Latest news with #humananatomy
BBC News
04-07-2025
- Science
- BBC News
The body parts evolution still can't explain
Human testicles are much smaller, in proportion, to some of our primate cousins. Evolution can tell us why. But the size of other body parts is a little bit more of a mystery. The human body is a machine whose many parts – from the microscopic details of our cells to our limbs, eyes, liver and brain – have been assembled in fits and starts over the four billion years of our history. But scientists are still puzzling over why we evolved into this particular form. Why do humans uniquely have a chin, for example? And why, relative to body weight, is a human testicle triple the size of a gorilla's but a fifth that of a chimpanzee? As I show in my new book, The Tree of Life, we are still searching for the answers to many of these "why" questions. But we are starting to find answers to some of them. The story of evolution tells us how, starting from simple beginnings, each species was built – when each of the components that make a living creature was added to its blueprint. If we climb the evolutionary tree of life, we can follow a twisting path that visits the increasingly specialised branches that a species belongs to. We humans, for example, were animals before we became vertebrates; mammals before evolving into primates and so on. The groups of species we share each of these branches with reveal the order our body parts appeared in. A body and a gut (inventions of the animal branch) must have come before backbone and limbs (vertebrate branch); milk and hair (mammals) came before fingernails (primates). There is a way we can study the separate problem of just why we evolved each of these body parts, but it only works if the feature in question has evolved more than once on separate branches of the tree of life. This repeated evolution is called convergence. It can be a source of frustration for biologists because it confuses us as to how species are related. Swallows and swifts, for example, were once classified as sister species. We now know from both DNA and comparisons of their skeletons that swallows are really closer relatives of owls than swifts. Size matters when it comes to evolution But convergent evolution becomes something useful when we think of it as a kind of natural experiment. The size of primate testicles gives us a classic example. Abyssinian black and white colobus monkey and bonnet macaque adult males are roughly the same size. But, like chimps, humans and gorillas, these similar monkeys have vastly dissimilar testicles. Colobus testicles weigh just 3g (0.1oz). The testicles of the macaques, in contrast, are a whopping 48g (1.7oz). You could come up with several believable explanations for their different testicle sizes. Large testicles might be the equivalent of the peacock's tail, not useful per se but attractive to females. But perhaps the most plausible explanation relates to the way they mate. A male colobus monkey competes ferociously for access to a harem of females who will mate exclusively with him. Macaques, on the other hand live in peaceful mixed troops of about 30 monkeys and have a different approach to love where everyone mates with everyone else: males with multiple females (polygamy) and females with multiple males (polyandry). The colobus with his harem can get away with producing a bare minimum of sperm – if a droplet is enough to produce a baby, then why make more? For a male macaque the competition to reproduce happens in a battle between his sperm and the sperm of other males who mated before or after. A male macaque with large testicles should make more sperm, giving him a higher chance of passing on his genes. It's a sensible explanation for their different testicle sizes, but is it true? This is where convergent evolution helps. If we look across the whole of the mammal branch of the tree of life we find there are many groups of mammals that have evolved testicles of all different sizes. In almost all these separate cases, larger testicles are consistently found in promiscuous species and smaller in monogamous. A small-testicled, silverback male gorilla has sole access to a harem. Big-testicled chimps and bonobos are indeed highly promiscuous. Dolphins, meanwhile, may have the biggest mammalian testicles of all, making up as much as 4% of their body weight (equivalent to human testicles weighing roughly 3kg (9.9lb)). Although wild dolphins' sex lives are naturally hard to study, spinner dolphins at least fit our expectations, engaging in mass mating events called wuzzles. It was thanks to the multiple observations provided by convergent evolution that we were able to discover this consistent correlation between testicle size and sex life right across the mammals. And as for humans, we have testicle size somewhere in the middle – you can make of this what you want! But what of the human chin? More like this:• When it comes to our brains, size isn't everything• How dinosaurs reached 'titanic' size• How humans lost their fur The human chin has been fertile ground for arguments between scientists over its purpose. As with testicles, there are half a dozen plausible ideas to explain the evolution of the human chin. It could have evolved to strengthen the jaw of a battling caveman. Maybe the chin evolved to exaggerate the magnificence of a manly beard. It might even be a by-product of the invention of cooking and the softer food it produced – a functionless facial promontory left behind by the receding tide of a weakening jaw. Intriguingly, however, a chin can be found in no other mammal, not even our closest cousins the Neanderthals. Thanks to the uniqueness of the Homo sapiens chin, while we have a rich set of possible explanations for its evolutionary purpose, in the absence of convergent evolution, we have no sensible way of testing them. Some parts of human nature may be destined to remain a mystery. * Max Telford is the Jodrell Professor of Zoology and Comparative Anatomy, at University College London ** This article is adapted from a piece that originally appeared on The Conversation, and is republished under a Creative Commons licence. -- For more science, technology, environment and health stories from the BBC, follow us on Facebook, X and Instagram.
The Independent
27-06-2025
- Science
- The Independent
Why our chins remain an evolutionary mystery
Scientists are still trying to understand the evolutionary reasons behind unique human features, such as the chin and the relative size of testicles. The concept of convergent evolution, where a feature evolves multiple times independently, serves as a natural experiment to determine the purpose of body parts. Analysis of testicle size across various mammals, including monkeys, gorillas, chimps, and dolphins, reveals a consistent correlation between larger testicles and promiscuous mating behaviors. This correlation suggests that larger testicles evolved to facilitate sperm competition in species with multiple partners, with human testicle size falling in the middle. The human chin remains an evolutionary mystery because its uniqueness among mammals, including Neanderthals, prevents the use of convergent evolution to test hypotheses about its purpose.
The Independent
27-06-2025
- Science
- The Independent
The unique human body part that evolution cannot explain
The human body is a machine whose many parts – from the microscopic details of our cells to our limbs, eyes, liver and brain – have been assembled in fits and starts over the four billion years of our history. But scientists are still puzzling over why we evolved into this particular form. Why do humans uniquely have a chin, for example? And why, relative to body weight, is a human testicle triple the size of a gorilla's but a fifth of that of a chimpanzee? As I show in my new book, The Tree of Life, we are still searching for the answers to many of these 'why' questions. But we are starting to find answers to some of them. The story of evolution tells us how, starting from simple beginnings, each species was built, when each of the components that make a living creature was added to its blueprint. If we climb the evolutionary tree of life, we can follow a twisting path that visits the increasingly specialised branches that a species belongs to. We humans, for example, were animals before we became vertebrates; mammals before evolving into primates and so on. The groups of species we share each of these branches with reveal the order our body parts appeared. A body and a gut (inventions of the animal branch) must have come before backbone and limbs (vertebrate branch); milk and hair (mammals) came before fingernails (primates). There is a way we can study the separate problem of just why we evolved each of these body parts, but it only works if the feature in question has evolved more than once on separate branches of the tree of life. This repeated evolution is called convergence. It can be a source of frustration for biologists because it confuses us as to how species are related. Swallows and swifts, for example, were once classified as sister species. We now know from both DNA and comparisons of their skeletons that swallows are really closer relatives of owls than swifts. Size matters when it comes to evolution But convergent evolution becomes something useful when we think of it as a kind of natural experiment. The size of primate testicles gives us a classic example. Abyssinian black and white colobus monkey and bonnet macaque adult males are roughly the same size. But, like chimps, humans and gorillas, these similar monkeys have vastly dissimilar testicles. Colobus testicles weigh just 3 grams. The testicles of the macaques, in contrast, are a whopping 48 grams. You could come up with several believable explanations for their different testicle sizes. Large testicles might be the equivalent of the peacock's tail, not useful per se but attractive to females. But perhaps the most plausible explanation relates to the way they mate. A male colobus monkey competes ferociously for access to a harem of females who will mate exclusively with him. Macaques, on the other hand, live in peaceful mixed troops of about 30 monkeys and have a different approach to love where everyone mates with everyone else: males with multiple females (polygamy) and females with multiple males (polyandry). The colobus with his harem can get away with producing a bare minimum of sperm – if a droplet is enough to produce a baby, then why make more? For a male macaque, the competition to reproduce happens in a battle between his sperm and the sperm of other males who mated before or after. A male macaque with large testicles should make more sperm, giving him a higher chance of passing on his genes. It's a sensible explanation for their different testicle sizes, but is it true? This is where convergent evolution helps. If we look across the whole of the mammal branch of the tree of life, we find there are many groups of mammals that have evolved testicles of all different sizes. In almost all these separate cases, larger testicles are consistently found in promiscuous species and smaller in monogamous. A small-testicled, silverback male gorilla has sole access to a harem. Big-testicled chimps and bonobos are indeed highly promiscuous. Dolphins, meanwhile, may have the biggest mammalian testicles of all, making up as much as 4 per cent of their body weight (equivalent to human testicles weighing roughly 3 kilos). Although wild dolphin sex lives are naturally hard to study, spinner dolphins at least fit our expectations, engaging in mass mating events called wuzzles. It was thanks to the multiple observations provided by convergent evolution that we were able to discover this consistent correlation between testicle size and sex life right across the mammals. And as for humans, we have testicle size somewhere in the middle, you can make of this what you want! But what of the human chin? The human chin has been fertile ground for arguments between scientists over its purpose. As with testicles, there are half a dozen plausible ideas to explain the evolution of the human chin. It could have evolved to strengthen the jaw of a battling caveman. Maybe the chin evolved to exaggerate the magnificence of a manly beard. It might even be a by-product of the invention of cooking and the softer food it produced – a functionless facial promontory left behind by the receding tide of a weakening jaw. Intriguingly, however, a chin can be found in no other mammal, not even our closest cousins, the Neanderthals. Thanks to the uniqueness of the homo sapiens chin, while we have a rich set of possible explanations for its evolutionary purpose, in the absence of convergent evolution, we have no sensible way of testing them. Some parts of human nature may be destined to remain a mystery.
Malay Mail
16-05-2025
- Health
- Malay Mail
Universiti Malaya opens public access to one of Asia's most unique medical collections
Universiti Malaya's Tan Sri Lim Wee Chai Medical Museum provides a starkly educational view of human anatomy and disease through preserved specimens for public and student learning. The museum, named after a key donor, highlights both medical history and the donor's philosophy of health and societal contribution. Presenting normal and diseased specimens together, the museum aims to foster holistic understanding and empower individuals to make informed health choices. KUALA LUMPUR, May 17 — The first thing that greets you is a haunting sight: a pair of infant twins suspended in glass, locked in a permanent embrace. Preserved in perfect stillness, the two infants float in their glass case with tiny arms wrapped around each other. Their chest is dissected, revealing the intricate web of organs beneath translucent skin. This is no ordinary museum exhibit. These are conjoined twins, separated only in death, now serving as an unforgettable introduction to Universiti Malaya's Tan Sri Lim Wee Chai Medical Museum. This intimate glimpse into tragedy becomes the entry point to a broader, unfiltered journey into medical science. This singular exhibit sets the tone for the rest of the museum — a place where science meets history and education in an eye-opening experience. Ascaris lumbricoides infestation in a child's liver. This worm is the most common found in humans. This is one of the rarest pieces. — Picture by Firdaus Latif Tucked within UM's medical faculty, this is Malaysia's only open collection of diseased human specimens. It offers a rare opportunity for the public to confront the fragile reality of our bodies. From cancerous tumours to parasitic infestations, from malformed foetuses to organs ravaged by syphilis, the museum presents medicine's most profound lessons without filters. Visitors may view preserved organs ravaged by cancer, lungs damaged by illness, and hearts destroyed by syphilis. There are also preserved foetuses at various stages of development, showing the intricate process of human gestation. As visitors move past the conjoined twins, they encounter a historical video documenting Malaysia's first successful conjoined twin separation surgery, performed at Hospital Kuala Lumpur in 1967. This pioneering procedure marked a milestone in the country's medical history. A hand preserved in Kaiserling solution to preserve and stabilise tissue specimens. — Picture by Firdaus Latif Rare and fascinating specimens The museum is home to an array of rare and striking exhibits, including: Congenital Diaphragmatic Hernia (CDH) Infant — A preserved specimen of a baby with a hole in the diaphragm, allowing internal organs to push into the chest cavity, compressing the lungs and shifting the heart to the right. Sirenomelia (Mermaid Syndrome) Baby — A foetus with fused legs, a rare and often fatal congenital disorder. Anencephaly Specimen — A baby born without parts of the brain and skull, showcasing the devastating effects of neural tube defects. A Liver Infested with Worms — One of the rarest specimens in the collection, featuring the remains of parasitic worms that had consumed a man's liver. A Heart Destroyed by Syphilis — A shocking display of how untreated venereal disease can devastate the body. A Massive Ovarian Tumour — A large, preserved tumour, including one removed from a child. Horseshoe Kidney — A congenital condition where the kidneys are fused together, forming a U-shape. There is a full-time curator, Rizqullah Bariq Azmi, who is knowledgeable and affable, ready to answer any question. A heart infested with syphilis causing aneurysms in the aorta. — Picture by Firdaus Latif 'This is a unique specimen of a heart and liver that have been eaten by worms. You can actually see the dead worms inside. This is one of the more unusual pieces. 'We also have a heart that belonged to someone with syphilis. The infection caused severe swelling and damage and you can clearly see the heart destroyed. We also have a seminoma of the testes, a tumour that completely replaced the testicle. You'll see it cut open in different sizes,' he said as he took Malay Mail around the museum. Tan Sri Lim Wee Chai is the founder and executive chairman of Top Glove Corporation Bhd. He donated RM2 million for this project and expressed gratitude for his personal and professional growth, attributing much of it to his time at Universiti Malaya. As an alumnus, he sees it as both a privilege and a duty to give back to the institution that shaped him. He stressed the importance of education in driving progress and believes in supporting institutions that nurture future leaders. Having the medical museum named after him is a great honour, and he hopes it will inspire and benefit generations of students to come. A room for students to examine and study the parts up close. — Picture by Firdaus Latif 'My passion for lifelong learning, promoting healthy living, and advancing healthcare drives me to support this cause. I am pleased to contribute towards the enhancement of this facility so that it can continue to educate and inspire future generations,' he told Malay Mail. 'I believe that health is the foundation for success both in business and in life, as without health we cannot work or contribute positively, and will become a liability instead.' Lim believes that sustainable success rests on mental, physical, and financial health. Mental well-being, he says, is built through integrity and transparency. Physical health stems from what he calls the 'Five Wells': clean living, balanced eating, purposeful work, regular exercise, and restful sleep. Only when these first two pillars are strong, he argues, can financial stability flourish. Beyond individual prosperity, Lim calls for corporate responsibility, urging industry leaders to invest in education, healthcare, and sustainability. 'Industry leaders should give back to society, it is an opportunity to create lasting positive change, because businesses grow alongside the communities they serve,' Lim said. 'Supporting education, healthcare, and sustainability helps build a stronger workforce and a healthier society, which benefits everyone in the long run. By leading with purpose, businesses can inspire others and contribute to a better future for all,' he added. Meanwhile, UM's Dean of the Faculty of Medicine, Professor Datuk Dr Yang Faridah Abdul Aziz, said the museum serves a purpose not only for the public but also for medical students. They have a separate room where students can hold and examine specimens up close. Pictures of old hospitals from the 1930's shows how far medicine has come. Right below the picture display are the old tools used for operating patients. — Picture by Firdaus Latif 'When we talk about teaching healthcare professionals, information should not exist in silos. You shouldn't be learning the normal state of the diseased state at a different time, it creates a break in their thinking. 'We want to create healthcare workers who think holistically. Seeing the normal form side by side to a diseased state creates curiosity which is far more powerful than learning in isolation. 'In addition, knowledge should be shared. A place like this empowers individuals to understand their own bodies, own diseases and to make informed decisions about their health. If a young person comes here and sees this they may say, 'Okay, I'm going to take charge of my health. I'm going to personalise my treatment, I'm going to be the decisions maker'. That's the future of medicine,' she said when met. Dr Yang said she hoped the museum would show how intricate the human body is and remind visitors not to take life for granted. The museum offers lessons from the past that give us knowledge to live better lives — and we should not squander it. More than a medical display, the museum stands as a reminder of life's fragility — and the power of knowledge to preserve it. A section of a foot. — Picture by Firdaus Latif The museum is open from Monday to Friday, 9am to 4pm. Last admission is at 3.30pm. Admission is free until May 31, 2025 and is accessible to wheelchair users. Email in advance if you are using a wheelchair so directions to a drop-off point can be arranged. The recommended age for visiting the museum is seven and above. Children under seven must be accompanied by adults. No photography or filming is allowed in the main exhibition area. This is to respect the individuals in the collections. However, photos may be taken at the museum counter, interactive learning area, the gallery, or in other zones without human specimens.
