The Evolution of the Genus Homo & The Neanderthal Problem

What might have caused the formation of new species and the subsequent extinction of others? To answer this, researchers have looked at evidence for sharp changes in environmental variability that occurred as early as 6 million years ago. This increased environmental variability resulted in the development of new habitats that could have produced different adaptations amongst hominid populations.

The appearance of the genus homo is marked by the earliest stone tools, known as Oldowan tools. Oldowan tools are also called pebble tools and are little more than water worn cobbles that have had a few flakes struck off them to produce a sharp edged tool. Oldowan Tools were first discovered by Louis and Mary Leakey in 1959 at Olduvai Gorge. They were originally attributed to Zinjanthropus, which is now known as Paranthropus Boisei.  Subsequent investigations have demonstrated that Paranthropus was not responsible for Oldowan tools, and that they can now be attributed to Homo habilis.
 
Homo habilis (2.4 - 1.6 mya) was first discovered by Mary and Louis Leakey in 1961. The inclusion of habilis in the homo genus is based upon a notable increase in brain size and their manufacture and use of stone tools. Habilis's cranium size was 680ml, with a maximum size of about 800ml. On average, this is about 200ml larger than the average Australopithecus or Paranthropus cranium.

Other species of early homo have been found throughout East Africa and perhaps in South Africa. Some of these are considered different enough that they have been given different species names. For example, early homo found in East Turkana and Kenya is called Homo rudolfensis. Homo rudolfensis is generally defined as having a larger body than habilis, and does not have the prominent brow ridge (torus) as compared to habilis. Rudolfensis also has a flatter face, smoother more rounded contours and brain case.

When we look at evolutionary relationships, some researchers suggest that habilis should be lumped into the Australopithecine genus and that rudolfensis is the first true species in the homo lineage. Others, suggest that the differences can be explained in terms of regional variation.

The Evolutionary Advantages of Tool Use
Stone tools allow for cutting meat off carcasses in a safer, faster and more efficient manner. This would reduce the amount of time that early homo were exposed while scavenging the prey of dangerous predatory animals.

The identification of the types of bones found at Oldowan tool sites indicates that early homo was a scavenger. The bones that have been recovered, and identified are often the lower limbs of antelopes, which carry little meat. Along with skull remains, lower limbs are most often left by carnivores at a kill site.

Following Homo habilis, there is a new widespread species that we identify as Homo erectus. These hominids with larger brains are documented to have lived just prior to the beginning of the Lower Pleistocene (which began about 1.6mya). The oldest and most primitive looking of these specimens is found in Africa, which suggests that they originated there and then spread to other parts of the world.

African Hominid Advancements
The major advancements in hominid evolution: bipedalism, tool manufacture and use, and the initial expansion of our brain, occurred in Africa. The movement of Homo erectus out of Africa into Europe and Asia between 2 and 1.5 mya, may have been triggered by a number of factors, including: population increase, climate changes and the search for food. This geographic expansion is known as hominid radiation.

While Africa is said to have been the birthplace of Homo erectus, there are some very early finds in China which date erectus between 1.96 and 1.78mya, making these specimens as old, if not older than the earliest finds in Africa. The state of Homo erectus in China would be better known if it were not for the loss of a spectacular collection of fossils, collectively known as "Peking Man", which were recovered from a cave site at Zhoukoudian, and subsequently lost during WWII. Although the fossils have yet to be recovered, casts were made of them that have allowed researchers some means to assess their significance.

Although the fate of Homo erectus was eventually extinction, there is some evidence that pockets of Homo erectus populations may have continued to survive as late as 27,000 years ago in places like Indonesia.  However, these claims are not yet wholly accepted.

Paleoanthropologists have recently further defined three additional species, based on cranial morphology: From Africa we have Homo ergaster; from Europe, Homo antecessor (followed by Homo heidelbergensis). Homo erectus now only generally applies to specimens found in East Asia.
 
Homo erectus (1.8 mya - 250,000 years ago?) was first discovered in the 1890s in Indonesia by Eugene Dubois (and originally named Pithecanthropus erectus - or upright ape-man and nicknamed "Java Man"). Along with Ergaster and Antecessor, Erectus has a wide geographical range throughout Europe, Africa and Asia. In many ways, Homo erectus was quite modern looking post-cranially, meaning that the bones of the arms, legs, pelvis, vertebrae, hands and feet are quite similar to modern humans, except for the fact that they are more robust - indicating a greater muscularity.

 In general, the crania of the genus homo, has up until about 250,000 years ago, tended to have the following characteristics:

As compared to early Homo habilis, erectus:
One of the most remarkable Homo erectus finds was discovered in 1984, and is known as KNM-WT 15000, and was nicknamed Turkana Boy. Turkana boy dates to about 1.6mya, and are the remains of a boy of about 12 years old assuming that Homo erectus and Homo sapiens had similar aging patterns. The age of Turkana Boy is based on the presence of juvenile dentition and the presence of unfused epiphyses on the long bones. If erectus matured more quickly, as some have suggested, Turkana boy's age may be closer to 9 at the time of his death.

The boy's cranium is about 880ml, which is much smaller than the 1350ml average for a modern human boy at 9 years old. Turkana Boy's height was 5'6", which suggests that as a fully-grown adult, he would have been approximately 6 feet tall. It's been suggested that if you wanted to picture what this individual looked like, you should picture 15 year old boy with a head the size of a one year old.

Cranial Development and Birth
Modern humans are born at a relatively immature stage of physical development. It's argued that this is a development based on the evolution of larger brain and the anatomical changes required in the pelvis for bipedalism - what this means is that human babies require a much greater care for a longer period of time than any other primate.

The Brain of Homo erectus
Despite the fact that Homo erectus had a larger brain than Homo habilis, it is not disproportionately so, since Homo erectus 's body was also larger than Homo habilis's. Endocasts, or cast of the inside of the brain of homo erectus have shown an asymmetry in brain size that appears to be a more modern development, and one that characterizes modern Homo's brain. It has been suggested that this similarity may have permitted erectus to have linguistic and motor skills that approached those possessed by modern humans.

Behavioral Innovations of Homo Erectus
With a larger brain and a greater capacity for learning and culture, Homo erectus probably made innovations in three key areas:

Tool Use - a major innovation of Homo erectus was the development of the Acheulian Tradition. This replaced the Oldowan pebble tool technology. The Acheulian tradition was first recognized in France at St. Acheul. The result of this development is known as the Acheulian hand ax, which is a symmetrical, edged, pointed tool that is bifacially flaked (flaked on both sides). It is a more sophisticated tradition, requiring much more skill than Oldowan. Hand axes are considered a multi-purpose tool that could pierce, butcher, scrape, cut, and even be used for digging. Like Oldowan, the Acheulian tool kit also includes flake tools.

Interestingly, there appears to be a geographic division in the making of Acheulian hand axes, which is known as the Movius Line. In general, hand axes are more common west of this line, which separates Indian and most of China. It had been suggested that the Homo erectus living west of this line were technologically more complex. While the data do not fully support this argument, it has also been suggested that the use of bamboo, in place of stone, which has not survived in the fossil record could be a reason for some of this difference. Alternatively, it seems more probable that the Movius Line may represent the fact that the first Homo erectus left Africa and moved into Asia before the invention of the hand axe, and that it's delayed acceptance in Asia was a result of the differences between the species (ergaster in Africa and erectus in Asia).

The Controlled Use of Fire
The advantages of fire are fairly obvious. It provides heat, light and can be used as a defense against predators. It also allows the cooking of food, which permits the digestion of certain foods that would otherwise not be digestible. Evidence for the production and controlled use of fire goes back possibly 1.6 mya at the Koobi Fora site in Kenya. The presence of four  reddish brown patches of burnt earth (which contained numerous phytolith remains) has been interpreted as evidence for the use of fire. Other sites, including a 750,000 year old site in France, known as L'Escale have also been documented.

Cooperative Hunting?
Some of the earliest and best known campsites are known from Torralba and Ambrona in Spain, Olorgesaile in Kenya and Olduvia BKII in Tanzania. These are dated prior to about 400,000BP. Collectively, these are examples of places where Homo erectus may have communally hunted. In each of these places, we find the remains of numerous animals. The level of knowledge and cooperation required for these kinds of hunts (which demonstrate an understanding of animal behavior, migration patterns and animal reactions) indicates a sophisticated level of understanding and communicative ability.

Notwithstanding the remains of these animals, some researchers have cast doubt onto the ability of Homo erectus as a hunter. The study of cut marks on bones from some of these sites (such as Torralba and Ambrona) has demonstrated that they were not actually cut marks, but rather, marks left by soil abrasions and root growth. In fact, from a collection of 3000 specimens, only sixteen tool marks were identifiable on 14 bones, and of these, there was no pattern that could demonstrate a systematic butchering process. While this does not prove that Homo erectus did not hunt big game, it seems more likely that such a practice was opportunistic.

Conclusion
In conclusion, Homo erectus was quite a successful development in the hominid lineage. It survived for almost 1.5 million years and during that time changed very little, even over huge geographic areas. While the large brain size of Homo erectus, as compared to the earlier Homo habilis is impressive, we see very little incremental increase in brain size during the time of Homo erectus. It's only with the appearance of archaic forms of Homo sapiens that we see another evolutionary surge in brain size.

The Neanderthal Problem
The emergence of pre-modern Homo sapiens occurred at about 400,000 years ago. These pre-modern species are also known as Archaic Homo sapiens. Included within this group are the Neanderthals. Archaic Homo sapiens is significantly different from Homo erectus relative to their cranial capacity. Archaic sapiens cranial capacities average about 1265ml, or about a 30% increase over erectus. In addition to being larger, the cranial features of sapiens are also more modern in appearance. They have a higher forehead, a smaller face, are made up of thinner bones, reduced brow ridges.
 
Homo neanderthalensis (300,000 to 40,000 BP)
Neanderthal had a large cranial capacity (about 1480ml average), equal to, and even greater than the mean size of modern homo sapiens. It's characteristics are a long low cranium, a flattened forehead, receding chin, occipital protuberance and huge thick brow ridges. 

The name Neanderthal was coined for fossils that were first discovered in 1856 by workers in the Neander Valley of the Rhine Province of Germany. Initially, Neanderthal was not accepted as a human ancestry, but rather, as a deformed pathological oddity. In 1913, Marcellin Boule produced an important reconstruction of Neanderthal from the La Chappelle-aux-Saints material and argued that Neanderthals should not form part of the main evolutionary line of Homo sapiens.
 
Present day comparisons show important differences. As compared to Homo sapiens, Neanderthals have: longer clavicles, wider rib cage, larger shoulder, knee and elbow joints, are more robust, wider hips, wider stronger hands and feet, shorter flattened lower leg bones, a long low cranium, sloping forehead, large brow ridges, a prognathous face, receding chin and a pointed occipital bones. 

We now known that some of the Neanderthal features that were originally interpreted as "ape-like" are actually physical indicators for increased strength and cold adaptation. For example, Neanderthal tended to be short and stocky, with compact heavily built features that would have reduced heat loss.

Studies of Neanderthal children and adult female pelvic bones suggest that Neanderthal was born at a more advanced stage of development and that they probably developed at a faster pace than Homo sapiens children did. While this might seem an adaptive advantage, it might also be a detriment in terms of the acquisition of culture and learning as compared to the longer maturation required for Homo sapiens.

DNA Studies
The extraction of ancient DNA is a recent development. It is far from conclusive at this point, but the initial studies have shown a significant degree of difference between Neanderthal and Sapiens. Initial DNA testing showed significant differences between Neanderthal and modern humans.

The Cultures of the Middle Palaeolithic
With the emergence of Archaic Homo sapiens during the Middle Palaeolithic, we begin to see the disappearance of the Acheulean hand ax, and an increased and regular presence of flake tool technologies. This is a gradual rather than a fixed boundary, and in general, it is fair to say that Middle Palaeolithic industries are more reminiscent of the Lower Palaeolithic than of the succeeding Upper Palaeolithic.

The classic Middle Palaeolithic is found in Europe, the Near East and Middle East, and in Africa. During this period there are hints of the Upper Palaeolithic, in the form the early appearance of true blade technologies in Africa and the Near East. The early appearances of some items that are interpreted as symbolic and related to language are apparently present, but remain controversial. The primary cultural traditions of the Middle Palaeolithic are: the Mousterian in Europe and North Africa, that associated with Neanderthal remains, and in the Near and Middle East with both Neanderthals and early anatomically modern Homo sapiens, and, the Middle Stone Age in Africa, associated with early anatomically modern Homo sapiens.

Levallois Technique
At about 200,000 years ago, we see an important technological development called the Levallois Technique, which is considered a great advancement in stone tool manufacture. This technique involves the creation of a carefully prepared core that then is struck to remove a large flake that can then be used and/or modified as tools. The Levallois technique is a very sophisticated method of flint knapping, and one that ensures a certain degree of consistency and one that would have required a great deal more forethought, preparation and skill.

Interpretation of the Mousterian Culture is complicated by evidence that some flake types may be controlled by the type of raw materials that were utilized, and by the fact that certain tool "types" may really be "subtypes" in the reduction sequence. An increasingly obvious factor is the presence of inter-assemblage variation. In fact, neither the Mousterian nor the Middle Stone Age tradition in Africa is homogeneous the same way that Oldowan and Acheulean industries were. Most regions show different variations in tool assemblages.

Changing Interpretations of the Mousterian Toolkit
Five or more variant industries were recognized by François Bordes, during his excavations at Combe Grenal during the 1950s and 60s. Bordes defined these variants as different cultural traditions with differing roots. He also saw them as biological groups. However, in 1966 Lewis Binford used Bordes' own data set to argue that the variation was a product of functional site use, together with possible seasonality factors. In 1987, Harold Dibble suggested that the varieties of tool types had a lot to do with the sequence in flake production. And that the tool types described by Bordes were little more than different stages in the production of tools.

The Mousterian in the Near and Middle East can be seen as the south-eastward extension of the European pattern. There are also some major new considerations stemming from some new and controversial dates. The major complicating factor is that while the Mousterian is always associated with Neanderthals in Europe, it contains both Neanderthals and anatomical moderns in the Middle East. This is one of the first good pieces of evidence for the lack of clear markers between the cultural and biological spheres of Neanderthal and anatomically modern humans. The sequence is also complicated by the fact that anatomical moderns may be older here [120 to 60 thousand years] than are Neanderthals [40 to 60 thousand years].

Diet and Subsistence
During the Mousterian we see a pattern of hunting and the gathering of plant foods, although the latter is only assumed, given the absence of such remains in the archaeological record. Evidence of co-operative hunting, and of the use of catastrophic hunting techniques is known from sites such as Combe-Grenal, France, where mortality profiles constructed for horse bones indicate the use of a catastrophic hunting strategy in which herds were driven off of nearby cliffs.

Middle Stone Age groups in Africa show a slightly different pattern than their European and Near Eastern Mousterian counterparts. Archaeological research at Klasies River Mouth indicates that early Middle Stone Age assemblages indicated an absence of fishing, bird hunting, and the pursuit of dangerous animals.

Social Organization
Evidence from Mousterian and Middle Stone Age burials suggests that social groups existed in the Middle Palaeolithic that provided care for injured and weak individuals.
 
A male Neanderthal from La Chapelle-aux-Saints appears to have suffered from arthritis and dental disease, and would have likely required care and nurturing from others in his social group in order to survive. Likewise, a burial from Shanidar Cave revealed evidence of healed fractures resulting from a crushing blow to the head, around the region of the left eye. The blow likely blinded the individual, and may have left him partially paralysed on his left side. This individual also had a broken right foot. The fact that all of these fractures were healed prior to his death suggest that he was cared for following his injuries.

Burial Ceremonialism
While burial evidence for Neanderthal was quite controversial over the last 20 years or so, there appears to be a growing body of evidence that indicates that Neanderthal did bury their dead. More recent evidence suggests that Middle Palaeolithic neanderthal societies were structured around age and sex lines. Of the 18 Neanderthal burials that can be aged and sexed, 11 appear to be male and 7 were female. Furthermore, only male skeletons contained grave offerings (of tools, animal bones, etc.). None of the female burials contained grave offerings. By comparison, 90% of their graves of Archaic Homo sapiens from this time period contained grave items.

Finally, evidence for cannibalism has been suggested for Neanderthal remains recovered from the site of Moula Guercy in France (100,000 -120,000 BP). Crushed and smashed bone, cut-marks on arm, leg, and cranial bones, burning, and disarticulation were interpreted as evidence of cannibalism, since similar cut marks were observed on the remains of wild goats and deer at the same site. However, they might also be interpreted as ceremonial acts, which are not so uncommon as we've discovered from archaeological and ethnographic studies of modern human cultures. More recently, it has been suggested that these modifications are the products of post depositional forces and not cultural processes.

Neanderthal Culture and Cave Bears?
Neanderthals have long been associated with worshiping Cave Bears, a now extinct species of bear that inhabited Europe. In a Neanderthal cave in Drachenloch, Switzerland, it was reported that a cache of cave bear skulls was found in a stone "chest". Upon review of the evidence, Chase and Dibble suggest that there is a clear lack of evidence to suggest that Cave Bears were especially important to Neanderthals. They cite a number of problems with the evidence, including: a lack of agreement between field notes and popular descriptions, particularly with regard to the construction of the "chests", which turned out to be natural clusters of rocks and cave-ins; and a lack of butchering marks to indicate that Neanderthal hunted Cave Bears.

Back to Course Outline