Humans, Homo sapiens, are the only species of Homo in existence today.
There have been many species in the human family tree belonging to the genus Homo in the past 2.3-million years or so.
Homo originated in Africa and then spread north around 2-million years ago. This is often referred to as the “Out of Africa I” hypothesis.
The genus Homo is characterised by a large brain, prominent nose and relatively small jaws and teeth, compared to Paranthropus and Australopithecus. The earliest known species of Homo is represented by a fossil of a maxilla (upper jaw) from Ethiopia.
Homo habilis emerged in Africa about 2-million years ago, and was first discovered at Olduvai Gorge in Tanzania in 1960. Homo habilis is the earliest named species of the genus Homo, though the jaw from Hadar may represent an older species or could be an early representative of Homo habilis.
Homo habilis had narrower teeth and a larger brain (600 to 800 cc) – up to a third larger than its Australopithecus predecessors – and it was probably responsible for the first primitive stone tools. (There is no clear indication that Paranthropus and Australopithecus made stone tools: they had the manual ability to do so, but probably lacked the mental capacity.) The trend towards a larger brain is the definitive feature of Homo’s evolution.
Homo habilis probably produced the choppers, sharp flakes and cores (off which flakes were struck) of stone referred to as Oldowan technology, in the Early Stone Age. These stone artefacts were used to cut meat and smash open bone for the marrow. The ability to make tools to process food meant that Homo habilis was not as reliant as Paranthropus on large teeth, powerful jaws and heavy cheek muscles. By contrast, their faces became more slender, or gracile, and their teeth smaller.
It was probably the use of tools that would ensure the continued success of the Homo lineage, as it was able to adapt to changes in climate. Homo habilis persisted for more than half-a-million years.
It was also probably Homo habilis that first spread north out of Africa, around 2-million years ago, in what is known as the “Out of Africa I” hypothesis.
The successor to Homo habilis in the fossil record is Homo ergaster, also referred to by some researchers as early Homo erectus from Africa, which lived about 1.7-million to 1.4-million years ago. Its brain size was about 850 cc to 900 cc (about two-thirds of the size of modern humans). The first discovery of Homo ergaster was made by palaeontologist Dr Robert Broom and his assistant, John Robinson, at Swartkrans in the Cradle of Humankind in 1949. They discovered a lower jaw (mandible), which they at first classified as Telanthropus capensis.
Another notable Homo ergaster find at Swartkrans was a partial cranium identified by palaeoanthropologist Dr Ron Clarke in 1969. A crushed mandible belonging to the species was also found at Sterkfontein.
More complete Homo ergaster fossils were discovered in Kenya in the 1970s and 1980s.
“Turkana Boy”, found near Lake Turkana in Kenya in 1984, is the most complete Homo ergaster specimen ever discovered. The boy, who died at about the age of 12, walked upright and had arms and legs similar in proportion to those of a modern human’s. The boy’s height was already 1.6m (5ft 3”) and palaeoanthropologists estimate he could have grown to over 1.82m (6ft) by the time he became an adult.
Palaeoanthropologists think Homo ergaster was the first human ancestor to have made Acheulean stone tools – an advancement on the earlier Oldowan technology - including the first hand-axes and cleavers. Early Acheulean tools have been found close to Homo fossils at Swartkrans and at Sterkfontein, dating to about 1.7-million years ago.
These tools, combined with the ability to control fire, allowed descendants of Homo ergaster to eventually leave Africa for colder northern climates. The use of fire made cooking possible, which expanded the range and quality of foods available for Homo ergaster. It also provided warmth, and a means to ward off predators.
Homo ergaster was about as tall as modern humans and always walked upright, but still had some ape-like features, such as a prominent, thickened browridge and no discernible chin. It weighed between 40 and 72 kg (88 and 160 lbs). Scratch marks on bones found near Homo ergaster fossils indicate that this species did cut and eat meat, although researchers aren’t sure whether this was obtained through scavenging or hunting.
As Homo developed, it is likely that family structures grew more complex, perhaps as a result of the relative immaturity of newborn babies. An enlarged infant brain size meant mothers had to give birth to children earlier, and therefore they had to be nurtured for longer. Due to their vulnerability, a young hominid of the genus Homo would have had a far greater chance of survival if its mother and father remained in a monogamous relationship – a trait that advanced through natural selection.
There is some debate in palaeoanthropology over whether Homo ergaster is a species on its own, or just an earlier variant of Homo erectus.
While both species share common traits such as a larger brain and smaller teeth, Homo erectus does exhibit differences from Homo ergaster, such as a thicker, more angular skull and a heavier browridge. Some palaeoanthropologists believe these and other characteristics indicate that these early Homo belong in two different species. Others simply class them both under Homo erectus. Nevertheless, the current trend is to classify them separately.
Homo erectus’ most prominent features are its low, angular braincase with massive browridges, and large brain of up to 1250 cc, which comes close to modern human brain sizes. Most palaeoanthropologists now believe that Homo erectus evolved in Asia about 1.6-million years ago, and used its relatively advanced mental capabilities to spread into Europe and to Africa.
In 1891, Eugene Dubois found a fossilised 700,000-year-old Homo erectus skullcap at Trinil on the Solo River, Java, Indonesia, and named it Pithecanthropus erectus. Since then, dozens of Homo erectus fossils have been recovered from Java. In the 1930s, about 40 Homo erectus fossils were excavated at Zhoukoudian, China, and originally named Sinanthropus pekinensis. Dubbed “Peking Man”, they date from about 530,000 to 230,000 years ago, and are less robust than the Java specimens.
Although most Homo erectus specimens have been discovered in Asia, they have also been found in Africa. Homo erectus fossils discovered by the Leakey team at Olduvai Gorge, Tanzania, date to between 1.5-million and 800,000 years ago.
In 1994, a very thick braincase of Homo erectus, fragmented by a bulldozer, was discovered by an archaeologist, Italo Bidittu, at Ceprano, Italy. Dating to between 900,000 and 740,000 years old, the cranium shows that Homo erectus spread into Europe far earlier than palaeoanthropologists at first thought.
Our recent ancestors
Our species, modern Homo sapiens, emerged about 200,000 years ago in Africa. Some of the oldest fossils of Homo sapiens have been found in South Africa and in Ethiopia. But our direct lineage to recent Homo species, which lived within the past 1-million years, is still contested and unclear.
Researchers continue to investigate the links between various Homo species which lived within the past 1-million years, and us.
A 1-million-year-old cranium apparently intermediate between Homo ergaster and later Homo was found at Buia, Eritrea in 1995.
Homo antecessor (Latin for “pioneer” or “explorer”), a species discovered in Spain dating to about 800,000 years ago, may bridge the gap between Homo erectus and Homo heidelbergensis, which lived in Europe between about 600,000 and 300,000 years ago. Homo antecessor may even be ancestral to Homo sapiens.
Homo sapiens idaltu, found in Herto, in Ethiopia, is dated to about 160,000 years ago, and was possibly a more recent human ancestor. Important finds of archaic (early) Homo sapiens similar to Homo sapiens idaltu have also been made at Omo, Ethiopia, dating to about 190,000 years ago, and in South Africa, at Florisbad in the Free State, dating to about 250,000 years ago. Present fossil information thus suggests that our species – Homo sapiens – first emerged in Southern or East Africa.
‘Out of Africa’
Most palaeoanthropologists agree that Homo ergaster first evolved in Africa. But some disagree on how Homo sapiens eventually emerged.
The predominant view is that Homo erectus populations, having reached Asia, ultimately became extinct there. According to this scenario, Homo sapiens evolved from the African descendants of Homo ergaster, about 200,000 years ago, and it was as Homo sapiens that humans spread, probably within the last 60,000 years, to populate the entire world.
This is known as the “Out of Africa II” hypothesis. (“Out of Africa I” refers to the first movement of Homo north from Africa, around 2-million years ago.)
DNA data seems to support this theory, placing the common ancestor of all humans on Earth today in Africa at around 200,000 years ago. An alternative view of “multi-regional evolution” enjoys less support. This view argues that various early Homo populations in different parts of the world evolved into the various Homo sapiens populations on Earth today.
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Maropeng 09h00 - 17h00 every day
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Children under 4: free
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