Human Origins – Hominin Species

Summary

Phylogeny

Here are some attempts to organise the above species into an ancestral tree:
Australian Museum Online – Introduction to Human Evolution – Family Tree
Smithsonian Institution – Human Origins – Early Human Phylogeny
Handprint – Human Evolution

And here are some attempts to show the chronology without attempting to link species up:
PBS – Origins of Humankind (click on SKIP INTRO)
Talk.Origins – Fossil Hominids – Timeline
Archaeology.Info – Species
BBCi – Walking with Cavemen – Human Family Tree

Classification of Australopithecines

It is traditional, when referring to australopithecines to group them into 'gracile' and 'robust' as follows:

Gracile australopithecines:

• Australopithecus garhi
• Australopithecus africanus
• Australopithecus bahrelghazali ?
• Australopithecus afarensis
• Australopithecus anamensis

Robust Australopithecines (Paranthropus):

• Paranthropus boisei
• Paranthropus robustus
• Paranthropus aethiopicus

Homo sapiens

140 to 0 kya. Found everywhere. Fossils quite abundant, especially for later modern humans e.g. the Cro-magnon 1 skull found at Abri Cro-Magnon, France in 1868 and dated to 32,000-30,000 years ago.

The species to which all living humans belong is Homo sapiens. Consensus now leans to the view that "modern humans" (H. sapiens), emerged in Africa and spread throughout Eurasia and ultimately the Americas, rather than that they emerged in situ throughout the Old World with sufficient genetic intermixing among regions to keep the species unitary. Two "almost-modern" 160-154,000 year-old crania found in 2003 in Herto, Middle Awash, Ethiopia link modern man back to African ancestors.

The oldest fossil evidence for Sapiens is about 140,000 years old in Africa, and there is evidence for the species in the Near East some time before 90,000 years ago. Sapiens reached Australia by at least 50,000 years ago, Europe by 40,000 years ago and the Americas by 12,000 years ago.

140,000 years ago, Africa was suffering a drought, causing the humans there to evolve a "modern mode of thought". This ability may have emerged from a near-extinction event. It very possibly saved the species from extinction. This small band of southern survivors, perhaps numbering just a few tens of thousands, came to dominate the world.

Sapiens has a characteristic look: the face is small and tucked under a high, domed braincase. The eyebrow ridges are small and the lower jaw ends in a prominent chin. On average, the body is less muscular than that of earlier hominids.

The emergence of Sapiens spells highly-crafted tools, complex hunting and gathering strategies and a complex social organisation. Early modern humans lived in mobile groups and established extensive trade and gift-giving networks. These networks probably helped to secure future favours when times were hard, and it seems that times did indeed get hard – during the last ice age, humans declined in numbers, perhaps because of famine and drought caused by a drop in global temperatures.

Molecular biologists have found evidence of a population bottleneck – an event that reduces the genetic diversity in a population. The bottleneck occurred in Africa. The likely date for this event is just before 100,000 years ago. Oxygen isotope data suggests that between 190,000 and 130,000 years ago, Africa became a parched wasteland. This could be the cause of the population collapse. The world human population may have dwindled to 10,000 people at one point.

There may also have been other bottlenecks that contributed to the small amount of genetic diversity in modern humans. One researcher believes that the eruption of the volcano Toba in Sumatra roughly 70,000 years ago caused a mini-ice age. The sulphur thrown into the atmosphere by the eruption would have reflected sunlight, causing temperatures around the world to fall. In Africa, they may have fallen by as much as 9°C, creating a freeze that lasted 1,400 years accompanied by another drought.

The harsh climatic conditions may have forced humans to co-operate with each other. Small bands may have formed larger societies – the 'troop-to-tribe transition'. This transition seems to have involved systems of gift exchange between distant peoples. Ostrich eggshell beads seem to have been important in this system of gift-giving, as they are today amongst South African !Kung San hunter-gatherers. These beads have been dated to as early as 40,000 years ago. They were exchanged over areas of 200km to secure future favours when times got tough. Because of these systems, modern humans were exploit unpredictable resources. In this way, humans spread the risk of non-survival.

Another important innovation was 'microlith' stone-tool technology which emerged in Africa about 70,000 years ago. Microliths are the small flakes and blades that characterise the Later Stone Age in Africa. Each tool was specialised for a task. Microliths reflect modern humans using exactly the right tool for the job. Microliths were also given as gifts in gift-exchange systems.

There appears to have been an amazing final 'Great Leap Forward' as recently as 40,000 years ago, when fully modern man sprang into life. In Europe, this manifested itself as the so-called Cro-Magnon culture. Tools became distinctly more specialised and used a wider variety of raw materials such as bone and antler. Polished stone tools appeared. New implements emerged for making clothing, engravings, and sculptures. Fine craftwork appeared: decorated tools, beads, ivory carvings of humans and animals, clay figurines and musical instruments. These and cave paintings appeared over the next 20,000 years. Long-distance trade appeared for the first time.

This take-off happened despite little skeletal change, and was perhaps a result of the development of speech and the associated throat equipment. See Jared Diamond, The Rise and Fall of the Third Chimpanzee, chapter 2.

Sapiens invaded the Americas from N. E. Asia via Alaska starting some time before 11,500 years ago. A famous flint spear-tip found in association with a mammoth skeleton at Clovis, Texas suggests that so-called Clovis Man hunted mammoth. An alternative view is that the Americas were invaded by Solutreans from S. W. France some time between 17,000 and 11,500 years ago by boat across the Atlantic following the southern fringe of the ice sheet and living like eskimos. Mytochondrial DNA evidence hints that both theories are true, with Alaska as the main entry route.

References:
BBCi – Walking with Cavemen – Fact File: Homo sapiens
BBCi – Walking with Cavemen – 150 kya
BBCi – Walking with Cavemen – episode 4 science
Modern Human Origins – Homo sapiens
PBS – Origins of Humankind – Homo sapiens
Smithsonian Institution – Human Origins – Homo sapiens
Steven Heslip – Homo sapiens

Homo neanderthalensis

250 to 30 kya. Europe and Middle East. An abundance of fossil evidence exists. Palaeoanthropology started when in August 1856 the specimen that was to become known as Neanderthal 1 was discovered in the Feldhofer grotto, in the Neander Valley, Germany.

Like Ergaster, Neanderthalensis had a protruding jaw, receding forehead and weak chin. The average Neanderthal brain was slightly larger than that of modern humans, but this is probably correlated with larger body size in general. Its mid-facial area protruded much more than the same area in Ergaster or Sapiens and may have been an adaptation to cold. Neanderthals lived mostly in cold climates, and had short, stocky bodies like modern cold-adapted peoples. Men averaged about 5 feet 6 inches tall. Neanderthals had thick and heavy bones with powerful muscle attachments. Neanderthal skeletons show that they endured brutally hard lives.

Neanderthal remains are found throughout Europe and the Middle East. Western European Neanderthals usually have a more robust form. The climate in those regions was much colder than it is today, and several ice ages occurred during the time of Neanderthal occupation. Neanderthal localities are known today from Spain to Uzbekistan. Several important sites in the vicinity of Qafzeh Cave, Israel, suggest that Neanderthals arrived in the region after Homo sapiens. This would indicate that the population of modern humans in this area was not descended form Neanderthals, and that there was some period of coexistence, or an alternating series of migrations into this region by the two species.

Neanderthals and modern humans are very anatomically similar – so similar, in fact, that in 1964, it was proposed that the two forms represent two subspecies: Homo sapiens neanderthalensis and Homo sapiens sapiens. This classification was popular through the 1970's and 80's, although many authors today have returned to the previous two-species hypothesis.

The stone tools made by the Neanderthals were more advanced than anything produced by previous hominins – Mousterian technology. Until Neanderthals emerged, tools had been made from whatever stone was handy without preshaping. The Neanderthals planned the tool they wanted and they gave the stone the required basic shape before starting to strike and chip this core. New types of tools were made: new scrapers, points and toothed edges were created by fine trimming. The Mousterian tool culture was more varied than anything that came before.

The arrangement of soils around certain fossils indicates that these individuals were buried. Pollen grains close to the body point to flowers having been laid with the body. Tools as well as animal bones have been found with the bodies also, suggesting that the people believed in an afterlife. If this is true (and not all palaeontologists accept this) then the Neanderthals may have been the first of our ancestors to develop a belief in a spiritual existence – religion.

There is controversy as to when the Neanderthals emerged, with estimates varying from 150 kya to 250 kya. Neanderthals disappear from the fossil record about 30,000 years ago and were replaced by anatomically modern forms.

References:
BBCi – Walking with Cavemen – Fact File: Neanderthal
BBCi – Walking with Cavemen – 200 kya
BBCi – Walking with Cavemen – Were the Neanderthals our ancestors?
Neanderthal-Modern.com
Modern Human Origins – Homo neanderthalensis
PBS – Origins of Humankind – Homo neanderthalensis
Smithsonian Institution – Human Origins – Homo neanderthalensis
Steven Heslip – Homo neanderthalensis

Homo heidelbergensis

600 to 100 kya. Europe and East Africa. Found at only a few sites. The type specimen, the Mauer mandible, was found at Mauer near Heidelberg, Germany in 1907.

Many have been found at Atapuerca, N. Spain. Boxgrove man belongs to this species.

The males were tall, as much as 180cm (6'0") in some cases, and very muscular. They were noticeably bigger than the females. Heidelbergensis often had very large faces, and most had heavy brow ridges and receding foreheads and chins. They had a larger brain than Ergaster and smaller than most modern humans. Their skull was more rounded than in Ergaster. The skeleton and teeth are usually smaller than in Ergaster, but larger than in modern humans.

There is no clear dividing line between late Ergaster and Heidelbergensis, so many fossils between 500,000 and 200,000 years ago are difficult to classify as one or the other.

They were proficient hunters. In Europe, they seem to have targeted large animals to hunt, e.g. horses, hippos and rhinos.

Production of Acheulean stone tools around 500,000 years ago by them is debated. These include double-sided, teardrop-shaped tools, e.g. lanceolate hand axes. Production of Mousterian stone tools around 200,000 years ago is also debated. These are most often associated with Neanderthals, but elsewhere were made by Heidelbergensis.

Stone bifaces are found in many parts of Europe. They are the trademark tool of Heidelbergensis. Experiments have shown just how handy they are for butchering large animals. Life was local for Heidelbergensis. The sources of the stones they turned into artefacts was invariably within a few kilometres of where they were dropped.

Wooden spears have been found in a bog at Schöningen, Germany. They are associated with horse bones and are dated to 400,000 years ago. They are weighted at the ends to be thrown like a javelin, and provide the first hard evidence of human hunting.

Earliest use of fire around 500,000 years ago is debated (location: throughout Africa, Europe, and western Asia). They may have had some sort of language. They may have worn clothes.

The manner in which many intact tools were abandoned at Boxgrove may open up the possibility of ritual. Is the pink quartzite hand-axe discovered in the Pit of Bones at Atapuerca also evidence of ritual in Heidelbergensis? Its strange colour can be taken as evidence of the first funeral rite, which suggests the hominins were deposited in the pit deliberately. For Heidelbergensis, tools and hunting weapons may have played an important role in social display, one that we don't yet fully understand and may even border on ritual.

References:
BBCi – Walking with Cavemen – Fact File: Homo heidelbergensis
BBCi – Walking with Cavemen – 1 mya
BBCi – Walking with Cavemen – episode 4
BBCi – Walking with Cavemen – first Europeans
Modern Human Origins – Homo heidelbergensis
PBS – Origins of Humankind – Homo heidelbergensis
Smithsonian Institution – Human Origins – Homo heidelbergensis
Steven Heslip – Homo heidelbergensis

Homo antecessor

800 kya. Spain. All specimens are from Atapuerca, and were assigned the new species name Homo antecessor in 1997.

The first hominins in Europe. Some consider this material to be Heidelbergensis.

Its brow-ridges are double-arched (as is the case with Chinese Erectus and the Neanderthals), and it has triple-rooted molars, a trait recognized in Ergaster. Antecessor has been dated to greater than 780,000 years, but that date has since been revised closer to 800,000 years.

The discoverers of this new species argue that it is descended from African Ergaster, and is the common ancestor of on the one hand the Neanderthals (via Heidelbergensis), and on the other Sapiens. These interpretations have been contested. In a variety of respects, particularly the area of the face around the nose, Antecessor resembles Sapiens more closely than anything else of comparable age does. There is little evidence however of any lineal connection to later populations in Europe, especially the Neanderthals. These fossils possibly represent an initial attempt to colonize Europe that failed.

References:
Modern Human Origins – Homo antecessor
Book: Extinct Humans, Tattersall & Schwartz
Steven Heslip – Homo antecessor

Homo erectus

1.8 to 0.03 mya. East Asia. About 40 individuals found in Java and 40 in China. The first early human fossil found outside of Europe was the famous Trinil 2 fossil skullcap from the Solo River in Java.

"Java Man" was named Pithecanthropus erectus by its discoverer Eugene Dubois. The Zhoukoudian, China fossils were originally named Sinanthropus pekinensis.

Homo erectus used to be thought of as evolving in Africa and migrating from there to Europe and Asia. Recently, the term Homo ergaster has come into use to refer to the African portion of that population, with Homo erectus denoting the Asian descendants and Homo heidelbergensis denoting the European descendants. The new narrowly Asiatic definition is used here.

Erectus was thought to have disappeared as other populations of archaic Homo evolved roughly 400,000 years ago. But this is apparently not the case: recent studies of the stratigraphy of the Java Homo erectus sites have dated the deposits thought to contain Homo erectus bones near the Solo River in Java to only 50,000 years ago. This would mean that at least one population of Homo erectus in Java was a contemporary of modern humans.

Erectus had a long skull with thick cranial walls. The back of the skull had a protruberance known as a transverse torus. Over the eyes was a prominent brow-ridge. Erectus had teeth nearly identical to modern humans, although the cheek teeth are larger and the jawbone was more robust albeit showing no chin. Homo erectus had a more robust face than ergaster. Cranial capacities of Erectus average around 1000 cc – far greater than earlier australopiths and even early Homo.

Erectus apparently did not use stone tools despite that fact that its apparent ancestor, Ergaster, did. Perhaps bamboo was exploited for tool use in Asia instead.

References:
BBCi – Walking with Cavemen – Fact File: Homo ergaster/erectus
BBCi – Walking with Cavemen – 2 mya
BBCi – Walking with Cavemen – episode 3
BBCi – Walking with Cavemen – episode 3 science
BBCi – Walking with Cavemen – Erectus's success
Modern Human Origins – Homo erectus
PBS – Origins of Humankind – Homo erectus
Smithsonian Institution – Human Origins – Homo erectus
Steven Heslip – Homo erectus

Homo ergaster

1.9 to 0.6 mya. Africa, Europe. The term H. ergaster was introduced in 1975, based on specimen ER 992, an isolated mandible, found in Kenya. Another key find is Nariokotome Boy (KNM WT 15000), a near-complete skeleton discovered in 1984 onwards also in Kenya.

The term Homo ergaster is here taken to mean the population of Africa formerly referred to as Homo erectus, that latter term being retained only for the mainly Asian population. It seems most likely that Ergaster so defined migrated out of Africa (the first hominin to do so) and evolved into Erectus in Asia and Heidelbergensis in Europe.

Ergaster probably evolved during a period of rapid global cooling and drying that tended to clear tropical rain-forest and create grassland and desert in Africa.

They had large molars (but smaller than the Austalopithecines), an unpronounced chin, heavy brow ridges, and a long, low skull, relative to modern Sapiens. They were taller and had a heavier skeleton than the average modern human. Body proportions varied greatly from individual to individual. Slim hips and long legs enabled them to walk long distances.

They probably fed by scavenging or by chasing animals across the savanna until they died from exhaustion. They were quite possibly capable of interpreting such environmental clues as animal tracks.

It is thought that their skin was hairless to aid sweating, so that they no longer needed to cool themselves by panting, and so could talk on the move. They had long, modern-looking noses, which cooled air as they breathed.

By 1.6 mya, Ergaster had developed a more advanced stone tool technology known as the Acheulean technology. It consisted of large cutting tools, primarily hand-axes and cleavers. This new tool set was originally thought to be responsible for the spread of early humans out of Africa, but it is now known that that migration predates this tool industry. They did not have spears, it is thought, but perhaps this is because no stone spear-heads have been found – thus if they had spears, they were untipped.

There was no technological advance between 1.5m years ago and 0.5m years ago, then fire was invented.

They had big brains – nearly two-thirds the size of modern humans. The most important thing they use their big brains for was understanding other people. Ergaster lived in large social groups and spent a lot of their time socialising with each other. The whites of their eyes were visible for the first time, to aid socialisation. Their society was held together not by a dominant male, but by the bonds of family and friends. For the first time, hunters brought meat back to give to those left behind, using it to forge alliances and reinforce relationships. They lived for the first time in monogamous couples, at least for a time. These social skills and their enhanced understanding of the world around them enabled them to move out of their ancestral home in Africa. This is all of course fairly speculative stuff.

References:
BBCi – Walking with Cavemen – Fact File: Homo ergaster/erectus
BBCi – Walking with Cavemen – 2 mya
BBCi – Walking with Cavemen – episode 3
BBCi – Walking with Cavemen – episode 3 science
Modern Human Origins – Homo ergaster
PBS – Origins of Humankind – Homo erectus
Smithsonian Institution – Human Origins – Homo ergaster
Steven Heslip – Homo ergaster

Homo georgicus

1.8 mya. Georgia. Few fossils found, all in the same place, including skull D2700. Discovered in 2001.

D2700 is the smallest and most primitive hominin skull ever discovered outside of Africa. It and two others discovered nearby form a near-perfect transition between Habilis and Ergaster. The height, as estimated from a foot bone, would have been about 1.5 m (4'11").

References:
Talk.Origins – Fossil Hominids – Homo georgicus
Talk.Origins – Fossil Hominids – Skull D2700

Homo habilis

2.2 to 1.6 mya. Kenya, also Ethiopia, Tanzania, South Africa. Homo habilis = "Handy Man". The specimen that led to the naming of this species (OH 7) was discovered in 1960.

It had a short body and long arms, but it was distinguished from earlier hominins by its big brain, small teeth and tools. The tool set is known by the term Oldowan.

It evolved in Africa at a time when traditional forest foods like fruit were becoming scarce forcing animals to seek out new nutritional sources. It ate meat by scavenging from animal carcasses. It used crude stone implements to smash open animal bones and extract the marrow. Cut marks on bones 2 mya indicate stone-tool use.

It lived in East Africa at the same time as Boisei, but they they occupied different ecological niches and so were not direct competitors. While Habilis was an omnivore, Boisei survived on a tough vegetarian diet.

It was once thought to be ancestral to modern man, but grave doubts now exist.

References:
BBCi – Walking with Cavemen – Fact File: Homo habilis
BBCi – Walking with Cavemen – 3 mya
BBCi – Walking with Cavemen – episode 2
BBCi – Walking with Cavemen – episode 2 science
Modern Human Origins – Homo/Australopithecus habilis
PBS – Origins of Humankind – Homo habilis
Smithsonian Institution – Human Origins – Homo habilis
Steven Heslip – Homo habilis

Homo rudolfensis

2.4 to 1.6 mya. Kenya. Few specimens found. In 1986 the key specimen ER 1470 was originally named Pithecanthropus rudolfensis.

It was very tall, towering above other hominins alive at the time – especially the stumpy Habilis. Compared with the australopithecines, it had less robust mandibles with smaller cheek teeth. Compared with the Habilis, it had a flatter, broader face and broader postcanine teeth, with more complex crowns and roots, and thicker enamel. It also had a larger cranium.

Like Habilis, Rudolfensis probably combined foraging with scavenging meat from animal carcasses. This may have put the two species in competition with each other. The large body size of Rudolfensis may have helped it scare away other animals from kills, turning it into an effective scavenger.

All the non-australopithecine specimens found at Olduvai Gorge are known to be Habilis, whereas the ones found at Lake Turkana are a mixture of Habilis and Rudolfensis.

It is not yet certain if Rudolfensis was ancestral to the later species of Homo, or if Habilis was, or both, or neither!

References:
BBCi – Walking with Cavemen – Fact File: Homo rudolfensis
Modern Human Origins – Homo/Australopithecus rudolfensis
Smithsonian Institution – Human Origins – Homo rudolfensis
Steven Heslip – Homo rudolfensis

Australopithecus garhi

2.5 mya. Ethiopia. The type specimen, BOU-VP-12/130, a set of cranial fragments, was discovered in 1997.

It is held by some that Garhi is a direct ancestor of modern humans and is derived from Africanus, which is probably derived from Afarensis.

It had very large teeth, suggesting that it may have descended from one of the other Australopithecus species, quite possibly Afarensis.

Circumstantial evidence exists that Garhi was the earliest tool user. Antelope bones excavated from the same site as Garhi show cut marks made by a stone tool; both the hominin and antelope fossils being 2.5 million years old. The earliest stone tools, thought to be 2.6 million years old, were found nearby in Gona, Ethiopia.

References:
Modern Human Origins – Australopithecus garhi
Talk.Origins – Fossil Hominids – Australopithecus garhi
PBS – Origins of Humankind – Australopithecus garhi
Steven Heslip – Australopithecus garhi

Paranthropus boisei

2.5 to 1.4 mya. Mainly Kenya; also Tanzania, Ethiopia. A lot of fossils exist. Also known as Nutcracker Man. The most famous fossil from Olduvai Gorge, OH 5, was discovered in 1959 and originally called Zinjanthropus boisei.

A heavy vegetarian, similar to Robustus.

Its massive skull had a broad concave face, strong jaws, enormous flat molars and very robust cranial adaptations for efficient chewing: the sagittal crest and large area for muscle attachments on the zygomatic arch. Its cranial capacity was 530 cc. It is presumed to have specialised in eating nuts, roots and tubers.

References:
BBCi – Walking with Cavemen – Fact File: Paranthropus boisei
BBCi – Walking with Cavemen – 3 mya
BBCi – Walking with Cavemen – episode 2
BBCi – Walking with Cavemen – episode 2 science
Modern Human Origins – Australopithecus/Paranthropus boisei
Smithsonian Institution – Human Origins – Paranthropus boisei
Steven Heslip – Paranthropus boisei
PBS – Origins of Humankind – Australopithecus boisei

Paranthropus robustus

2.0 to 1.5 mya. South Africa. Quite a lot of fossil evidence exists. Also (formerly) known as Australopithecus robustus. Discovered in 1938.

A heavy vegetarian, similar to Boisei.

Its brain size was much like that of Afarensis. It had a massive flat or concave face. The front teeth were small relative to the massive grinding teeth and thickly enamelled molars and premolars. Most specimens also have sagittal crests (large ridges of bone running along the top of their skulls), which indicate powerful chewing muscles used for grinding tough foods. Males and females differed markedly in body size: males on average 4 feet 4 inches tall and about 92 pounds; females 3 feet 7 inches tall and 71 pounds.

Modified bones found near Robustus skeletons suggest they used tools to help them dig out buried food. Robustus probably inhabited woodland and savanna habitats where they foraged for foods like roots, nuts, and possibly insects.

References:
Modern Human Origins – Australopithecus/Paranthropus robustus
PBS – Origins of Humankind – Australopithecus robustus
Smithsonian Institution – Human Origins – Paranthropus robustus
Steven Heslip – Paranthropus robustus

Paranthropus aethiopicus

2.7 to 2.4 mya. Ethiopia, Kenya. Not many specimens have been found, but the "Black Skull" (KNM-WT 17000) is important. The first fossil was found in 1967; the Black Skull was found in 1985. P. aethiopicus has variously been called Paraustralopithecus aethiopicus and Australopithecus aethiopicus.

Possibly ancestral to the robust australopithecines.

Brain size: comparable to that of modern apes and Afarensis. Its massive face was flat or concave with no forehead. A very large sagittal crest (a bone ridge running along the top of the skull) and other thickened areas of the skull would have provided strong attachments for chewing muscles. Its powerful chewing muscles and extremely large and thickly-enamelled molars and premolars, suggest that it ate tough, grainy foods.

References:
Modern Human Origins – Australopithecus/Paranthropus aethiopicus
PBS – Origins of Humankind – Australopithecus aethiopicus
Smithsonian Institution – Human Origins – Paranthropus aethiopicus
Steven Heslip – Paranthropus aethiopicus

Australopithecus africanus

3.3 to 2.5 mya. South Africa. Not many fossils found. First specimen (Taung Child) found 1924.

Smaller than Boisei/Robustus, and nearly identical in body and brain size to Afarensis.

Would probably have foraged for fruits, seeds, and roots in open woodland habitat.

References:
Modern Human Origins – Australopithecus africanus
PBS – Origins of Humankind – Australopithecus africanus
Smithsonian Institution – Human Origins – Australopithecus africanus
Steven Heslip – Australopithecus africanus

Australopithecus bahrelghazali

3.5 to 3.0 mya. Chad. As of April 2003, little more than a mandible exists (KT12/H1). Discovered in 1995.

Similar to Afarensis. Insufficient evidence to say much more. May simply be a regional variant of Afarensis.

References:
Modern Human Origins – Australopithecus bahrelghazali
Steven Heslip – Australopithecus bahrelghazali

Kenyanthropus platyops

3.5 to 3.2 mya. Kenya. As of April 2003, a nearly-complete skull and a partial jaw exist (KNM-WT 40000). Discovered in 1999.

Might sideline the australopithecines as human ancestor.

It occupied parts of Africa at the same time as Afarensis. Relative to Afarensis, it included primitive traits like small ear holes and advanced traits like a relatively flat face and small molars. It may be comparable with Rudolfensis or Habilis, species that lived as many as 1 million years later. Its brain size was similar to that of the australopithecines.

References:
Kenyanthropus.com
Talk.Origins – Fossil Hominids – Kenyanthropus platyops
PBS – Origins of Humankind – Kenyanthropus platyops

Australopithecus afarensis

4.0 to 2.7 mya. First found in Ethiopia. In East Africa and South Africa, fragments of more than 300 individuals have been discovered, including the nearly-complete skeleton of an adult female ("Lucy", AL 288-1). Discovered in 1974.

Facial characteristics: very low forehead, far-projecting face, very prominent brow ridge. Brain: about 1/3 the size of an average modern human brain, or about the same size as a modern ape's brain. Males stood approximately 4 feet 11 inches tall and weighed 100 pounds while females stood only about 3 feet 5 inches tall and weighed about 62 pounds. Males typically had large crests atop their skulls; females did not. Like the chimpanzee, Afarensis had a small brain, long, dangly arms, short legs and a cone-shaped torso with a large belly, but it walked upright.

It's habitat was mixed: savanna and woodland beside lakes and flood-plains. It ate fruit, seeds and nuts and perhaps some meat. It probably climbed trees to escape from prey species and to sleep safely at night. It seems to have lived in groups of 20 to 30, probably with dominance hierarchies like those of chimpanzees. Males probably co-operated to drive away predators. Mature females may have joined other troops.

References:
BBCi – Walking with Cavemen – Fact File: Australopithecus afarensis
BBCi – Walking with Cavemen – 3.2 mya
BBCi – Walking with Cavemen – episode 1
BBCi – Walking with Cavemen – episode 1 science
Modern Human Origins – Australopithecus afarensis
PBS – Origins of Humankind – Australopithecus afarensis
Smithsonian Institution – Human Origins – Australopithecus afarensis
Steven Heslip – Australopithecus afarensis

Australopithecus anamensis

4.2 to 3.9 mya. N. Kenya. Fossil evidence scanty; no full cranium yet. Initially discovered (but not identified) in 1965; identified in 1994.

Possibly a precursor species to Afarensis, or a variant thereof.

Anamensis probably walked upright, on the basis of a partial tibia found. Its teeth were covered with an enamel layer much thicker than that of Ramidus, suggesting a diet of hard foods. The thick enamel is also characteristic of all later hominins. In size and shape, however, the teeth of Anamensis were more primitive than those of later hominins. Anamensis probably lived in open woodland in northern Kenya and southern Ethiopia.

References:
Modern Human Origins – Australopithecus anamensis
Archaeology.Info – Australopithecus anamensis
PBS – Origins of Humankind – Australopithecus anamensis
Steven Heslip – Australopithecus anamensis

Ardipithecus ramidus

4.5 to 4.4 mya. Ethiopia. Also known as Australopithecus ramidus. The site has yielded material from over 50 individuals so far. First discovered in 1994.

Possibly an early ancestor of man, but more likely a sideline to human lineage and even to australopithecine lineage. Possibly bipedal.

Its dentition was more apelike than of Afarensis. Its molar teeth were narrower and capped with thin enamel, unlike all other known hominins. The canines were larger, but not as large as those of living apes. Its arms had both apelike and non-apelike features. It probably lived in a wooded environment.

Its occipital condyles were as small as the those of smallest known australopithecines, which indicates a very small body size. Its foramen magnum (the hole in the skull for the spinal cord) was very anterior to the cranial base, as in other australopithecines. This feature, along with a deep digastric sulcus implying a short cranial base, strongly indicate that it held its head upright like other australopithecines. However, as no hip-bones or femurs have been found, it is impossible to know whether this hominin was bipedal.

The arm bones show that this hominin had very powerful arms and forearms, which were not used to support its body.

References:
Modern Human Origins – Australopithecus/Ardipithecus ramidus
Archaeology.Info – Ardipithecus ramidus
PBS – Origins of Humankind – Ardipithecus ramidus
GeoCities – Palaeoanthropology – Ardipithecus ramidus
Steven Heslip – Ardipithecus ramidus

Orrorin tugenensis

6.2 to 5.6 mya. Kenya. As of April 2003, 13 fossils exist, including a partial femur, bits of a lower jaw, and several teeth. Discovered in 2000.

Possibly bipedal. Possibly an ancestor of modern humans, sidelining the australopthecines.

Grooves in its femurs, presumably points where muscles and ligaments attached, suggest that the species was bipedal. Because its molars, like those of modern humans, were small compared to those all australopithecines, and because its teeth had very thick enamel like ours, some believe that the australopithecines should be relegated to a side branch in favour of Orrorin.

References:
BBCi – BBC News – 'Oldest' ape-man fossils revealed
Modern Human Origins – Orrorin tugenensis
PBS – Origins of Humankind – Orrorin tugenensis

Sahelanthropus tchadensis

6 to 7 mya. Chad. Nicknamed Toumai (more correctly Toumaï). Only one specimen known as of April 2003 (TM 266-01-060-1). Discovered in 2000.

Possibly bipedal. Possibly an ancestor of modern humans.

The main evidence is a mostly-complete cranium of small capacity (320-380 cc) – comparable to that of a chimpanzee. Since no bones below the skull have been found, it is not known whether Toumaï was bipedal. It may have been a habitual biped because it shares characteristics with other hominins known to be bipedal. These include smaller canines and thicker tooth enamel than apes. The point at the back of the skull where the neck muscles attached suggests that this species walked upright. On the other hand, the foramen magnum (the hole in the skull for the spinal cord) of Toumaï is positioned towards the back of the skull, indicating that the skull was held forward and not balanced on top of an erect body. It is not at all certain that Toumaï is a hominin i.e. descended from the human side of the chimp-human split.

References:
Sahelanthropus.com
Talk.Origins – Fossil Hominids – Sahelanthropus tchadensis

Copyright © 2004 Alan J. White; all rights reserved.    Last updated January 2004.