By Natural Philosopher Mike Prestwood
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Timeline

The Evolution Timeline

From LUCA 3.6 billion years ago to primates.

This timeline of evolution brings some sense of perspective to the very long and complicated history of life on Earth. This timeline is intended to help with the big picture. This timeline brings together various scientific disciplines including plate tectonics, evolution, anthropology, and genetics.

Quick Summary of Evolution: Check out A Short Summaroy of Evolution for an introduction to how evolution works.

Evolution
Switch To: March to Life | Evolution | Human Evolution | Consciousness

LUCA – Last Universal Common Ancestor
LUCA – Last Universal Common Ancestor
3.6 Billion BCE
Spedulative guess: 3.5 to 3.8 Billion Years Ago

First DNA Life: From chemical reactions before 4 billion years ago to replicating molecules about 4 billion years ago to DNA based life then to LUCA, the only DNA based branch to survive. Meaning, DNA based life likely started before LUCA, and LUCA is the only branch to survive the test of time. From LUCA to humans, RNA and DNA are essentially the same as today. They serve as the tools for genetic information storage, transmission, and expression through prokaryotes to eukaryotes, underpinning the diversity and complexity of life on Earth. The last universal common ancestor (LUCA) is estimated to have lived approximately 3.5 to 3.8 billion years ago. It is the organism from which all current life on Earth descended from. Your greatest grandparents.

Imagined image: LUCA in a variety of shapes that they might have resembled, set in an ancient, deep-sea hydrothermal vent environment.

Second Oceans: From Fresh to Salty
Second Oceans: From Fresh to Salty
3.5 Billion Years Ago
3.5 to 2.5 Billion Years Ago

The process of salination likely began soon after the oceans formed but took hundreds of millions of years to reach the salinity levels similar to what we see today. The oceans were likely significantly salty by about 3.5 billion years ago.

Salinity increased primarily through the weathering of rocks and the leaching of minerals (including salts) into the water. Rivers and streams carried these salts into the oceans. Volcanic activity also contributed ions to the seawater. Over time, as water cycled through evaporation and precipitation, salts became more concentrated in the oceans.

By about 2.5 Billion years ago, the oceans were likely had salinity levels similar to modern oceans.

Oldest Known Fossil-Microorganisms
micro organisms cells background
3.42 Billion BCE
3.42 to 3.7 Billion BCE

The earliest known life on Earth are fossilized microorganisms found in hydrothermal vent precipitates. Currently dated to about 3.42 billion BCE. These microorganisms were prokaryote cells. Single celled organisms with no nucleus and had early simple DNA. More complex DNA in a nucleus evolved about 1.5 billion years later in Eukaryotic cells, circa 2 billion BCE.

The First True Eukaryotes
The First True Eukaryotes
2.7 Billion BCE

All life today are either Prokaryote or Eukaryote. Around 2.7 billion years ago, Eukaryotes evolved from Prokaryotes. The evolutionary leap to eukaryotes introduced cells with a nucleus and membrane-bound organelles, a compl

Mitochondrion
Mitochondrion

ex architecture derived from prokaryotic predecessors through endosymbiosis. This process, crucial for eukaryotic evolution, involved the incorporation of prokaryotic cells into the cytoplasm of early eukaryotes, giving rise to essential organelles like mitochondria and chloroplasts.

Mitochondria are a key component of eukaryotic cells, contributing to their ability to generate energy more efficiently than prokaryotic cells

Cyanobacteria: Sun Energy as Food!
top view of woman holding paper cut sun and planet with renewable energy sources on turquoise
2.4 Billion BCE
2.4 to 2.3 BYA

The Dawn of Photosynthesis and the Oxygenation of Earth: Around 2.4 billion years ago cyanobacteria emerged, the architects of the planet’s first photosynthetic processes. These microscopic prokaryotes harnessed the Sun’s energy, transforming it along with water and carbon dioxide into glucose and, crucially, oxygen. This period, known as the Great Oxidation Event, marked a dramatic increase in atmospheric oxygen levels, fundamentally altering the course of life’s evolution. Before this event, Earth’s atmosphere was largely devoid of oxygen, dominated instead by methane, ammonia, and other gases. 

Most life on Earth today consumes the Sun’s energy directly or indirectly, but not all life. Plants consume the Sun’s energy directly, plant eaters indirectly, and meat eaters one more step away. In addition to this chain of food, some life on Earth do not consume the Sun’s energy at all. Instead they consume nutrients found in extreme envorinments. Food to them like hydrogen sulfide.

 

Third Atmosphere: Oxygen Atmosphere
planet-blue-atmosphere
2.4 Billion Years Ago
2.4 BYA to about 540 MYA

GOE: The Great Oxidation Event started enriching the atmosphere with oxygen beginning around 2.4 billion years ago. It marked one of Earth’s most dramatic transformations. Initiated by the widespread activity of photosynthetic cyanobacteria, this period, known as the Great Oxidation Event, gradually saw the accumulation of oxygen that was initially absorbed by oceanic iron. As these iron sinks saturated, oxygen spilled into the atmosphere, paving the way for profound environmental and biological changes. The creation of an ozone layer, the oxygenation of the oceans, and the consequent rise of aerobic life forms set the stage for the later explosion of complex life on Earth, fundamentally altering the course of our planet’s history.

Breathable air to animals, including humans, started about 540 million years ago.

Animals, Plants, and Fungi Split
Animals, Plants, and Fungi Split
1.5 Billion BCE

Eukaryote cells evolve into three separate lineages, the ancestors of modern plants, fungi and animals. Later animals evolve into the animal kingdom which includes mammals, birds, reptiles, amphibians, fish, insects, crustaceans, arachnids, echiniderms, worms, mollusks, and sponges.

Sexual Reproduction
Sperm and egg cell on microscope. Scientific background.
Before 1 Billion BCE
Precambrian era

Sexual reproduction, genetic material from two parents, emerged as a fundamental evolutionary innovation, before the advent of multicellular life forms. This critical development enabled the mixing of genetic material, leading to increased genetic diversity and adaptability among early eukaryotic organisms, setting the stage for the complex tapestry of life that would eventually populate Earth.

Touch Emerges: Proto-Sensing.
Touch Emerges: Proto-Sensing.
800 Mya
Proto-Sensing.

Long before the complexity of full-fledged nervous systems, elaborate senses, and brains, life on Earth developed the basic ability to perceive and react to mechanical stimuli—a process known as cellular mechanosensitivity. A contemporary manifestation of this can be observed in the movement of some plants today, such as the Venus flytrap, which responds to touch by snapping shut to capture prey. This early form of proto-sensing, relying on signal transduction pathways within single-celled organisms, represents the precursor to the sophisticated sensory and nervous systems found in later multicellular life. Through mechanisms like ion channel activation and signal transduction cascades, these primitive organisms could respond to touch and pressure, paving the way for the evolutionary journey towards more advanced forms of perception. This foundational stage of sensory evolution, occurring as early as 800 million years ago, underscores the deep biological roots of our ability to sense and interact with the world around us.

First Multicellular Animals
green and black abstract painting
640 Million Years Ago
640 to 600 Million Years Ago

Organisms that consist of more than one cell took several billion years to evolve from unicellular organisms. All species of animals, land plants and most fungi are multicellular, as well as many algae. A few organisms are partially both such as slime molds and social amoebae.

First Egg Layers
First Egg Layers
638 Million Years Ago
640 to 600 Million Years Ago

The evolution of egg-laying evolved before fish. It is thought to have developed with or shortly after the emergence of the first multicellular animals, around 640 million years ago.

Presentient Animals Emerge: The Ediacaran Prelude
Presentient Animals Emerge: The Ediacaran Prelude
635-600 Million Years Ago
Proto-brain; Pre-brain memory; Presentient.

Creatures of this time evolved into fish (us), jellyfish, cephlapods, and arthropods. In the deep waters of the late Precambrian era, the seeds of sentience were sown with the evolution of the earliest common ancestors to later cephalopods and fish. These primordial creatures, equipped with the most basic nervous systems, embarked on the path toward sensing and interacting with their surroundings in novel ways. Some of these species might have evolved some pre-brained memory, setting the foundational capabilities for interaction and adaptation within their environments. While far removed from the complex behaviors of their future descendants, these early organisms’ ability to respond to environmental cues marked the dawn of simple sentience in the animal kingdom. This pivotal moment laid the foundation for the intricate tapestry of life that would evolve, branching into the diverse forms of sentience observed in the animal world today.

Ediacaran biota (about 635 to 541 million years ago): By about 635 million years ago, clearly identified plant eaters evolved. Thriving in the oceans. Characterized by their unusual and diverse shapes, ranging from frond-like patterns to disk and tubular structures, the Ediacaran biota’s body plans defy easy comparison with modern life forms. The significance of the Ediacaran biota lies not just in their ancientness but in their representation of life’s experimental forays into multicellularity, offering clues to the evolutionary transition from simple microbial life to the complex organisms that would come to dominate the Earth. While we don’t know if this creature had a proto-nervous system, their existence set the stage for the Cambrian Explosion.

Chemorecption: Taste and Smell Emerge
Chemorecption: Taste and Smell Emerge
600 Mya

Chemoreception, the ability to detect chemical stimuli, likely emerged around 600 million years ago among some of the earliest soft-bodied multicellular organisms. This evolutionary leap did not necessarily require a proto- or pre-brain in the complex sense associated with later animals but rather relied on cellular mechanisms capable of processing chemical information. These early forms of chemoreception enabled organisms to make rudimentary distinctions necessary for survival, such as identifying nutritive substances versus harmful ones. They could “taste” potential food sources upon direct contact and “smell” chemicals dissolved in the water, guiding them towards nourishment or away from danger. These primitive sensory mechanisms laid the groundwork for the sophisticated development of taste and smell in more complex animals.

Kimberella (circa 560 Mya): The Kimberella, while not an ancestor of vertebrates, is a likely early example of a creature with chemoreception. It is potentially an early mollusk, and exemplifies the importance of chemoreception in early animal life. Its grazing on microbial mats would have necessitated a basic form of chemoreception to discern between nutritious and non-nutritious substances. The distinction between food sources implies an elementary ability to ‘taste’ and ‘smell,’ integral for selecting suitable food. This behavior marks a significant step in the evolutionary sophistication of sensory systems, foreshadowing the complex senses of taste and smell found in later species.

First True Animals – Comb Jellyfish
Jellyfish moving through water
560 Million BCE
560 to 550 Million Years Ago

Through genetic analyses, scientists now believe the Comb Jellyfish is the earliest known true animal to evolve on Earth. Prior to this genetic analyses, simple sponges were thought to have evolved first.

Vision Emerges: The Pre-fish Chordates
Vision Emerges: The Pre-fish Chordates
540 Mya
Vision Emerges; Proto-Simple Brains; Pre-vertebrate Cord.

Vision evolved as early as 540 million years ago during the Cambrian explosion. The ability to see, alongside the development of hearing, provided organisms with the evolutionary advantage of sensing their environment from a distance. This sensory evolution necessitated the development of larger brains for the complex processing of visual data, marking a pivotal moment in the cognitive evolution of life.

Pikaia Gracilens (520 to 505 Mya): In the ancient seas of the Middle Cambrian, starting around 520 million years ago, Pikaia gracilens swam into the annals of evolutionary history as one of the earliest known chordates, a group that would eventually give rise to vertebrates, including fish and, much later, humans. Measuring up to 6 centimeters in length, Pikaia boasted a series of notable features for its time, including a notochord—a flexible rod running along its back, which would become the backbone in its vertebrate descendants—and rudimentary structures suggesting the early development of a circulatory and nervous system. While Pikaia itself lacked well-defined eyes, its place in the evolutionary lineage hints at the beginnings of the complex sensory organs that would become eyes in later vertebrates.

First Vertebrates
First Vertebrates
530 Million BCE
530 to 520 Million Years Ago

The earliest known vertebrates originated about 530 million years ago during the Cambrian explosion. 

Earliest Known Hunter
Earliest Known Hunter
520 Million Years Ago
First Simple Brains; Proto-Short-Term Memory; Simple Sentience.

The emergence of the first brains were likely in the earliest known hunters. By about 520 million years ago, hunters roamed the seas. In the Cambrian explosion, a period of rapid evolutionary development that began around 541 million years ago, the earliest known animals with structures recognizable as brains made their debut in the Earth’s oceans. They possessed rudimentary beginnings central nervous systems, including a brain. This allowed for advanced sensory processing, decision-making, and coordinated movement.

Anomalocaris (518 to 500 Million Years Ago): Among these early pioneers, creatures like Anomalocaris canadensis stand out. During the Cambrian Period, the Anomalocaris was a formidable predator of the seas. It reached lengths of up to three feet. With its large, compound eyes, flexible, segmented body, and a pair of grasping appendages in front of its mouth, it was perfectly adapted to detect and capture prey. Anomalocaris swam the ancient oceans with undulating movements, using its circular mouth lined with serrated plates to consume trilobites and other early marine animals.

 

Simple Sentience Settles: Haikouichthys
Simple Sentience Settles: Haikouichthys
520 Million BCE
Simple Brains; Proto-Short-Term Memory; Simple Sentience.

From no sentience or presentience to solidly “Simple Sentience,” early fish during this time represent our ancestral beings that started to suffer and feel the dichotomy of pleasure and pain.

Haikouichthys (circa 520 Million Years Ago): Dwelling in the ancient seas of the Cambrian period, Haikouichthys is among the earliest forms of vertebrate life, showcasing fundamental advancements in the complexity of the nervous system. Unlike its precursors in the Ediacaran period, which exhibited only the most rudimentary forms of interaction with their environment, Haikouichthys possessed a more developed nervous system, allowing for more nuanced responses to stimuli. This development marks a significant evolutionary leap towards the ability to experience basic forms of what we might consider suffering and pleasure. Its existence underscores a pivotal transition in the evolution of life, bridging the gap between the simplicity of early multicellular organisms and the complexity required for the nuanced experiences of sentience."<a href="https://commons.wikimedia.org/w/index.php?curid=19461018" target="_blank" rel="noopener noreferrer">Haikouichthys NT</a>" by <a href="https://commons.wikimedia.org/w/index.php?title=User:ArthurWeasley&amp;action=edit&amp;redlink=1" target="_blank" rel="noopener noreferrer">Nobu Tamura email:nobu.tamura@yahoo.com www.palaeocritti.com</a> is licensed under <a href="https://creativecommons.org/licenses/by-sa/3.0/" target="_blank" rel="noopener noreferrer">CC BY-SA 3.0</a>

Simple Cephalopod Sentience Evolves
Simple Cephalopod Sentience Evolves
510 Million BCE
Not a fish ancestor, not our ancestor.

Nectocaris pteryx lived during the Middle Cambrian period, approximately 508 to 505 million years ago. From presentient animals branched cephalopods and fish. Both later evolved Simple Sentience. An example of convergent evolution that might suggest sentience is one of the natural stepping stones of life.

The Cambrian and subsequent periods saw the emergence of early cephalopods, ancestors to modern octopuses, squids, and cuttlefish. These ancient cephalopods, navigating the Cambrian seas, possessed a more developed nervous system compared to many contemporaneous organisms, capable of processing information from their environment in sophisticated ways. This evolutionary development marked a significant leap towards simple sentience, with early cephalopods able to exhibit behaviors such as hunting strategies, escaping predators, and possibly even social interactions. The evolution of these early cephalopods highlights a pivotal moment in the history of life, demonstrating the beginnings of nervous system sophistication that would eventually lead to the complex forms of sentience observed in higher animals, including humans.

First Land Plants
yellow and red flowers on gray rock
470 Million BCE

The first land plants appeared during the Ordovician period. Life was diversifying rapidly during the Ordovician period.

Keratin Genes & the Rise of Scales in Fish
Keratin Genes & the Rise of Scales in Fish
425 Million Years Ago
425 MYA (+/- 15 Million Years)

These early scales provided a vital protective layer, acting like underwater armor against predators, abrasions, and environmental threats. The keratin genes that led to scales are an interesting part of our story. When amphibians evolved onto land, scales near the tips of their evolving toes transformed into thicker protection and traction, eventually giving rise to claws, nails, and hooves. Meanwhile, cold temperatures and sun exposure led to the development of warming and protective traits like feathers, fur, and hair. Specialized “scales” evolved into horns in various species, such as triceratops and rhinos, despite their unrelated lineage. Additionally, keratin genes influenced the formation of beaks in birds. All these diverse traits originated from the same keratin genes.

Oldest Known Air Breather
Oldest Known Air Breather
414 Million BCE

The millipede Pneumodesmus newmani is the oldest air-breathing animal known to date. This ancient denizen of the Scottish waters once roamed the Earth during the early Silurian era. The millipede likely supplemented its oxygen intake through air as well as using its gills while in water.
 
 

 

Lungs Evolve: Lobe-Finned Fish and the Lungfish Ancestor
Living fossil fish, Coelacanth.
400 Million BCE

The Dawn of Lungs: In the oxygen-poor waters of the Devonian period, roughly 400 million years ago, or a bit earlier. It was a significant evolutionary leap. A group known as Sarcopterygii were presentd with a formidable challenge in ancient waters that were shallow and variable. It was here that the first lungs emerged. Evolving from structures akin to modern fish’s swim bladders, these early lungs enabled them to extract oxygen directly from the air. This innovation marked a pivotal moment , setting the stage for land vertebrates.

Lung Fish” by Nagyman is licensed under CC BY-SA 2.0

The Legacy of the Lungfish: Descended from them, the lungfish epitomize the resilience and adaptability of life. Presently represented by six species across Africa, South America, and Australia, lungfish possess both gills and well-developed lungs, enabling them to survive in environments that would be inhospitable to other fish. During dry seasons, some lungfish can aestivate in mud, breathing air through their lungs until water returns. 

Long-Term Memory Evolves: Tiktaalik
Long-Term Memory Evolves: Tiktaalik
375 Mya
Complex Brains; Long-Term Memory; Simple Sentience.

Long-Term Memory: By about 375 million years ago, the foundations for long-term memory were likely established among the more complex vertebrates, facilitating survival in increasingly varied and challenging environments.

Tiktaalik is a prime example of this evolutionary milestone. It is an extraordinary creature that bridged the gap between aquatic fish and amphibians. With its forward-facing eyes—an adaptation indicative of its predatory lifestyle, it  navigated both the waters and the emerging land habitats. This semi-aquatic way of life, combining elements of both aquatic and terrestrial existence, would have necessitated the use of long-term memory for tasks such as remembering the locations of feeding sites, water bodies, and safe paths between them. Its adaptations, including limbs capable of supporting its weight on land, suggest a complex lifestyle that likely benefited from the development of long-term memory, enabling it to exploit the resources of both realms effectively.

Land Hearing Emerges: Amphibians
Land Hearing Emerges: Amphibians
370 Mya
Land Hearing Emerges; Yet Larger Brains.

Hearing, which initially appeared in early fish, underwent a remarkable transformation as vertebrates transitioned to terrestrial life a bit after 400 million years ago. Early forms of hearing involved simple pressure-sensitive cells that could detect vibrations in water. As amphibians moved onto land, rudimentary hearing evolved into processing airborne sound. This transition further drove the need for enhanced brain capacity to process increasingly complex sensory information.

Acanthostega (circa 365 Mya): Hearing, a critical evolutionary advancement, underwent significant changes as vertebrates transitioned from aquatic to terrestrial environments. While the earliest forms of hearing evolved in water, allowing organisms to detect vibrations through their bodies, the move onto land posed new challenges and opportunities for auditory systems. Acanthostega, an early amphibian, exemplifies this transition. This period marks a crucial phase in the development of auditory systems capable of detecting a broader range of sounds, setting the stage for the complex hearing abilities observed in later terrestrial vertebrates.

Reptile Amniotic Eggs
Corn snake hatching, Pantherophis guttatus guttatus, also know as red rat snake
318 Million BCE

After about 320 million years, the next significant leap in egg evolution came with reptiles, which developed amniotic eggs. These eggs have a protective shell and specialized membranes to support development outside of water, enabling reptiles to lay eggs in terrestrial environments.

Early Complex Sentience Emerges: Dimetrodon
Early Complex Sentience Emerges: Dimetrodon
295 Million BCE
Complex Brains; Long-Term Memory; Early Complex Sentience.

Both reptiles and our ancestor synapsids evolved from amphibians. While reptiles evolved better amniotic eggs, synapsid eggs were like amphibian eggs. Synapsid’s birthing process eventually led to mammalian live births. These are the animals that evolved Complex Sentience, the ability to feel various emotions. While it is unknown when this complex spectrum fully evolved, it is defined as the ability to suffer and feel the dichotomy of pleasure and pain. Dimetrodon is an example of a meat eater, which if any of our ancestors were meat eaters. Although not a While dimetrodons were not direct ancestor of mammals, our mammalian ancestors might have been similar to our direct-line ancestors around this time. 

Class: Synapsids (pre-mammal, not a dinosaur, not pre-dinosaur)
Time Period
: Late Triassic to Early Jurassic; 295-272 Mya; Diet: Carnivore

Plate Tectonics
Plate Tectonics
Circa 260 Million BCE

By dating rocks and fossils scientists can document the movement of the continents over time. 

To confirm and refine this science, geologists study rocks, paleontologists study fossils, and anthropologists study human societies, cultures, and relics. The location and dating of rocks, fossils, and relics allow us to understand the distant past.

  • Cynognathus, circa 242 million BCE
  • Lystrosaurus, circa 250 million BCE
  • Glossopteris, circa 275 million BCE
  • Mesosaurus, circa 285 million BCE
Pangaea Super Continent Breakup
Pangaea Super Continent Breakup
250 Million BCE to 1 CE

Animation of the break-up of the supercontinent Pangaea and the subsequent drift of its constituents, from the Early Triassic to recent (250 Million BCE to 1 CE). The super continent Pangaea existed from about 335 to 175 Million BCE.

 

Morganucodon: An Early Mammalian Herbivore
Morganucodon: An Early Mammalian Herbivore
205 Million BCE
around 205-200 million years ago

Class: Mammaliaforms or maybe Synapsida 
Time Period
: Late Triassic to Early Jurassic
Diet: Likely Herbivore

Morganucodon is an example of a plant eater likely similar to our direct-line ancestors around this time. It is not a direct human ancestor but is among the early mammaliaforms, close to the lineage leading to true mammals. It likely had a varied diet, but its inclusion here highlights the transition towards more specialized mammalian diets from the broader reptilian ones.

Mammals: First Live Births
Mammals: First Live Births
185 Million BCE

An example of early live birth is the protomammal Kayentatherium, Jurassic period. This cynodont is related to early mammals and its clutch size suggested egg-laying, providing clues about the transition to live birth. The switch to live birth in mammals, including marsupials and placentals, likely evolved once at their common ancestor, suggesting live birth in mammals has a deep evolutionary history.

 

Complex Sentience Settles: Eomaia scansoria
Complex Sentience Settles: Eomaia scansoria
circa 125 Million BCE
Complex Brains; Long-Term Memory; Complex Sentience; Likely Proto Self-aware.

The rise of Eomaia scansoria, an early placental mammal, marks a definitive leap towards “Complex Sentience” in the evolutionary saga leading to humans. Unearthed from the Early Cretaceous period, Eomaia’s sophisticated array of mammalian features heralds the advent of deeply emotional and social behaviors. Possessing a brain and nervous system capable of supporting complex emotions, Eomaia represents a lineage increasingly equipped for the nuanced experiences of joy, suffering, pleasure, and pain. This small, shrew-like creature’s life history likely involved care for its young, suggesting the presence of emotional bonds and a capacity for emotional experiences that go beyond mere survival instincts. As one of the earliest examples in the mammalian lineage, Eomaia embodies the evolutionary moment when our ancestors began to navigate the world not just physically but emotionally, setting the stage for the rich tapestry of sentient experiences that characterize human life and our closest animal relatives today.

Likely Proto Self-aware: It’s plausible that it possessed a foundational level of self-awareness, or what can be termed as Proto Self-awareness. This rudimentary sense of self would not meet the criteria for self-recognition observed in modern species but likely included basic self-directed behaviors and an emerging sense of individuality advantageous for survival and social interactions. The cognitive capacities of its descendants suggest that the earliest forms of these traits, essential for navigating complex environments and social dynamics, began to develop around this pivotal point in mammalian evolution.

Appendix
Appendix
80 Million BCE

The appendix is a small, finger-shaped pouch attached to the large intestine. It has long been considered a vestigial organ, meaning that it has no function in the human body. However, recent research suggests that the appendix may actually serve as a reservoir for beneficial gut bacteria.

The appendix is an example of a Phenotype Variation — a trait that varies among individuals. In fact, something like 1 in 100,000 people are born without an appendix. The presence or absence of the appendix is one example of a variation in humans. However, the presence or absence of the appendix is not a typical example of phenotype variation, as it is not a continuous range of variation within a population. Nonetheless, it is an interesting variation that our descendants over the next eons will certainly observe.

Purgatorius — Earliest known proto-primate.
© N. Tamura (CC BY-SA)
66 Million BCE
Cretaceous End -- Tertiary Start

Within mammals, only primates have binocular vision, grasping hands, and flat nails–instead of claws. Purgatorius might have had all three earning it the earliest known proto-primate label. It lived in Eastern Montana about 66 million years ago during the very last years of the Cretaceous period. It lived through the K-T extinction event and the extinction of dinosaurs.

Class: Mammal; Early Proto-Primate
Time Period: Late Cretaceous to the early Paleocene
Diet: Likely Frugivorous (fruits) / Insectivorous (insects)

Plesiadapis: First fruit-insect eaters.
Plesiadapis: First fruit-insect eaters.
58 Million BCE
circa 55-58 million years ago

Plesiadapis, a proto-primate, is an example of a fruit-insect eater likely similar to our direct-line ancestors around this time.

Class: Mammal; Early Primate (Plesiadapiformes)
Time Period: Late Paleocene
Diet: Likely Frugivorous/Insectivorous

Opening of the North Atlantic Ocean
Fama Clamosa, CC BY-SA 4.0 , via Wikimedia Commons
56 Million BCE

North America splits from Europe causing diverging evolutionary lines. Over millions of years, the modern-day Europe (Eurasian plate) and North America (North American Plate) separated during the final breakup of Pangaea in the early Cenozoic Era. This split is a later part of that breakup and created the North Atlantic Ocean.

Early Self-Awareness: Miacis
Early Self-Awareness: Miacis
50 Million BCE

Emerging in the lush forests of the Eocene, Miacis signifies a pivotal moment in the evolution of cognitive abilities among mammals. As a basal member of the Carnivora, this small, tree-dwelling creature exhibited behaviors and social dynamics suggesting the early stages of self-awareness. Though not akin to the self-recognition seen in humans or other highly intelligent animals, the life of Miacis and its interactions with its environment and conspecifics likely involved a level of awareness and individual recognition. These early forms of cognitive complexity mark the beginning of the path toward the rich inner lives characterized by self-awareness in later mammals.

Early Intelligence Emerges: Aegyptopithecus zeuxis
Early Intelligence Emerges: Aegyptopithecus zeuxis
30 Million BCE
Complex Brains; Long-Term Memory; Complex Sentience; Semi Self-awareness settles in.

True Primate: Within mammals, only primates have binocular vision, grasping hands, and flat nails–instead of claws.

Intelligent: Within the dense forests of the Oligocene epoch, Aegyptopithecus zeuxis marked a significant advance in the evolution of intelligence among primates. As an early forerunner to both the great apes and humans, Aegyptopithecus possessed adaptations crucial for enhanced cognitive function, such as a larger brain relative to its body size and eyes positioned for depth perception. These physical traits supported the development of behaviors requiring problem-solving, learning, and adaptation—hallmarks of emerging intelligence. The social life of Aegyptopithecus, inferred from its anatomy and fossil context, likely involved complex interactions and the use of rudimentary tools, setting the stage for the exponential growth in intelligence that characterizes later primates, including humans.

Self-Awareness Settles: Proconsul
Self-Awareness Settles: Proconsul
18 Million BCE
Complex Brains; Long-Term Memory; Complex Sentience; Maybe Self-aware; Likely Simple EI.

Early Primate; Early Ape (hominoid): Proconsul, an inhabitant of the Miocene forests, stands as a landmark in the evolutionary journey toward self-awareness. This early ape lacked a tail and exhibited a mixture of arboreal and terrestrial traits, providing clues to the social and environmental challenges that likely spurred cognitive advancements. While direct evidence of self-awareness in Proconsul is beyond our reach, its position in the ape lineage suggests the development of social structures and cognitive abilities that predate the sophisticated self-awareness observed in modern great apes, elephants, and dolphins. Proconsul’s world was one of increasing cognitive complexity, setting the stage for the emergence of true self-aware beings, capable of recognizing themselves as distinct entities within their social and natural environments.

Early Emotional Intelligence Emerges: Orangutans Branch Off
Orangutan standing
circa 12 Million BCE
Complex Brains; Long-Term Memory; Complex Sentience; Self-aware; Complex EI.
480,000 Generations Ago

Ancestral Hominids (us, pre-split): The evolutionary journey of the great apes witnessed a significant branching around 12 to 16 million years ago, when the ancestors of modern orangutans diverged from the common lineage shared with other great apes, including humans. This divergence marked the emergence of a distinct evolutionary path leading to the orangutans of today, known for their remarkable intelligence and the striking reddish hair that sets them apart from their African cousins. Inhabiting the rainforests of Borneo and Sumatra, orangutans became the masters of arboreal life, showcasing a suite of adaptations to a life spent mostly in trees. This pivotal moment in great ape evolution underscores the deep and diverse evolutionary heritage shared among all great apes, including humans.

In the dense rainforests where orangutans reside, a subtle yet profound evolution unfolds, revealing the roots of emotional intelligence among great apes. Orangutans, with their solitary but socially intricate lives, exemplify early forms of emotional intelligence that resonate through the primate lineage. Their nuanced social interactions, empathetic behaviors, and problem-solving capabilities underscore a deep-seated capacity to understand and navigate the emotional landscapes of their lives. This early emergence of emotional intelligence in orangutans represents a crucial evolutionary step, shedding light on the social and cognitive complexities that would be further refined in the human lineage. By studying orangutans, we gain insights into the evolutionary pressures that shaped the emotional intelligence of primates, providing a window into the past that helps us understand the cognitive and emotional bonds we share with our closest living relatives.

Complex EI Emerges: Orangutans fall into the Complex EI category. They exhibit a broad spectrum of emotionally intelligent behaviors, including empathy, where they show concern for the welfare of others; the use of emotional cues to communicate and navigate complex social landscapes; self-control and mood management; and problem-solving that incorporates emotional states. Their ability to engage in morally influenced behaviors, such as sharing based on social bonds or altering their behavior to maintain social harmony, underscores their capacity for complex emotional intelligence. Orangutans’ nuanced social interactions, care for their young, and responses to environmental and social challenges demonstrate a sophisticated understanding and management of emotions that align with the hallmarks of complex EI.

Gorillas Branch Off
Gorillas Branch Off
8 Million BCE
Ancestral Hominids (us, pre-split)
320,000 Generations Ago

Following the divergence of the orangutans, the gorilla lineage branched off from the rest of the great ape family around 8 to 9 million years ago. This split led to the evolution of the largest of the living apes, the gorillas. They exhibit a fascinating social structure and exhibit impressive displays of strength, yet are known for their gentle nature. The divergence of gorillas from the common ancestor they shared with humans, chimpanzees, and bonobos further highlights the rich tapestry of evolution that has given rise to the variety of great ape species seen today.

Location: Emerged in Western or Central Africa; spread to Eastern Africa and no further.
Size: Up to 5’8″ and 550 pounds (Eastern Lowland Gorillas)

Emergence of the Chimpanzee Family
Bonobo chimpanzees in the wilderness in Democratic Republic of the Congo
2 Million BCE
Hominids, Not Us (different branch)

Around 1.5 to 2 million years ago, the evolutionary branches of ancient primates led to the distinct emergence of what we now recognize as the chimpanzee family, under the genus “Pan.” This pivotal event in primate evolution unfolded approximately 5 million years after our last common ancestor with chimpanzees and bonobos took separate paths. As with many significant chapters in the story of primates, this one too unfolded on the diverse and vibrant stage of Africa, a continent that has been the cradle for the unfolding drama of human and primate evolution alike. This era marks not just the divergence of chimpanzees and bonobos but a defining moment in the rich tapestry of hominid history.

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