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Alien From Earth

Who's Who in Human Evolution

Despite a fragmentary fossil record augmented by rare, sometimes surprising new finds like Homo floresiensis, paleoanthropologists have assembled a very solid general picture of human evolution. In this clickable illustration, follow the trajectory of hominin development as it is currently known. As the illustration makes clear, scientists have traced hominins—that is, species more closely related to humans than to other apes—all the way back through the australopithecines, like the three million-year-old Lucy, to Sahelanthropus tchadensis, who lived over six million years ago. The key feature that all these hominins share is bipedalism, which separates hominins from the primate line that eventually produced today's chimpanzees and other great apes.—Peter Tyson

Who's Who in Human Evolution


Sahelanthropus tchadensis  

Sahelanthropus tchadensis

CHIEF SPECIMENS: cranium, jaw fragments, teeth found in western Chad, 2001

WHEN LIVED (est., in years ago): 7.6—6 million

BRAIN SIZE (est., in cu cm): 360-370 (slightly smaller than a male chimp's)

SPECIAL FEATURES: oldest known hominin; set apart from other fossil apes by smaller canines, thicker and larger cheek teeth, and more downwardly oriented foramen magnum (hole where spinal cord exits brain), suggesting upright posture and locomotion

ORIGIN OF NAME: skull nicknamed Toumai, "Hope of Life" in local Goran language



Orrorin tugenensis  

Orrorin tugenensis

CHIEF SPECIMENS: arm and leg bones and teeth found in northern Kenya, 2000

WHEN LIVED (est., in years ago): 6.1—5.8 million

BRAIN SIZE (est., in cu cm): unknown (no skulls or even skull fragments found so far)

SPECIAL FEATURES: size and shape of femur suggests it may have been bipedal

ORIGIN OF NAME: species name from Kenya's Tugen Hills, where found



Ardipithecus ramidus, Ardipithecus kadabba  

Ardipithecus ramidus, Ardipithecus kadabba

CHIEF SPECIMENS: skull, mandible, teeth, and arm bones of Ar. ramidus found in central Ethiopia, 1992-1993; type specimen (right lower jaw fragment) of a second species, Ar. kadabba, also found in Ethiopia, 1997

WHEN LIVED (est., in years ago): 4.5—4.3 million (ramidus); 5.8—5.2 million (kadabba)

BRAIN SIZE (est., in cu cm): unknown (only skull fragments)

SPECIAL FEATURES: features of leg bones and foramen magnum suggest bipedalism, but more evidence needed

ORIGIN OF NAME: in local Afar language, Ardi means "ground floor," ramidus comes from ramid ("root"), and kadabba means "basal ancestor"; pithecus comes from the Greek for "ape"



Australopithecus anamensis  

Australopithecus anamensis

CHIEF SPECIMENS: first fossil, a lower arm bone, found in Kenya, 1965; other bones, including a piece of ear canal and a jaw joint used as type specimen, also found in Kenya

WHEN LIVED (est., in years ago): 4.1—3.9 million

BRAIN SIZE (est., in cu cm): unknown (insufficient cranial material)

SPECIAL FEATURES: the lower leg bone, including surface for a knee joint, indicates species was bipedal

ORIGIN OF NAME: Australopithecus means "southern ape"; anamensis from word anam ("lake") in Turkana language



Australopithecus afarensis  

Australopithecus afarensis

CHIEF SPECIMENS: adult lower jaw from Laetoli, Tanzania, is type specimen; many other fossils known, including Lucy, a ~40%-complete skeleton found in Ethiopia's Afar region in 1974

WHEN LIVED (est., in years ago): 4—3 million

BRAIN SIZE (est., in cu cm): 446 (avg. of five skulls)

SPECIAL FEATURES: Lucy's shoulder joint is a mixture of ape and human features that suggests it also still spent time in the trees

ORIGIN OF NAME: afarensis honors Ethiopia's Afar region; Lucy nicknamed after Beatles' "Lucy in the Sky With Diamonds," playing in camp when fossil discovered



Australopithecus africanus  

Australopithecus africanus

CHIEF SPECIMENS: Taung Child, ~3.5 years old when died, found in quarry in South Africa, 1924; many other A. africanus fossils also found in South Africa

WHEN LIVED (est., in years ago): 3—2 million

BRAIN SIZE (est., in cu cm): 400-560 (mean = 460)

SPECIAL FEATURES: bipedal, but probably also good at climbing trees; thicker teeth than A. afarensis

ORIGIN OF NAME: binomial name means "southern ape of Africa"



Australopithecus garhi  

Australopithecus garhi

CHIEF SPECIMENS: first fragments (of skull, jaw, and arm) found in 1990, and type specimen (partial skull with upper dentition) found in 1997, both in central Ethiopia

WHEN LIVED (est., in years ago): 2.5 million

BRAIN SIZE (est., in cu cm): 450 (based on one cranium)

SPECIAL FEATURES: limb proportions thought to be more human-like than those of A. afarensis (Lucy)

ORIGIN OF NAME: garhi means "surprise" in local Afar language



Paranthropus aethiopicus  

Paranthropus aethiopicus

CHIEF SPECIMENS: toothless lower jaw (type specimen) and "Black Skull" found in 1967 and 1985, respectively, both in Ethiopia; other fossils known from Kenya

WHEN LIVED (est., in years ago): 2.5—2.3 million

BRAIN SIZE (est., in cu cm): 410 (based on one specimen, the "Black Skull")

SPECIAL FEATURES: skull and teeth adapted for eating very mechanically demanding diet

ORIGIN OF NAME: Para given by namer because he considered Paranthropus a side branch of the human lineage; species named aethiopicus because it was the first fossil hominid found in Ethiopia



Paranthropus robustus  

Paranthropus robustus

CHIEF SPECIMENS: Gert Terblanche, a schoolboy, found first fossils, including a damaged skull and half a jawbone, in 1930s in South Africa, from which all P. robustus fossils are also known

WHEN LIVED (est., in years ago): 2—1 million (deposits have not yielded absolute dates)

BRAIN SIZE (est., in cu cm): 530

SPECIAL FEATURES: generally considered a dead-end side branch of the human family that nevertheless flourished for perhaps 1 million years

ORIGIN OF NAME: robustus refers to its robust teeth and skull, adapted for a tough vegetarian diet



Paranthropus boisei  

Paranthropus boisei

CHIEF SPECIMENS: several complete skulls, including famous "Zinj" skull found by Mary Leakey in Olduvai Gorge, Tanzania, in 1959; fossils also known from Kenya, Ethiopia, and possibly Malawi

WHEN LIVED (est., in years ago): 2.3—1.3 million

BRAIN SIZE (est., in cu cm): 400-550

SPECIAL FEATURES: similar to P. robustus, but with greater development of the big cheek teeth, large chewing muscles, and other masticatory features that set the genus apart from the gracile australopithecine and Homo lineages

ORIGIN OF NAME: boisei honors Charles Boise, who helped cover the Leakeys' expenses during excavation at Olduvai



Homo habilis  

Homo habilis

CHIEF SPECIMENS: first fossil, a lower jaw fragment, found in Olduvai Gorge, Tanzania, in 1959; subsequent fossils found there and in Kenya and Ethiopia

WHEN LIVED (est., in years ago): 1.8—1.4 million

BRAIN SIZE (est., in cu cm): 510-687

SPECIAL FEATURES: considered first definite stone toolmaker, and first species of the genus Homo ("human")

ORIGIN OF NAME: habilis ("able, handy" in Latin) given to emphasize this species' mental capacity and tool-making skills



Homo erectus  

Homo erectus

CHIEF SPECIMENS: braincase unearthed in Java, Indonesia, in 1891 (Java Man); important fossils from other sites on Java and in China, Georgia, and Africa, including the remarkably complete Turkana Boy skeleton found in Kenya in 1984; perhaps also found in Western Europe

WHEN LIVED (est., in years ago): 1.8 million—ca. 50,000

BRAIN SIZE (est., in cu cm): 600-1,200

SPECIAL FEATURES: large brain and oblong braincase, large browridges, small teeth, and relatively vertical face distinguish H. erectusfrom earlier species; also, well-adapted for endurance running

ORIGIN OF NAME: erectus refers to this species' upright posture



Homo floresiensis  

Homo floresiensis

CHIEF SPECIMENS: "Hobbit" skull discovered on island of Flores, Indonesia, in 2003; two jaws and limb bones from perhaps eight more individuals found in same cave in 2004

WHEN LIVED (est., in years ago): 95,000—12,000

BRAIN SIZE (est., in cu cm): 400

SPECIAL FEATURES: one-third the size of contemporaneous H. erectus and H. sapiens, and had smallest brain size ever found in a tool-using hominin; its status remains controversial—it has been claimed, for instance, to represent a pathologically diseased population

ORIGIN OF NAME: floresiensis honors Flores, the island where the species was found



Homo heidelbergensis  

Homo heidelbergensis

CHIEF SPECIMENS: type specimen is a lower jaw found in 1907 in Germany; later fossils found elsewhere in Africa and Europe

WHEN LIVED (est., in years ago): 500,000—200,000

BRAIN SIZE (est., in cu cm): 1,274 (mean for 10 individuals)

SPECIAL FEATURES: big-brained, big-bodied, sophisticated hunter; probable ancestor of Neanderthals and modern humans

ORIGIN OF NAME: heidelbergensis honors Heidelberg, the German university town near where type specimen found



Homo neanderthalensis  

Homo neanderthalensis

CHIEF SPECIMENS: skull cap and partial skeleton found in Germany's Neander Valley in 1856; other fossils found throughout Europe and in Asia as far east as Uzbekistan

WHEN LIVED (est., in years ago): 200,000—30,000

BRAIN SIZE (est., in cu cm): 1,420 (mean of 24 skulls)

SPECIAL FEATURES: rugged physique adapted to survival in Ice Age Europe; made and used sophisticated tools, hunted, and buried dead; sparse evidence for personal ornaments or art; considered by most anthropologists to be a dead-end side branch of the human family; extinct in most of Europe by ~30,000 B.C.

ORIGIN OF NAME: neanderthalensis honors Neander Valley, where type specimen found



Homo sapiens  

Homo sapiens

CHIEF SPECIMENS: fossils found on all continents except Antarctica; oldest known sapiens fossils (195,000 years old) found in Ethiopia in 1960s

WHEN LIVED (est., in years ago): 195,000—present

BRAIN SIZE (est., in cu cm): today's mean = 1,350 (range 1,100-1,800)

SPECIAL FEATURES: rounder cranial vault with vertical forehead; smaller, more retracted face; and a chin

ORIGIN OF NAME: sapiens means "to know"


Note: The illustration, adapted with permission from the Smithsonian Intimate Guide to Human Origins by Carl Zimmer (Smithsonian Books, 2005, p. 41), does not include all hominin species that experts have proposed but rather offers a representative sample. Thanks to Daniel Lieberman, Professor of Biological Anthropology at Harvard University, for consultation on this feature.

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