by Paul Jordan
Neanderthal people, then, and especially the classic form of them did look very different from any modern peoples of the Earth, and were probably genetically very different too. If we put together a picture of their distinctive physical traits, we can readily see them as something so particular to their time and place (to which they seem to have been heavily adapted) that no modern people look likely to be their direct descendants, especially when the time of the last of the Neanderthalers is seen to be so close to the time of the first Crô-Magnon people, with no duration during which the latter could have evolved, however quickly, out of the former. At the same time, downplaying the very distinct peculiarities of the Neanderthalers, we can conclude that they basically belonged with other fossil finds from Africa and the Far East to a certain (and important) stage of human evolution when modern brain size was achieved in a skull architecture still strongly adapted to powerful facial musculature for heavy working of the jaw and teeth. It was out of that general stage of human evolution that modern people evolved, with teeth and jaw reduction, lightening of the skull architecture, change of cranial shape and flexing of the skull base, to the accompaniment of cultural changes that included better-made and more versatile tool kits, more competitive hunting skills, and very likely more sophisticated use of language and better organized minds than had gone before. It is possible that the Neanderthal people of Eurasia did not play any part in the further evolution of mankind, remaining only an isolated and perhaps terminally overspecialized human species until the better-endowed Crô-Magnon people came along to out-compete them into oblivion. This is a common view of the matter among anthropologists and archaeologists today. On the other hand, it is possible that even the classic Neanderthalers contributed something to the genetic make-up of the modern people of Europe, since some of their peculiarities – like the shovel-shaped incisors for example – do occur at higher rates among Europeans today than elsewhere in the world. One may point to some apparent continuity of physical traits between the Neanderthalers and the Crô-Magnons, like (among some other traits) the bony lip to a nerve hole in the jaw that two-thirds of the Neanderthal sample and one-quarter of the Crô-Magnon share in common, which is sometimes seen in Europe today but is otherwise rare, and unknown among earlier forms of men and the apes. And some anthropologists hold to the view put forward by Weidenreich before the Second World War that envisages a worldwide sequence of stages of human evolution whereby mankind, having spread over Africa, the Middle East, Europe and the Far East by at least a million years ago, went on to evolve in the same direction everywhere as a result of both common selective pressures and uninterrupted sharing of genetic improvements by constant interbreeding between the spread-out populations. In this way, it is proposed, all the peoples of the world could come on together through broadly the same stages of evolution while retaining locally distinctive characteristics through many generations. Nowhere are the implications of this theory, when taken neat, more vivid than in the case of the Neanderthalers, for it requires us to consider the possibility that some of them at least, with all their peculiarities, evolved in short order into the Crô-Magnon people and so on into the modern populations of Europe.
Not only genetics but also the archaeology of the behavioural patterns of the Neanderthalers and their contemporaries (their tools, their food debris, their dwellings) have a bearing on the questions thrown up by the bones of the Neanderthal and Crô-Magnon people and their successors and predecessors. In later chapters we will follow the Neanderthalers into their own prehistory, tracing their evolution out of earlier forms of Man and seeing how their evolution relates to that of other types in other parts of the world. Before that, having seen what the Neanderthal people looked like and how they differed from ourselves, we will consider the world in which they lived and how they managed to live in it.
The World of the Neanderthalers
The classic type of the Neanderthal people lived in the world of the last ice age, or latest ice age as we should perhaps say while we await the seemingly inevitable onset of another one. Not all the classics, whose range was quite large, from Western Europe into Central Asia with a southerly outpost in the Levant, lived in glaciated circumstances but all of them lived in times that were affected in one way or another by the freeze-up. Most of the more generalized sort of Neanderthal folk lived in the warmer times of the interglacial period that came between the last ice age and the one before, and their evolving ancestors take us back into previous interglacial and glacial phases. The past seven million years or so, in which the human line arose out of an ape ancestry, have been a period of relatively cold conditions in the long history of the Earth, albeit with substantial warmer fluctuations within it. In fact, colder times have gripped the Earth since much earlier than that: until about 55 million years ago (mya), the world was enjoying stable warmth with little difference in conditions between the poles and the equator; a slow fade over millions of years reached a temperature low (but still not as low as today’s) between about 35 and 25 mya. An improvement thereafter peaked at about 16 mya, to be followed by further drops at about 12, 10 and 7 mya, after which a more severe drop in temperature heralded the epoch of fluctuating ice ages in which we still live, with permanent ice in Antarctica. The earlier drops probably resulted as much as anything from changes in the configurations of the continents, but the potential factors leading to subsequent climatic deteriorations, especially over the last few millions of years, include: changes in the output of solar heat, which goes up with sunspots and down with less stormy times on the Sun; variability in the Earth’s reception of solar heat as a result of the overlapping effects of variations in the Earth’s orbit around the Sun and the angle (and the wobble of that angle) of its axis to the plane of the solar system; and further variability in the strength of the Sun’s heat at the Earth caused by blocking from interstellar or volcanic dust in the Earth’s atmosphere. With the exception of the random effect of vulcanism and interstellar dust, there are cycles in all the other factors which mesh together in interactions too complicated to model with any certainty. Fortunately, the Earth’s geology contains a detailed record of the climatic changes of the long period during which human evolution has so far taken place, so that a reasonably sure framework of climatic change, with details of changing vegetation and animal life, is now in place, decked out with dates arrived at by means of various scientific techniques. By the early twentieth century a relative chronology of the ice ages had been worked out for the still glaciated Alpine region, with four glaciations (during which the Alpine glaciers had expanded beyond their present extent) and three interglacials (during which the glaciers had shrunk in size), but the scheme was flawed because it carried no real dates in years, no single site could record all its phases and the evidence was damaged by the inevitable fact that successive glaciations had advanced over the moraines left by earlier ones, obscuring and confusing the details. The worldwide application of the scheme was not easy to make.
Nowadays, the basis of our glacial chronology is provided by deep sea cores from the oceans’ beds. These cores, of great length in some cases, can be correlated to provide a scheme covering the entire span of human evolution. They chart, most significantly, the changing volumes of the oceans during the epoch of ice ages. During an ice age, ocean volume contracts with the cold and precipitation fails to find its way back into the oceans in full strength, since much of it becomes locked up at the poles and in the mountains as ice, with the result that sea levels fall all over the world. Evidence of low sea levels is evidence of ice ages and evidence of high sea levels is evidence of interglacial periods. When the volume of the world’s oceans is low, the heavier oxygen isotope Oxygen 18 is more richly present in the water in proportion to the lighter Oxygen 16, which evaporates more readily than when the seas are full, and the ratio of these two isotopes is reflected in the composition of the shells of the sea’s foraminifera. Determination of the oxygen isotope ratio can tell us whether sea volume was low or h
igh, and so whether the tiny creatures were living in an ice age or not. Up to a point, the species of these micro-organisms also indicate in themselves whether they were warm- or cold-sea types. The deep sea cores, then, constitute a detailed record of the fluctuations of the ice ages. The convention is to call our own postglacial (or interglacial) period by the number 1, with odd numbers representing the warm interglacial episodes and even numbers the periods of glaciation. The heyday of the classic Neanderthalers was thereby Stage 4 of the scheme, and the generalized Neanderthal type belonged to Stage 5 or earlier, but it has to be said straightaway that fluctuations within the main stages, denoted by the addition of small letters, require us to keep in mind a much more complicated picture of climate changes and the human comings and goings which have been heavily influenced (perhaps crucially for human evolution) by them. Warmer episodes within glacial periods that do not merit the full-blown status of interglacials are called interstadials.
Putting dates to the phases evidenced in the deep sea cores relies, as far as the cores taken by themselves are concerned, on estimates based on depth of deposits forward and backward from a fixed point, dated by other means in terrestrial rocks, at which the Earth is known to have experienced one of its periodic reversals of magnetic polarity: at 730,000 BP, or perhaps as far back as 790,000 according to the latest determinations. The top of the deep sea core sequence can additionally be dated by the radiocarbon technique, which does not reliably go back beyond about 40,000 BP.
The data from the deep sea cores is buttressed by physical evidence of altered sea levels at different times during the ice age epoch, which can in some cases be dated by one or more scientific methods. Coral reefs and terraces in New Guinea and Barbados, with dates by the radiocarbon and uranium series techniques, are the principal source of information, but evidence of higher than today’s sea levels is also available round Mediterranean and Atlantic coasts. Britain, of course, was connected to the European mainland during periods of glaciation (and during interstadials within them) and the Atlantic coast of France extended some 30 to 40 km to the west when the sea level was low.
Another chronological scheme is afforded by the deep deposits of loess that are found across northern Europe from Brittany in the west into Central and Eastern Europe, and in China. Loess is a loamy deposit of wind-blown origin which, during the ice age, built up to great thickness in some places when howling winds blowing off the glaciers carried away loads of material from river margins or beaches or maybe glacial outwashes, areas with little or no vegetation to prevent it, and deposited them far away – to deepen during glacial times and weather during interglacials. For the past three quarters of a million years, the loess deposits show the same subdivisions of cold and warm phases as the deep sea cores, with the addition of faunal remains and archaeological deposits that can sometimes be dated – not that anyone lived in the loess areas during their periods of deposition, when they must have been fearful places indeed. They would have been deserts at the best of times, and only habitable during weathering phases of the interstadials and interglacials, when they resembled steppe country today.
Other lines of evidence that throw light on the glacial chronology of the ice age epoch come from polar ice cores, Andean lake bottoms, the study of the pollen sequences in archaeological sites and the succession of animal life – some of it extinct nowadays – from similar sources. Again there are the alternations of warm- and cold-loving forms, shading through all the intermediate situations.
The evidence taken as a whole builds up a detailed picture of the environmental circumstances of human evolution. After about 5 mya worldwide temperatures recovered a little from the cold spell that saw the formation of the Antarctic ice-cap and the aridification of parts of Africa in which our ape ancestors had been flourishing – globally, cold times are also dry times because, with so much moisture locked up in the ice, evaporation and precipitation are reduced. But after about 3 mya the cold returned and glaciers this time formed in the northern hemisphere, establishing a still-ongoing pattern of relatively longer cold spells and shorter warm ones, with seriously cold episodes at about 2.5 mya, 1.7 mya and 800–900,000 years ago. There have been more than twenty glaciations in the last two-and-a-half million years, averaging perhaps 100,000 years in length apiece, with interglacials running to much shorter durations of about 10,000 years each. At their worst, glaciations have seen ice sheets covering up to one-third of the present land surface of the Earth, though in areas of presently shallow seas more land was exposed by the lower sea levels of the ice ages, notably between Siberia and Alaska and in the region of Indonesia, Papua and Australia. Temperatures fell by perhaps 3 °C even at the equator, and by as much as 16 °C in higher latitudes, with enormous impact on the flora and fauna – to say nothing of the humanity – of these regions.
Climate will continue to be an important factor in the whole story told by this book of human evolution from our ape-man ancestors in Africa to Neanderthal Man and beyond. For the moment, we need a more detailed picture of the world in which the Neanderthal people in particular emerged, thrived and, somehow, disappeared. That all happened in the world of the last interglacial and the first part of the last ice age. The pattern of glacial-interglacial fluctuation involves possibilities of changes in temperature, in wind force and direction, in precipitation, in animal life and vegetation, and in sea level and coastline. Taken as a whole, such changes in the environment must have had a great impact on the career of the Neanderthalers (as they did on earlier forms of humanity, and as they may yet do on us).
The Last Interglacial followed a previous ice age of intense cold, probably every bit as cold as the final phase of the most recent ice age which reached its severest at about 18,000 BP, long after the last of the Neanderthal people had disappeared. The Last Interglacial began in about 130,000 BP and, like our own postglacial times which date from about 13,000 years ago, it probably came on rather quickly, with swift warming and melting of the glaciers at the poles and in the mountains of Scandinavia and the Alps. There seems to have been a sharp increase in solar radiation at the start of the Last Interglacial, with temperatures that went markedly higher than those we enjoy today to begin with, settling down to perhaps some 2 to 3 degrees higher; the glaciers retreated to at least their present positions, if not further back, and with similar sea levels coastlines assumed about their present configurations, though there is evidence of raised beaches at 5 to 6 m higher than today’s which may only mean that some spreading of the ocean floor with continental drift has since been a factor in lowering our present sea level below that of those Last Interglacial times. As with the end of the last ice age, the Last Interglacial saw the recolonization of areas at high latitudes and altitudes by plant and animal life that had been driven south, or in some places downhill, by the cold weather of the previous glaciation. Typically, pollen sequences in the stratified levels of north European sites of the Last Interglacial show a progression through a brief episode of birch and pine, on to elm and oak, then alder, hazel, yew and hornbeam, finally indicating the beginning of the return to cooler conditions with pine, spruce and silver fir as the interglacial period drew to a close. Open and relatively treeless conditions obtained only at the beginning and end of the interglacial. By 125–120,000 BP conditions were a little warmer than they are today, with a warm fauna of rhino, hippo, elephant, lion and hyena even in northern Europe; but this range of animals need not imply that things were equatorially warm in our own terms, for the details of land connections and migration routes and even perhaps of human activity or comparative lack of it were factors in the spread of the wildlife. All in all, the world of the interglacial Neanderthalers was not unlike today’s, except that the animals they might want to avoid or hunt if they could were a very different lot from the present Eurasian complement, and for that matter from the fauna they would encounter in the ice age that was to ensue.
