For most of Earth's history, humans weren't here. For billions of years, life evolved without cities, writing, computers or anything resembling human civilisation.
Yet intelligence itself is much older than humanity. Crows can solve problems.
Octopuses can manipulate objects and escape enclosures. Dolphins cooperate and communicate. Elephants appear to recognise individuals and respond to death. Chimpanzees use tools.
Even some insects display surprisingly sophisticated forms of learning and navigation.
If intelligence has evolved repeatedly in living animals, an obvious question follows: How intelligent were the animals that are now extinct?
We have fossils of enormous numbers of creatures that disappeared millions of years ago. We can reconstruct their skeletons. We can examine their teeth. We can sometimes identify their diet. We can estimate how they moved.
We can even reconstruct aspects of their brains using the internal spaces preserved inside fossil skulls.
But intelligence is different.
A fossil doesn't tell us what an animal was thinking. It doesn't reveal whether it could plan, whether it remembered individuals, whether it understood cause and effect, or whether it was capable of solving problems in ways comparable to intelligent animals alive today.
This creates a fascinating possibility.
Could some extinct animals have possessed sophisticated intelligence that the fossil record has failed to reveal?
The problem with measuring intelligence
Humans tend to measure intelligence using human criteria. Language, mathematics, tool manufacture, abstract reasoning, writing and technology.
But intelligence doesn't have to look like ours.
A dolphin doesn't need to build a machine to demonstrate sophisticated cognition. An octopus doesn't need a written language. A crow doesn't need a civilisation.
Intelligence is better thought of as a collection of abilities. Learning, memory, problem-solving, planning, communication and social awareness.
Some animals excel in certain areas while performing poorly in others. This makes comparisons extraordinarily difficult.
The fossil record is mostly about bodies
A fossil preserves physical structure. Bones, teeth, shells. Sometimes skin impressions. Sometimes feathers. Occasionally exceptionally preserved soft tissues.
But behaviour rarely fossilises.
This means an extinct animal could have been remarkably intelligent while leaving behind a skeleton that tells us almost nothing about its mental abilities.
Imagine finding the skeleton of a modern crow millions of years from now.
You might conclude that it was a small flying animal with lightweight bones and a sharp beak. You wouldn't necessarily discover that it could remember human faces, bend wire to obtain food, or solve multi-step problems.
The same problem applies to extinct species. We may be underestimating them simply because intelligence doesn't fossilise well.
The dinosaurs are an obvious place to look
For decades, dinosaurs were portrayed as little more than oversized reptiles. Slow, ectothermic, instinctive. And intellectually limited.
That picture has changed dramatically. We now know that birds are living dinosaurs. Crows, ravens, parrots and other birds demonstrate sophisticated cognitive abilities.
That doesn't mean every dinosaur was intelligent. Far from it.
But it destroys the old assumption that being a dinosaur necessarily meant having primitive cognition. Some dinosaur groups may have possessed surprisingly sophisticated brains.
Troodontids: the intriguing dinosaurs
One group attracts particular attention. The troodontids were small, lightly built theropod dinosaurs that lived during the Mesozoic.
They possessed relatively large brains for their body size and their senses appear to have been well developed. They had grasping hands and other anatomical features that have led researchers to investigate their potential cognitive abilities.
This has produced some genuinely intriguing speculation.
Could troodontids have been among the more intelligent dinosaurs?
Possibly. But there is a major caveat. A large brain doesn't automatically equal human-like intelligence. Brain organisation matters.
Different species can have large brains for different reasons. Sensory processing requires neural capacity, motor control requires neural capacity, and complex vision requires neural capacity.
So when scientists reconstruct an extinct animal's brain, they are looking at clues, not a direct intelligence meter.
Birds complicate everything
If we want to understand dinosaur intelligence, modern birds provide perhaps the most useful comparison.
Bird brains were once considered relatively simple. That view has been overturned.
Some birds display sophisticated cognition despite having very different brain structures from mammals.
Crows can use tools, ravens can solve complex problems and parrots can learn large repertoires of sounds. Some birds even appear capable of planning for future events. And certain birds can remember large numbers of locations.
The lesson is profound. There is more than one evolutionary route to intelligence.
A mammal doesn't have to evolve a human-like brain architecture to become cognitively sophisticated. Birds evolved their own solutions. And that raises an important question about extinct dinosaurs.
Perhaps some of them did too.
Intelligence may evolve in unexpected forms
Evolution doesn't have a predetermined destination. There is no evolutionary law saying that every intelligent animal must eventually become human-like.
Instead, natural selection is merely an adaption process which favours traits that help organisms survive and reproduce.
In one environment, intelligence might help an animal remember hundreds of food locations. In another, it might help recognise individuals. In another, cooperation might be crucial. In another, manipulating objects might provide an advantage.
Different ecological pressures can therefore produce different kinds of intelligence. An extinct animal may have been highly intelligent in ways that would be difficult for us to recognise.
The octopus is a warning
Consider the octopus. It is separated from humans by an enormous evolutionary distance. Our last common ancestor lived hundreds of millions of years ago.
Yet octopuses can solve puzzles, manipulate objects, learn from experience and explore unfamiliar environments.
Their nervous systems are also radically different from ours. A substantial proportion of their neurons are distributed throughout their arms.
They are intelligent without looking anything like us.
This demonstrates something important. Complex intelligence can evolve independently.
If evolution produced advanced cognition in cephalopods once, it could potentially have produced sophisticated cognition in other extinct lineages too.
What about marine reptiles?
The oceans of the Mesozoic were dominated by creatures that have no modern equivalent: Ichthyosaurs, Plesiosaurs, Mosasaurs and other marine reptiles.
Some possessed large brains relative to their body size. Some had sophisticated sensory systems. Some lived in social environments. And some occupied ecological niches that required fast responses and complex hunting strategies.
But can we say they were intelligent?
Not confidently.
Brain size and shape provide clues. Endocasts — reconstructions of the internal shape of fossil skulls — can reveal the approximate size and geometry of the brain.
But soft tissue is rarely preserved in enough detail to tell us how neural circuits functioned.
We can estimate.
We cannot directly observe cognition.
Mammals provide another possibility
Dinosaurs weren't the only animals evolving sophisticated brains. Mammals have existed for more than 200 million years.
Early mammals were generally small. Many were nocturnal. Some probably occupied ecological niches requiring excellent hearing, smell and memory.
Later, mammals diversified dramatically.
Primates evolved increasingly sophisticated visual systems and manipulative abilities. Carnivores evolved complex hunting behaviours. Elephants evolved exceptional memory and social cognition. Cetaceans developed remarkable communication and cooperation.
And eventually, one mammalian lineage produced humans.
But did any extinct mammal develop intelligence that we would find surprising?
Almost certainly some did. The problem is that behavioural evidence is scarce.
The strange case of the Neanderthals
Neanderthals provide an unusually good example because they were close relatives of modern humans.
They made sophisticated stone tools, controlled fire, hunted large animals, used pigments, cared for injured individuals. And possessed brains at least as large as those of modern humans on average.
Whatever definition of intelligence we use, it is difficult to describe Neanderthals as primitive in the simplistic sense.
They were cognitively sophisticated hominins. Yet they disappeared. Their extinction is a reminder that intelligence does not guarantee survival.
Intelligence isn't the same as technological progress
This distinction matters. Humans often equate intelligence with technology. But technology is partly cumulative.
One generation learns something. The next improves it. The next builds upon that. Over thousands of generations, knowledge compounds.
This creates an enormous advantage.
But a highly intelligent animal living alone doesn't necessarily accumulate technology. A raven can solve a complex problem, but that doesn't mean ravens are going to build a spacecraft. A dolphin can learn sophisticated behaviours, but that doesn't mean it can manufacture tools outside its aquatic environment.
Intelligence is therefore only one ingredient.
Culture, communication, dexterity, social learning and environmental circumstances matter too.
What if an extinct animal was intelligent but lacked hands?
This is one of the most interesting questions. Suppose an extinct predator possessed excellent memory, communication and problem-solving abilities. But it had no limbs capable of manipulating objects.
Its intelligence might never have produced technology.
Humans possess an unusual combination:
- large brains
- complex social structures
- language
- fine motor control
- upright posture
- hands capable of precision manipulation
- long childhoods
- extensive social learning
- cumulative culture
It may be this combination, rather than intelligence alone, that allowed technology to explode.
An intelligent dinosaur without hands might never have crossed that threshold.
Could dinosaurs have developed culture?
We don't know. But the possibility is not absurd. Culture doesn't require writing. Young animals can learn behaviours from adults.
Birds do it. Whales do it. Primates do it. Some populations develop traditions that differ from neighbouring populations.
If certain dinosaurs lived in complex social groups and learned behaviours from one another, they may have possessed forms of culture.
Unfortunately, cultural transmission leaves almost no direct fossil evidence.
We might therefore be looking at extinct animals and seeing only their bodies while missing their social worlds completely.
What about language?
This becomes much harder. We have no evidence that dinosaurs possessed anything resembling human language. But communication is widespread throughout the animal kingdom.
Birds have complex vocalisations, whales produce elaborate songs and primates use calls with different meanings. Some animals communicate through body posture, colour, scent and touch.
An extinct species could therefore have had sophisticated communication without possessing language as humans understand it.
The fossil record is almost completely silent on the subject.
The brain leaves clues
Although brains rarely fossilise, skulls can preserve their approximate shape. Scientists can sometimes create digital endocasts of the brain cavity.
These can reveal:
- relative brain size
- major brain-region proportions
- sensory structures
- possible visual-processing regions
- olfactory structures
- vascular features
Combined with comparisons to living animals, these clues can provide insight into the probable behaviour of extinct species.
But there is a limit. An endocast isn't a brain: it is the imprint left by a brain. That distinction is critical.
The intelligence of an extinct animal may be impossible to recover
Imagine two extinct species with identical skull sizes. One was solitary. The other lived in large cooperative groups. One relied almost entirely on instinct. The other learned complex behaviours from its parents.
Their skeletons might look surprisingly similar. Their mental lives could have been completely different.
Without behavioural observations, we may never know. This means the fossil record has an inherent bias. It preserves anatomy far better than cognition.
The intelligence we do recognise may be only the visible fraction
There is an interesting implication here. Modern scientists have repeatedly underestimated animal intelligence.
For a long time, many researchers assumed that sophisticated reasoning was uniquely human. Then studies of chimpanzees challenged that.
Later, corvids, parrots, dolphins, elephants and cephalopods complicated the picture further. Again and again, animals have demonstrated abilities that surprised us.
If our understanding of living animals has repeatedly changed, it is reasonable to ask whether our understanding of extinct animals may also be incomplete.
But we shouldn't turn every dinosaur into a genius
There is an opposite danger. Once we recognise that some extinct animals may have been intelligent, it becomes tempting to exaggerate.
A large-brained dinosaur isn't evidence of a lost dinosaur civilisation, a complex skull isn't evidence of language and a grasping hand isn't evidence of toolmaking.
A social animal isn't evidence of human-like culture. Scientific reconstruction has to stop where the evidence stops.
That doesn't make the question less fascinating. It makes the genuine unknowns more interesting.
The evolutionary arms race
Intelligence can evolve because organisms compete with one another. Predators become better at hunting. Prey become better at avoiding predators.
Competitors become better at finding food. Social animals become better at predicting the behaviour of others.
This creates what is sometimes called a cognitive arms race.
If an animal has to constantly anticipate what another intelligent animal will do, greater cognitive flexibility can become advantageous.
This may have happened repeatedly throughout Earth's history. Different environments could therefore have produced different peaks of animal intelligence.
Some may have left no obvious trace.
Social intelligence may be especially difficult to detect
Imagine an extinct species living in a large social group. Individuals recognise one another, young animals learn from adults, groups coordinate movement and members cooperate to defend themselves.
Older individuals remember seasonal migration routes. Such an animal could possess a sophisticated social intelligence.
But what would we find in the fossil record? Bones, teeth, perhaps a mass burial, tracks, and maybe evidence that individuals lived together.
The actual social relationships would largely disappear. This is one reason fossil behaviour is so difficult to reconstruct.
Trackways can help
There are exceptions. Fossilised footprints can preserve behaviour. A series of parallel tracks may suggest group movement. Different-sized individuals can indicate adults and juveniles travelling together. Nest sites can reveal reproductive behaviour.
Mass accumulations can provide clues about social organisation and pepeated trackways can show how animals moved through a landscape.
These clues are incomplete.
But they demonstrate that behaviour can sometimes leave a physical signature.
Nesting colonies raise questions
Some dinosaurs nested in colonies. Eggs were laid in organised nesting sites. In some cases, evidence suggests repeated use of nesting grounds.
This immediately raises questions.
Did adults guard nests?
Did they recognise their offspring?
Did juveniles remain with adults?
Were nesting colonies social?
Did information about nesting locations pass between generations?
Some dinosaur species clearly had more complex reproductive behaviour than the old image of solitary reptiles wandering across a landscape suggests.
But exactly how sophisticated that behaviour was remains uncertain.
The age of intelligence may be far older than we think
One of the biggest assumptions humans make is that intelligence is a relatively recent development.
That may be partly because the most obvious example — ourselves — is recent.
But natural selection has had hundreds of millions of years to experiment with nervous systems.
Animals with nervous systems have been learning, hunting, avoiding predators and navigating environments for extraordinary lengths of time.
The basic ingredients of cognition are ancient. What may be unusual about humans isn't intelligence itself. It may be the extreme combination of intelligence with language, social learning and cumulative culture.
Could there have been an extinct “genius” species?
Possibly. But the term genius is misleading when applied to extinct animals.
There may have been species with exceptional problem-solving abilities. There may have been animals with remarkable memories. There may have been sophisticated social cognition. There may have been species whose behavioural complexity approached that of some modern intelligent animals.
But we currently have no evidence for a prehistoric animal that developed human-level technological intelligence and then mysteriously disappeared.
The real possibility is more subtle
Perhaps Earth repeatedly produced animals that were very intelligent by animal standards.
Then they disappeared. Their environments changed, their food sources vanished, competitors evolved, climate shifted, asteroids struck, volcanoes erupted and continents moved.
And the evolutionary experiments ended.
A species can become remarkably sophisticated without leaving behind anything resembling a technological civilisation. Its entire mental world can vanish with its extinction.
Mass extinctions may have erased cognitive experiments
Earth has experienced several major mass extinction events. The largest known wiped out enormous proportions of marine and terrestrial species. Others dramatically reorganised ecosystems.
When this happens, evolutionary experiments disappear. A lineage may have spent millions of years evolving specialised behaviours. Then a climate shift or ecological catastrophe ends it.
We usually remember the skeleton. We may never know what the animal could do.
This creates an unsettling possibility. The history of intelligence may contain many dead ends.
What if intelligence evolved repeatedly?
Imagine Earth's history as a series of experiments. One lineage develops excellent memory. Another evolves sophisticated communication. Another develops advanced social cooperation. Another becomes highly dexterous.
Most disappear.
Then another lineage begins the experiment again.
Humans might not be the first intelligent animals Earth has produced. We might simply be the most successful surviving example.
There is currently no evidence that another extinct species reached our level. But there is strong evidence that sophisticated cognition evolved independently in multiple living lineages.
That makes repeated evolution of advanced intelligence a scientifically interesting possibility.
The strange thing about birds
Perhaps the best demonstration comes from an animal group we see every day. Birds.
Their ancestors survived the extinction event that eliminated the non-avian dinosaurs. They then diversified into thousands of species.
Some became extraordinarily intelligent.
Corvids and parrots demonstrate problem-solving and learning abilities that rival or exceed those of many mammals.
This means that one branch of the dinosaur family tree is still with us. When we watch a crow manipulate an object, we are not looking at an evolutionary newcomer.
We are looking at the surviving descendants of an extraordinarily ancient lineage.
Maybe we have been looking at dinosaurs the wrong way
For much of modern history, dinosaurs were treated as evolutionary failures.
Then came discoveries of feathers, evidence of parental care, complex nesting behaviour, sophisticated senses, bird-like respiratory systems, evidence of social behaviour, and increasingly detailed reconstructions of their brains.
The image has changed.
Dinosaurs were not simply giant lizards.
They were an extraordinarily diverse group of animals that occupied almost every terrestrial ecological niche for more than 160 million years.
Some were almost certainly cognitively sophisticated. The unanswered question is how sophisticated.
Intelligence doesn't leave ruins
This is perhaps the central point. If an intelligent animal disappears, what evidence would remain?
If it built houses from wood, they could decay. If it communicated through sound, the sounds vanish instantly. If it taught its young complex behaviours, those behaviours disappear with the population. If it had an excellent memory, there is no fossil trace.
Human intelligence is unusually visible because we build things that persist. Stone tools, buildings, roads, writing and machines.
We have created an archaeological footprint on a planetary scale. Most intelligent animals don't.
The fossil record may therefore underestimate cognition
This doesn't mean every extinct animal was secretly brilliant. It means we should be cautious about assuming that a lack of evidence for intelligence is evidence of a lack of intelligence.
The distinction is subtle but important. Absence of evidence is not evidence of cognitive simplicity. We need multiple lines of evidence.
The next breakthrough may come from unexpected evidence
A spectacular fossil isn't necessarily required. A new dinosaur endocast could reveal an unusually developed sensory system. A fossil nesting site could provide evidence of prolonged parental care. Trackways could demonstrate coordinated group movement. A preserved feather could reveal sensory structures. A new comparison with living birds could change our interpretation of dinosaur brains.
And a better understanding of how intelligence evolved in modern animals could provide a completely new framework for interpreting extinct species.
The revolution may therefore happen gradually. Piece by piece.
So, did Earth once have animals far more intelligent than we assume?
Almost certainly, in some sense. We already know that intelligence has evolved independently in many animal groups. We know that modern birds — descendants of dinosaurs — can display remarkable cognition.
We know that extinct hominins such as Neanderthals possessed sophisticated abilities. We know that fossil skulls can reveal clues about the brains and sensory systems of extinct animals.
What we don't know is how far extinct intelligence actually went.
There may have been animals whose cognitive abilities were comparable to the most intelligent creatures alive today. There may have been others whose mental capacities were unlike anything we have seen.
And there may have been evolutionary experiments in intelligence that disappeared so completely that we will never know they existed.
Perhaps the greatest mystery isn't what they looked like
Fossils have allowed us to reconstruct the appearance of extinct animals with astonishing detail. We can determine their approximate size, their posture, their diet, their movement. Sometimes even their colour.
But the one thing we struggle to reconstruct is what it was like to be them.
- What did they notice?
- What did they remember?
- Did they recognise individuals?
- Did they understand their environment?
- Did they play?
- Did they teach?
- Did they plan?
- Did they communicate?
- Did they solve problems?
We may never know.
Intelligence leaves almost no fossil
That is what makes the question so difficult. A brain can be gone, memory can be gone, a conversation can be gone.
A learned behaviour can disappear in a single generation. And yet the animal's skeleton can remain buried for millions of years.
We can hold its bones in our hands while knowing almost nothing about the mind that once controlled them.
Perhaps somewhere beneath the rocks are the remains of animals that were extraordinarily clever. Perhaps they were only moderately intelligent. Perhaps some were capable of forms of cognition we haven't even imagined.
The evidence will decide.
But there is one conclusion we can already draw. Humanity does not own intelligence. Evolution has discovered it repeatedly.
The remarkable question is not whether intelligence existed before us.
It did.
The remarkable question is how many intelligent worlds came and went before humans ever appeared — and how much of their story has been lost forever.
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