Humans

By Krista Charles

When looking at a scene (left), each quick eye movement creates motion streaks (right) on the retina that we don’t consciously perceiveMartin Rolfs
It has sometimes been assumed that we experience brief periods without vision every time we shift our focus from one point to another – but it turns out this is wrong.
Several times each second, we quickly change our line of sight, shifting our focus from one point in a scene to another. These fast, jerky eye movements, or saccades, each last less than 50 milliseconds, and our vision is reduced during that time. Some people have argued that our eyes lose their ability to process visual information in this time.
Richard Schweitzer and Martin Rolfs at Humboldt University of Berlin in Germany have shown that this isn’t the case: we are, in fact, able to absorb information from our surroundings during such rapid eye movements.Advertisement
“This kind of changes the way we approach perception because we used to think about motor actions and perception as two distinct things,” says Rolfs. “What this insight shows, I think, is that as we continue to interact between how we move and what we perceive, that it’s not two separate processes. It’s two things working together; they go hand in hand.”

The pair worked with 20 volunteers who were asked to seek out and focus on a visual target displayed on a screen, which naturally encouraged their eyes to dart around performing saccades. However, the target on the screen was shown using a high-speed projector that was capable of generating about 70 images during each 50-millisecond-long saccade. This meant the researchers could have the target move smoothly so that its position at the end of the saccade was different from its position at the start.
The volunteers detected this within-saccade movement: at the end of the saccade, when their eyes looked for the target again, they seemed to have anticipated where the target would now be located. The researchers could confirm this because the volunteers were able to correct their eye movement to locate the target more quickly than would have been the case had their eyes not detected the target’s movement during the saccade.
“The paper suggests that during eye movements, what is left of motion streaks (the traces left in our visual system by fast-moving objects) helps perception, whereas it is a disturbance when the eyes are steady,” says Paola Binda at the University of Pisa in Italy. “This point would need direct testing, of course, but it is an intriguing one.”
“The only potential criticism I can see is that the results were obtained with stimuli ingeniously designed to investigate these effects, but it is not clear whether any of this occurs in natural vision – as the authors admit,” says Karl Gegenfurtner at Justus Liebig University Giessen in Germany.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abf2218

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By Krista Charles

Reconstruction of the roman road in the Treporti channel in the Venice lagoonAntonio Calandriello and Giuseppe D’Acunto
An ancient and now submerged road has been discovered in the Venice lagoon in an area that would have been accessible by land 2000 years ago during the Roman era.
Fantina Madricardo at the Marine Science Institute in Venice and her colleagues made the discovery after mapping the floor of an area of the lagoon called the Treporti channel.
“We believe it was part of the network of Roman roads in the north-east of the Venice area,” says Madricardo.Advertisement
In the 1980s, the archaeologist Ernesto Canal proposed that there are ancient human-made structures submerged in the Venice lagoon. This suggestion prompted decades of debate, but couldn’t be confirmed until now as the previously available technology was insufficiently advanced to explore such a challenging environment.
“The area is very difficult to investigate by divers because there are strong currents and the water in the Venice lagoon is very turbid,” says Madricardo.
The team used a multibeam echosounder mounted on a boat to form a picture of what lies underwater. This device sends out acoustic waves that bounce off the lagoon floor, allowing the team to reconstruct images of whatever structures are down there.

The researchers found 12 structures up to 2.7 metres tall and 52.7 metres long that extended along 1140 metres in a south-west to north-eastern direction in the configuration of a road. The presence and layout of these structures suggest that there may have been a settlement in the area. It was then submerged about 2000 years ago – partly due to human activity that diverted the flow of rivers and starved the area of the sediment that was needed to keep it above water.
“Presumably, the road is giving access to this rich environment. The margins of the land and the water are full of resources that people might have been exploiting,” says James Gerrard at Newcastle University in the UK. “It’s not normal to find, if you like, ‘drowned’ landscapes or be able to study them in this kind of detail.”
Journal reference: Scientific Reports, DOI: 10.1038/s41598-021-92939-w
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By Christa Lesté-Lasserre

The well-preserved head of Tollund Man A. Mikkelsen
An ancient man ate a simple meal of cooked cereals and fish before being hanged and dumped in a bog 2400 years ago.
Tollund Man was roughly 40 years old when he died in what is now Denmark. He was probably offered as a human sacrifice, and the peat bog he was buried in mummified his body in extraordinary detail. Dozens of other Iron Age Europeans were sacrificed in the same way, and they are collectively referred to as “bog bodies”.
Danish scientists first analysed Tollund Man’s intestinal contents shortly after his body was discovered in 1950. They found 20 plant species and one species of parasite.Advertisement
But now Nina Helt Nielsen at Museum Silkeborg in Denmark and her colleagues have run new analyses on the contents of Tollund Man’s large intestine, investigating plant fossils, pollen and – for the first time in any bog body – a full range of non-pollen microfossils, steroids and proteins.
Ingredients that made up Tollund Man’s last mealN.H. Nielsen
The research revealed the presence of intestinal worm proteins and eggs – belonging to whipworm (Trichuris), tapeworm (Taenia) and mawworm (Ascaris) – as well as the man’s partially digested dinner. He ate porridge made up of around 85 per cent barley, 5 per cent flax and 9 per cent seeds from a plant called pale persicaria. Food crust indicated that the porridge was slightly burned and had been cooked in a clay pot.

About 20 other species represented less than 1 per cent of the whole meal and were probably consumed accidentally. Tollund Man had also eaten a fatty-boned fish, like eel. He probably picked up the parasites from eating poorly cooked meat and drinking unclean water well before his death, says Nielsen.
As for his last meal, it was mostly ordinary for the time. “I’m pretty sure we would see something similar if we analysed the gut contents of other bog bodies,” says Nielsen – although the pale persicaria seeds might have been a special addition as part of a sacrificial ritual.
At about 1350 kilocalories, Tollund Man’s last meal would have provided half his daily nutritional needs – and has been preserved in such detail that “we could almost reproduce the recipe”, she says.
Journal reference: Antiquity, DOI: 10.15184/aqy.2021.98

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A project testing great apes’ puzzle-solving abilities could offer insight into the mental abilities underpinning language. Solving the puzzles involves the same sorts of mental abilities humans use in speech, so by studying the gorillas, Birkbeck researchers hope to learn more about language development in another great ape: us. New Scientist has been following this pioneering research, discovering that humans are not as unique as we’d like to think.

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By Clare Wilson

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There are many ways that our great ape relatives can remind us of ourselves: through their anatomy, cleverness and social relationships, for instance. But never has the resemblance been so striking for me as today, when I watch gorillas carrying out a very human past-time: solving puzzles.
The gorillas in question live at Port Lympne Reserve in Kent in the UK. The task involves moving a hazelnut treat down a vertical maze using sticks or the inbuilt cogs, until it is released at the bottom. It is very similar to a game I loved as a child, called Downfall, … More

By Krista Charles

A very small part of our genome might be unique to modern humansCueImages/Alamy
Modern humans have been around for about 350,000 years. In that time, we have continued to evolve and our DNA has changed – but, only a small per centage of our genome may be unique to us.
Nathan Schaefer at the University of California, San Francisco, and his colleagues created a tool called the Speedy Ancestral Recombination Graph Estimator (SARGE), which allowed them to estimate the ancestry of individuals.
More specifically, it helped identify which bits of the modern human genome aren’t shared with other hominins – meaning they weren’t present in the ancient ancestors we shared with Neanderthals and Denisovans, and also haven’t been introduced to the human gene pool through interbreeding with these ancient humans.Advertisement
“Instead of building a tree across the genome that shows how a bunch of genomes are related on average genome-wide, we wanted to know what the ancestry of individuals looks like at specific sites in the genome,” says Schaefer. “We basically wanted to be able to show how everyone is related at every single variable position in the genome.”
The team analysed one Denisovan, two Neanderthal, and 279 modern human genomes to distinguish what parts of the genome separate modern humans from archaic hominins. They found that only 1.5 to 7 per cent of the modern human genome is unique to us.

The figure may seem low but that is partly because we inherited plenty of DNA from the ancient ancestral species that ultimately gave rise to modern humans and the Neanderthals and Denisovans.
What’s more, modern humans then interbred with Neanderthals and Denisovans, picking up even more DNA that isn’t unique to our lineage.
“It’s true that individual humans have a very low per cent of their genome that might have been from Neanderthal or Denisovan ancestry – non-Africans can have between 1.5 to 2.1 per cent of their genome that originated from Neanderthal ancestry,” says Schaefer.
But we know that the exact form taken by that small amount of Neanderthal DNA varies from individual to individual – meaning two people can both have 2 per cent Neanderthal DNA but share little Neanderthal DNA in common. These differences add up, says Shaefer. Some estimates suggest about 40 per cent of the Neanderthal genome can be pieced together by combining genetic information from a wide variety of living people.
The mutations that contribute to uniquely human features are contained within a small part of the genome and seem to mainly affect genes related to brain development.
“Knowing how those variants affect human mental capacities would help us understand the cognitive differences between humans and Neanderthals,” says Montgomery Slatkin at the University of California, Berkeley.
Journal reference: Science Advances, DOI: 10.1126/sciadv.abc0776
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To become an interplanetary species, we may have to genetically engineer ourselves to be more resilient, says geneticist Chris Mason. He has a 500-year plan for life away from Earth

Earth

14 July 2021

By Joshua Howgego

Rocio Montoya
CHRIS MASON likes to think about the future. He isn’t dreaming about a summer holiday, or even planning his retirement. His thoughts extend much further – to the point where Earth is no longer a suitable home for humans.
Alarmed at the prospect, Mason has sketched out a plan of action in the form of his book The Next 500 Years: Engineering life to reach new worlds. It covers some of the usual ground: how we will first establish bases on the moon and Mars, and later on the solar system’s outer moons. Eventually, we will make an epic trip … More

By Layal Liverpool

Race-based adjustments are widely used in some diagnostic testsSean Justice/Getty Images
THE assumption that Black people have a lower level of cognitive function than white people was, until recently, built into a formula used by the US National Football League to settle head injury lawsuits. The NFL has now pledged to stop using this “race-norming” formula, but race-based adjustments in routine diagnostic tests remain pervasive in mainstream medicine. Although some scientific organisations are working to remove such adjustments, many contacted by New Scientist declined to take a stance on the issue, which … More