Humans

Read
The Spike is computational neuroscientist Mark Humphries’s vivid tale of the epic 2.1-second journey taken by a single electrical impulse as it propagates through the billions of neurons of a human brain.
Hulu
Watch
Boss Level, a new film streaming on Hulu from 5 March, stars Frank Grillo, Naomi Watts and Mel Gibson in a not entirely serious sci-fi shoot-em-up involving a dastardly government project, time loops and a race to save tomorrow.

Read
Under the Blue, by debut novelist Oana Aristide, sees speculation about artificial intelligence collide with the story of an artist fleeing a global plague: a startling, intellectual, post-covid adventure.
More on these topics: More

Evolutionary psychologist Robin Dunbar has found that our friendships are governed by secret rules, based on everything from your sex to your sleep schedule. Our unique social fingerprints help determine who we are drawn to, which friendships last and why some friends are ultimately replaceable

Humans 3 March 2021
By Robin Dunbar
Anđela Janković
FACEBOOK users used to have a lot more friends. The social networking site pursues a commercial strategy of trying to persuade people to “friend” as many others as possible. However, sometime around 2007, users began to question who all these people they had befriended were. Then, someone pointed out that we can only manage around 150 relationships at any time. A flurry of “friend” culling followed and, since then, the number 150 has been known as “Dunbar’s number”. Thank you Facebook!
Modern technology may have brought me notoriety, but Dunbar’s number is rooted in evolutionary biology. Although humans are a highly social species, juggling relationships isn’t easy and, like other primates, the size of our social network is constrained by brain size. Two decades ago, my research revealed that this means we cannot meaningfully engage with more than about 150 others. No matter how gregarious you are, that is your limit. In this, we are all alike. However, more recent research on friendship has uncovered some fascinating individual differences.
My colleagues and I have made eye-opening discoveries about how much time people spend cultivating various members of their social networks, how friendships form and dissolve and what we are looking for in our friends. What has really surprised us is that each person has a unique “social fingerprint” – an idiosyncratic way in which they allocate their social effort. This pattern is quite impervious to who is in your friendship circle at any given time. It does, however, reveal quite a lot about your own identity – and could even be influencing how well you are coping with … More

By Michael Marshall
The skull of the Australopithecus fossil known as “Little Foot” is preserved well enough to maintain evidence of blood vessels
Themba Hadebe/AP/Shutterstock
A famous member of an extinct human group went through hard times early in her life. The fossil, known as Little Foot, has telltale signs in her teeth that suggest she was either deprived of food or seriously ill during her childhood. Analysis of the fossil also revealed blood vessels in the skull, which could help us better understand the evolution of human brains.
Little Foot lived about 3.67 million years ago in what is now South Africa. She was an ape-like hominin with a much smaller brain than modern humans. She belonged to the genus Australopithecus, but there is disagreement about her exact species. Little Foot was old when she died, and her remains were found with those of a baboon, suggesting she died in a fight.

Advertisement

To find out more details of Little Foot’s biology, Amélie Beaudet at the University of Cambridge and her colleagues scanned the fossil’s skull using the X-ray synchrotron at the Diamond Light Source in the UK. This allowed them to see details as small as 3 micrometres, compared with 100 micrometres in a CT scanner.
“In the teeth, we can see some defects, like lines or grooves,” says Beaudet. “It means at some point the enamel could not form properly.” This must have happened during childhood when Little Foot’s body was still developing.

There are several possible explanations, says Beaudet. One is that Little Foot’s environment changed, perhaps because the climate shifted, and, as a result, she found herself short of food. “We know that the environment was not always stable,” says Beaudet.
But it is also possible that Little Foot was ill, perhaps due to an infection. “We cannot say it was because of a food shortage, or because she was sick, or something else,” says Beaudet.
The team was also able to see tiny blood vessels in the bones of the skull and lower jaw. Beaudet says it was a “big surprise” that the fossil was preserved well enough to see such details.
Understanding Little Foot’s blood supply may ultimately shed light on the evolution of our unusually large brains. The brain needs to receive a lot of nutrients and it generates heat that must be carried away. Blood does both, so as our ancestors’ brains evolved to be larger, the blood vessels must have also evolved. “What part of the system had to evolve first for the rest to happen?” asks Beaudet.

Journal reference: eLife, DOI: 10.7554/eLife.64804
Sign up to Our Human Story, a free monthly newsletter on the revolution in archaeology and human evolution
More on these topics: More

By Christa Lesté-Lasserre
People mask how they feel about an ongoing conversation and leave others unsure of whether to stop talking, suggests a study in the US
KT images/Getty Images
Conversations often end later than people would like – and sometimes too early – because people mask how they really feel about the ongoing dialogue, according to a study in the US. This leaves all partners in a conversation unsure of whether to stop talking.
“People feel like it’s a social rupture to say: ‘I’m ready to go’, or to say: ‘I want to keep going although I feel like you don’t want to keep going’,” says Adam M. Mastroianni at Harvard University. “Because of that, we’re pretty skilled at not broadcasting that information.”

Advertisement

Mastroianni remembers attending a black-tie event and wondering how many people at the party were engaged in conversations that they really wanted to end. So, he and his colleagues later surveyed more than 800 people – 367 women and 439 men, three-quarters of whom were white – randomly recruited from a crowdsourcing marketplace website. Participants responded to questions about recent conversations they had had with a friend or family member, including how they felt about the conversation’s length and how it ended.
The researchers also recruited more than 250 students and non-students pooled from volunteers available for studies in the Harvard University psychology department. The group, slightly under half of whom were white, included 157 women, 92 men, and three people of unspecified gender. These people participated in one-on-one conversations with another participant, who they didn’t already know, in the laboratory.

Mastroianni’s team recorded each conversation and asked the two participants to talk about anything they liked for at least a minute. When the conversation had ended, both study participants could leave the room, where they were each – separately – quizzed about the conversation. If the conversation lasted 45 minutes, someone stepped into the room to end it.
The conversations rarely ended when people wanted them to – whether it was one participant or both participants who wanted to stop, says Mastroianni. In fact, on average, the length of the conversations were off by about 50 per cent compared with how long people would have liked them to last.
Mastroianni also found that that some people – 10 per cent of the participants – were actually ending the conversations even though both people wanted to continue.
“They could have kept going; they had time left,” Mastroianni says. “But for some reason they stopped, maybe thinking they were doing a nice thing by letting the other person go.”

Essentially, people in conversations not only want different endpoints, but they also know “precious little” about what their conversational partners really want, he says.
That doesn’t mean the people don’t enjoy their conversations. On the contrary: when asked, his study participants said they found the conversation more entertaining than they expected it to be.
“But what we didn’t realise as scientists – and what they didn’t realise as people – was that beneath that good time that people generally have is this whole coordination failure,” says Mastroianni.
The study only covered people from the US and conversations might play out differently in other languages and cultures.
Journal reference: PNAS, DOI: 10.1073/pnas.2011809118
More on these topics: More

By Krista Charles
A reconstruction of a Neanderthal man and woman
S. ENTRESSANGLE/E. DAYNES/SCIENCE PHOTO LIBRARY
Virtual reconstructions of Neanderthal ears show that our extinct cousins had the same physical capacity for hearing as modern humans, and by inference could also make the same sounds we can – although whether they actually spoke a language is still unknown.
“We don’t know if they had a language, but at least they had all the anatomical parts needed to have the kind of speech that we have,” says Mercedes Conde-Valverde at the University of Alcalá in Spain. “It’s not that they had the same language, not English, not Spanish, nothing like this. But if we could hear them, we would recognise that they were humans.”

Advertisement

Conde-Valverde and her colleagues used medical imaging software to create virtual reconstructions of Neanderthal external and middle ear cavities, based on CT scans of their skulls. With these models, they could determine the range of sounds that Neanderthals could hear, and thus probably produce as speech. This technique has previously been used to study speech and hearing in other ancient humans and chimps.

The team also did the same for a group of fossils known as the Sima de los Huesos hominins that are thought to be the immediate ancestors of Neanderthals. The results showed that, unlike these ancestors, Neanderthals had the same capacity for hearing as modern humans.
Neanderthal hearing was optimised towards production of consonants that often appear in modern human languages, such as “s”, “k”, “t” and “th”, in the same way our hearing is, says Conde-Valverde.
While we don’t know if this means they had the mental capacity for language development, Conde-Valverde says that recent archaeological evidence, including stone tool use, jewellery making and art hint towards complex behaviour in Neanderthals that could indicate language ability.

“It becomes more and more hard to dismiss the fact that probably they had some sort of speech,” says Dan Dediu at Lumière University Lyon 2 in France. It was likely very similar to ours, but not identical, he says.
Journal reference: Nature Ecology and Evolution, DOI: 10.1038/s41559-021-01391-6
Sign up to Our Human Story, a free monthly newsletter on the revolution in archaeology and human evolution

More on these topics: More

By Karina Shah
The skull of Ardipithecus ramidus – a hominin that swung from branches?
PvE/Alamy
Our distant ancestors may have swung from branches and knuckle-walked like a chimpanzee – challenging recent thinking that the earliest hominins did neither. That is the conclusion of an analysis of 4.4-million-year-old Ardipithecus ramidus, thought to be one of the earliest known hominins.
In popular thinking, humans are often imagined to have evolved from a chimpanzee-like ape, but many researchers now challenge this idea – particularly in light of fossil evidence from A. ramidus that was published in 2009. One well-preserved individual – nicknamed Ardi – had bones that suggested it typically walked along branches like a monkey rather than swinging below them like a chimp. This hinted that our last common ancestor with chimps also walked along branches, and that chimps evolved to swing and knuckle-walk after they branched off from hominins.

Advertisement

Thomas C. Prang at Texas A&M University and his colleagues disagree with this conclusion. They have taken the measurements of Ardi’s hands reported in 2009 and compared them with 416 measurements from hands across 53 species of living primates, including chimpanzees, bonobos and humans.
“The analysis of this hand, one of the earliest hands in the human fossil record, suggests that it is chimpanzee-like, implying that both humans and chimps evolved from an ancestor that was chimp-like,” says Prang.

They found that Ardi’s metacarpals and phalanges – the bones of the fingers and palms – were similar in size to those of living apes, with relatively large joint and knuckle dimensions. These adaptations are present in existing primates that move around forests by swinging below branches and may have helped the hominin to grasp onto branches, and even knuckle-walk.
“Ardi also has elongated, more curved finger bones, and we see this increased elongation and curvature in animals that habitually hang from branches,” says Prang.
Larger-bodied primates tend to hang from branches and climb trees, while smaller-bodied animals, like monkeys, are able to walk along the branches.
“[The study] quite convincingly demonstrates that the Ardipithecus hand has some suspensory adaptations, which I think makes more sense given the body size,” says Tracy Kivell at the University of Kent, UK.

The researchers also confirmed this using evolutionary modelling. This involved comparing traits of different primates, both living and extinct, to understand the evolutionary relationship between physical features and movement. “In short, this approach models the evolution of traits across a tree of life, which in this case includes all the species in our analysis,” says Prang.

Understanding hand morphology of our earliest human relative brings us one step closer to explaining why humans are so different from our close relatives. This may suggest that the last common ancestor of chimpanzees and humans was relatively chimpanzee-like, before the major evolutionary shift towards bipedalism and hand dexterity.
Tim White at the University of California, Berkeley, who discovered the A. ramidus fossil and helped describe it in 2009, remains unconvinced. “This is another failed resurrection of the antiquated notion that living chimpanzees are good models for our ancestors,” says White. He says that the Ardipithecus hand, aside from having five fingers and the ability to grasp, wasn’t specifically chimpanzee-like, as he and his colleagues originally reported in 2009.
Sergio Almécija at the American Museum of Natural History in New York is also largely unconvinced. “We need more Miocene [epoch] ape fossils pre-dating the human-chimp split to test fundamental aspects of our last ancestor with apes,” he says.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abf2474
More on these topics: More

By Bethan Ackerley
Signature Entertainment
Synchronic
Justin Benson, Aaron Moorhead
Now available to rent online

Advertisement

WHEN they aren’t busy being the darlings of indie horror cinema, film-makers Justin Benson and Aaron Moorhead are, by their own admission, armchair enthusiasts of astrophysics, philosophy and futurism. That heady cocktail of interests has influenced all their films to date, but perhaps none more so than their latest and most ambitious creation: Synchronic.
The film stars Anthony Mackie and Jamie Dornan as paramedics and friends Steve and Dennis, who are called out to a series of unusual drug overdoses across New Orleans. Although the victims are found in very different circumstances – one has been stabbed by a centuries-old sword, while others have been burned or frozen to death – they have all taken Synchronic, a designer drug based on the hallucinogen DMT.
Aside from those grisly incidents, the first third of Synchronic is a slow-burning drama about the quiet miseries that Steve and Dennis are mired in. Steve is a disaffected womaniser who has recently been diagnosed with a brain tumour, while Dennis’s marriage is strained by a new baby and his daughter Brianna’s teenage angst. Thankfully, these personal troubles are just a vehicle for a much more intriguing concept.
When Brianna (played by Ally Ioannides) vanishes after taking Synchronic at a frat party, Steve starts to buy up the remaining supplies. He eventually meets the drug’s creator, Dr Kermani (Ramiz Monsef), who matter-of-factly reveals that Synchronic manipulates your pineal gland, the same region of the brain as Steve’s brain tumour. It is reminiscent of the resonating device in H. P. Lovecraft’s short story From Beyond, which lets the user see alternative planes of existence. However, instead of seeing monsters from another dimension, Synchronic changes how you experience the flow of time.

Kermani explains that time isn’t linear, instead working like a vinyl record: you play one track, but the other grooves are always there. “Synchronic is the needle,” he says, letting people travel to the past while physically remaining in the present. The catch is that you have no control over where you end up, and if you manifest in the middle of a forest fire or in the path of a rampaging bull, you will still die in the present.
“Time works like a vinyl record: you play one track, but the other grooves are always there”
As soon as Steve starts experimenting with Synchronic in an attempt to find Brianna, the film’s real potential emerges. He approaches the task methodically, rationing out his limited supply to establish the rules of the drug. I won’t reveal much about which time periods Steve travels to, but his encounters are surreal and upsetting in equal measure. The past is a particularly dangerous place for a Black man, and the film is at its best when it explores how time travel is disproportionately terrifying for Steve.
While there are a few holes in the plot – why does the drug never take people to the future, for instance – the potential of Synchronic‘s central conceit is obvious. Unfortunately, while the film-makers are no strangers to small budgets, their ambitions were clearly hamstrung by a lack of funds.
The environments in the past are severely limited, with a few brief glimpses of deserts and snowstorms being about as adventurous as the film-makers can afford. Although they make up for that with some clever tableaux and eerie, roving camerawork, you still sense that Synchronic would have benefited immeasurably from having twice as much cash, and twice as much time spent mining the horrors of history.
All that said, Benson and Moorhead have still created a grim, uneasy thriller with truly hair-raising moments. For all that I mourn the unfulfilled potential of the concept, Synchronic is yet more evidence that these film-makers should be given the tools with which they can fully realise their mind-bending ideas.
More on these topics: More

Proto-cities built from 6200 years ago in eastern Europe upend our ideas about when civilisation began and why people made the move from rural to urban living

Humans 24 February 2021
By Laura Spinney
Stuart Mcreath
AROUND 6200 years ago, farmers living on the eastern fringes of Europe, in what is now Ukraine, did something inexplicable. They left their neolithic villages and moved into a sparsely inhabited area of forest and steppe. There, in an area roughly the size of Belgium between the modern cities of Kiev and Odessa, they congregated at new settlements up to 20 times the size of their old ones.
This enigmatic culture, known as the Cucuteni-Trypillia, predates the earliest known cities in Mesopotamia, a civilisation that spanned part of the Middle East, and in China. It persisted for 800 years, but then, as mysteriously as it had begun, this experiment in civilisation failed. The inhabitants left the lightest of footprints in the landscape, and no human remains have been found. “Not a pinkie, not a tooth,” says palaeogeneticist Alexey Nikitin at Grand Valley State University in Michigan.
This puzzling lack of evidence has fuelled a lively debate about what Nikitin calls the “Dark Ages” of European prehistory. “You talk to five Trypillian archaeologists, you get five different opinions,” he says.
But the data gap hasn’t stifled interest – quite the opposite. Several projects in recent years have tried to make sense of the Trypillian proto-cities. Despite big disagreements, what is emerging is a picture of an early and unique attempt at urbanisation. It may be the key to understanding how modern Europe emerged from the Stone Age – and even throw new light on the emergence of human civilisation in general.

Uruk and Tell Brak, which … More