Plants came first, and by a wide margin. The oldest recognized plant-lineage fossil, a red alga called Bangiomorpha pubescens, dates to roughly 1.05 billion years ago, while the earliest convincing animal body fossil is a sponge-like organism from about 600 million years ago. That gap of over 400 million years is larger than the entire span from the first dinosaurs to today. But the answer gets more interesting once you start pressing on what “plant” and “animal” actually mean in deep evolutionary time, and on the surprising twist that unfolds when these lineages eventually crawled onto dry land.
It Depends on What You Mean by “Plant”
When most people say “plant,” they picture something rooted in soil with leaves and stems. Biologists call those embryophytes, or land plants, and they are relative latecomers. Molecular clock analyses place the emergence of embryophytes in a window from the mid-Cambrian to the early Ordovician, roughly 515 to 470 million years ago.1PubMed Central. The evolutionary emergence of land plants By that point, animals had already been around for well over 100 million years. If “plant” means a fern, a moss, or a daisy, animals win the race easily.
But the broader plant lineage, called Archaeplastida, includes green algae, red algae, and a small group called glaucophytes. All of them trace back to a single ancient event in which an early eukaryotic cell swallowed a cyanobacterium and kept it as an internal solar panel, the chloroplast.2PubMed Central. The endosymbiotic origin, diversification and fate of plastids Molecular clock estimates place the origin of Archaeplastida in the late-to-mid Palaeoproterozoic era, and the green-plant lineage (Viridiplantae) in the late Mesoproterozoic to late Neoproterozoic.3Trends in Plant Science. What came first, plants or animals? In that broader sense, the plant lineage is far older than animals.
What the Fossils Say
The fossil record backs this up, though the evidence is patchy for organisms that were small and soft-bodied. Bangiomorpha pubescens, a filamentous red alga preserved in rocks on Baffin Island in Arctic Canada, holds a special status: it is the only recognized crown-group eukaryote older than about 800 million years. Precise radiometric dating brackets its first appearance at roughly 1.047 billion years ago, making it the earliest known example of eukaryotic photosynthesis and of a recognizable form of multicellularity.4Geology. Precise age of Bangiomorpha pubescens dates the origin of eukaryotic photosynthesis
On the animal side, the earliest well-preserved body fossil with clear sponge-like features is about 600 million years old, predating the famous Cambrian explosion by roughly 60 million years.5PubMed Central. Sponge grade body fossil with cellular resolution dating 60 Myr before the Cambrian After the final Ediacaran glaciation around 579 million years ago, the first macroscopic animal communities, including the strange frond-shaped rangeomorphs, appeared on the ocean floor and quickly built ecologically complex communities.6Cell Press. Bottom-up controls on marine ecosystem revolutions Within another 40 to 60 million years, body plans for nearly every animal phylum had appeared, and marine food webs were about as complex as modern ones.6Cell Press. Bottom-up controls on marine ecosystem revolutions
So the gap in the fossil record between the first algae and the first animals spans hundreds of millions of years. Even accounting for the imperfection of fossilization, that is a real and substantial difference.
What Molecular Clocks Add
Fossils tell you the minimum age of a group: a lineage must be at least as old as its oldest fossil, but it could be older. Molecular clocks try to fill that gap by measuring how much genetic change has accumulated between living species and working backward. These estimates come with wide uncertainty bands, but they consistently place the deep split between plant, animal, and fungal lineages very far back in time.
One major molecular clock analysis estimated the three-way split of plants, animals, and fungi at roughly 1.58 billion years ago.7PubMed Central. Divergence time estimates for the early history of animal phyla and the origin of plants, animals and fungi That does not mean there were recognizable plants or animals walking around at that date. It means the ancestral populations that would eventually give rise to each kingdom went their separate evolutionary ways around then. Another study, using 129 proteins from 36 species, estimated that the major eukaryotic kingdoms diversified between about 950 and 1,260 million years ago, and that animals split from their closest single-celled relatives (choanoflagellates) between 760 and 960 million years ago.8PubMed Central. The timing of eukaryotic evolution: does a relaxed molecular clock reconcile proteins and fossils?
The picture that emerges is that the plant lineage started accumulating its distinctive features, especially photosynthesis via chloroplasts, earlier than the animal lineage assembled its toolkit for multicellular bodies. Animals’ closest single-celled cousins were still swimming around as individual cells long after algae had already become recognizably plant-like.
Why Photosynthesis Came Before Complex Animal Life
This ordering is not a coincidence. It reflects a deep dependency: animals need oxygen, and for most of Earth’s history there was not nearly enough of it. Photosynthetic organisms, first cyanobacteria and later algae, are the ones that produced it.
Suggestive evidence points to photosynthetic organisms existing as far back as 3.2 to 3.5 billion years ago, based on stromatolites and microfossils resembling modern cyanobacteria.9PubMed Central. Early Evolution of Photosynthesis These were bacteria, not plants in any eukaryotic sense, but they were the biological engines that first began pumping oxygen into the atmosphere. The eukaryotic plant lineage inherited that capacity when an ancestor engulfed a cyanobacterium and turned it into a chloroplast, as described earlier.
For most of the Proterozoic eon, roughly 1.8 to 0.8 billion years ago, atmospheric oxygen remained far below modern levels. Modeling work suggests that this kept ocean-floor environments largely oxygen-free and imposed severe ecological constraints on any would-be animal life.10PubMed Central. Earth’s oxygen cycle and the evolution of animal life Large, active animals, especially predators, require substantially more oxygen than single-celled organisms or passive filter-feeders. It was not until the Ediacaran and Cambrian periods that oxygen levels appear to have crossed the physiological thresholds needed for such organisms to thrive.11Annual Review of Ecology, Evolution, and Systematics. The Ecological Physiology of Earth’s Second Oxygen Revolution
In other words, plants (or at least their photosynthetic algal ancestors) had to come first, because animals could not have evolved without the oxygen those organisms had been generating for billions of years. The sequence was not random; it was almost chemically inevitable.
A Crucial Plot Twist in the Family Tree
Here is something that surprises most people: animals are more closely related to fungi than to plants. Multiple independent lines of molecular evidence, from protein sequences to shared genetic insertions, place animals and fungi together in a group called Opisthokonta, with plants as a separate lineage.12PubMed. Animals and fungi are each other’s closest relatives: congruent evidence from multiple proteins This relationship has held up consistently across different genes and analytical methods, with no statistical support for any animal-plant grouping.13PubMed. A Search for the Origins of Animals and Fungi: Comparing and Combining Molecular Data
This matters for the “what came first” question because it means the animal and plant lineages have been on separate evolutionary tracks for an extremely long time. They do not share a recent common ancestor that was partway between a plant and an animal. Their last shared ancestor was a single-celled eukaryote that was neither, and reconstructions of that ancestor suggest it was heterotrophic, meaning it ate other things for energy rather than photosynthesizing.14Genome Biology and Evolution. Evidence for a Syncytial Origin of Eukaryotes from Ancestral State Reconstruction Photosynthesis in the plant lineage came later, after that ancestor’s descendants acquired a cyanobacterial endosymbiont. Animal ancestors never took that path; they stayed heterotrophic and eventually developed complex bodies built for finding, catching, and digesting food.
The Unicellular Ancestors of Animals Were Already Complex
Although animals appeared much later than plants in the fossil record, the single-celled organisms that would eventually give rise to animals were not sitting around doing nothing. They were accumulating a surprisingly rich molecular toolkit, one that would later be repurposed for building multicellular bodies.
Choanoflagellates, the closest living single-celled relatives of animals, carry genes for cadherins, proteins essential for cell-to-cell adhesion in animal tissues. One species, Monosiga brevicollis, has cadherin genes in numbers comparable to those found in complex animals.15PubMed. The premetazoan ancestry of cadherins Similarly, Capsaspora owczarzaki, an amoeba-like organism that sits on another branch close to the animal-choanoflagellate clade, carries at least 17 types of transcription factors previously thought to be unique to animals.16PubMed Central. Unexpected repertoire of metazoan transcription factors in the unicellular holozoan Capsaspora owczarzaki These are molecular switches that control which genes turn on or off during animal development, and they were already present in single-celled ancestors before true animals existed.
The implication is that the genetic groundwork for animal multicellularity was being laid down over hundreds of millions of years while unicellular organisms swam in oceans that were still too oxygen-poor for large animal bodies. When conditions finally improved, the transition to multicellular animal life may have been faster than it would look from scratch, because so much of the underlying machinery was already in place.
Multicellularity Evolved More Than Once
It is worth stepping back to note that “becoming multicellular” is not a single event that happened once and spread. Simple multicellularity, where cells stick together but do not specialize much, has evolved dozens of times across the tree of life. Complex multicellularity, with specialized cell types and intricate body plans, is rarer but has still arisen independently in at least six separate lineages: animals, land plants, two groups of fungi, red algae, and brown algae.17Annual Review of Earth and Planetary Sciences. The Multiple Origins of Complex Multicellularity
This means plants and animals did not just diverge from a common multicellular ancestor. They each independently figured out how to build complex bodies from single-celled starting points, using partly shared and partly unique genetic toolkits. Extensive gene duplications that occurred before the divergence of plants, animals, and fungi provided some of the raw material: among roughly 2,600 gene-family groups analyzed in one study, at least 300 retained duplications that predate the split of all three kingdoms.18PubMed Central. Phylogenetic detection of numerous gene duplications shared by animals, fungi and plants These ancient duplicated genes gave each lineage extra copies to tinker with as they evolved their own forms of complex multicellular life.
On Land, the Order Gets Murkier
Everything discussed so far applies to life in the ocean, where both plants and animals first evolved. On land, the story is different and genuinely debated.
The conventional view has been that land plants came first, greening the continents and creating soil and habitable environments before animals followed. The earliest land-plant fossils and molecular clocks support a Cambrian-to-Ordovician origin for embryophytes, and the physical evidence of their influence is dramatic. Before significant vegetation, rivers were wide and braided with unstable banks. As plants evolved root systems and grew taller, they trapped sediment, stabilized riverbanks, and created the muddy floodplains and forests that terrestrial animals eventually colonized.19PubMed. The Invasion of the Land in Deep Time: Integrating Paleozoic Records of Paleobiology, Ichnology, Sedimentology, and Geomorphology Arthropod and worm-like organisms made temporary incursions into coastal environments during the Cambrian, but permanent terrestrial animal communities did not become established until the Silurian and Devonian, after vascular plants had already begun reshaping the landscape.19PubMed. The Invasion of the Land in Deep Time: Integrating Paleozoic Records of Paleobiology, Ichnology, Sedimentology, and Geomorphology
But newer analyses have complicated this picture. Some research suggests that animals may have colonized land sooner than previously believed, possibly even before embryophytes did.20Current Biology. Dispatch Evolution: Out of the Ocean Trace fossils of arthropod tracks in Cambrian-aged rocks hint at brief terrestrial excursions well before robust plant communities existed. However, there is an important distinction between organisms briefly venturing onto land and actually establishing self-sustaining populations there. The fossil and geological evidence consistently shows that plants reshaped terrestrial environments in ways that made them far more hospitable, and that stable animal communities followed those changes rather than preceding them.21PubMed Central. A timeline for terrestrialization: consequences for the carbon cycle in the Palaeozoic
So even on land, where the question is genuinely closer, the weight of evidence favors plants as the group that established itself first in any lasting ecological sense. The debate is about whether some animals briefly preceded plants on shore, not about which group built a permanent terrestrial presence first.
How Algae Made the Animal Explosion Possible
The relationship between early plant-lineage organisms and the rise of animals was not just about oxygen accumulating passively over billions of years. There appears to have been a more specific and dramatic trigger. Biomarker evidence points to a major turnover in marine primary production between two global glaciation events in the Neoproterozoic: green algae and other eukaryotic algae expanded from freshwater into the oceans and displaced bacteria as the dominant food source.6Cell Press. Bottom-up controls on marine ecosystem revolutions Eukaryotic algae are larger and more nutritious than bacterial primary producers, and this shift in the base of the food web may have been essential for fueling the larger, more energy-hungry animal body plans that followed.
The timing is striking. The earliest macroscopic animal fossils appear roughly 574 million years ago, just five million years after the last Ediacaran glaciation.6Cell Press. Bottom-up controls on marine ecosystem revolutions The implication is that the animal explosion was not just waiting for enough oxygen; it was also waiting for the right kind of food. Algae provided both: the oxygen animals needed to breathe and the calorie-dense nutrition they needed to grow large and active.
Why the Question Is Harder Than It Looks
The straightforward answer, that plants came first, holds up under every reasonable definition and line of evidence. But the difficulty is in the details. If you define “plant” as a green thing on land, then animals beat plants by hundreds of millions of years. If you define “plant” as any eukaryote that photosynthesizes, including single-celled algae, then the plant lineage has a commanding head start. And if you zoom all the way out to photosynthetic life in general, including cyanobacteria, then photosynthesizers predate both plants and animals by over two billion years.
The animal side has its own ambiguity. Molecular clocks suggest that animal ancestors split from choanoflagellates somewhere between 760 and 960 million years ago,8PubMed Central. The timing of eukaryotic evolution: does a relaxed molecular clock reconcile proteins and fossils? but what exactly those ancestors looked like is unknown. They were single-celled organisms that had not yet become “animals” in any recognizable sense. The transition from a single-celled creature with animal-like genes to an actual multicellular animal with tissues and body plans took hundreds of millions of years, and it may have been constrained by environmental factors, especially low oxygen, for most of that time.10PubMed Central. Earth’s oxygen cycle and the evolution of animal life
Researchers have gone back and forth on the exact dates, and molecular clock estimates carry wide uncertainty ranges that sometimes overlap. But the direction of the answer has been consistent for decades: the photosynthetic, plant-allied lineage established itself in recognizable form well before animals did, and that ordering reflects a fundamental ecological logic. You need producers before you can have consumers. The planet’s oxygen levels, its food webs, and the very chemistry of its oceans all had to be transformed by photosynthetic life before complex animal bodies became viable.