In East Anglia in Britain there are two more sites, separated by a mere 56 kilometres (35 miles) of coastline. Both of these made headlines in the 2000s: in 2005 Pakefield was dated by the teeth of an extinct vole species to 700,000 years ago, earlier than archaeologists had thought that humans could have reached as far north as Britain, and in 2010 Happisburgh, lying even further north, was dated as slightly older by the same vole, along with other species, and by the magnetic orientation of fine-grained sediments.
Map showing key sites discussed in this chapter of some of the earliest human activity outside Africa.
In both the Spanish and British cases, there were fortuitous local conditions that led to the original preservation of the sites and to their recent exposure. This explains why in the two countries we find sites within a relatively small area. What can we infer about the population over the rest of Europe? The secure dates from Spain and Britain have led to a reassessment of a host of other sites in countries ranging from Spain to Russia, where archaeologists had previously claimed to find stone tools from this early period but where the evidence was ambiguous. One such site, Ceprano in central Italy, has produced a human brain case and simple stone tools which some argue may be as old as 800,000 years, though others put it much later. Even if all these older dates are confirmed, and there is plenty of debate, the evidence from the period 1 million to 600,000 years ago is thin and indicates a small population of European colonizers.
For the most part, the distribution of the early sites shows that the human population was still adapted to living in warm climates like its African ancestors. Most of the sites are found in southern Europe; even sites located as far north as Britain were in use mainly when the climate was very warm. The lone exception to this is Happisburgh, the excavators of which argue was occupied during chillier times. In any case, these sites signal the end of the long-held belief that Europe was isolated from the first human expansion out of Africa until half a million years ago. In this chapter, we will explore the evidence of the first human occupation of Europe during the time before ice played a significant role in its climate, and consider what became of the initial settlement of Europe: did it ultimately fail, or did it succeed and lead to the evolution of the Neanderthals?
The first world traveller
The genus Homo evolved in Africa, but the ability to leave the continent was one of its earliest defining traits; it is a key part of what it means to be human. The first human exodus from Africa occurred around 1.9 million years ago, and descendants of these early hominins seem to have inhabited the warmer parts of Asia to as late as 100,000 years ago. This is an extraordinarily long occupation, perhaps twenty times longer, for example, than our own species’ presence in Asia.
The human ancestor that we tend to give credit for this first world conquest is Homo erectus (‘upright man’), although some now argue that an earlier species related to Homo habilis (‘handy man’) may have been the first to leave Africa. (Evidence is so scattered that others consider at least the possibility that the genus Homo evolved in Asia and back-migrated into Africa.) All agree, however, that erectus was among the most successful of our ancestor species. The main features that separate Homo erectus from its predecessors are in its legs and pelvis, the most important part of the body for long-distance walking, and its brain size, which grew to about 75 per cent of ours.
What gave rise to these changes? The most popular explanation links them to the beginning of the current Ice Age about 2.5 million years ago. When we think of the Ice Age, we might think of desolate, glacier-filled landscapes. But geologists consider even the present day to be part of this Ice Age, which is characterized by long eras of cold climate (glacials), in which glaciers expanded, punctuated by shorter warm periods (interglacials), like the Holocene we currently enjoy. As the Ice Age progressed, the cold periods became increasingly extreme and long-lasting, and by about 650,000 years ago Europe suffered its first major glaciation.
When the Ice Age began, it brought drier conditions to Africa (forests giving way to savannahs) which in turn may have forced our ancestors to modify their plant-based diet, as their woodland habitat contracted, in favour of a more meat-heavy one that required greater long-distance travel to find food. Scavenging and possibly hunting for meat and fat required an enormous expansion in feeding range and led Homo erectus to follow migrating animals. These may be key factors in explaining why erectus was able to penetrate deep into Asia almost as soon as it first appeared.
The change to more intensive meat consumption had many advantages. Animal protein is digested more easily than plants and nuts and allowed for a reduction of the intestinal tract and commensurate expansion of the brain. The logic behind this, known as the expensive tissue hypothesis, developed by anthropologists Leslie Aiello and Peter Wheeler, is that the intestines require a large amount of energy, though not quite as much as that required by the brain, the most ‘costly’ organ in our bodies. Therefore a shorter intestinal tract would have freed up energy for a larger brain.
This evolutionary development may have triggered a positive feedback loop, where increased meat consumption enabled a larger brain to develop, which in turn led to an increased ability to obtain meat. Some researchers believe that our species continues to evolve towards improvements in the brain, while, ironically, we have advanced to the point where we know how to control our diet so that we can ‘feed’ our demanding brains without needing to eat meat at all.
The fossil record is fairly sparse for this period, especially outside of Africa. How much do we know about Homo erectus? With Homo erectus, we have either the most successful human species to date (measured by its longevity) or we have something of a generic term that conceals a more complicated story. In the nebulous world of early human evolution, where there are almost as many named human species as there are known fossil sites, Homo erectus is really the one solid point of reference. It is the only Asian hominin (other than ourselves and the Neanderthals) whose very existence as a separate species is not under serious dispute. Homo erectus’s privileged position in the human story has a lot to do with its extraordinary discovery.
At a time when the only known pre-sapiens fossils were Neanderthals, a Dutch anatomist called Eugène Dubois travelled to Indonesia and started digging in a quixotic bid to find a ‘missing link’. In the early 1890s his teams began, incredibly, to succeed on the island of Java. At the site of Trinil he discovered a small, primitive brain case near a long leg bone and proposed the name Pithecanthropus erectus (‘upright ape-man’).
The great dinosaur hunter O. C. Marsh celebrated the discovery in the American Journal of Science, saying: ‘He has proved to science the existence of a new prehistoric anthropoid form, not human indeed, but in size, brain power and erect posture, much nearer man than any animal hitherto discovered, living or extinct.’ Marsh wrote these words more than thirty years after the naming of Homo neanderthalensis, but the Neanderthals were, to him, even less human than erectus. By the mid-20th century, as the humanity of the species Dubois discovered was becoming more apparent, the designation became Homo erectus.
Ironically, the leg bone that was so central to the naming of erectus may in fact be modern. Nevertheless, Dubois’s concept of a transitional species that walked upright and ranged over Asia has been supported by discoveries of a number of individuals who are clearly similar to the first fossils he found.
The brain case that Dubois unearthed is now the type-fossil for Homo erectus, which means that it is the reference point for classifying later discoveries. Yet it is probably less than a million years old and is too fragmentary to be of great use in comparing it to other fossils. In other words, Homo erectus has the benefit of a vague definition, which in any case dates to perhaps a million years after the first African exodus.
The earliest hominin site outside Africa is Dmanisi in Georgia, which is dated to between 1.7 and 1.8 million years ago. The site lies under the ruins of a medieval hilltop village, and its discov
ery came about in the early 1980s when archaeologists found a fossilized rhinoceros tooth (long extinct in western Asia) within the medieval habitation. The five hominin individuals unearthed there have small brains for Homo erectus, and the variation in size and robustness among them leaves open the possibility that more than one species is represented. Many view the Dmanisi fossils as more closely related to an earlier African species, Homo habilis, and some researchers use the term Homo georgicus, arguing that the fossils are unique. The relationship between Homo habilis, Homo erectus and erectus’s more gracile African relative, Homo ergaster, is the subject of some debate, making classification less than straightforward. What we can safely say about Dmanisi is that the people there were probably a primitive version of Homo erectus or perhaps one of its immediate predecessors.
The stone tools from Dmanisi are similar to those found in African sites of the same age: simple flakes with sharp edges, produced in a few minutes by striking a piece of raw stone with a hard hammer. Like the humans at Dmanisi, some of the animal fossils were from species that had also emigrated recently from Africa, and it is possible that the hominins simply followed animal herds as they migrated and that the environment of Dmanisi was not very different from that of the subtropical areas of northern Africa or south Asia.
The next oldest Eurasian fossils are from Java and China and may date as far back as 1.5 or 1.8 million years ago, but most of the exact findspots are unknown. In China the earliest erectus fossils probably date to about a million years ago, though there are also controversial claims for finds as old as the earliest of the Java fossils. Ubeidiya in Israel dates to 1.5 million years ago.
The sites in Georgia and Israel show that early humans were at the doorstep of Europe close to the time of Homo erectus’s first appearance. But erectus was adapted to tropical and sub-tropical environments. Europe lies at a high latitude, and its harsh winters and short growing seasons for vegetation may have made it unattractive to the early pioneers out of Africa.
Homo erectus’s signature stone tool, which appeared 1.76 million years ago in east Africa and in Israel shortly afterwards – well after the first wave left Africa – is the handaxe. The handaxe is a large, multi-purpose cutting device, knapped into shape on both sides, and which in most cases fits comfortably in the hand. It was useful for virtually all aspects of butchering large game (whether hunted or scavenged), including separating flesh from bone, skinning to make hides and possibly also killing the animals. It may have had other uses as well.
Three views of a handaxe found at Abbeville, France. In the 19th century, the discovery at Abbeville of handaxes such as this one, in association with bones of extinct animals, led to the recognition of the great age of human existence on Earth.
The importance of this tool in the history of science, let alone for human evolution, is generally underappreciated. One of the greatest achievements of modern science is the establishment of human antiquity, which can be traced to the discovery of handaxes in the Somme River gravels at Abbeville, France, in the 1830s and 1840s. Jacques Boucher de Perthes unearthed many handaxes in a layer with bones of animals such as elephants, rhinoceroses, hippopotamuses and tigers, which belonged to an earlier geological epoch. These were among the first artifacts that showed that humans have existed on the Earth for more than just a few thousand years, which was the time-frame that had been generally accepted before this discovery.
For the wider scientific community, the presence of these tools in ancient strata – and therefore the great antiquity of their human makers – was confirmed after British geologists Joseph Prestwich and John Evans visited the gravels in April 1859. One of the key sites they visited was at Saint-Acheul, and today the technical term for these handaxes is Acheulian. These events were a major factor in the 1863 publication of Charles Lyell’s Geological Evidences of the Antiquity of Man, which was widely praised at the British Association meeting where William King named the Neanderthals, as we discussed in Chapter One.
Handaxes continue to have an enormous impact on our knowledge of prehistory. For example, at Happisburgh on Britain’s Norfolk coast, a cluster of five separate sites from different periods – including the very ancient one discussed in this chapter – came to light thanks to the discovery of a handaxe in tidal waters.
Judging by its longevity, the handaxe is the greatest-ever human invention. From its first appearance, humans continued to use this tool until around 40,000 years ago. This means that the tradition of making handaxes lasted far longer than its original inventors and was practised by a number of erectus’s successor species, probably including our own. Although early Homo erectus handaxes were common in east Africa and Asia west of the Himalayas, the European pioneers did not use them until 500,000 years ago. This suggests that the east Asian and European populations may have been isolated from later innovations arising in Africa. In east Asia, however, we can attribute the difference to raw materials, as bamboo was probably used as a more convenient alternative. In Europe, the handaxe simply arrived late.
When humans did arrive in Europe, what route did they take? On current evidence, it took more than half a million years for humans to reach the continent following their initial occupation of Dmanisi. The earliest known site in Europe is all the way on the other side, at Atapuerca, in Spain. But Spain is not the most likely gateway to the continent, because there was no land bridge to north Africa, and there is no evidence that any hominin crossed the sea at such an early date. This leaves open the possibility that there are other ancient sites in central or eastern Europe that have not yet been discovered. We are currently experiencing something of a golden age of discovery of sites from this period, and the textbooks may need to be rewritten yet again.
Explaining the Ice Age cycles
Once Homo erectus and its successor species became widespread throughout Eurasia, the increasing frequency of glacial cycles became a major driver of evolutionary changes, culminating in the appearance and subsequent extinction of the Neanderthals. We therefore divert our attention briefly to the phenomenon of Ice Age cycles, which played a prominent role in the Neanderthals’ changing fortunes.
Over the past million years, glaciers have expanded and retreated in Europe perhaps ten separate times. Some of these glaciations have been severe, others less so. The alternation between cold glacial periods and warm interglacials has itself not been uniform, and there have been major changes in climate that have been as short as a human lifetime. Since the existence of these glacial cycles was discovered in the 19th century, their causes have confounded researchers. However, a combination of astronomical observations, deep sea drilling and complex computer modelling has moved us closer to understanding this pattern.
These climate fluctuations, which have become more extreme in the past million years, started when the Earth entered the current Ice Age about 2.5 million years ago thanks to a number of factors: the drift of the continents towards higher latitudes; the emergence of the isthmus of Panama to join North and South America, diverting warm equatorial waters away from the poles; and the uplift of the Himalayas and Tibetan plateau. These provided favourable conditions for the expansion of ice sheets while also reducing the amount of the greenhouse gas CO2 in the atmosphere. Once the Earth cooled to a critical point, astronomical cycles, which affect the amount of solar radiation the Earth receives, began to have an influence on global temperature, and glaciations became more severe.
During the Ice Age, the climate is influenced by three key astronomical cycles, called the Milankovitch cycles, after Milutin Milanković, the mathematician who first proposed them in the early 20th century. The effect of the Milankovitch cycles is that the amount of sunshine that reaches different parts of the Earth’s surface does not remain the same over time. For Milanković, a key factor in glaciations is the amount of solar heat that falls in the high latitudes of the northern hemisphere during the summer. If the summers are cool, he reasoned, then the winter snows do not melt entirely, and each ye
ar there is a build-up of snow and ice which extends gradually southwards.
Everyone is familiar with two basic cycles that affect sunshine penetration in similar ways to the Milankovitch cycles: the day/night rotation of the Earth and summer/winter seasonality. Seasonality is caused by the tilt of the Earth’s axis which, over a year, alternates exposure of the northern and southern hemispheres to more direct sunlight. The three Milankovitch cycles operate over much longer intervals, but with the same basic principle.
The dominant Milankovitch cycle has to do with the shape of the Earth’s orbit around the Sun. The Earth’s orbit is not a perfect circle, but is in the shape of an ellipse, with the Sun set off the centre. This shape varies over a cycle of about 100,000 years, as the orbit oscillates between a near-perfect circle and an elongated egg shape. During the millennia when the orbit is egg shaped, the Earth travels further away from the Sun than when the orbit is nearly circular. This can lead to an accumulation of ice if the Earth receives less sunlight at key points in the calendar.
Within this major cycle, there are two shorter cycles. Every 42,000 years the tilt of the Earth’s axis of rotation fluctuates between 22.1 and 24.5 degrees, affecting the intensity of winters and summers. And there is a 21,000-year cycle, set by the way the Earth ‘wobbles’ as it spins, affecting the temperature swing between seasons. If, as at present, winter in the northern hemisphere begins when the Earth is closest to the Sun, winters are relatively mild and summers are temperate. But in the other half of the 21,000-year cycle, the Earth will be furthest away from the Sun at the onset of winter in the northern latitudes, and the differences between seasons will be more pronounced, with harsher winters and hotter summers.
The Neanderthals Rediscovered: How Modern Science is Rewriting Their Story Page 3
