yet sharks as we recognize them today, but they possessed key ancestral characteristics like cartilaginous skeletons and spines.
These ancient fish, such as Qianodus and Fanjingshania, provide the earliest unambiguous remains of jawed vertebrates. Further into the Early Devonian, around 416 million years ago, the first more fully developed shark, the Leonodus Shark, evolved. The oldest intact fossil of a shark-like creature, Doliodus problematicus, dates to roughly 409 to 400 million years ago from the Early Devonian. This fossil is significant because it exhibits a blend of features from both sharks and their acanthodian predecessors, offering valuable insights into this early transitional period.
The Rise of Trees
Life on land began to diversify significantly much later than marine life, with plants gradually colonizing terrestrial environments. The first primitive land plants, belonging to the genus Cooksonia, emerged during the Middle Silurian period, approximately 433 to 393 million years ago. A recently described species, Cooksonia barrandei, is dated to about 432 million years ago. These pioneering plants were small, typically only a few centimeters tall, and lacked true leaves, flowers, or deep roots.
Despite their simple appearance, some Cooksonia species possessed vascular tissue, which allowed for the internal transport of water and nutrients. This was a significant step towards developing taller, more complex plant structures. The emergence of the first true “trees,” characterized by woody tissue and significant height, occurred during the Devonian period. Fossils of Armoricaphyton chateaupannense, dating to about 400 million years ago in the Early Devonian, represent some of the oldest known plants with woody tissue. By the Middle Devonian, around 380 million years ago, early forests composed of tree-like plants such as cladoxylopsids and progymnosperms began to appear.
Comparing Ancient Timelines
Examining the fossil record reveals that shark ancestors appeared on Earth long before the first trees. While early shark-like creatures date back to the Late Ordovician period, and more definitive shark-grade fossils emerged in the Early Silurian, the first primitive land plants (Cooksonia) appeared later in the Middle Silurian. True woody trees did not develop until the Early Devonian. This means shark ancestors preceded the earliest land plants by at least 15 to 20 million years, and they appeared tens of millions of years before the evolution of the first true trees. This vast difference highlights the immense stretches of geological time and the independent evolutionary paths that led to these successful life forms.