Recently, Hafthor “The Mountain” Bjornsson, a star from the show Game of Thrones, made headlines by breaking the deadlift world record with an astonishing 501-kilogram lift. Imagine if he had the strength of a leafcutter ant—he could lift a medium-sized car over his head! And if he had the power of a dung beetle, he could pull a fully loaded airplane. These small creatures are amazing because they achieve these feats without bones.
Have you ever wondered why humans have internal skeletons instead of external ones? Our bodies are made of soft tissues supported by a framework of bones. These bones are rigid enough to give us structure and flexible enough to allow movement. While most people have 206 bones, some might have extra ribs or fewer bones. Our hands and feet alone contain more than half of the bones in our bodies.
Bones are made up of about 70% minerals, mainly hydroxyapatite, which is strong under pressure, and flexible collagen to prevent breaking. This combination allows the average human skeleton, which weighs around 20 pounds, to withstand a ton of compression. Bones are essential for many functions, including producing blood that carries oxygen to the brain and enabling us to hear through tiny bones in our ears.
The story of bones goes back at least 1.5 billion years. Back then, tectonic plates shifted, washing minerals into ancient oceans. Life was soft and squishy, relying on water for support. Around 558 million years ago, evolution took a turn, leading to two paths: one developed hard protective parts, the precursors of exoskeletons, and the other developed soft cartilage-like structures that evolved into vertebrate skeletons.
Exoskeletons, like those of insects and crustaceans, are made of chitin, a strong material. However, they have trade-offs. Growth is challenging because creatures must molt, leaving them vulnerable. As creatures grow larger, their exoskeletons can’t support their increased mass. Internal skeletons, on the other hand, grow with the organism and provide larger attachment points for muscles.
If ants were human-sized, they would struggle to survive. Insects have a limited circulatory system and breathe through tiny openings in their exoskeletons. The distance oxygen can travel in these systems is limited, which is why larger insects existed in prehistoric times when oxygen levels were higher. Thus, while chitin exoskeletons are strong, they are only effective at smaller sizes.
The evolution of bones was not a single event but a series of chance occurrences influenced by the environment. Our ancestors used available minerals, like calcium, to build early bone-like tissues. If evolution had taken a different path, we might have developed differently, perhaps with exoskeletons and pincers.
Understanding the evolution of skeletons helps us appreciate the diversity of life and the unique adaptations that have allowed different organisms to thrive. Keep exploring and stay curious about the wonders of nature!
Conduct a simple experiment to compare the strength of different materials. Gather materials like paper, plastic, and cardboard. Create small bridges using each material and test their strength by adding weights until they collapse. Record your observations and discuss how these materials might compare to the strength of bones and exoskeletons.
Create a model of the human skeleton using materials like clay, straws, or sticks. Focus on the major bones and joints. As you build, think about how the structure allows for movement and support. Present your model to the class and explain the function of different bones.
Research the evolution of skeletons and create a timeline that highlights key events in the development of internal and external skeletons. Include illustrations or images to make your timeline visually engaging. Share your timeline with classmates and discuss how these evolutionary changes have impacted different species.
Observe insects in your local environment or use online resources to study their exoskeletons. Take notes on how their exoskeletons function and protect them. Consider how these structures compare to human bones. Share your findings in a short presentation or report.
Imagine a world where humans evolved with exoskeletons instead of internal skeletons. Write a short story or essay describing how daily life, movement, and society might be different. Share your creative piece with the class and discuss the potential advantages and disadvantages of having an exoskeleton.
Here’s a sanitized version of the transcript:
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Game of Thrones star Hafthor “The Mountain” Bjornsson recently broke the deadlift world record with a 501-kilogram lift, which is truly impressive. If he had the lifting power of a leafcutter ant, he could lift a medium-sized sedan completely over his head and carry it home. Not bad! And if The Mountain had the same relative strength as the Taurus scarab dung beetle, he could pull a fully loaded Boeing 787 Dreamliner. Compared to us, ants, dung beetles, and other small creatures are remarkable because they perform their incredible feats of strength without bones.
This leads to an interesting question: why do we have internal skeletons instead of external ones?
Hey smart people, Joe here. It’s time to face the truth: we are essentially made up of soft tissue supported by a framework of bones. Our skeletons are rigid enough to provide structure and flexible enough to allow movement. It’s said that we have 206 bones, but about 1 in 8 of us have an extra pair of ribs, while some may have one less. This doesn’t even include the small sesamoid bones found in our tendons.
Speaking of bones, there are 52 bones in your feet alone, which is twice as many as in your spine. Our hands and feet contain more than half the bones in our bodies. Consider that the movements you make with your fingers are powered by muscles and nerves, and the oxygen fueling your brain comes from blood produced in your bones. You can hear me talking thanks to tiny bones in your ears.
Bones are composed of about 70% minerals, primarily hydroxyapatite, which is strong under compression, combined with flexible collagen to prevent breaking. As a result, the average human skeleton, weighing around 20 pounds, can withstand a ton of compression. For most of us, bones are the last thing we leave behind.
So, where did bones come from? The story goes back at least 1.5 billion years, long before animals existed. At that time, tectonic plates were shifting and washing minerals into ancient oceans, which would eventually contribute to the formation of skeletons.
For a long time, life was soft and squishy. Early multicellular organisms relied on the water around them for support. But around 558 million years ago, evolution took a turn, leading to two different paths: one branch developed hard protective parts, the precursors of exoskeletons, while the other branch saw the emergence of soft cartilage-like structures that provided support for muscles and movement.
Over time, these early backbones became mineralized, forming the basis of the vertebrate skeleton. Nature has discovered various ways to provide support for organisms, including the lignin and cellulose in plants, calcium-rich shells of mollusks, and mineral bones like ours. Insects and crustaceans, on the other hand, build exoskeletons from chitin, a strong and stable material.
If exoskeletons are so strong, why don’t we have them? There are trade-offs. An external skeleton makes growth more challenging; creatures like lobsters must molt, leaving them vulnerable during the process. Additionally, as creatures grow larger, their volume and mass increase faster than the strength of their exoskeletons can support.
Internal skeletons, however, provide larger attachment points for muscles and grow with the organism. But larger vertebrates require more massive bones, which can limit agility. For example, an elephant is about 13% bone by weight, while a shrew is only 4%. Humans are about 8.5%, striking a balance between strength and mobility.
Another consideration is that a human-sized ant would struggle to survive. Insects have a limited circulatory system filled with hemolymph and breathe through tiny openings in their exoskeletons. The distance oxygen can travel through these systems is limited, which is why larger insects were more common in prehistoric times when atmospheric oxygen levels were higher.
So, while chitin exoskeletons are strong, they are only effective at smaller sizes. A human-sized ant would be sluggish and unable to perform many movements.
The divergence we discussed earlier led to the development of exoskeletons in one branch and internal skeletons in another. It’s fascinating to think that our current form is a result of chance and environmental influences. Our ancestors utilized the minerals available to them, like calcium from tectonic activity, to build the earliest bone-like tissues.
The evolution of bone was not a singular moment but rather a series of chance events influenced by the environment. Invertebrates also use calcium for their support structures, while arthropods opted for chitin due to their evolutionary paths. If we could replay the story of evolution, perhaps we would have developed differently, potentially resulting in smaller forms with armor and pincers.
Stay curious!
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This version maintains the original content’s essence while removing any informal language and ensuring clarity.
Strength – The ability of an organism or a part of its body to withstand force or pressure. – The strength of a bird’s wings allows it to fly long distances without getting tired.
Evolution – The process by which different kinds of living organisms develop and diversify from earlier forms during the history of the earth. – The evolution of the giraffe’s long neck is believed to help it reach leaves high in trees.
Bones – Rigid organs that form part of the endoskeleton of vertebrates, providing structure and protection. – The bones in a human arm include the humerus, radius, and ulna.
Skeletons – The internal framework composed of bones that supports and shapes the body of an organism. – The skeletons of mammals are made up of many bones that protect vital organs.
Exoskeletons – External skeletons that support and protect an organism’s body, commonly found in arthropods. – Crabs have hard exoskeletons that protect them from predators.
Cartilage – A flexible connective tissue found in various forms in the bodies of humans and other animals. – The cartilage in a shark’s body makes it lighter and more flexible than bony fish.
Insects – A class of invertebrates within the arthropod phylum, characterized by a three-part body, compound eyes, and antennae. – Insects like bees play a crucial role in pollinating flowers.
Minerals – Inorganic substances required by organisms for various bodily functions, including building strong bones and teeth. – Calcium is a mineral that is essential for the development of healthy bones.
Adaptations – Changes in an organism’s structure or behavior that improve its chances of survival in its environment. – The thick fur of polar bears is an adaptation to the cold Arctic climate.
Organisms – Individual living entities that can react to stimuli, reproduce, grow, and maintain homeostasis. – All organisms, from the smallest bacteria to the largest whales, are part of Earth’s diverse ecosystems.
