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Just in case you were wondering, humans are also subject to the forces of evolution and natural selection. Although we have somewhat removed ourselves from the more obvious selection pressures of nature that our ancestors, as outlined below, had to deal with, we are still no doubt evolving. Even though the “fittest” are not selected by saber-tooth tigers anymore, there are still pressures from sexual selection, environmental determinants, etc.

Wondering what evidence we have for human evolution? Wondering what age they are, what describes the fossils, where they were found, what are the proverbial “missing links”? Don’t worry baby birds, I’ll feed you…

Human Evolution Timeline: Pre-Australopithecine

Sahelanthropus tchadensis age: 6 – 7 mya
fossils found: nearly complete cranium, some fragments lower jaw & teeth
brain size: 350 cc
adaptations: ape-like, including small brain size, hominid features: brow ridges, small canine teeth
location found: Chad, Central Africa
notes: close to common ancestor of chimpanzees and humans in the human evolution timeline; unlikely to be bipedal
Orrorin Tugenensis age: c. 6 mya
brain size: no cranium found
fossils found: 13 fossils; partial femur, bits of jaw and teeth
adaptations: unknown
location found: Kenya, Africa
notes: some indications of bipedality, but evidence is scant
Ardipithecus ramidus age: 5.8 – 4.4 mya
brain size: approx. 400 cc (chimp-size)
fossils found: 110 specimens, almost complete skeleton
adaptations: canine teeth intermediate between earlier apes & A. afarensis
location found: Ethiopia
notes: bipedal forest dweller(!), Canines smaller, not pointed
Ardipithecus kadabba age: 5.8 – 5.2 mya
brain size: no evidence
fossils found: fragments, mostly teeth
adaptations: smaller canines than apes (a feature of hominids)
location found: Ethiopia
notes:

Human Evolution Timeline: Genus Australopithecus

Lucy herself

Australopithecus anamensis age: 4.2 – 3.9 mya
brain size: unknown
fossils found: tibia, lower jawbone
adaptations: very likely bipedal, thick enamel on teeth (hominid characteristic)
location found: Kenya, Africa
notes: tibia shape indicates bipedalism
Australopithecus afarensis age: 3.9 – 2.9 mya
brain size: 375 – 500 cc (large male–female size difference)
fossils found: hundreds of fossils, fourteen partial skeletons, and footprints(!)
adaptations: certainly bipedal, chimp-like skull, flat nose, no chin w/ human-like teeth, jaw between ape & human
location found: Ethiopia, Tanzania, Cameroon
notes: This is Lucy’s species; she’s an original, important “missing link.”
Kenyanthropus platyops age: 3.5 – 3.3 mya
brain size: unknown
fossils found: two partial skulls
adaptations: small ear canals, small teeth like Homo rudolfensis (branch of Homo habilis)
location found: Lake Turkana, Kenya, Africa
notes: scientists disagree whether these skulls deserve their own species
Australopithecus africanus age: 3 – 2 mya
brain size: 420 – 500 cc
fossils found: partial skull, cranium, body & pelvis
adaptations: fully human-shaped jaw, canine teeth reduced from afarensis, human-like pelvis
location found: South Africa
notes: everything seems clearly adapted from afarensis
Australopithecus garhi age: 2.5 mya
brain size: ?
fossils found: partial skull
adaptations: ?
location found: Ethiopia
notes: some evidence for tool use, otherwise not much known
Australopithecus aethiopicus age: 2.6 – 2.3 mya
brain size: 410 cc
fossils found: “The Black Skull” and some minor fossils
adaptations: baffling; small brain, massive face & very strong jaw
location found:Ethiopia, Kenya
notes: some say this is perfect intermediate between afarensis and boisei, limited information
Australopithecus robustus age: 2 – 1.5 mya
brain size: 530 cc
fossils found: many, mostly cranial and dental
adaptations: body like africanus, but larger skull, molars, and massive face & brow ridge, small canines
location found: South Africa
notes: bones found w/ robustus fossils may have been tools, this line of hominids had strong jaws and huge molars for crunching rough food, then probably went extinct (no descendants in southern Africa)
Australopithecus sediba age: 1.95 – 1.8 mya
brain size: 420 cc
fossils found: two partial skeletons, most of cranium in juvenile
adaptations: more Homo adaptations than any other Australopithecine, pelvis is particularly advanced for bipedality so that it may have been capable of running, and brain case is shaped more towards human
location found: South Africa
notes: New discovery, described in April, 2010; pelvis and leg indicate it’s bipedal; more recent than many Homo fossils, thus unlikely to be human ancestor; probable adult height 4’6″ for male, 4’2″ for female
Australopithecus boisei age: 2.1 – 1.1 mya
brain size: 530 cc
fossils found: many, mostly cranial and dental
adaptations: may just be robustus
location found: Tanzania, Kenya, & Ethiopia, Africa
notes: used to be Zinjanthropus; an unlikely human ancestor, probably went extinct due to over-specialization with its huge molars and small canines; some make them Paranthropus boisei

Human Evolution Timeline: Genus Homo

Homo gautengensis age: 2 million to 600,000 years ago
brain size: awaiting publication
fossils found: partial skull, several jaws, teeth and other bones
adaptations: bipedalism, further information awaiting publication
location found: Sterkfontein Caves, South Africa
notes: Very stocky! 3 foot tall and 110 pounds; bipedal tree dweller
Homo habilis age: 2.4 – 1.5 mya
brain size: 500 – 800 cc
fossils found: many
adaptations: primitive face, smaller teeth than australopithecines, human-shaped brain, had “Broca’s area,” a section of brain we currently use for speech
location found: Kenya & Tanzania, Africa
notes: named habilis for tools found with fossils, may need to be more than one species, Homo rudolfensis is suggested in addition
Homo georgicus age: 1.8 mya
brain size: 600 – 780 cc
fossils found: thirty or so partial skulls & a partial skeleton
adaptations: intermediate between habilis and erectus
location found: Dminisi, Georgia (eastern Europe)
notes: First hominids out of Africa, a huge surprise because they didn’t have the brains or tools of Homo erectus
Homo floresiensis age: 1.1 mya to 17,000 years ago (possibly 2 mya!)
brain size: 420 cc
fossils found: several almost full skeletons
adaptations: dwarf hominim found on island; large feet, ape-like hands, small brain, similar features to H. habilis
location found: Flores, Indonesia
notes: dwarves of species commonly develop on islands, these were 3 feet tall; hunted dwarf elephants and large rats; new research on relative brain size suggests they descended from H. georgicus or habilis rather than erectus
Homo erectus age: 1.8 million – 300,000 years ago
brain size: 750 – 1225 cc
fossils found: lots and lots
adaptations: jaw still protrudes, no chin, thick brow ridges, small forehead, but larger brains and excellent walkers
location found: Africa, Europe, Asia
notes: probably used fire, brains got larger over time
Homo ergaster age: same as erectus
brain size: slightly smaller than erectus
fossils found: these would be the African erectus fossils reclassified
adaptations: taller & thinner & different-shaped brow ridges than European & Asian erectus fossils
location found: Africa
notes: some scientists make the African erectus fossils to be Homo ergaster
Homo antecessor age: 780,000 years ago
brain size: 1000 cc
fossils found: six individuals
adaptations: mid-facial area modern, other parts primitive
location found: Spain
notes: oldest European hominids, may just be erectus or early heidelbergensis
Homo sapiens
or
Homo heidelbergensis
age: 500,000 years ago
brain size: 1200 cc
fossils found: many skulls
adaptations: intermediate between erectus and human in thickness of bones & size of teeth, receding foreheads and chins
location found: Europe
notes: some scientists consider these the European version of Homo erectus; later ones are difficult to distinguish from early Homo sapiens; sometimes heidelbergensis is called Homo sapiens (archaic) in contrast to modern humans who are Homo sapiens sapiens
Homo neanderthalensis age: 230,000 – 30,000 years ago
brain size: 1450 cc
fossils found: lots and lots
adaptations: midfacial area protrudes, long low brain case, thick & strong, near our height; many adaptations seem like adaptations for cold
location found: Europe & Middle East
notes: first hominids to bury dead, lots of tools & weapons, lived brutal lives; brain was larger than ours!
Cro-Magnon
(Homo sapiens)s
age: 50,000 – 10,000 years ago
brain size: 1350 cc
fossils found: many
adaptations: These are now classified as anatomically-modern humans
location found: Europe
notes: Our ancestors in Europe were thicker in tooth and bone than we are
Homo sapiens age: 195,000 years ago – 2009
brain size: 1350 cc
fossils found: living samples available in large quantities
adaptations: forehead rises sharply, small or non-existent brow ridges, prominent chin, thin skeleton
location found: everywhere
notes: tooth and face bone size is still decreasing over the last 20,000 years of the human evolutionary timeline!
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