Dung beetles have been ever-present in the history of the West – but oddly, less so elsewhere – in religion, art, literature, science and the environment. What we understand about them now mirrors our greater understanding of the important role they play in keeping our planet healthy.
The story of these beetles, which we tell in our new book “The Dance of the Dung Beetles”, comes with a few unexpected twists. It moves from the tombs of the pharaohs to the drawing rooms of directors of the Dutch East India Company to the remote forests of Madagascar. It is a big story carried on the back of a family of small creatures who seldom diverge from their dogged pursuit of dung in its infinite variety and abundant supply.
Like the housemaids of Victorian Britain, who tended fires and households in the small hours while the Empire swept across the globe, they remain largely unseen and ignored. Yet without those housemaids, the world would have a lot more dirt in it. In the same way, dung beetles are largely invisible. And yet without their vital activities, the world would have a lot more faeces in it.
More than “dung-grubbers”
Dung beetles have relatively minuscule brains, much of which is devoted to analysing smells. But they also process visual information that even humans with their vast brains struggle to comprehend. This was shown in a study we conducted with other scientists that revealed how dung beetles use the light of the Milky Way to orientate.
The original story was picked up way beyond the scientific literature and spread rapidly around the world. We were struck by how the tale of a lowly beetle and the distant Milky Way engaged popular imagination when so much other information about dung beetles is equally impressive, if not even more fascinating.
Wearing a cap prevents this beetle seeing orientation cues in the sky. As a consequence it rolls its ball around in circles, like a human lost in a featureless desert.
Courtesy Marcus Byrne
This realisation prompted us to respond on behalf of these little creatures, which can be found on every continent except Antarctica, to show that they deserve better press than to be seen as mere dung-grubbers – some of whom happen to orientate by the stars.
Together with earthworms and ants, dung beetles represent a trinity of earth transformers. They literally change the earth beneath us, and they do so at absolutely no cost to us. Dung beetles play a largely unexplored role in soil health, which is increasingly important in a hungry world full of people. There is still so much we do not know about the 6,000 species that clean our world.
We do not know, for example, exactly what they eat. Most eat dung, some eat carrion (dead animals). But getting by on low nutrient waste requires careful selective feeding performed by specialised mouth parts. Microorganisms in the dung and soil might also have a role, fixing nitrogen from the atmosphere to increase food quality and soil health.
We know how dung beetles use celestial cues to orientate, but it’s not clear how a brain so small can process or remember such information. We know they are attracted to the smell of dung, but we do not really understand how that works, or if that sense switches off when they turn their attention to the visual task of rolling a dung ball. Does their neural limitation preclude parallel processing of disparate information?
Evolution of science
In our history of the development of contemporary science, we have seen the evolution of belief in magic, to one of stocktaking and empirical observation, to interpretation and deepening levels of sophisticated tunnelling into the smallest known particles. We have gone from myth, symbols, vague observation and interpretation of a world run by the gods, to a world with one God, and then a world in which the boundaries of religion no longer act as the limit to our knowledge.
The quest for money rather than scientific or natural interests drove much early exploration. Gold, and then trade, became the vehicles for global expansion and settlement. The knowledge we now have of how the world works comes with the recognition that so much of what there is, is threatened by the very pursuits that opened up our world.
It is an irony that cannot be lost on us as we look at the growing list of flora and fauna on the brink of destruction and extinction. The relevance to what we still do not know about creatures as small and seemingly insignificant as dung beetles is that we are beginning to understand what German naturalist and artist Maria Sibylla Merian showed in her paintings: that the world is deeply and fundamentally interconnected.
Biological evolution represents the history of a dynamic process – but evolution has its own timetable. So, even though many creatures can adapt relatively rapidly to the environmental changes we have induced, there are hundreds of thousands of species that cannot. Dung beetles are however, excellent models of rapid evolution and speciation.
The development of the magnificent horn of many dung beetles can be switched on or off in the same gene carried by males and female dung beetles, allowing natural selection – that is, chances of survival – to be balanced against sexual selection (chances of reproducing) in different habitats. The export of dung beetles to different continents, for control of dung-breeding flies, has created a massive natural experiment which will eventually reveal which way evolution will drive those species.
If we need a reminder of how much we do not know, then the study of one little sub-family of unseemly beetles is instructive. Their endless complexity and variety has absorbed the energies of so many researchers across the globe since the Egyptian Horapollo recorded the first observation of them rolling their ball “from East to West, looking himself towards the East” 3,000 years ago.
For years scientists have tried to reconcile the fungal fossil record with estimates from analyses of fungal DNA. But some of their key morphological characters, that is the shapes they take, can only be established via microscopic and chemical analyses. That includes the complex networks of microscopic thread-like filaments and cell walls made of chitin, which are also not visible to the naked eye. The effort seemed hopeless, until now.
Corentin Loron, a graduate student at the University of Liege in Belgium and colleagues, discovered microscopic, fossilized specimens of a fungus called Ourasphaira giraldae in shale rock from the Grassy Bay Foundation in the Northwestern Territories of Canada. Given that Ourasphaira is found on 1,000-900- million-year-old rocks, the new fossil pushes back the origin of fungi by half a billion years.
A very revealing fossil
But how did Loron deduce that these fossils are fungi? While most of us are quite familiar with the large reproductive structures of some fungi, such as mushrooms, most of us are less familiar with the fungal network of microscopic thread-like filaments that makes up their “bodies.”
Microscopical analyses of Ourasphaira show that it formed a network just like those made by modern fungi; and chemical analyses show that the cell walls of these microfossils contain chitin, again just like modern fungi.
The implications of this discovery are twofold.
First, the fossil singlehandedly reconciles DNA-based and paleontological estimates of fungal origins, pushing back the origin of Opisthokonta, a supergroup comprising fungi, animals and their single-celled relatives to at least a billion years ago. And second, the fossil gives us clues about the environments where the first fungi lived. Ourasphaira was found in a shale, a type of rock that forms at the muddy bottom of lakes and rivers. Since this particular shale appears to have been formed as a result of sedimentation from a shallow-water estuary, it may be the first fungi evolved where rivers met the seas a billion years ago.
It’s one more clue that helps fill in the picture on how life on earth evolved and one more step toward bringing this fascinating group of organisms to the limelight.
Antonis Rokas receives funding from the National Science Foundation, the John Simon Guggenheim Memorial Foundation, the Burroughs Wellcome Trust, the National Institutes of Health, the Beckman Scholars Program and the March of Dimes.
“I fought the law,” the 1977 song popularized by the English punk-rock band The Clash, features catchy lyrics about the dire consequences of life as an outlaw. In human affairs, the set of rules codified in our laws helps protect individuals and maintain order in our societies. Without rules, order is lost and chaos reigns. Life’s organisms have evolved their own set of checks and balances that help fight off chaos and ensure their survival and success.
During our studies of budding yeast genome evolution, we serendipitously discovered that an ancient lineage of budding yeasts named Hanseniaspora appear to have lost genetic law and order. Specifically, Hanseniaspora yeasts have done away with parts of their systems of checks and balances, in much the same way as cancerous cells do, challenging the existing paradigm that these processes are essential for cellular life.
Checks and balances are evolutionarily conserved
The entirety of an organism’s DNA, or the genome, serves as the blueprint for life. From metabolism to movement, the DNA present in each cell contains the instructions for all aspects of its life. Alterations, or in biologists’ lingo “mutations,” in the parts of the DNA carrying these instructions are generally harmful – it is easier to break something than to improve it, and keeping mutations at very low levels is one of cellular life’s major rules.
Increases in the occurrence of mutations lead to cancer and the death of an organism. Two central mechanisms that help cells do so are cell division and DNA repair processes. These two systems of biological checks and balances not only ensure that cells divide properly but also that they detect and repair any damage that their DNA may have acquired.
Why is that so? Because tens of millions of years ago, Hanseniaspora yeasts appear to have lost numerous genes known for their roles in cell division and repairing DNA damage. As a consequence, the genomes of Hanseniaspora yeasts are riddled with many more mutations than other yeast species and show evidence of diverse types of DNA damage, such as that caused by UV radiation, which is associated with skin cancers in humans.
In short, like cancer cells, Hanseniaspora have dismissed typical cellular checks and balances and embraced chaos in their genome. But the lives of cancer cells are short-lived because they generally kill their host, whereas the single-celled Hanseniaspora yeasts appear to have inhabited the planet for tens of millions of years. How can they survive without such critical genes? What, if any, was the advantage of losing these genes?
The speed-accuracy trade-off
We believe the Hanseniaspora life strategy is a quantity-over-quality issue. By losing genes that control the pace of cell division, Hanseniaspora cells start dividing too early and speed through the process. Like a NASCAR driver racing through red lights, Hanseniaspora cells sometimes make errors that have grave consequences. For example, their fast-paced cell division can, in the process of dividing, lead to the death of daughter cells.
However, by dividing quickly these yeasts also produce lots of offspring, which means that they can outnumber competing microbes. Strikingly, Hanseniaspora yeasts can divide nearly twice as fast as the baker’s yeast, one of the champions of rapid dividing.
Hanseniaspora uvarum vs Saccharomyces cerevisiae - YouTube
Hanseniaspora uvarum (left) grows roughly twice as fast as baker’s yeast Saccharomyces cerevisiae (right). Video uploaded by Genetik Universität Osnabrück.
So, it appears that Hanseniaspora yeasts have fought the law and the yeasts won. Understanding how Hanseniaspora yeasts have done so – a major question we’re now addressing – may hold clues that could one day be used in the war against cancer.
Jacob L. Steenwyk receives funding from the Graduate Program in Biological Sciences at Vanderbilt University.
Antonis Rokas receives funding from the National Science Foundation, the John Simon Guggenheim Memorial Foundation, the Burroughs Wellcome Trust, the National Institutes of Health, the Beckman Scholars Program, the March of Dimes, and Vanderbilt University.
Pregnancy, labour and delivery are incredibly physically demanding for women. But birth is no walk in the park for the baby either.
A new paper reveals just how much a baby’s head is pushed and distorted by vaginal delivery.
By recording MRI scans before and during labour, the researchers show the degree to which a baby’s skull bones ride over each other, allowing the whole skull to morph. The baby’s head becomes a sugarloaf shape – an elongated cone, with a rounded tip at one end – to get through the pelvis. The brain itself changes form as this happens too.
Three-dimensional fetal brain MRI reconstruction shows the shape of a baby’s brain before labor (purple in A, C, E) and during the second stage of labor (orange in B, D, F).
Olivier Amie and co-authors, CC BY
Head compression is just one of the many incredible physical changes that takes place in infants during birth. Babies undergo a massive transition during labour and delivery as they move from the supported environment of the uterus to independent existence.
Many body systems change to do this. Some have already been in transition. For example, urine output from the fetus contributes to the amniotic fluid (the liquid that surrounds the baby) in the later part of pregnancy. Other organs require a sudden change in the first few moments after delivery, such as expansion of the lungs.
These biological events are vital to maximise chances of survival in the first few minutes “outside”. But surprisingly, we are still learning many of the details.
Before the baby is born, blood goes through the placenta to get rid of waste and to pick up oxygen and nutrients that come from the mother. The developing baby manages on relatively low oxygen levels while in the uterus.
After birth the child is exposed to suddenly higher (potentially dangerous) oxygen levels. This shift requires different ways to protect the newborn – so the baby has systems ramped up to cope with this sudden flood of oxygen. Mild jaundice, a temporary yellowing of the skin resulting from a delay in liver enzymes kicking in, may be one such protective mechanism seen in many infants.
Physical changes plus shifts in biology and chemistry of the body’s systems are required to cope with the outside world.
Before birth, most of the baby’s blood circulation passes through the placenta, but bypasses the lungs.
After delivery, the placental flow stops. Instead of going from the baby’s heart to the placenta, the blood from the heart needs to redirect through the newly expanded lungs.
New research helps us understand the relationship between baby’s first breaths and the expansion of lung blood flow.
Understanding these processes in the first few minutes guides us in knowing when exactly to clamp the umbilical cord, and to time any breathing help needed for sick or premature newborns.
Once born, the baby must take over many of the biological processes the placenta performed during pregnancy.
It doesn’t always go to plan
The many changes a baby needs to be ready for delivery do not always have a chance to take place.
For example, if a baby is born prematurely then some or all of these adaptations may not have occurred.
Premature babies may have trouble opening up their lungs, or they may not close off the relevant bits of “plumbing” to redirect blood flow to the lungs. Or they may have difficulty exchanging oxygen and other gases in the lungs.
Other body systems such as skin, guts and the body’s chemistry systems may also be relatively unprepared.
Despite this, all but the most premature of babies benefit from the boost of labour if possible. The changes associated with the onset of labour, particularly inflammation, trigger the biological signals that tell a baby to get ready for being born.
Surprisingly, even a small deviation from normal, full-term (around 40 weeks) timing of labour may have effects.
Babies born by caesarean section without labour do not transition to the outside world as smoothly as those where labour has commenced. They have a higher rate of admission to neonatal units for respiratory problems, even after adjusting for other risk factors. Every week earlier than delivery at 40 weeks roughly doubles the risk of neonatal unit admission for babies.
Birth by caesarian section is an entirely different biological experience for the baby – and may have some health consequences.
Current recommendations for birth timing are to balance the risks of delivery with these immaturity risks, and not deliver too early unless it is medically required.
Some of these effects can be altered by steroids. Steroids are made naturally by our bodies, including in babies. Also referred to as “the body’s stress hormones”, these are particularly important in making sure lung maturity happens at birth.
Sometimes steroids given to the mother can trick the baby into “preparing an escape plan” and getting lungs ready for delivery before term.
Independent of mild prematurity, researchers are looking closely to determine if there are any long term health and developmental effects of being born by caesarean section, without the process of labour and delivery.
But why do we have such a high-risk delivery system, one where the baby has to actually deform its skull to be born?
Humans are defined by our brains. In our species, the process of evolution has been a balancing act, where brain size and maturity have been weighed up (in terms of survival) against the risk of obstruction in labour.
Human babies are relatively immature compared with some of our close primate relatives, but we cannot safely achieve more brain growth before delivery. For us, this extra growth has to occur over the first year or so after birth.
Gorillas and other primates give birth to babies that are much more developmentally advanced than human babies.
In addition, because we walk upright, this has created a tilt in our pelvis which narrows the birth canal (the gap in the bones of the pelvis through which the baby has to pass).
Birth is still risky. Globally, obstructed labour is still a significant cause of both mother and baby deaths, and a major cause of long-term incontinence disabilities in mothers that do survive. This tightrope we humans walk between head size and the potential of terrible mother and baby outcomes is essentially the driver for the existence of modern obstetrics.
We hope that more research aimed at understanding the balance of those risks, plus looking at how babies transition from uterus to the outside world, will help us better manage safe birthing. This will improve immediate and long-term health for mothers and their babies.
Ian Wright receives funding from the Australian National Health and Medical Research Council.
A male guppy looks good when he looks different. Mitchel Daniel, CC BY-ND
If you’re looking for love, it pays to stand out from the crowd. Or at least that’s how it works in some parts of the animal kingdom. Scientists have found that in several species – green swordtail fish, Trinidadian guppies, fruit flies, Poecilia parae fish – ladies overwhelmingly go for the guy that looks different from the rest.
The guppy has long been a workhorse for biologists like me who are interested in understanding the mating decisions that animals make, and the evolutionary forces behind those decisions. Male guppies attempt to woo females using courtship dances that show off the elaborate color patterns adorning their bodies. The females of the species are color pattern connoisseurs, carefully choosing among their suitors based, in large part, on their visual appeal. This tendency has made the guppy an excellent model for studying mate choice.
Male Guppy courting dance - YouTube
Male guppies showcase their colors during their courtship dances.
What’s less clear, though, is why females should value unusualness in a mate.
When puzzling over why this mating preference arose, it occurred to me that attraction to novelty fits with a simple kind of learning called habituation. Psychologists have long known that when an animal is repeatedly exposed to some stimulus – be it a sound, a touch, or in this case a visual pattern – it responds to the stimulus less and less. This occurs because the nervous system starts to “tune out” repetitive information. Since repetitive information is usually unimportant, habituation helps to free up the animals attention for other, more important things.
What’s interesting about habituation is that it’s pervasive: virtually every animal species, including human beings, can habituate to a wide range of things. It’s the reason why the noise from the air conditioning unit seems loud and distracting when it first turns on, but before long you barely notice it.
I wondered if this might be happening in guppies. If females are tuning out the color patterns they commonly see, then a male with a different-looking pattern is going to have a huge advantage attracting mates.
Why does new colorful flair pay off with the ladies?
Mitchel Daniel, CC BY-ND
Testing whether habituation is what’s happening
To test this idea, I had to determine whether preference for novel-looking males meets four key criteria of habituation.
First I needed to see whether repeated exposure to a stimulus – like the noisy air conditioner, or a particular color pattern – made the animals less interested in that thing. Scientists call this “responsiveness decline.” To test it, I took a group of female guppies and exposed them to a series of males that looked alike. Then, I observed how the females behaved toward a male with the now-familiar pattern.
Male guppies are persistent suitors, and females mostly ignore their courtship dances. But when a male catches their fancy, females will turn and approach the male, which can lead to copulation. The effect of exposure to males was striking: females already familiar with the pattern responded about half as often to male courtship compared to females that had never seen any male color patterns before. I also found it took just 12 minutes of exposure to reduce female responsiveness, which shows that female interest is fleeting.
Next, I had to show whether isolating females from the stimulus causes their responsiveness to increase again, something called “spontaneous recovery.” This would be like the air conditioning unit turning off for a while, and then being noticeable again when it flips back on. I found that isolating females for a short period after exposure made them more responsive when I observed their behaviors with the familiar-looking male, meeting this criterion.
The third criterion is called dishabituation: after responsiveness to a stimulus has declined, exposure to a different stimulus should cause responsiveness to increase again. For instance, hearing the siren of a passing police car would make you notice the droning of the air conditioner again. And yes, showing females a different-looking male before observing their behavior towards the familiar-looking male caused them to show more mating interest, demonstrating dishabituation.
The fourth criterion is that exposure to one stimulus – like the familiar pattern – should not reduce interest in another stimulus – such as a different-looking pattern. This is why getting used to the noisy air conditioner doesn’t prevent you from noticing that passing siren. I tested this by exposing females to males that looked alike, as before, but this time I observed how they behaved towards males with a different-looking pattern. As expected, they showed the same level of interest as other females that had never seen any male color patterns before, meeting this criterion.
These results ticked all four of the habituation boxes. Female guppies do habituate to male color patterns, explaining their attraction to novelty. This means females tune out familiar-looking males, so that when a male with a new pattern shows up it really turns their heads. Females grow bored of males that look like all the rest, giving an edge to the distinctive.
It was exciting to discover the why of this behavior because while habituation has been extensively studied by psychologists, no one had linked it to attraction to unusual mates. Our study reveals the psychology behind this preference, and shows how ideas from other fields can help to explain biological phenomena.
These results also provide clues about why attraction to novelty evolved.
There are a lot of reasons why habituation can be advantageous. The environment is constantly bombarding our senses with information, much of which is repetitive and unimportant. For example, when trying to meet an urgent deadline at work, you don’t want to be distracted by the lingering smell of the lunch you ate earlier. So when your brain keeps getting this same information, it starts to filter it out. By shifting your attention away from repetitive information, habituation frees you up to focus on what matters. Habituation can benefit guppies, too, helping them to notice an approaching predator, or a new food source.
Habituation probably evolved because it helps animals navigate these aspects of the environment, which are unrelated to choosing mates. Attraction to novel mates could therefore be a byproduct of the evolutionary forces that favored habituation in these other contexts. In other words, preference for unusual-looking mates might just reflect a general evolutionary advantage of habituation.
Because habituation is found in many species, preference for novel-looking mates may be a common and under-appreciated force shaping mating decisions. Indeed, there is evidence that we humans find novel-looking features attractive. The mating habits of these tiny, colorful fish may be revealing something broader about the animal kingdom, and perhaps even our own desires.
Mitchel Daniel receives funding from Florida State University. Funding for this study was also provided by the National Science Foundation (IOS-1354775 and DEB 1740466).
Measles cases in the US have hit a 25-year high, with 78 new infections in the past week alone. In a sign of the times, a cruise ship with hundreds of Scientologists on board was quarantined in St Lucia after one passenger was diagnosed with the disease. It’s the sort of news you can expect when parents stop vaccinating their children, which many did from the 1990s onwards for fear that scientists were foisting remedies on them that were more dangerous than the diseases themselves.
As society has become ever more convenient, hygienic and wrapped in cling film, many hark back with dewy eyes to the natural and supposedly wholesome lifestyles of our ancestors in pre-industrial times. Besides the fear around vaccines, growing numbers of people put their faith in the organic movement, the anti-GM lobby and New Age philosophies. They have increasingly rejected the ability of science to improve our lives, placing an almost religious trust in the benevolence of Mother Nature instead.
Coupled with this is a very positive view of evolution. It is seen as a caring and compassionate force which has shaped us and the rest of the natural world. It almost seems that there is the growing belief that if natural evolution were left to its own devices, then everything would work out for the best.
But this idea of evolution as benign is extraordinarily wide of the mark. Evolution is a brutal and uncaring, even obscene opponent, which the medical world is constantly trying to outmanoeuvre and overcome. Perhaps because of the brilliance of Charles Darwin’s theory, evolution has been getting an easy ride for far too long. It’s time we started facing the truth about what it really means – before it eats any more of our children.
Evolution stems from the inability of any organism to always hand down a perfect copy of its DNA to the next generation. For this we can thank factors such as the fallibility of the machinery in living organisms that copies DNA; and the basic instability of DNA when exposed to certain chemicals or types of radiation that have always existed in our environment. It means that nobody has ever inherited a perfect copy of their parents’ DNA. Indeed, one of the reasons we have two parents is to ensure that, if one copy of our genes going wonky, we have a second back-up gene to cover.
When our DNA mutates, natural selection steps in – and this is where things get really ugly. Natural selection is the process through which the mutations in a species which are “best suited” to their environment thrive, while “less suitable” ones die off. It has dictated everything we see around us, from the length of giraffes’ necks to the shape of sharks’ fins.
In the past, our ancestors were subjected to full-strength, undiluted, CFC-free, pure-organic, additive-free natural selection. The biggest recipients were young children, for which evolution had the greatest appetite of all. Those with the least useful mutations could look forward to a horrific death by starvation, predators, cannibalism, disease, drought, flash floods, drowning and much more besides. During an average 30 to 40 year human life span, mothers would produce eight to ten children only to see four to five of them die before reaching the age where they might pass their genes to the next generation.
This was evolution writ large: the inexorable cruel erosion of the vast majority of individuals, who had one set of genes, in favour of the tiny lucky minority who had the genetic ability to survive until they could perpetuate this cruel cycle. By running that little bit faster than their brother or sister, the genetic winners avoided getting ripped apart by a pack of hungry wolves. While they clung to life in times of famine or disease, they watched their siblings fade and die. If we believe the human diversity data, we are a species which was reduced to only around 600 individuals over 100,000 years ago. This is the reality of where we came from, of how “Mother Nature” shaped us as individuals.
Unfortunately, of course, humans are still evolving today. People are still dying from disease and starving from deprivations perpetrated by unequal societies and a lack of access to food and medicine. We remain at the mercy of natural selection, the least moral way for a species to develop. And for the majority of us who deplore cruelty and feel compassion for our fellow man, woman and child, I would argue it creates a moral obligation: to aggressively stop evolution of the human species as a matter of urgency.
The only way to do this is to embrace the results of scientific enquiry. Our greatest achievement as a species has been to break free from the sheer naked ferocity of evolution. It means we need GM food to avoid starvation. We need additives to ensure that the food we grow can be safely consumed before it spoils – an important consideration for an increasing population. And most importantly of all, we need vaccines to prevent disease. We must never again expose our children to the wholesome, fully organic, unblemished and obscene fury of Mother Nature unleashed. Love science, hate evolution. Coming to a car bumper sticker near you soon, I hope.
Alasdair Mackenzie receives funding from the BBSRC and Medical Research Scotland.
Here's a close-up picture of a head louse. The eggs of the female head louse are what we call 'nits'. CC BY-SA
Curious Kids is a series for children. If you have a question you’d like an expert to answer, send it to email@example.com You might also like the podcast Imagine This, a co-production between ABC KIDS listen and The Conversation, based on Curious Kids.
What’s the point of nits?! – Connie, age 9, Nambour, Queensland.
Great question, Connie. I often find myself scratching my head trying to figure out the answer to that question too!
What we commonly call “nits” are actually the eggs of very small insects known as head lice. And head lice are found nowhere else on the planet except in human hair.
Head lice have adapted perfectly to life on us. They have specially designed claws at the ends of each of their six legs that are perfect for scuttling up and down the shafts of hair.
In fact, they’re so perfectly designed for life on our hair that once they come off they’re incredibly clumsy and have a tough time getting around at all. That’s why they’re most commonly spread between children through direct head-to-head contact. Lice are tricky enough to navigate the tangle of two people’s hair.
Once lice have infested someone, they will climb down the hair to the scalp and bite. They need our blood to live and lay eggs. While we’ll sometimes get a reaction to their bites, that reaction is rarely as bad as they type we get from mosquitoes or ticks. Importantly, head lice don’t transmit the germs that make us sick like those other pests. At worst, we’ll just get a little itchy.
You can remove head lice and their eggs (nits) with a fine-tooth comb. But just one comb-out session is never enough.
So, what is the point of head lice? Perhaps they don’t have a “point” at all. We like to think that all creatures play a role in the local ecosystem. We’re especially interested in insects that provide a benefit for people too. A great example are the bees and other insects that pollinate our crops that are crucial in providing food.
But perhaps head lice don’t play what we would traditionally see as an important role in the ecosystem. They don’t pollinate plants, they’re not food for other animals, and they don’t exactly bring joy to our lives in the way other, cuter animals do. When it comes to charismatic insects, head lice aren’t quite up there with butterflies or dragonflies!
I think lice see us as playing a role – providing them with food – but the reverse may not be true.
Lice attach their eggs to the hair with a special glue.
Perhaps we need to take a different perspective when thinking about the “point” of head lice. We marvel at the ability of plants and animals around the world to adapt to all the weird and wonderful cracks and crevices in the environment. Why shouldn’t we take inspiration from head lice being able to adapt to life on the human body?
Please tell us your name, age and which city you live in. We won’t be able to answer every question but we will do our best.
Cameron Webb and the Department of Medical Entomology, NSW Health Pathology and University of Sydney, have been engaged by a wide range of insect repellent and insecticide manufacturers to provide testing of products and provide expert advice on the biology of medically important insects. Cameron has also received funding from local, state and federal agencies to undertake research into mosquito-borne disease surveillance and management as well as risk assessment of a wide range of arthropod pests of public health importance.
Curious Kids is a series by The Conversation, which gives children of all ages the chance to have their questions about the world answered by experts. All questions are welcome: send them – along with your name, age and the town or city where you live – to firstname.lastname@example.org. We won’t be able to answer every question, but we’ll do our best.
Thanks for the question, Florence. The short answer is, we humans can’t tickle ourselves because we’ll already be expecting it. And a big part of what makes tickles ticklish is the element of surprise.
Tickling is an important sign that someone or something is touching you. In general, there are two types of tickles. There are good tickles, like when your family or friends tickle you and make you laugh. And there are bad tickles, like when you can feel a bug on you.
Both types of tickles help us in different ways.
Over the hundreds of thousands of years that humans have been around, being ticklish has had its advantages. Tickling tells us when there is a bug or something else crawling on our skin.
The reason why we feel ticklish is because our body is covered in small hairs. These help us to feel danger that might be too small to see – like bugs.
People who are ticklish can feel bugs land on them, and flick them off before they bite. This helps to avoid getting bitten by poisonous insects.
Over the ages, ticklish people would have been less likely to be bitten by poisonous bugs, so they would have lived longer and had more babies, who were also ticklish.
In other words, humans have evolved to be ticklish, because it can help us to sense danger, such as bugs. If we could tickle ourselves, then we might have more trouble telling when there’s a bug on us or when we are just touching ourselves.
So it makes sense that we cannot tickle ourselves, so that we can be sure when dangerous things, such as bugs, are on us.
Good tickles feel good and can make us laugh. It can be a fun way to play – and humans aren’t the only animals that can tickle.
Did you know that when chimpanzees chase and tickle each other they make panting sounds? These pants do not mean that the chimp is tired – they actually mean that it wants to play!
Pets, such as rats, also make noises like laughter when people stroke them.
Eavesdrop on Ultrasonic Rat Giggles - YouTube
Laughter and play are good ways for animals (including us!) to make friends . And if you could tickle yourself, you might be less likely to laugh and play with others.
So, there are good reasons why we can only be tickled by others, and not ourselves. But to understand how tickling really works, we’ll have to look inside the human body.
The motor system
The motor system is a thing that most animals – including humans – have in their body. It’s made up of our muscles and brain, and it’s what lets us move
Every time that you move, your brain sends a plan to your muscles. It does this by sending the plan, in the form of electrical signals, along the nerves that run like wires through your body.
This plan tells the muscles when and how to move, and also what to expect when we have moved.
We have five senses: sight, smell, taste, touch and hearing. The plans sent to your muscles guess how each of these senses may change, after you have moved.
So, when you try to tickle yourself, your brain sends the plan through the nerves: it tells the muscles in one arm to move to do the tickling, and it also tells your other muscles that the tickle is coming.
When somebody else tickles you, your muscles haven’t got a plan from your brain, so the feeling is surprising – and ticklish!
But you can’t tickle yourself, because your brain is always one step ahead, telling your muscles and senses what to expect and stopping you from giving yourself a surprise. But then, maybe it’s better that way.
Aysha Bellamy does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.
We have so much more to learn about Australia. Shutterstock/Lev Savitskiy
The Australian continent has a remarkable history — a story of isolation, desiccation and resilience on an ark at the edge of the world.
It is a story of survival, ingenuity, and awe-inspiring achievements over many years.
Shortly after the dinosaurs died out 65 million years ago, Australia was torn from the supercontinent of Gondwana by immense tectonic forces and began its long, lonely, journey north towards the equator.
The lush temperate forests of Gondwana slowly disappeared as the Australian landmass pushed north, preserving a snapshot of faunal life from a much earlier evolutionary time.
This antipodean ark carried a bizarre cargo of marsupials who were spared the fate of their kin on other continents who were decimated by the rise of placental mammals.
By about 5 million years ago the slow-motion collision of Australia into the Pacific and Indian tectonic plate began to push-up the now four-kilometre high mountains of central New Guinea.
This collision also formed the small stepping stones of islands across the Wallace Line which almost, but never quite, connected Australia to Asia through the Indonesian archipelago. They will meet in another 20 million years or so and Australia will become a vast appendix of the Asian landmass.
At the beginning of the Pleistocene period around 2.8 million years ago, global climate began to cycle dramatically between glacial periods, or ice ages, and interglacials, the warm phases between them. As the ice sheets waxed and waned over these cycles, each lasting between 50,000 and 100,000 years, sea levels rose and fell by up to 125 metres.
While remnants of the Gondwanan forests persisted in cooler and wetter parts like Tasmania and high in the Australian Alps, the continent became a wide brown land of desert, grassland and savanna; of droughts and flooding rains.
Fast forward to 130,000 years ago to a period scientists call the last interglacial — the stretch of time between the last two ice ages. This was a time when Australia’s climate and landscape looked a like lot it does today.
An impression of a giant lizard, Megalania, stalks a herd of migrating Diprotodon, while a pair of massive megafaunal kangaroos look on.
Kangaroos that could browse on leaves growing on trees three metres from the ground, three ton wombat-like Diprotodons and giant flightless birds the size of a moa (Genyornis newtonii) foraged across the landscape. These monsters became meals for the carnivorous marsupial lion (Thylacoleo carniflex) and the 4.5m long venomous goanna Megalania.
A strange menagerie indeed had evolved on the evolutionary ark that became Australia!
Meandering rivers channelled monsoon rains from the north into Australia’s vast arid centre. Kati-Thanda (Lake Eyre) was 25 metres deep and joined up with Lake Frome and other smaller basins to create a massive inland water body the size of Israel, with a volume equivalent to 700 Sydney harbours.
When sea levels dropped
Over the next 70,000 years or so the ice slowly began to build up on Antarctica and in the northern Hemisphere. As a result, sea levels dropped, exposing huge areas of once drowned land as Australia once more joined its island neighbours to form the enlarged continent of Sahul.
About this time a new kind of placental mammal – Homo sapiens – had begun to move out of Africa, and would eventually make its home across Asia.
Around 74,000 years ago, the Mt Toba volcano’s supereruption — the largest in the last 2 million years – spread 800 cubic kilometres of volcanic ash and debris widely across Asia.
By plunging the planet into a long volcanic winter, Mt Toba may have delayed human ancestors making their way out of Africa to our doorstep. However, sometime before 50,000 years ago Homo sapiens finally reached Southeast Asia.
And so, the most potent placental mammal to ever walk the earth was now poised to enter a continent dominated by ancient marsupial giants – Sahul.
The first Australians
Making landfall on Sahul was no easy task and says much about the capabilities of the first people who entered the continent; the first Australians.
Even with sea level 70 metres lower than today the journey by any route involved at least six island hops followed by a final open ocean crossing of around 100 kilometres before Australia could be reached.
Of course, this is science’s story; for many Indigenous Australians their ancestors have always been here.
The time of human arrival has been progressively pushed back over the last few decades. It’s now widely accepted that humans first made landfall on Sahul by 50,000 years ago, or perhaps even as early as 65,000 years ago.
It’s also clear that once people arrived, they settled the continent very rapidly. In only a few thousand years people were living from the western desert coasts to the highly productive (now dry) Willandra Lakes in western New South Wales.
The large inland lakes, in total about the size of England, began to dry out from around 50,000 years ago. This drying has been ascribed to natural climate change and human modification of the environment through burning and the hunting of megafauna.
Sahul, during the last ice age (beginning 30,000 years ago and peaking 20,000 years ago) was cold – around 5 degrees colder – and much drier than present. Sea level was 125 metres lower and, as a consequence the continent was almost 40% larger than it is today.
Shifting sand dunes expanded over much of the arid interior, ice caps and glaciers expanded over interior Tasmania, the southern highlands of New South Wales and along the mountainous spine of New Guinea.
Strong winds carried dust from the now dry interior lake basins southeast into the Tasman Sea and northwest into the Indian Ocean. A large brackish inland sea, bigger than Tasmania, occupied the Gulf of Carpentaria.
Humans and animals alike retreated into locations where water and food were more assured in a broader inhospitable landscape – some perhaps around the coastal fringes of Sahul.
When sea levels rise again
Ten thousand years later and everything began to rapidly change again. From shortly after 20,000 years ago global climate began to warm and the planet’s ice sheets began to collapse. The water flooded back into the oceans and sea-levels began to rise, at times up to a whopping 1.5 centimetres per year.
In some parts of Sahul this shifted the coastline inland by 20 metres or more in a given year. This radical reconfiguration of the coastline went on for thousands of years with a significant impact on Aboriginal societies.
Sea level rise severed the connections to Tasmania and New Guinea for the final time, reaching a peak about 1-2 metres above modern levels some 8,000 years ago, thereafter stabilising slowly to pre-twentieth century levels.
Climate settled into a pattern broadly similar to present, with the last few thousand years seeing increased intensity of the El Nino-La Nina climate cycles leading to the boom and bust cycles we live with today.
Over the last 10,000 years, Aboriginal populations increased, possibly in the later stages with the help of the recent placental mammal import, the dingo.
There’s a lot that’s fascinating about the coelacanth Latimeria. Now under threat, this deep-sea fish is closely related to humans and other back-boned, land dwelling animals (tetrapods).
The coelacanth Latimeria is a relatively large fish (reaching about 2 metres long) but has a very tiny brain lying within a hinged braincase – a very primitive feature found in many fossil fishes.
How the coelacanth skull grows and why the brain remains so small has puzzled scientists for years. Our new study published today in Nature illuminates for the first time the development of the brain and skull of this curious animal.
It’s another piece of evidence that might help us see where humans once came from.
The first Latimeria ever found was accidentally caught in a trawl off the South African coast. Amazingly, its overall body shape was strikingly similar to some of its fossilised relatives that had been known by palaeontologists since the 19th century.
The fossil coelacanth Trachymetopon from the Jurassic of Germany. This specimen is housed in the collections of the Museum der Universität Tübingen.
Hugo Dutel (no commercial use)
The scientific frenzy around Latimeria was really sparked by what the animal could reveal about the origin of humans and other four-limbed animals.
At the time of its discovery, Latimeria held a pivotal position in the family tree of vertebrates (animals with backbones). It was considered the direct descendant of lobe-finned fishes, the group of fish from which tetrapods evolved.
So the discovery of a living Latimeria coelacanth was expected to shed light into the biology of our very early ancestors.
Nowadays, expectations have been tempered. The development of new methods for reconstructing the evolution of organisms, the discovery of new fossils, and, more recently, information extracted from DNA and other molecules have slightly changed this picture.
Simplified phylogeny of the bony fishes (osteichthyans). Coelacanths and lungfishes are the only living lobe-finned fishes and are closely related to tetrapods, the land-dwelling vertebrates. The intracranial joint is a primitive feature of sarcopterygians, the group that includes lobe-finned fishes and tetrapods. It is found in many fossil lobe-finned fishes from the Devonian, but has been independently lost in tetrapods and living lungfishes. The coelacanth is the only living vertebrate which possesses an intracranial joint.
Hugo Dutel (no commercial reuse)
Yet, the Latimeria coelacanth possesses some unusual features that are still of interest for understanding the evolution of our fossil relatives.
The skull of Latimeria is completely split in half by a joint called the “intracranial joint”. This joint is a very primitive feature that is otherwise found only in many extinct lobe-finned fishes.
In contrast with other vertebrates, the brain of Latimeria is ridiculously small compared with the cavity that houses it (1% of the entire braincase volume).
The rear of the skull of Latimeria and extinct lobe-finned fishes also straddles a surprisingly huge structure called the notochord.
3D virtual reconstruction of the coelacanth skull in right lateral view. Left: Overall view of the skull. Right: the braincase isolated and virtually cut open along the midline to show the brain (yellow) and the notochord (green). The brain represents about 1% of the volume of the cavity which houses it.
The question of how this skull and brain develops, and what it means to vertebrate evolution, triggered our work published today.
Latimeria is ovoviviparous, meaning that eggs develop in the female abdomen, and then she gives birth to live young.
But studying the development of this fish is not an easy thing. Latimeria cannot be bred in an aquarium, so embryos and fetuses cannot be easily obtained. Moreover, we cannot capture any coelacanths in the wild as they are protected.
Many adult coelacanths are held in natural history collections. However, earlier life stages are extremely scarce as they came from the rare captures of pregnant females. For a long time, scientists thus could not dissect these precious specimens to study their anatomy.
The growth series of Latimeria collected for our study.
So we used state-of-the-art X-ray scanning facilities at the European synchrotron and powerful MRI to visualise the internal anatomy of these precious museum specimens.
Thanks to these data, we generated digital 3D models of the skull at each stage of its growth. The detailed 3D models allowed us to describe how the form of the skull, the brain and the notochord changes from a very early fetus to an adult.
How the brain grows but stays tiny
We found that the relative size of the brain dramatically decreases during development. The brain grows, but not as much as the surrounding structures in the head.
This is is very unusual, and not seen in other vertebrates (and especially us primates, in which the brain expands dramatically during growth).
On the other hand, the notochord expands considerably to become much bigger than the brain in the adult. This is very unique, as the notochord usually degenerates in the early development of most vertebrates.
The brain (yellow) within the braincase (blue) at different developmental stages of Latimeria.
Why is the brain of Latimeria so small?
As is often the case, there is probably not a single explanation. It might be due to the way the notochord develops, and the position and function of the intracranial joint (which is probably plays a role in biting). It is also possible that the energy needed by a huge electrosensory organ in Latimeria‘s snout, the rostral organ, may come at the expense of having a bigger brain.
Together with a recent study on its lung (which has bony plates on it), these findings represent the best of our knowledge on the development of Latimeria. It remains one of our most mysterious cousins, as many aspects of its biology and ecology remain unknown.
For sure, Latimeria still holds many promising clues for our understanding of vertebrate evolution and our distant origins.
But this only survivor of a 400 million year old group and its marine ecosystem are in jeopardy and need to be protected more than ever.
Hugo Dutel receives funding from the Natural Environment Research Council (NE/P013090/1).
John Long receives funding from The Australian Research Council