"If it does turn out to be Neanderthal, this would be the first proper mainland late Neanderthal from Britain," says Prof Chris Stringer, of the Natural History Museum, one of the research team and author of Homo Britannicus: The Incredible Story of Human Life in Britain.

Our ancient cousin, Homo neanderthalensis, was formidable. Using methods of manufacture dating back more than a million years, he fashioned weapons and probably hunted in packs.

His peace was disturbed when modern humans made an initial foray into Neanderthal territory some 135,000 to 115,000 years ago but that encroachment ended in the Levant a few tens of millennia later. However, at around the same time, according to one theory of human migration, another group of modern humans set out much further south, at the mouth of the Red Sea, and headed east.

By around 50,000 years ago, the group had pushed into the Levant. They moved on Europe, where they lived side by side with Neanderthals between 43,000 to 38,000 years ago. It was soon after the Neanderthals encountered this second invasion of modern humans that they disappeared from the fossil record.

What happened? To quote Prof Stringer: "When these populations met, did they regard each other as simply people, enemies, alien or even prey?"

One difficulty in working out how these ancient humans rubbed along is that there is a lack of clear evidence of close encounters. That changed two years ago when a paper was published by Prof Paul Mellars, of Cambridge University, and his student Brad Gravina, suggesting the two kinds of human lived together at Grotte des Fées at Châtelperron in France.

The study was criticised but the Cambridge team published a detailed rebuttal. "The importance of the new paper is that it confirms at least 2,000 years of coexistence/overlap between Neanderthals and modern humans in this one small region," said Prof Mellars. "This is the only direct, unambiguous evidence of this so far."

But if they coexisted there for many generations - and this is still subject to dispute - how can it be argued that modern humans wiped out Neanderthals? And if they did not make war, surely they made love?

One important clue comes from shreds of DNA from Neanderthal bone being studied by teams in America and the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany. Although it will take a couple of years to reconstruct the entire genetic makeup - genome - of Neanderthals, interbreeding appears unlikely to have been significant, according to the latest findings from Svante Pääbo, head of the Max Planck team.

A paper published in last week's issue of the journal Nature reached a similar conclusion. The study of human genetic diversity by Dr Andrea Manica of Cambridge University was combined with measurements of more than 6,000 skulls. "There was no significant flow of genes from Neanderthal (or other ancient human species) to anatomically modern humans," he said.

Not everyone is convinced. Some, like Sarah Tishkoff, of the University of Maryland, point out that the pattern of inheritance of some human genes could be consistent with interbreeding. And there is tantalising evidence of apparent hybrids. Prof João Zilhão, of the University of Bristol, and Prof Erik Trinkaus, of Washington University, described one mosaic of modern and ancient features in a 40,000-year-old modern human cranium found in the Pestera cu Oase (the Cave with Bones) in southwestern Romania.

The reconstructed cranium - named Oase 2 - was flattened at the front and featured exceptionally large upper molars with a size progression found principally among Neanderthals.

Slightly younger bones found at another site in Romania, Pestera Muierii, also suggest hybrid features, along with the 24,500-year-old skeleton of a young boy from Portugal: his prominent chin was characteristic of early modern humans, while the stocky trunk and short limbs of this four-year-old arguably reflected Neanderthal origins. Most recently, a possible hybrid skeleton has been found in China and dated to approximately 40,000 years old by Prof Trinkaus and colleagues.

But there are sceptics who say we need more examples of early modern humans from Africa between 40,000-80,000 years ago to be sure of what really represents Neanderthal features. And it could have been that the hybrids were infertile or shunned by their peers, explaining why DNA studies suggest little interbreeding.

Another remarkable find has been of the last refuge of the Neanderthals, revealed in Gorham's Cave in Gibraltar by Prof Clive Finlayson, of The Gibraltar Museum. He believes there has been too much emphasis on Moderns versus Neanderthals. In the journal Trends in Ecology and Evolution, he suggests there were a number of populations at different stages of becoming "modern", followed by extinction of many - including Neanderthals - with only one surviving: our ancestors.

The culprit for the demise of the last Neanderthals, he believes, was rapid climate change which triggered arid conditions. About 45,000 years ago, Europe's climate suddenly switched between warm, and cold and dry. Sediment cores drilled from the sea bed near the Balearic Islands show the average sea surface temperature plunged to 8C (46F), while the modern equivalent ranges from 14C (57F) to 20C (68F).

As a result of the retreat of the forests, the Neanderthals could only survive in ever smaller groups, becoming confined to bolt holes on the Mediterranean coast. They hung on until 28,000 years ago, perhaps even 24,000 years ago. As there is little evidence of our ancestors being present there, it seems that climate change could have delivered the coup de grâce. Here, at the southernmost tip of Europe, the last of the Neanderthals died, isolated and alone.

Factfile

• Although Neanderthals had bony ridges on the front of their skulls, and an odd depression on the back, their brains were actually bigger, on average, than ours are today. They were heavily muscled, stocky and barrel chested.

• Some Neanderthal skeletons reveal brutal injuries that could only have healed if they had been helped to survive. They buried their dead. Some may even have paid tribute with flowers, judging by the quantities of pollen present in one grave in Iraq, although sceptics argue these were gerbil nesting materials.

• Whether these archaic humans had fully articulated speech, rather than grunts, gestures and pre-language is not known. By one analysis, Neanderthals had a shorter and wider vocal tract than modern humans, which in theory could manage the complex range of sounds needed for speech, albeit at higher pitches.

• Unlike our ancestors, who had dark skins, Neanderthals could have been fair-skinned according to genetic evidence and their use of black pigments for body decoration, such as manganese.

• Some Neanderthal remains bear scrape marks consistent with cannibalism.

  Not so very different

  Teeth are central to efforts to reconstruct Neanderthal lifestyles. The degree of development at birth, maturation rate and length of childhood is locked up in growth lines of tooth enamel - like tree rings - along with the growth of molars and roots.

  One French study of Neanderthal front teeth suggested that life was brutish and short, with adulthood reached at15, three years earlier than our own ancestors. However, the theory of an attenuated adolescence has been questioned.

  One team from Newcastle University found tooth growth was comparable to that of modern populations. And Christopher Dean's team at University College London, analysed two 130,000-year-old Neanderthal teeth found in La Chaise-de-Vouthon, Charente, France. They found the crowns and roots of Neanderthals grew at the same rate, with permanent molar eruption at about seven years and root growth complete by age nine, as in modern children.

  The prolonged childhood of modern humans is unique among living primates, and is related to our large brains, which require time to grow and learn. It seems that Neanderthals also took time to develop their brains.

  However, the differences between us would have been evident soon after birth, according to a study at the Museo Nacional de Ciencias Naturales, CSIC, Madrid, led by Markus Bastir. "Neanderthal faces were slightly larger than humans," he said. The part of the mouth that carries incisors and canines and affects the size the nasal cavity, appears broader, as one would expect from the big .nose.

   

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