Creatures that bridged the gap between reptiles and mammals may have been bearing live young 90 million years earlier than we thought.

One of the hallmarks of all mammals apart from monotremes – echidnas and the platypus – is that they give birth to live young. This “viviparity” contrasts with the “oviparity” seen most other vertebrates, in which females lay eggs that hatch outside their bodies.

One long-standing question has been whether creatures known as cynodonts, which emerged around 260 million years ago during the Permian geological period and are directly ancestral to all mammals, laid eggs or gave birth to live young, as no evidence of their reproduction has been discovered either way.

“Whether mammalian ancestors were oviparous or viviparous has been considered a mystery,” says  at Argentina’s National Scientific and Technical Research Council. “We had no clues on how or when one of the most distinctive traits of the majority of present-day mammals, viviparity, evolved in the mammalian lineage.”

This has now changed, thanks to a chance observation made during a postgraduate class at the University of Buenos Aires in Argentina. The students were examining a fossil of Chiniquodon theotonicus, a cynodont that lived 236 million years ago and was unearthed in the Talampaya National Park in north-western Argentina in 2011. Part of the analysis involved using a microscope to examine thin slices taken from one of the ancient animal’s leg bones. At that point, the class noticed a curious growth line inside the bone.

Gaetano and his colleagues investigated further and eventually concluded that this line, analogous to a tree’s growth ring, recorded the moment that the ancient mammal relative went through a growth spurt after its birth. 

The researchers reconstructed how large the leg bone and the animal itself would have been when the growth line formed. They calculated that the animal would have weighed 1.68 kilograms at that point. When the animal died as a full-grown adult, it was just shy of 12 kilograms.

This gave the researchers a ratio of newborn to adult size in the ancient animal. They then compared this figure to similar ratios obtained from a wide variety of modern animals: 1869 mammals, 2619 non-avian reptiles and 782 birds.

“We were amazed to find that ��󾱲Ծ���ܴǻ�Dz���grouped with extant placental mammals,” says Gaetano.

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Egg-laying animal groups produce young that are far smaller than adults when they hatch, he says.

For example, some species of large birds have newly hatched young that are just 0.002 per cent of adult body mass, whereas placental mammals often give birth to young that are over 20 per cent of the size of their parents.

“Only placental mammals produce relatively large newborns, whereas reptile and bird hatchlings are comparatively very small,” says Gaetano. “Hence, we propose that [the] Chiniquodon theotonicus reproductive strategy was most similar to that of placental mammals.”

 at the University of Bristol in the UK says the findings are convincing.

“Further, as they argue, the apparent absence or rarity of actual eggs of any kind in the Permian and Triassic has always been puzzling – the so-called amniote egg gap,” he says.

 at Macquarie University in Sydney says his gut reaction is to be sceptical of the claim of live birth, as we have only indirect evidence. But he is impressed that, in the absence of any direct fossil evidence, the team is still trying to solve the puzzle.

“We may never get any of the kind of direct evidence that solves the
mystery, for example a fossilised mammalian egg or a fossil mother during
pregnancy,” he says. “So it is kind of cool that they’re taking a different approach to trying to find an answer to that question.”

Running with a pram or stroller might make parents less susceptible to ankle pain and injuries to their calf muscles, foot arches and Achilles tendons. A survey of parents suggests there is a 37 per cent drop in injury risk with pram use. This may be partly due to changes in vertical forces – how much force our legs absorb with each step – when pushing a child.

“You get a little bit of a walker effect where you’re leaning and putting some weight on the stroller,” says at Pennsylvania State University, who ran with a pram after the births of her two children. “That led me to wonder, you know, is this actually protective?”

Previous research suggests that people running with a pram tend to have . They also lean forward more, with . Last year, Altman Singles and her colleagues found there is a when running with a pram, but whether this affects injury risk was unclear.

To learn more, Altman Singles and her team analysed self-reported running and injury data from 196 parents who used any kind of pram on at least some of their runs while their children were younger than 3 years old. These individuals were compared against another 53 mothers or fathers who ran when their children were the same age, but without prams. All the participants had some running experience before becoming parents.

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The two groups of parents covered similar total distances and were relatively well matched in terms of factors like age, height and weight. But there were many more women than men in both groups, particularly the pram one.

Overall, 30 per cent of the non-pram runners reported having had running-related injuries, compared with 19 per cent of the pram runners. These included a higher incidence of ankle pain, calf muscle injury, plantar fasciitis (heel pain that occurs when the thick band of tissue on the bottom of the foot becomes irritated or inflamed) and Achilles tendinitis (injury of the Achilles tendon).

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“Generally, stroller running involves rapid steps with short stride lengths,” says at Seattle Pacific University. “Although this can increase metabolic cost, it can also decrease the force production at each foot strike, which might explain some of these injury reductions.”

Wall-Scheffler says we should see this paper as a “great start” to understanding an important topic. However, future work should include a more balanced mix of men and women, she says. For instance, oestrogen and progesterone , which could affect a woman’s injury risk.

Future studies should also collect injury-related data more regularly over time and could even investigate the effects of different pram-pushing styles, such as using one or two hands, says Wall-Scheffler.

Watch as a total solar eclipse sweeps across parts of Europe and the Atlantic ocean as the moon passes between Earth and the sun, blocking out sunlight.

Parts of the US and Africa, along with the entire UK and much of Europe and Canada, will see a partial solar eclipse. Thanks to our friends at The European Space Agency (ESA), you can watch their live broadcast, allowing you to experience this rare event from anywhere in the world.

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Three massive black holes have been discovered in a galaxy located in the early universe, 12.5 billion light years away. This has left astronomers surprised that such a complex system could have formed so soon after the big bang.

“This system is in the very, very early universe,” says at the University of Sydney, who wasn’t involved in the discovery. “So, how have we ended up in a situation where these three supermassive black holes have formed and come close together in only a billion years or so since the big bang?”

In December 2024, at the Max-Planck Institute for Extraterrestrial Physics in Germany and her colleagues were observing a galaxy known as J0148-4214 through the James Webb Space Telescope when they saw something strange.

At 12.5 billion light years’ distance, the team observed the galaxy as it looked around 1.2 billion years after the big bang, says Übler. “We [also] quickly noticed that the central emission profile of the galaxy had a peculiar shape,” she says.

An analysis revealed two separate regions of high-velocity hydrogen gas in the centre of the galaxy, indicating two so-called accreting black holes that were separated by about 620 light years – a hop, skip and a jump in cosmic terms.

An accreting black hole is a super dense area of space, so compressed that light can’t escape, but that continuously drags in surrounding gas, dust and even stars. Our own galaxy, the Milky Way, has just one massive black hole at the core of its spiral arms.

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“During examination of the whole galaxy, we also noticed another region in the galaxy outskirts with high-velocity hydrogen gas, indicating another, third growing black hole,” says Übler. This one is more than 5500 light years away from the other two.

“We have explored several alternatives ranging from a single black hole to supernovae, shocks, winds and massive stars, but these were all unsatisfactory or incompatible based on our data and previous observations of this system,” she says.

Until now, there was no evidence that massive black hole triplets existed within the first 1.2 billion years of cosmic history, says Übler. “This discovery shows us that processes in the early universe were efficient at bringing massive black holes together,” she says. “It also suggests that black hole merging may have been an additional, fast route for their rapid growth in the early universe.”

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at the University of New South Wales in Sydney, Australia, says that based on the information the researchers have presented, she agrees with their conclusion. “The fingerprints look like black holes and the ‘shape’ is best explained with two separate ones,” she says. “The third black hole is better separated, so it is a much cleaner result. Maybe it is falling into the galaxy for the first time, or maybe it has been ejected by interactions with the other two.”

Having three black holes in close vicinity and in a single system suggests there has recently been a merger of separate galactic entities, says Foster. But she says other interpretations may arise in the future, as more observations of the galaxy are made.

Dobie says that a triple black hole system “seems to be the most promising interpretation of the data that they’re seeing”. He also suspects that as more telescopes come online and technology advances, more such galaxies will be found.

On 12 August, a total solar eclipse will sweep across parts of Europe and the Atlantic ocean as the moon passes between Earth and the sun, blocking out sunlight. Parts of the US and Africa, along with the entire UK and much of Europe and Canada, will see a partial solar eclipse.

Where can I see the eclipse in the UK and US?

While the total eclipse will be short and only visible in a few areas, a partial eclipse, with the moon taking a “bite” out of the sun, will last much longer across about a quarter of the entire planet. It won’t be as dramatic as a total eclipse – the corona will not become visible, and the ambient light levels and temperatures won’t drop as dramatically – but will be watchable for many more people.

In the UK and Ireland, 90 to 96 per cent of the sun will be covered by the moon. In London, the eclipse will last from 6.17 to 8.06pm, with the maximum at 7.12. The sun will be setting, so you need to be somewhere with a clear view to the west.

In most of Canada, Alaska and the northeastern US, the moon will cover less than half of the sun. Montreal will get an 18 per cent eclipse at 1.45pm and New York will get a 9 per cent eclipse at 1.54pm.

Where can I see the total eclipse?

Totality, which occurs when the moon lines up perfectly with the disc of the sun and blocks it out entirely, will begin in Russia around midday before sweeping eastward across the Arctic ocean. It will pass just south of the North Pole and make landfall in northeastern Greenland just after 4.00pm local time.

The shadow will then rush along the eastern coast of Greenland at a speed of more than 3400 kilometres per hour. The maximum length of totality will be about 2 minutes and 18 seconds, as the moon’s shadow crosses from Greenland into the Atlantic ocean. It will cross to Iceland, at which point the eclipse will become visible from more heavily inhabited areas – everywhere it will have passed so far is home only to small villages, research stations and those specifically making the journey to see the eclipse. In Reykjavík, though, totality will be visible for just over one minute at 5.48pm local time. This is the first time a total eclipse has been visible in Iceland since 1954, and the last time one will be visible there until 2196.

After skimming the western coast of Iceland, the total eclipse will make another ocean crossing and reach land again in northern Spain just before 8.30pm local time, grazing the northeast corner of Portugal and crossing the Balearic Islands off Spain’s east coast before the sun sets and the eclipse is over.

How can I watch the eclipse safely?

During a total or partial eclipse, eye protection is needed the whole time. If you don’t have eclipse glasses, you can use a pinhole camera or even natural shadows to create a projection of the sun’s shape as the moon passes in front of it. Read this article for more details of how to do that.

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What happens during a total solar eclipse?

During totality, when the disc of the sun is completely concealed by the moon, temperatures on the ground rapidly drop by several degrees and daytime transforms into twilight. The stars and the outer reaches of the sun become visible. Usually, the sun’s outermost layer, the corona, is completely lost in the glare from its far brighter inner regions, but when those are blocked out, its shimmering sheets of extraordinarily hot plasma become briefly visible to the naked eye. In all other phases of the eclipse, it is crucial to wear eclipse glasses or use a solar filter while looking directly at the sun to prevent eye damage, but during totality it is safe to look at the corona.

That is precisely what many solar scientists will be doing during August’s eclipse. Total eclipses mark a valuable opportunity to observe the corona and try to unravel its many mysteries, including why it is so much hotter than the sun’s surface.

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