In the Red Sea, a tiny fish has been cornered by a group of hunters working as a team. One of them chased it into a coral crevice, while the others circled around to block off any exists. With no escape, the predators – a group of yellow saddle goatfish – close in on their prey.
The goatfish are one of the few examples of fish that hunt in groups, and their strategy has just been described by Carine Strubin, Marc Steinegger and Redouan Bshary from the University of Neuchatel. Bshary has spent over a decade in the Red Sea, studying the local fish. “I spent a long time working on cleaner wrasses,” he says. “During that time, one happens to see a lot of things.”
To round off my brief stint at the Guardian, here’s a piece about a mastodon specimen with what looks like a spear-tip stuck in its rib. This specimen, the so-called “Manis mastodon” has been a source of controversy for several decades. Is that fragment man-made or simply one of the animal’s own bone splinters? Does it imply that humans hunted large mammals hundreds of years earlier than expected, or not?
Having re-analysed the rib in an “industrial-grade” CT scanner, Michael Waters thinks it’s definitely a man-made projectile. He even extracted DNA from the rib and the fragment and found that both belonged to mastodons. So these early hunters were killing mastodons and turning them into weapons for killing more mastodons. How poetically gittish.
Anyway, read the piece for more about why this matters. In the meantime, I want to draw your attention to this delicious tete-a-tete at the end between Waters and Gary Haynes, who doesn’t buy the interpretation. Note, in particular, the very last bit from Waters, which made my jaw drop.
But despite Waters’ efforts, the fragment in the Manis mastodon’s rib is still stoking debate. “It’s not definitely proven that it is a projectile point,” says Prof Gary Haynes from the University of Nevada, Reno. “Elephants today push each other all the time and break each other’s rib so it could be a bone splinter that the animal just rolled on.”
Waters does not credit this alternative hypothesis. “Ludicrous what-if stories are being made up to explain something people don’t want to believe,” he says. “We took the specimen to a bone pathologist, showed him the CT scans, and asked if there was any way it could be an internal injury. He said absolutely not.”
Waters adds, “If you break a bone, a splinter isn’t going to magically rotate its way through a muscle and inject itself into your rib bone. Something needed to come at this thing with a lot of force to get it into the rib.”
The spear-thrower must have had a powerful arm, for tThe fragment would have punctured through hair, skin and up to 30 centimetres of mastodon muscle. “A bone projectile point is a really lethal weapon,” says Waters. “It’s sharpened to a needle point and little greater than the diameter of a pencil. It’s like a bullet. It’s designed to get deep into the elephant and hit a vital organ.” He adds, “I’ve seen these thrown through old cars.”
“Living fossils” abound in popular science writing. The phrase refers to modern species that are uncannily similar to extinct ones. Their bodies seem to have gone unchanged over millions of years, as if evolution took its foot off the pedal and allowed them to coast. These species are painted as either relics desperately clinging onto existence, or great survivors triumphing against the odds. They range from the famous coelacanth, to the horseshoe crab, to a new eel discovered just months ago.
But one classic example – a group of plants called the cycads – shows just how slippery the concept of the “living fossil” can be.
Cycads look superficially like palm trees, but they belong to a very different group. They first appeared on the planet around 280 million years ago, but they really hit their stride in the Jurassic and Cretaceous period, between 200 and 65 million years ago. But their time would soon be over. Out-competed by flowering plants, and suffering from the decline of their dinosaur polliantors, the cycads started to disappear.
I’m getting somewhat inundated with spam and it’s a pain, so I’m going to click the little button that says “Comment author must have a previously approved comment”. If you’ve commented before, there shouldn’t be any problems. Otherwise, I’ll have to approve, which I will do frequently.
Let’s see how that works for the moment.
This week, I’m filling in for one of the Guardian’s science correspondents (the excellent Alok Jha), and I’ve been asked to cover a few stories that I would otherwise do here. So, let me direct you to the Guardian website where you’ll find the two pieces I filed today.
I did my first ever radio skit tonight for a series called Four Thought, a set of talks about interesting ideas that include a mix of personal storytelling. I elected to witter on about one of my favourite topics: the microbiome. That’s the legion of bacteria and other microbes (and their collective genes) that live inside us, and affect our health, lives and minds. As the official description reads: “he asks whether he should be seen as a human, or a universe of bacteria in a “human shaped sack”?”
It was fun to record, the audience were great, I got to meet David Baddiel, and I follow in the footsteps of such scientific luminaries as Steve Rose and Charles ffrench-Constant.
If you’re in the UK or Ireland, you should be able to listen to it on iPlayer soon enough. You can also download a podcast of the actual talk. Or if the thought of hearing me speak fills you with dread, you can read an edited version of the talk script on the BBC website.
And for more on the topic, check out the slideshow below for links to my previous posts.
For the residents of Lakeshore, Ontario, the black fungus caking their homes was a problem, and they blamed the local distillery. For James Scott, the Sherlock Holmes of fungi, the identity of the unsightly mold was a mystery waiting to be solved. And for Adam Rogers, senior editor at WIRED, Scott’s quest was a story that needed to be told. Rogers spent three days tailing the fungus detective, and the result is a beautiful, sensory, fungal whodunit, with a brief history of alcohol on the side.
I was recently asked if I wanted to contribute anything to the Open Notebook, a site where science writers write about science writing. It specialises in taking big, important stories and dissecting how they were conceived, crafted and refined. It’s about the stories behind the stories. I’ve been a fan of the Open Notebook from the beginning. Not only does it highlight the best science writing around but we get a wonderful look at how the best professionals in the field do their work. It’s an antidote to the caricature of the lazy, uninformed science journalist, and it helps those of us who care about the profession to aspire to higher standards.
When I was thinking which story to delve into, Adam’s whiskey tale was an obvious choice. It was one of my favourite pieces of the year. All of the elements of a great science feature are here. It’s a story, not a review, and it uses a compelling central character to explore the fascinating and overlooked world of fungal science. The explanatory element is crystal clear without skimping on detail. The prose is vivid with sensory detail and has a light, lilting cadence to it. And more than any piece I have recently read, it bares open the process of science, and the curiosity and passion that drives its practitioners. It’s science as a quest: frustrating and never-ending, but always captivating.
Check out Adam’s story if you haven’t already, and then read about how he built it at the Open Notebook.
Image by Shadle
If you look at the skeleton of the flesh-eating dinosaur called Carnotaurus, two features instantly stand out: the skull and the arms. The fearsome skull is short, deep and topped by two devilish horns. Hence, its name: “meat-eating bull”. The arms are much less fearsome – they’re so short that they make Tyrannosaurus’s stunted fore-limbs looks like those of a wrestler. These body parts are distinctive, but Scott Persons and Phillip Currie from the University of Alberta think that the most interesting parts of Carnotaurus are its hips and tail.
By reconstructing the meat-eating bull’s hindquarters, Persons and Currie have found evidence that this dinosaur was much faster than anyone had thought. Powered by an enormous tail muscle, Carnotaurus was the Usain Bolt of the Cretaceous, well-adapted for short-burst sprinting.
Carnotaurus is the most famous member of the abelisaurids, a group of large predatory dinosaurs that hunted in the southern hemisphere, while the tyrannosaurs dominated the north. When Argentinean palaeontologist Jose Bonaparte discovered the animal in 1990, he suggested that it would have been a good runner. Others called this view into question when they discovered other closely related abelisaurids whose hind limbs hinted at a slower pace.
But leg bones don’t tell the whole story about a dinosaur’s running speed. You also have to look at its tail. The flesh-eating theropods, like Carnotaurus and Tyrannosaurus, had a pair of large muscles that ran along the sides of their tails. These muscles, known as the caudofemoralis, attached to the animals’ thigh bone. When they contracted, they pulled the leg backwards, powering a forceful running stroke.
Last year, Persons and Currie analysed the caudofemoralis of Tyrannosaurus to show that it probably ran faster than people had previously thought. But Carnotaurus was probably faster still. It could have been one of the fastest of all the large theropods, although Persons and Currie haven’t calculated a top speed yet.
The duo found that the dinosaur had a particularly butch caudofemoralis. Its tail bones each have a pair of unusual crescent-shaped flanges that protrude off to either side. Persons and Currie think that these flanges – also known as “caudal ribs” – served as anchor points for an unusually large caudofemoralis muscle. It was larger for the animal’s size than that of any other theropod, and would have accounted for 15 percent of its total body weight. When Carnotaurus contracted this mighty muscle, it would have pulled its hind leg backwards with extreme force, allowing for “sudden, straightforward sprints and charges”.
But Carnotaurus paid a price for its speed. Its caudal ribs may have anchored a powerful running muscle, but they also made its tail very rigid. When theropods ran, they turned in an almost snake-like way, leading with their heads and following with necks, torsos, hips and tails. But Carnotaurus’s tail was so rigid that its entire back half would have had to rotate as one. It could dash hell for leather in a straight line, but tight turns were out of the question. Its prey could probably have dodged and weaved around it.
Carnotaurus was one of the latest abelisaurids on the scene, and many of its contemporaries, like Skorpiovenator and Aucasaurus, also had caudal ribs. These species could probably have mustered the same bursts of speed. However, earlier members of the group had less distinctive tails, which suggests that these hunters gradually evolved to become sprinters.
When Carnotaurus was still alive, it shared South America with a far larger group of theropods – the carcharodontosaurids, or shark-toothed lizards. These included some of the largest theropods that ever lived, including Giganotosaurus and Tyrannotitan, large enough to hunt truly gargantuan prey like titanosaurs.
Persons and Currie think that Carnotaurus and its ilk went the other way – evolving to chase smaller, nimbler prey with rapid bursts of speed. Perhaps they were the Cretaceous equivalents of cheetahs, sprinting after smaller prey while they left the bigger quarry to the more powerfully built lions. If an asteroid hadn’t finished off the dinosaurs, perhaps Carnotaurus would have eventually evolved go-faster stripes and a rear spoiler…
Reference: Persons, W., & Currie, P. (2011). Dinosaur Speed Demon: The Caudal Musculature of Carnotaurus sastrei and Implications for the Evolution of South American Abelisaurids PLoS ONE, 6 (10) DOI: 10.1371/journal.pone.0025763
Image: by Lida Xing and Yi Lu
More on theropods:
Two people are dancing a waltz, and it is not going well. One is tall and the other short; one is graceful, the other flat-footed; and both are stepping to completely different rhythms. The result is chaos, and the dance falls apart. Their situation mirrors a problem faced by all complex life on Earth. Whether we’re animal or plant, fungus or alga, we all need two very different partners to dance in step with one another. A mismatch can be disastrous.
Virtually all complex cells – better known as eukaryotes – have at least two separate genomes. The main one sits in the central nucleus. There’s also a smaller one in tiny bean-shaped structures called mitochondria, little batteries that provide the cell with energy. Both sets of genes must work together. Neither functions properly without the other.
Mitochondria came from a free-living bacterium that was engulfed by a larger cell a few billion years ago. The two eventually became one. Their fateful partnership revolutionised life on this planet, giving it a surge of power that allowed it to become complex and big (see here for the full story). But the alliance between mitochondria and their host cells is a delicate one.
Both genomes evolve in very different ways. Mitochondrial genes are only passed down from mother to child, whereas the nuclear genome is a fusion of both mum’s and dad’s genes. This means that mitochondria genes evolve much faster than nuclear ones – around 10 to 30 times faster in animals and up to a hundred thousand times faster in some fungi. These dance partners are naturally drawn to different rhythms.
This is a big and underappreciated problem because the nuclear and mitochondrial genomes cannot afford to clash. In a new paper, Nick Lane, a biochemist at University College London, argues that some of the most fundamental aspects of eukaryotic life are driven by the need to keep these two genomes dancing in time. The pressure to maintain this “mitonuclear match” influences why species stay separate, why we typically have two sexes, how many offspring we produce, and how we age.