Last updated: February 2, 2026
The fossil evidence for human evolution.
Age: 7-6 million years | Location: Chad
Nearly complete cranium, possibly the earliest known hominin. Shows reduced canines, more forward-positioned foramen magnum (suggesting bipedalism), and mosaic of ape/human traits. Brain size ~350cc.
Age: 6 million years | Location: Kenya
Known from teeth and postcranial fragments. Femur morphology suggests bipedalism. Found in Tugen Hills, Kenya.
Age: 5.8-5.2 million years | Location: Ethiopia
Known from teeth and partial skeleton fragments. Toe bone suggests bipedal adaptations. Older species than A. ramidus. Brain size estimated ~350cc.
Age: 4.4 million years | Location: Ethiopia
45% complete skeleton with unique mix of ape (divergent toe) and human (pelvis adapted for upright walking) traits. Brain size ~350cc.
Age: 4.2-3.9 million years | Location: Kenya
Likely ancestor to A. afarensis. Tibia shows weight-bearing adaptations for bipedalism. Brain size ~370cc.
Age: 3.9-2.9 million years (Lucy: 3.2) | Location: Ethiopia, Tanzania, Kenya
Fully bipedal (Laetoli footprints) with ape-like proportions and tree-climbing adaptations. Brain size 380-430cc.
Age: 3.5-3.2 million years | Location: Kenya
Flat-faced hominin. Possible separate lineage from Australopithecus. Brain size ~400cc.
Age: 3.3-2.1 million years (Taung: ~2.8) | Location: South Africa
First australopithecine discovered (1924). More human-like face than A. afarensis. Brain size 420-500cc.
Age: 2.7-2.3 million years | Location: Kenya, Ethiopia
Robust skull with large sagittal crest for chewing muscles. "Black Skull" KNM-WT 17000. Brain size ~410cc.
Age: 2.5 million years | Location: Ethiopia
Associated with earliest known stone tools (Oldowan). Possible Homo ancestor. Brain size ~450cc.
Age: 2.4-1.5 million years | Location: East and South Africa
First species in our genus. Associated with Oldowan stone tools. Brain size 500-650cc.
Age: 2.3-1.2 million years | Location: East Africa
Massive molars and jaw muscles for tough plant foods. Brain size 500-550cc.
Age: 2.0-1.2 million years | Location: South Africa
South African robust australopithecine, specialized for heavy chewing. Brain size ~530cc.
Age: 2.0-1.8 million years | Location: South Africa
Mosaic of australopith and Homo features. Possible transitional species. Brain size 420-450cc.
Age: ~1.9 million years | Location: Kenya
Well-preserved cranium with larger brain capacity (~750cc) but primitive face. Discovered at Koobi Fora.
Age: ~1.8 million years | Location: Georgia
Earliest definitive evidence of hominins outside Africa. Shows remarkable variation within a single population. Brain size ~550-780cc.
Age: ~1.6 million years | Location: Kenya
Nearly complete skeleton of a juvenile. Body plan very similar to modern humans but with smaller brain (~880cc projected adult). Considered African variant of H. erectus.
Age: 1.2-0.8 million years | Location: Spain
Earliest known European hominin (Gran Dolina fossils). Brain size ~1000cc.
Age: 600k-130k years | Location: Europe, Africa, Asia?
Potential ancestor to both Neanderthals and modern humans. Brain size 1100-1400cc.
Age: ~400k-50k years | Location: Siberia, Tibet?
Known primarily from DNA (finger bone, teeth, mandible). Revealed previously unknown hominin species that interbred with modern humans.
Age: 335k-236k years | Location: South Africa
Over 1,500 specimens from Rising Star cave. Small brain (465-560cc) with human-like hands/wrists. Interpreted by some researchers as evidence of deliberate body placement.
Age: ~315k years | Location: Morocco
Earliest known H. sapiens fossils. Modern-looking face and teeth with a more elongated braincase. Suggests the origin of our species is earlier than previously estimated.
Age: 100k-50k years | Location: Indonesia
Adult female only ~3.5 ft tall. Brain size 380cc. Island-dwelling species that made sophisticated tools despite small brain.
Age: 70k-45k years | Location: Iraq
Neanderthal skeleton showing healed injuries, suggesting care from others. Part of multiple burials in Shanidar Cave, some with possible flower offerings. Brain size 1200-1750cc.
Age: ~134k years | Location: Philippines
Discovered in Callao Cave, Luzon. Mix of primitive (curved phalanges for climbing) and derived features. Initial dates of ~67,000 years were revised upward by improved uranium-series dating methods.
Age: ~60k years | Location: France
Well-preserved "Old Man" skeleton. Distinctive robust features, large brain case, evidence of deliberate burial.
Age: ~30k years | Location: France
One of the first early modern human fossils discovered (1868). Fully modern anatomy. Associated with advanced Upper Paleolithic tools.
Adaptations for upright walking appear earliest, with evidence in Sahelanthropus (7 mya, foramen magnum position), Orrorin (6 mya, femoral neck), and Ardipithecus (4.4 mya, pelvis). The Laetoli footprints (3.6 mya, Tanzania) provide evidence of bipedal walking in Australopithecus. Bipedalism appears before significant brain expansion, with early hominins showing chimp-sized brains but upright posture.
Gradual increase in cranial capacity: Early hominins (350-400cc), Australopithecines (400-550cc), Homo habilis (500-650cc), Homo rudolfensis (700-750cc), Homo ergaster/erectus (700-1100cc), Homo heidelbergensis (1100-1400cc), Neanderthals (1200-1750cc), Homo sapiens (1000-1700cc). Brain size increased approximately three-fold over 7 million years.
Reduction in tooth size and jaw robusticity over time. Canine reduction and molar shape changes are earliest hominin traits. Australopithecus still had relatively large molars; gradual reduction through Homo. Dental formula remained consistent (2:1:2:3) while tooth morphology changed. Paranthropus species show specialized megadont dentition for tough plant foods.
Progressive changes include: reduced prognathism (facial projection), decreased postorbital constriction, reduced supraorbital torus (brow ridge), increased cranial globularity, development of chin (unique to H. sapiens), and reduced cranial thickness. Early Homo species show mosaic of primitive and derived traits.
Changes include: shortened arms relative to legs, curved lumbar spine, bowl-shaped pelvis, angled femur, arched feet, and non-opposable big toe. Homo ergaster/erectus (1.8 mya) shows first fully modern body proportions. Neanderthals developed cold-adapted features: barrel chest, shortened distal limbs, robust build.
The following tables present measurable anatomical data across hominin species, demonstrating evolutionary trends over millions of years.
Brain volume increased approximately three-fold from early hominins to modern humans. Data from peer-reviewed sources including Nature Communications and F1000Research.
| Species | Time (Ma) | Brain Size (cc) | Mean (cc) |
|---|---|---|---|
| Sahelanthropus tchadensis | 7-6 | 360-380 | ~378 |
| Ardipithecus ramidus | 4.4 | 300-350 | ~325 |
| Australopithecus anamensis | 4.2-3.8 | 365-370 | ~370 |
| Australopithecus afarensis | 3.9-2.9 | 365-550 | ~446 |
| Australopithecus africanus | 3.3-2.1 | 402-515 | ~458 |
| Australopithecus garhi | 2.5 | 446-450 | ~450 |
| Australopithecus sediba | 2.0 | 420-450 | ~440 |
| Paranthropus aethiopicus | 2.7-2.3 | ~410 | ~410 |
| Paranthropus boisei | 2.4-1.2 | 444-545 | ~488 |
| Paranthropus robustus | 2.0-1.2 | 476-530 | ~530 |
| Homo habilis | 2.4-1.4 | 510-687 | ~612 |
| Homo rudolfensis | 2.1-1.8 | 700-775 | ~750 |
| Homo erectus (early) | 1.9-1.0 | 600-900 | ~850 |
| Homo erectus (late) | 1.0-0.1 | 900-1,225 | ~1,050 |
| Homo antecessor | 1.2-0.8 | 1,000-1,150 | ~1,000 |
| Homo heidelbergensis | 0.7-0.2 | 1,165-1,325 | ~1,250 |
| Homo naledi | 0.34-0.24 | 465-610 | ~513 |
| Homo floresiensis | 0.1-0.05 | 380-426 | ~426 |
| Homo neanderthalensis | 0.4-0.04 | 1,172-1,740 | ~1,450 |
| Homo sapiens (archaic) | 0.3-0.1 | 1,100-1,467 | ~1,350 |
| Homo sapiens (modern) | 0.1-present | 1,000-1,700 | ~1,350 |
Body height shows significant increase with the emergence of genus Homo. Data from Royal Society Open Science and Journal of Human Evolution.
| Species | Time (Ma) | Height Range (cm) | Key Specimen |
|---|---|---|---|
| Ardipithecus ramidus | 4.4 | 117-124 | Ardi: 120 cm |
| Australopithecus afarensis | 3.9-2.9 | 104-152 | Lucy: 105 cm; Kadanuumuu: 152 cm |
| Australopithecus africanus | 3.3-2.1 | 114-140 | Males: 140 cm; Females: 114 cm |
| Australopithecus sediba | 2.0 | 126-156 | MH1 projected adult: ~150 cm |
| Paranthropus boisei | 2.4-1.2 | 124-137 | Males: 137 cm; Females: 124 cm |
| Paranthropus robustus | 2.0-1.2 | 110-132 | Males: 132 cm; Females: 110 cm |
| Homo habilis | 2.4-1.4 | 100-135 | OH 62: ~100-120 cm (debated) |
| Homo erectus/ergaster | 1.9-0.1 | 145-185 | Turkana Boy: 160 cm at death |
| Homo heidelbergensis | 0.7-0.2 | 157-175 | Males: 175 cm; Females: 157 cm |
| Homo naledi | 0.34-0.24 | 140-150 | Average: ~144 cm |
| Homo floresiensis | 0.1-0.05 | 105-110 | LB1: 106 cm |
| Homo neanderthalensis | 0.4-0.04 | 152-169 | Males: 165 cm; Females: 155 cm |
| Homo sapiens (early) | 0.1 | 170-183 | Skhul/Qafzeh avg: 177 cm |
The encephalization quotient (EQ) measures brain size relative to expected body size. Modern humans have an EQ approximately double that of early hominins.
| Species | EQ | Interpretation |
|---|---|---|
| Chimpanzee | 2.2-2.5 | Baseline great ape |
| Australopithecus afarensis | ~3.1 | 25% above chimp |
| Australopithecus africanus | ~3.4 | 36% above chimp |
| Homo habilis | ~4.0 | 60% above chimp |
| Homo erectus | 4.0-5.5 | Variable, increasing over time |
| Homo heidelbergensis | ~5.3 | Near-modern |
| Homo neanderthalensis | ~5.5 | Comparable to humans |
| Homo sapiens | 6.0-7.6 | Highest of any species |
The intermembral index measures arm length relative to leg length. Lower values indicate longer legs, an adaptation to bipedal walking. Formula: (humerus + radius) / (femur + tibia) × 100.
| Species | Index | Interpretation |
|---|---|---|
| Chimpanzee | ~106 | Long arms for climbing |
| Gorilla | ~117 | Long arms for knuckle-walking |
| Australopithecus afarensis (Lucy) | ~88 | Intermediate: bipedal with climbing ability |
| Homo erectus | ~72 | Near-modern proportions |
| Homo sapiens | 68-72 | Fully adapted to bipedalism |
Multiple independent dating methods are used to estimate the age of human fossils:
Archaeological evidence shows gradual development of human behaviors:
The human fossil record presents hominin diversity over millions of years. From hundreds of specimens found across four continents, scientists interpret a progression of anatomical forms with transitional features.
The fossil record indicates that modern human traits appear at different times in the record: bipedalism first (7-4 million years ago), followed by tool use (2.6 million years ago), brain expansion (starting ~2 million years ago), and modern anatomy and behavior (300,000-100,000 years ago).
This evidence is used to interpret human evolutionary history and the relationship of humans to other primates.