The Human Evolutionary Series

Appearance Taxa Relationships Status Description Image

36–32 Ma Genus Apidium The oldest primitive monkey known in the fossil record, dating back before the split between Old and New World monkeys. Basal to both Old and New World monkeys. Primitive traits Smaller canines than later monkeys such as Parapithecus

Retains some post-cranial characters seen in prosimians Derived traits Fused mandibular symphysis

Scapula similar to modern squirrel monkeys

Low rounded molar cusps rather than high cusps as is seen in tarsiers and strepsirrhine

33 Ma Genus Aegyptopithecus A Miocene monkey which bridges the gap between the Eocene ancestors of Old World monkeys and Miocene ancestor of Hominoidea. Tentatively positioned transitional form prior to the Old World monkey/ape split. Primitive traits Retained auditory features similar to Old World monkeys

Incapable of true brachiation unlike extant apes

Reduced capitular tail, but was proportionally smaller than Apidium Derived traits Ape-like teeth including broad, flat incisors and sexually dimorphic canines

A low sagittal keel and strong temporalis muscles

Increased size in the visual cortex

27–14 Ma Genus Proconsul This primate exhibits very ape-like features like its teeth, but much of its post-cranial remains are more similar to monkeys. Universally accepted to be intermediate between 'ape-like monkeys' such as Aegyptopithecus and later apes including hominids. Primitive traits Monkey-like wrist

Narrow, monkey-like illium Derived traits Completely lacked a fully formed tail

5-Y pattern on lower molar cusps as also seen in hominoids

13 Ma Genus: Pierolapithecus A European ape which is considered to be the predecessor of the great apes. Some objections have been raised to this fossils status due to its location in Spain, but Pierolapithecus is likely a transitional taxon between generalized apes and the lineage which led to great apes. Pleisomorphic traits Relatively short fingers and walked in a similar quadrupedal fashion like baboons

Lacks adaptations for both gibbon-style brachiation as well as derived knuckle-walking like in chimpanzees and gorillas Derived traits Flat, wider rib cage like great apes for tree-climbing

The clavicle is large and similar to modern chimps suggesting a dorsally positioned scapula

4.4 Ma Genus: Ardipithecus A woodland hominid adapted to quadruped arboreal locomotion, but also for bipedalism. Intermediate between the last common ancestor of chimps and humans, and the australopithecines. Primitive traits Brains smaller than later hominids ranging from about 300-350 cc

Foot thumb is not retracted into the foot as a 'big toe'

Phalanges are more heavily curved than in Australopithecus Derived traits Reduced size in canines, however still retained dimorphic characters

Hind leg dominant, bipedal locomotion while walking, however were quadrupedal while climbing trees

4.4–2.0 Ma Genus: Australopithecus First known genus of fully bipedal apes which are probably ancestral to robust australopiths and the genus Homo. Intermediate between extinct quadrupedal and bipedal apes. While the relationship between some species are being revised, Australopithecus afarensis is considered to be, by most experts, the ancestor to all later hominids. Primitive traits Some species retain a sagittal crest

Curved phalanges, indicating semi-arboreal lifestyle

Semisectorial premolar is present

Prognathic face to varying degrees Derived traits Fully bipedal as indicated by many features including the knee joint, hips, lumbar curve in the spine, position of the foramen magnum, and feet

Increase in brain size ranging from about 375-500 cc

Development of a parabolic jaw

2.3–1.4 Ma Species: Homo habilis An early human which is the morphological link between australopithecines and later human species. Perfect intermediate between early hominids and later humans, possibly ancestral to modern humans. Primitive traits Pronounced brow ridge

Foramen magnum is not positioned as anteriorly like in modern humans, giving a slightly semi-erect appearance

Although reduced in size the teeth are still fairly large Derived traits Increase brain size ranging from 510-800 cc

Face is slightly prognathic, but at a much steeper angle

Bulge in the Broca area, possibly the first hominid to use rudimentary speech

Associated with the first use of stone tools

2.0–1.0 Ma Species: Homo erectus Very successful hominid, which was probably ancestral to both modern humans and neanderthals. Probably the first hominid to leave and successfully colonize territories outside of Africa. Ancestral to modern humans and neanderthals. Primitive traits Still retains a heavy brow ridge and nuchal torus

Lacked the complexity of modern human language, but does show increase in the Broca area

Thicker bones and larger teeth than modern humans Derived traits Rounder and larger brain (about 900–1,100 cc) than H. habilis

Face is orthognathic compared to H. habilis

Probably lived in bands and was an active group hunter

Associated with advanced stone tools and possibly the first hominid to use and produce fire