Philippa Kaur

Ohn Bavaro Fine Art/Science Photo Library
Today we are alone. But just a few hundred thousand years ago, our ancestors shared the world with at least five other ancient human species, including diminutive hobbits and burly Neanderthals.
It may now be time to add to that list. As we report in “An incredible Denisovan skull is upending the story of human evolution”, there are growing calls to give species status to a group of ancient humans known as the Denisovans.
This is hardly a rushed decision, given that the first Denisovan fossils were identified 15 years ago. Ancient DNA extracted from these remains revealed that they belonged to humans with a discrete evolutionary history. But it also suggested that these mysterious ancient people had interbred with our own ancestors, leaving many researchers reluctant to consider them a separate species.Advertisement
However, some definitions of a species allow for interbreeding, as long as the species involved maintain a defined appearance. The problem was that we didn’t yet know what Denisovans looked like. But earlier this year, we learned that an unusually thickset ancient skull, unearthed in China, is associated with Denisovan DNA. With the confirmation that the Denisovans were distinct in appearance, it is easier to argue that they should be given a formal species name.

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It is possible that the Denisovans could help us work out why we were the last humans standing
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Biologists’ desire to divide nature up into species is sometimes dismissed as mere stamp collecting, where the aim is to categorise organisms rather than truly understand them. But in this case, at least, there is value to the exercise. Anatomical evidence from the Denisovan fossils points to the intriguing possibility that these enigmatic humans were very closely related to our species – perhaps, in fact, more closely related than any other. That suggests we might gain a particularly clear insight into the early behavioural development of Homo sapiens by comparing them with the Denisovans.
At some point, our ancestors learned new behaviours that helped them outcompete all other human species. It is just possible that the Denisovans could help us work out how we came to be the last humans standing.

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Some two millennia on, Christianity is still a dominant religionSam Pelly/Millennium Images, UK
DominationAlice Roberts (Simon & Schuster)
Alice Roberts’s latest book is something of a left turn. In her previous works Crypt and Buried, she fused expertise in osteoarchaeology – the study of preserved human bones – with more traditional historical approaches, such as the analysis of ancient texts. Technical science was interwoven with empathic and thoughtful discussions of the historical record as she aimed for, and often achieved, nuanced, three-dimensional portraits of past human lives and cultures.
In Domination: The fall of the Roman Empire and the rise of Christianity there is virtually no osteoarchaeology. The focus is much more on historical documents. That isn’t a criticism – Roberts is a careful and curious reader of history – but it just might take some fans by surprise.
Roberts’s topic here is the rise of Christianity from humble eastern Mediterranean sect to a religion with billions of adherents. How and why did it become dominant, when most faded away?
At the centre of the narrative is the Roman Empire. When Christianity emerged, the empire controlled almost all the lands around the Mediterranean, from Britain all the way to Syria. The Romans had many gods, but Christianity gradually became more popular. There are several obvious turning points. One was when Constantine I, who ruled from AD 306 to 337, decriminalised Christianity (and supposedly converted, but Roberts points out gaps in the evidence on that front). Another came when Theodosius I, who reigned from AD 379 to 395, made Christianity the state religion.
Roberts is sceptical about traditional explanations for this: that the ideas of Christianity were especially appealing, say, or that its followers were more dedicated. Such claims, she argues, are little more than Christian propaganda.

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The eternal truth is not theological: gods come and go, temples rise and fall – but business is always business
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Instead, Roberts says the real secret to Christianity’s success is how swiftly it penetrated the upper echelons of Roman society. Jesus may have hung out with lepers and sex workers, but the evangelists who followed in his wake targeted moneyed Romans, soldiers and the educated elite. This recruitment effort succeeded wildly. “Early adopters were to be found, not among the rural, or even the urban, poor of the Empire – but among the urban middle and upper classes,” writes Roberts.
In the following decades and centuries, the church acquired a portfolio of moneymaking enterprises. As Roberts writes, “peel away the religious overlay and what you’re left with is a huge, sophisticated system of interconnected businesses: welfare, health, legal, agribusiness, shipping, education”.
The church also took on many state functions, especially charitable efforts directed at poverty. However, it did so in a way that looks distinctly cynical. “Christian charity,” writes Roberts, “was never intended to solve the problem of poverty.” Instead, it enabled the church to market itself to all levels of society: “The poor were to be told that they would reap rewards in heaven. The rich were to be told that the only way they’d get to heaven was by donating to the Church.”
This was a system built on steep social inequality. One can’t help but compare it to modern billionaires’ philanthropy.
Eventually, the entire Roman socioeconomic system was reorganised around the church, says Roberts. Elite, educated Romans pursued church careers, in part because they were lucrative.
When the Western Roman Empire collapsed, this elite aligned themselves with the new regimes but kept the system intact, and often retained their positions. “Whatever the rhetoric, whatever spiritual messages were being adduced, the entity as a whole is looking very much like Roman business, Roman society as usual,” writes Roberts. “The eternal truth is not theological: gods come and go, temples rise and fall – but business is always business.”
Domination is a little hard going at first: there are a great many names to keep track of, and the narrative jumps around in space and time. Everything shifts up a gear, however, once Roberts’s argument comes into focus. The result is an incisive, provocative and sometimes polemical account of one of the most important organisations in human history.
Michael Marshall is a writer based in Devon, UK

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DNA evidence indicates that a skull unearthed in Harbin, China, belonged to a DenisovanHebei GEO University
One of the biggest mysteries in human evolution has just been solved. In 2010, a groundbreaking genetic analysis revealed that east Asia was once home to a previously unknown group of enigmatic ancient humans. We knew them as the Denisovans, but until very recently, we had no idea what they looked like.
That has now changed thanks to a 146,000-year-old skull unearthed in Harbin, China, in mysterious circumstances more than 90 years ago. In June, we learned that it carries Denisovan DNA in the ancient gunk attached to the surface of a tooth, suggesting that the cranium belonged to this ancient relative of modern humans. The discovery shows that these hominins had an unusual combination of features: their faces were similar to ours, but they had thick brow ridges and lacked our tall foreheads.

This finding closes one chapter of the Denisovan story. But another has just begun – and it looks set to bring even bigger revelations. For one thing, we can expect a new name for this extinct hominin, with at least two rival proposals for what it should be. There will also be a battle over how to accommodate the Denisovans in our family tree, particularly given the suggestion that they are more closely related to living people than any other ancient human – potentially ousting the Neanderthals from their position as our sister species.
That controversial idea has big implications in the ongoing search for Ancestor X, the population that gave rise to modern humans. It will also prompt a scramble to learn more about Denisovan lives and behaviour – because it is only by studying our closest cousins that we can really understand how we differ from the other humans that once walked the planet.
The story of the Denisovans, in terms of our recognition of them, begins just a decade and a half ago. They have been a puzzle since their unconventional discovery in 2010. Unlike other ancient humans, all of which are defined by the physical features of their skeletons, these hominins were originally defined solely on the basis of unusual DNA signatures in a tooth and tiny finger bone – both now thought to be between 51,000 and 84,000 years old – found in Denisova cave in Siberia, Russia. That DNA turned out to come from a human lineage that was related to, but distinct from, the Neanderthals.
Interbreeding
Bence Viola at the University of Toronto, Canada, who was a member of the team that made the discovery, says the researchers considered placing the fossils in a new species: Homo altaiensis. They ultimately decided not to, in part because the DNA showed that ancestors of living humans had interbred with the mysterious lineage. We now know that there were several episodes of this interbreeding, and that some human populations – particularly in the islands of South-East Asia and Oceania – inherited between 4 and 6 per cent of their DNA from Denisovans.
“Species names are problematic when you’re looking at populations that are so closely related,” he says. The team opted instead to give the lineage an informal name – the Denisovans – which some researchers view as merely a population within our species, Homo sapiens.
There isn’t universal agreement that this was the correct decision, however. Species can be defined in dozens of ways, many of which allow for a limited degree of interbreeding with other species. This means, for instance, that many researchers argue that Neanderthals deserve to be considered as a distinct species – Homo neanderthalensis – despite evidence that they interbred with modern humans. In a study published last year, Andra Meneganzin at KU Leuven, Belgium, and Chris Stringer at the Natural History Museum, London, advocated for this position because the Neanderthals developed a unique set of physical features and exploited resources in a distinct way.
With such ideas in mind, Christopher Bae at the University of Hawaiʻi at Mānoa recalls being intrigued by the fact that the original Denisovan tooth and a handful of others from Denisova cave were strikingly large. They strongly reminded him of teeth associated with ancient human remains that had been unearthed in China during the 20th century. “I said that it was only a matter of time before the Denisovans were given a Chinese species name,” he says.
The trouble was, says Bae, that no existing names were available there. Researchers in China had traditionally opted for a simple, linear picture of human evolution and so chose to label any human fossils from the past 200,000 years as either H. sapiens or – if the fossil had a primitive appearance – archaic H. sapiens.

Today, most researchers in China think our evolutionary tree is more complicated. As such, when Xijun Ni at the Chinese Academy of Sciences in Beijing and his colleagues examined the Harbin skull and concluded it didn’t belong to a Neanderthal or a modern human, they were comfortable with placing it in a new species. In 2021, they named this species Homo longi, derived from a Chinese term meaning “dragon”.
A few years later, in 2023, Bae attended a scientific meeting in Novi Sad, Serbia, to discuss the human evolutionary tree. “We basically agreed that H. longi is OK,” he says.
Denisovan DNA discovery
So, with news earlier this year that the Harbin skull contains Denisovan proteins and there is Denisovan mitochondrial DNA in the tartar adhering to its single tooth, a strong case can be made for saying the Denisovans and H. longi are one and the same. But Bae doesn’t see it that way.
For a few years, he has suspected that H. longi wasn’t the only ancient human wandering around east Asia in the Stone Age. In particular, he points to fragments of hominin skulls from Xujiayao and Xuchang in north China that are between 100,000 and 200,000 years old. He says they would have accommodated truly enormous brains with a volume of 1700 to 1800 cubic centimetres – much larger than the 1350 cc of the average living human.
Last year, he and his colleague Xiujie Wu at the Chinese Academy of Sciences placed these fossils and some others in a new species named Homo juluensis, which Bae is convinced is where the Denisovans really belong.

“You just have to look at the molars,” says Bae. The unusually large teeth from Denisova cave are, he says, virtually indistinguishable from the teeth associated with the fossils he and Wu placed in H. juluensis. And while he accepts that the Harbin skull carries Denisovan-like DNA and protein signatures, he suspects that, if DNA can be extracted from some of the H. juluensis fossils, they will provide an even closer genetic match with the remains from Denisova cave.
As things stand, then, there are now three potential ways to think about the Denisovans. The research community may begin to refer to them as H. longi or as H. juluensis – or a decision may be made to continue using the informal term Denisovan on the assumption that they really belong in H. sapiens. Currently, there is no consensus, but one is needed, says Bae. “You have to give them some kind of name because otherwise it’s really difficult to have a conversation about the variation and the evolutionary history of these human groups.”
Names are particularly important in light of new research. In an as-yet-unpublished study, Ni and Stringer have teamed up, together with other colleagues, and used anatomical information from dozens of ancient fossils to reconstruct the evolutionary relationships among species in our human genus. The results led to a radical redrawing of our family tree (see diagram below). Traditionally, the Neanderthals have been viewed as the closest ancient humans to living people. But Ni and Stringer’s team concluded that Denisovans are more closely related to us than the Neanderthals are. According to their analysis, the Denisovans and modern humans last shared a common ancestor about 1.32 million years ago. The Neanderthals branched away from our evolutionary line earlier, around 1.38 million years ago.

Ni and Stringer won’t discuss their conclusions until the work is accepted for publication in a scientific journal, but many researchers consider them to be controversial, given they clash with the DNA evidence. Not only does that DNA evidence suggest that Neanderthals and Denisovans are equally closely related to living humans, it also implies that the divergence between the Neanderthal-Denisovan line and our own occurred between 500,000 and 700,000 years ago – far more recently than Ni and Stringer’s team found.
“It’s very clear from the genetic data that a major split between the lineages leading to modern humans on the one hand, and Denisovans/Neanderthals on the other, occurred within the last 500-700,000 years,” says David Reich at Harvard University.
That being said, Aylwyn Scally at the University of Cambridge says such divergence estimates depend to some extent on the methods used to analyse the genetic data. José María Bermúdez de Castro at the National Human Evolution Research Centre (CENIEH) in Spain also thinks there is wiggle room on the divergence date. “The last common ancestor may be up to 1 million years old,” he says.
Last common ancestor
Conventionally, it is believed that this Ancestor X was located somewhere in Africa. But if Denisovans – a group that seems to have been largely confined to east Asia – emerged from the Ancestor X population too, an African location might seem less likely.
Some researchers are already willing to entertain the idea that Ancestor X lived in Eurasia rather than in Africa. In a 2022 study, Bermúdez de Castro and María Martinón-Torres at CENIEH argued that south-west Asia might make more sense, particularly the Levantine region bordering the eastern Mediterranean Sea. “It’s the umbilical cord linking Africa to Eurasia,” says Bermúdez de Castro.

Ancestor X might even have existed further east. In their yet-to-be-published study, Ni and Stringer’s team took a fresh look at two complete, but slightly squashed, ancient human skulls found in Yunxian, central China, about 35 years ago. They used software to create an undistorted model of one of the skulls, and realised that its anatomy was almost exactly in line with that expected of Ancestor X. For instance, it has features of our modern human face coupled with a more primitive-looking braincase that originally housed a brain of roughly 1140 cubic centimetres – smaller than that of the average living human.
Moreover, its age – about 0.9 to 1.1 million years old – is roughly in line with the researchers’ estimate for when our last common ancestor with ancient humans roamed the world. As such, they reached a striking conclusion: this Yunxian skull came from a human very closely related to Ancestor X. What other researchers make of such a bold suggestion, however, remains to be seen.
Denisovan behaviour
With these ideas swirling around the research community, it has never been more important to understand the lives of the Denisovans. This is because assessing how much of a behavioural overlap there was between these ancient humans and our modern human ancestors could provide vital information about our own behavioural evolution.
But it is difficult to conclude much about Denisovan behaviour without excavating sites that they occupied. We have known since 2010 that Denisova cave is one such location, but ancient DNA indicates that Neanderthals and modern humans also occupied the cave at various times during the Stone Age. This complicates things when it comes to interpreting the artefacts unearthed there, which include plenty of stone tools, bone needles for sewing and even ancient jewellery, such as an ivory tiara and a bracelet of polished green rock. Simply put, we don’t know which Stone Age humans made those artefacts.
Other sites, however, are beginning to offer some insights into Denisovan lives. In 2022, for instance, a research team reported the discovery of a tooth with a Denisovan-like appearance in Tam Ngu Hao 2 – dubbed Cobra cave – in Laos. It suggested that some Denisovans adapted to humid tropical conditions quite unlike those found around Denisova cave – although such a conclusion was tentative given that it wasn’t possible to extract Denisovan-specific DNA or proteins from the tooth.
But it is Baishiya Karst cave on the Tibetan plateau that is emerging as perhaps the most important Denisovan archaeological site. A study published last year concluded there is DNA evidence that the Denisovans – and no other humans – sporadically occupied the cave between 160,000 and 60,000 years ago.
Excavations have yet to unearth anything as striking as the Denisova cave jewellery, but they are still revealing important information about the Denisovans. Perhaps most interesting is the fact that they occupied the cave at all given the extreme environment in which it is located. “It’s cold throughout the year,” says Dongju Zhang at Lanzhou University, China. “Snow covers the whole area in the wintertime, and you need a thick jacket even in July or August.”
This fragment of mandible bone, found in Baishiya Karst cave in 1980, now turns out to have been from a DenisovanDongju Zhang, Lanzhou University
Unsurprisingly, then, Zhang and her colleagues have found evidence that the Denisovans made fires inside the cave. It is also likely that they wore clothing to further protect themselves from the elements, with evidence that they skinned animals including the bharal (Pseudois nayaur), also known as the blue sheep. “We think they took the skins to cover their bodies and keep themselves warm,” says Zhang.
Adding to the challenges the Denisovans faced is that the site is 3200 metres above sea level. “I was at the cave last year for a scientific workshop and the lack of oxygen is shocking – I got a horrible headache,” says Viola. Astonishingly, there are now hints that the Denisovans took to even higher altitudes: in as-yet-unpublished work, Zhang and her colleagues have found evidence of an ancient archaeological site on the Tibetan plateau at about 3700 metres above sea level.
Hunting strategies
Finding food on the plateau can be difficult because prey is thin on the ground. This may explain why Zhang and her colleagues discovered that the Denisovans at Baishiya Karst cave hunted a wide range of animals, including large mammals like the bharal and snow leopards as well as rodents such as marmots, and even birds. “It seems they had to use all the animal resources available to them,” says Zhang. To do so, the Denisovans must have developed a range of hunting strategies, because each of their prey species had a unique suite of behaviours.
Collectively, these discoveries paint a picture of the Denisovans as remarkably adaptable. Indeed, some archaeologists have commented that their behavioural flexibility is strikingly reminiscent of modern humans.
But even as we are finding echoes of ourselves in the Denisovans, we are also identifying subtle ways in which we differed from them. For instance, the stable isotopes in fossil teeth – which can reveal information about the variety of plants and animals an individual ate – suggest that modern humans adapted to hunt and forage in the rainforests of south and South-East Asia tens of thousands of years ago. But a 2023 analysis of the suspected Denisovan tooth from Cobra cave in Laos indicates that our ancient cousins lacked the tools and skill set to do so: they seem to have hunted only on nearby savannahs, says Mike Morley at Flinders University in Australia.
Archaeological discoveries in the years ahead should help us more precisely define the similarities and differences between the Denisovans and modern humans. The odds of making such discoveries received a boost earlier this year. After analysing ancient proteins inside a jawbone dredged up off the west coast of Taiwan, a research team concluded that the bone came from a male Denisovan – providing the strongest fossil evidence yet that the Denisovans really did occupy a vast territory. “The geographic range for Denisovans was likely huge,” says Morley. “Just think how much more there must be to find.”

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Beekman suggests the complexity of childcare drove language’s spreadShutterstock/Artem Varnitsin
The Origin of LanguageMadeleine Beekman (Simon & Schuster)
Language is one of the few faculties that still seems to be uniquely human. Other animals, like chimpanzees and songbirds, have developed elaborate communication systems, but none appears to convey such a range and depth of meaning as ours. So how and why did our ancestors first develop language?
Evolutionary biologist Madeleine Beekman has spent much of her career studying insects, especially bees. In her first book for a non-specialist audience, she branches out in a big way to propose an explanation for the evolution of human language.
Her idea is that it evolved out of necessity, to enable us to cope with the demands of childcare. Compared with other mammals, human infants are exceptionally underdeveloped at birth, needing 24-hour care.
Following in the footsteps of decades of palaeoanthropological research, Beekman links helpless babies to two features of human bodies: bipedality and large brains. “As our skeletons adjusted to walking upright, our hips became narrower,” she writes. Later, our brains also expanded. “Babies with a large head and mothers with narrow hips do not make a good combination,” Beekman observes, drily.
To get around this “obstetrical dilemma”, babies are born early, before their heads get too big to squeeze through the birth canal. This enables humans to give birth relatively safely, at the cost of months spent caring for vulnerable infants.
So far, so familiar. Beekman’s big leap is her proposal that the demands of looking after human babies drove the evolution of complex language. “Taking care of human infants is so singularly difficult that evolution had to craft a completely new tool to aid the effort,” she writes, and “the design fault that started the problem in the first place also provided its solution”. Our brains made birth harder, but they also enabled us to evolve a capacity for rich and flexible language.
In proposing this idea, Beekman is wading into a very crowded marketplace. Many scenarios have been put forward for the evolution of language. Some say it developed in concert with technologies like stone tools: as we created more advanced tools, we needed more descriptive language to teach others how to make and use them. Or maybe language was a means of showing off, including through witty wordplay and insults. Then again, it might have allowed individuals to organise their own thoughts, and was only secondarily used to communicate with others.
One appealing aspect of Beekman’s proposal is that it places women and children at the centre. Because science has traditionally been skewed towards the male, ideas about human evolution tended to overly focus on them (“Man the Hunter” and all that), despite the fact that some of the most dramatic changes in our evolution involved pregnancy.

The author argues that language is only around 100,000 years old and is unique to our species

It is good to consider the roles of women and children in the origin of language. However, this doesn’t necessarily mean that Beekman is right. She marshals intriguing evidence, notably that all large-brained birds, including parrots and New Caledonian crows, produce under-cooked offspring. Why? A 2023 study showed that the strongest predictor of brain size in birds was the amount of parental provisioning.
This all sounds distinctly human-like and in line with Beekman’s narrative. But the biggest issue is timing. Humans have been bipedal for at least 6 million years and our brains grew rapidly from 2 million years ago. When, in this timespan, did childbirth become really difficult, and when did language evolve?
Beekman argues that language is only around 100,000 years old and is unique to our species. She cites a 2020 study identifying “unique gene regulatory networks that affect the anatomical structures needed for the production of precise words”. These networks are apparently only present in our species, suggesting other hominins like Neanderthals couldn’t speak as well as humans.
Beekman says this “nails it”, but other researchers have found evidence suggesting complex speech may have existed in other hominins. The evolution of human childbirth is equally tangled and uncertain. In short: nice idea, needs more evidence.
Michael Marshall is a writer based in Devon, UK

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Ferran Traite Soler/Getty Images
“I’ve always prided myself on my can-do attitude,” a reader told me this month. “Recently, however, I’ve started to feel resentful of the amount of work my boss puts at my door compared to colleagues. The more I do, the more he seems to expect of me, and I now feel that I’m cracking under the stress.”
Our reader’s frustration is surely justified. A good work ethic should be one of the most highly prized – and rewarded – qualities in an employee. Everyday experience, though, reveals this is rarely the case. Indeed, according to studies by Matthew Stanley at the National University of Singapore and his colleagues, a pernicious bias can lead managers to exploit the very people they should be prizing.
In one experiment, a group of managers were asked to read about a fictional employee named John, whose company was facing financial difficulties. They had to decide how willing they would be to give John extra hours and responsibilities without any extra pay. The researchers found that the managers were far more willing to do so if they learned that John had proved to be a loyal member of the team – compared with someone who was known to be more detached from their work.
Further studies confirmed that small displays of loyalty encouraged managers to take this attitude: the more “John” gives, the more his managers will take. As Stanley and his co-authors note, this could create a “vicious cycle” of suffering – while less loyal workers manage to escape the sacrifices. But before you start viewing your boss too harshly, it is worth noting that Stanley and his colleagues don’t believe that the managers are conscious of their behaviour, instead regarding this as a form of “ethical blindness”.
This may be compounded by the fact that many of us struggle to turn down extra responsibilities for fear of seeming disagreeable. If we are to break free from that pattern of behaviour, we need to learn how to say no. Research by Vanessa Bohns at Cornell University in New York state suggests it is easier to do so by email than in voice-to-voice or face-to-face conversations. If the request comes in person, or on the phone, I have found that it helps to ask whether you can check your schedule before agreeing. That small delay should prevent a knee-jerk “yes”, and if you want to refuse, it gives you time to formulate a polite response. Try to use assertive language. Saying “I don’t have time” is more persuasive than “I can’t make time”, for example, since it is simply reflecting the reality of your situation, rather than apologising for your inability to create more hours in the day.
But I can’t help think the onus should be on our managers to change their behaviour. A little self-awareness about their tendency to exploit their hardest workers might lead them to rethink how they reward that loyalty.

Vanessa Bohns’s book You Have More Influence Than You Think (W. W. Norton) explores the psychology and ethics of compliance, including many strategies to become more assertive.

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