Chimpanzees use grooming to show friendship and promote social cohesion. The social brain hypothesis states that at some point in our evolutionary past, the introduction of speech (small talk) achieved these functions more efficiently than grooming and allowed for larger social groups.
Having become adept at forward planning, using the Levallois technique to make stone tools and organizing themselves enough to hunt large animals in their prime, the Neanderthals were well positioned to take further leaps forward. Yet most of the period from 250,000 to 130,000 years ago had a climate of sustained cold conditions. Survival became the priority for them in the northern latitudes of Europe. When this difficult era ended, the Earth entered the Last Interglacial or Eemian, a 10,000-year-long warm period that was as mild as the planet would be until the current Holocene. It was at this time that the Neanderthals first ranged outside Europe. When they ventured forth and reached Asia, they were not alone.
CHAPTER five
An End to Isolation:
130,000 to 60,000 years ago
On a clear day it is possible to see the 14 kilometres (9 miles) across the Strait of Gibraltar, which separates Spain from Morocco, Europe from Africa and – more poignantly for our purposes – Neanderthal territory from modern human territory. Around 600,000 years ago our common ancestor with the Neanderthals, Homo heidelbergensis, had reached Europe, probably from Africa. For hundreds of thousands of years following this migration, the European and African descendants of heidelbergensis, separated by the Mediterranean, evolved into two separate lines. Both were developing in parallel, with their respective brain sizes growing ever larger and their behaviours becoming more complex. Yet their appearances were unmistakably and increasingly distinct.
By 130,000 years ago, at the start of the long and mild Eemian interglacial, Neanderthals occupied the land north of the Strait of Gibraltar at sites such as Gorham’s Cave, Gibraltar, while Homo sapiens lay to the south, at sites such as Cueva Benzu, Morocco. Here were two human species on either side of a narrow channel, almost able to see each other but probably unaware of each other’s existence. Both species would soon expand into Asia, ending hundreds of millennia of geographic isolation.
We know how this story ends, for it is we who are telling it. While there are many questions that are as yet unanswered about how we got from the beginning of the Eemian to where we are now, with more than seven billion living Homo sapiens and no other human species on the planet, the sequence of events is coming into focus. Recent discoveries and new scientific techniques have brought some real surprises. Since the 1980s our understanding of these first stages of global expansion by Neanderthals and modern humans has been turned completely upside down. In this chapter we look at the initial forays into Asia and reveal which species achieved a more stable presence there, pushing ever deeper into the continent. Hint: it’s not who you think.
Map showing Neanderthal and early modern human sites discussed in this chapter, with an inset showing sites in Israel.
In the previous chapter we looked at how Neanderthals and archaic Homo sapiens increased their forward-planning abilities, which we can see in the way they made stone tools and hunted. During the period we cover in the present chapter, another modern behaviour emerged in both species: burial of the dead. Back in the days of heidelbergensis, as we saw in Chapter Three, there was a collection of human remains that reached the bottom of the Sima de los Huesos at Atapuerca. These individuals arrived in what may be the world’s first mass grave either through intentional deposition (i.e. disposal down a long shaft) or through abandonment of corpses in a cave, from which they were later washed down into the deep pit. However it happened, the behaviour at Atapuerca was not burial, which involves the intentional digging of a grave and then the placing of a body (and sometimes burial goods) inside it.
There is evidence of mourning and attachment to a dead relative (especially a child) from many different species, even non-primates such as hippos, who have been known to wail in the face of loss. But intentional burial, especially within sheltered living spaces like caves, implies a more sophisticated understanding of death, perhaps even a belief in the soul. Burial demonstrates respect for the individual beyond life and the notion that if the dead are treated well, laid to rest as if in a permanent sleep, then their memory will live on, enabling them to continue to provide comfort to the living. Dealing with death is a life-cycle event that binds us together and reminds us of the sanctity of life and our shared humanity.
Around 100,000 years ago this particular human practice extended to both Homo sapiens and Homo neanderthalensis. It is not possible to say whether the oldest evidence of burial belongs to modern humans or Neanderthals, thanks to uncertainties in the dating. What is agreed is that both species started the practice in caves and rock shelters at roughly the same time and that the practice persisted.
By the end of this chapter our narrative will bring us well within the last hundred millennia. Were any differences yet evident between Neanderthals and modern humans that would indicate which variety of human might prevail? The answer is yes, but the differences were subtle. Modern humans were beginning to develop an advantage, not in hunting tools or muscle power, and not in overall brain size, but in ornamentation in the form of paint and jewelry. Our ancestors were exploring forms of symbolic expression, while there is limited evidence that the Neanderthals had taken this step. Was this the key to our success?
Asian arrival
Much of what we know about Neanderthals and modern humans in this period comes from a cluster of sites in northern Israel. In this tiny slice of Asia there are good sources of fresh water, a large number of caves, dry conditions and soil conducive to bone preservation. We are doubly fortunate that both species started intentionally burying their dead in caves at this time, making it easier for us to find complete skeletons, and also that there has already been around a century of Palaeolithic research in the area.
It is unusual for such a tiny region to be the main source of evidence for developments across a whole continent. This is akin to studying the changing population of a city over time by looking at the apartments on a single floor of a building. But this particular sample area has given us a tremendous amount of information. Remains of more than forty-five individuals from 130,000 to 60,000 years ago have been excavated from at least six caves or rock shelters in northern Israel. This is a truly staggering total from such a small area.
Most of the key hominin sites in northern Israel were discovered in the 1920s and 1930s, and much of the early work was done by two British archaeologists, Dorothy Garrod and Francis Turville-Petre. Both had gone to Oxford in 1921 to study under Robert Marett, who had earlier found Neanderthal teeth at La Cotte de St Brelade on Jersey.
Soon after his graduation, Turville-Petre joined a project through the British School of Archaeology in Jerusalem in what was then the British Mandate of Palestine. At just twenty-four years of age in 1925, Turville-Petre found ‘Galilee Man’, the name given to a skull he unearthed at a site called Zuttiyeh Cave. Debate continues about the species represented by ‘Galilee Man’. Estimated to be more than 250,000 years old, it probably pre-dates the emergence of Neanderthals and Homo sapiens. It seems to have various characteristics in common with both of these species and probably descends from Homo heidelbergensis as a regional variant – basically a cousin of the Neanderthals and perhaps tied to the enigmatic Denisovans, a population identified only recently through DNA extracted from bones in a single site in Siberia.
Francis Turville-Petre at the site of Zuttiyeh Cave in modern Israel, where he discovered ‘Galilee Man’ in 1925.
The first evidence that Neanderthals and Homo sapiens (which are called early modern humans, because they were not yet fully modern in appearance) reached this small slice of northern Israel began to emerge a few years later. In 1927 quarrying activity on Mt Carmel near Haifa turned up more sites, and Garrod began a multi-year excavation project in 1929. Garrod was older and mor
e experienced than Turville-Petre (her archaeology diploma from Oxford had come some years after she studied history at Cambridge). By this time she had already dug in Britain, France, Gibraltar and Iraq. Garrod excavated at Skhul and Tabun, two caves on Mt Carmel, and started to find a trove of ancient human remains. Despite their close proximity to each other, Skhul contained what appeared to be Homo sapiens, while Tabun had bones with decidedly Neanderthal features. Garrod soon expanded her operations to Kebara, another cave in the area, and invited Turville-Petre to help her. Kebara has produced some very important Neanderthal remains. In 1938, just after the conclusion of her extraordinary work on Mt Carmel, Garrod was elected to the Disney Chair in Archaeology at Cambridge and became the first female professor in any subject at the ancient university, almost ten years before women attained the same status and rights as men there. Turville-Petre, meanwhile, left archaeology, travelled widely throughout Europe and rented a Greek island.
Archaeologists revisit Kebara Cave, Israel. Dorothy Garrod began work in this cave in the early 20th century. In 1982, Ofer Bar-Yosef and his team discovered an adult Neanderthal that had been deliberately buried.
At the same time that Garrod and Turville-Petre were working on Mt Carmel, a Frenchman called René Neuville was digging at Qafzeh rock shelter near Galilee. This proved to be just as productive a site as the others. It is often uttered in the same breath as Skhul, for it was home to the other great collection of early modern human bones from the region. Rounding off the list of sites in northern Israel with human remains from this time is Amud Cave (pp. 70–71), which is close to Zuttiyeh, and which was first excavated by Hisashi Suzuki of the University of Tokyo in the late 1950s and early 1960s. Amud produced remains of some sixteen Neanderthal individuals, one of whom had the largest brain capacity (1,740 ml, 60 oz) of any ancient human ever found.
For the first time since the two human branches separated, we have a single region that contained remains of rival populations of Neanderthals and modern humans. It is here that we must look to try to answer two of our most pressing questions: who arrived in Asia first, and which of the two species was able to maintain a presence there? Along the way, we will begin to look at the question of whether there is evidence for interbreeding, or indeed any contact at all between the populations.
How can we judge which species was the first to reach Asia, or at least northern Israel? Since the pioneering work of the 1920s and 1930s, different methods of answering the question have been overtaken by more advanced dating technology. It was only in the 1980s that archaeologists had access to dating techniques that could give a reliable answer to the question. When the answer finally came, it did not just overturn the previous answer, but it signalled the end of an entire way of viewing human evolution.
Before the 1950s there were no absolute dating techniques that covered the Middle Palaeolithic era. And, unfortunately, there was no way to compare the stratigraphy of the different sites in the region to see whether the bones in one were older than the bones at another. So archaeologists fell back on the only tool left to them, which was the notion that stone tools that look older are older (according to an established sequence from France), and that skulls that look more archaic are more archaic than skulls that share more traits with today’s living humans. In other words, they simply fitted the evidence into pre-existing theories of how the evidence fitted together. They tried to come up with plausible chronologies. With the use of today’s dating techniques, we now know that what seemed implausible to this first group of archaeologists turned out to be the correct interpretation.
Many of these early researchers believed that the Neanderthal site of Tabun was older than the early modern human site of Skhul, just yards away, because they believed that Neanderthals in the region were generally older than the Homo sapiens. Others argued that the sites dated to the same time, and the Neanderthals and modern humans were part of one mixed and highly variable population. Still others saw these sites as evidence that the Neanderthals were not an isolated European species but represented a global phase in the evolution from Homo erectus to Homo sapiens.
It is entertaining, in a way, to look back to these debates in the early 20th century with the knowledge that everybody was wrong. Intriguingly, the development of the first radiometric absolute dating technique in the 1950s did little to expose the flaws of their theories. Carbon dating compares the ratio of regular 12C (carbon atoms with six protons and six neutrons) and the radioactive isotope 14C (carbon atoms with six protons and eight neutrons), which decays into 12C at a known rate. By seeing how much 14C is left, proportionally, in organic remains, one can discern how long the carbon has been undergoing radioactive decay and therefore how long ago the organism died (and stopped absorbing new carbon).
The key problem with carbon dating is that it is less and less reliable for material that approaches 40,000 years old. Before recent technological advances with carbon accelerators and the introduction of ultrafiltration, 40,000 years ago was the 14C limit, and older material gave the same signal no matter how much older it was. Coincidentally, 40,000 years ago used to be around the accepted time for the arrival of early modern humans in the Middle East. It turns out that the arrival came far earlier, but this was not possible to demonstrate with carbon dating. Instead, many researchers took a carbon-dated minimum age to be representative of a true age. This is like saying that if your mother must have been at least sixteen years old when she gave birth to you, then she was probably sixteen years old at the time.
Tabun and Skhul were put in a sequence, with Tabun at some 60,000 years old and Skhul at the carbon limit of 40,000 years. This had the benefit, at least, of fitting into various global ideas of human evolution. It could accommodate both the theory that Neanderthals evolved into modern humans and the theory that modern humans replaced the Neanderthals.
The first hint that all this might be wrong came from Chris Stringer’s PhD dissertation. Through a mathematical comparison of several different skull attributes, Stringer began to argue in the 1970s that the modern humans at Skhul were not related to the Neanderthals at Tabun and Amud, but instead were linked to two skulls that had been found in Africa in the 1960s. The second hint came from archaeologist Ofer Bar-Yosef’s projects in the 1980s when archaeozoologist Eitan Tchernov studied the microfauna of several sites in northern Israel. Like the ‘vole clock’ used to date the first sites in Britain, microfauna (small animals, such as rodents) evolve at a fast enough rate that the species present in an archaeological layer can be indicative of age. Tchernov and Bar-Yosef started to argue that the accepted sequence of the sites was incompatible with the microfaunal evidence.
The revolutionary moment came in 1989 thanks to the introduction of new absolute dating techniques. Just a year earlier Newsweek broke its circulation records when it printed a cover story entitled ‘The Search for Adam & Eve’ about a theory that all living humans have a recent (100,000–200,000-year-old) common ancestor who lived in Africa. For most researchers, the genetic Out of Africa theory marked the end of the notion that modern humans could have evolved out of Neanderthals or that Homo erectus evolved into Homo sapiens all over Eurasia and Africa at the same time. In 1989 the scientific dating of sites in northern Israel provided corroboration of the Out of Africa theory.
What were the new dating techniques? There were three. U-series dating is like carbon dating in that it compares ratios of the unstable uranium isotopes, 235U and 238U, with the elements into which they decay, although U-series is used on inorganic material such as stalagmites. Thermoluminescence, or TL dating, looks at how many free electrons have accumulated over time within little traps in material such as flint or quartz. If flint was burnt in a fire or if the quartz was exposed to the sun for long enough and then buried, the electrons would have been knocked out, effectively setting the ‘clock’ to zero, so that the amount of electrons that have been trapped tells us the amount of time that has since passed. Burnt flint is easy to recognize, as the pr
ocess leaves tell-tale pockmarks and can change the stone’s colour. And finally electron spin resonance, or ESR, works on the same principle as TL and is particularly useful when applied to ancient tooth enamel.
In the 1980s these techniques were new and experimental. Archaeologists decided to use them all in order to confirm their results, and in fact the results of the U-series, TL, ESR and microfauna were all in general agreement: Qafzeh and Skhul could no longer be considered the most recent of the Israeli sites. Instead, it appeared that they were the oldest. ESR and TL both place the early modern humans of Skhul between 100,000 and 135,000 years ago. Those of Qafzeh were dated by the same methods to be 90,000 to 120,000 years old. By contrast, the Neanderthals of Amud and Kebara turned out to be just about half of these ages (50,000–60,000 years old).
A modern human skull found at Qafzeh, Israel, dated to around 100,000 years ago.
Researchers were surprised to discover that the first modern humans reached northern Israel, and probably the Asian continent, much earlier than the Neanderthals did. This was the one possibility that no one entertained in the days before absolute dating. It stands as an important lesson in science: in the absence of evidence, one must always be wary of drawing conclusions based on expectations, no matter how obvious they may seem. The human past seems to have a ceaseless ability to surprise us.
The Neanderthals Rediscovered: How Modern Science is Rewriting Their Story Page 10