Fossils
Have you ever stepped in wet mud and left a clear footprint behind? What if that footprint survived for millions of years? Let us dig into the past and find out how the Earth preserves secrets in stone.
Can a Footprint Turn into Stone?
Evidence of ancient living things! Fossils are traces of organisms that have turned to stone. They can be bones, shells, or even outlines of leaves and footprints preserved perfectly over millions of years.
Over 99 percent! The vast majority of all plants and animals that have ever lived on Earth are now gone forever. We only know about them because of the fossil record left behind in the rocks.
Put Your Instincts to the Test
Think about what you already know about fossils. Pick an answer for each question, then see if your instincts were right.
Plants and leaves! Bill Nye the Science Guy shows us that flat, grinding teeth belong to vegetarians, while sharp, piercing teeth belong to meat-eaters.
Sedimentary rock! It is laid down in flat layers like a cake over millions of years. This gentle process traps and preserves the evidence of ancient life perfectly, slowly turning it to stone.
Its original material is replaced by minerals. The wood acts like a sponge, soaking up mineral-rich water (often from volcanic ash). Over time, the organic wood rots away and turns completely into stone!
Understanding the Science
Tap each card to reveal the explanation behind the science of fossils.
Key Concepts
Extinction
Tap to learn moreExtinction occurs when a species of plant or animal dies out completely and is gone forever. Over 99% of all living things that have ever been on Earth are now extinct. The fossil record is often our only evidence that they existed.
Cast and Mould
Tap to learn moreWhen a shell or bone is pressed into soft mud, it leaves an impression called a mould. If minerals eventually fill that mould and harden into stone, it creates a solid 3D copy called a cast. Together, they create a perfect picture of the past.
Petrifaction
Tap to learn morePetrifaction is a process where the original material of a living thing, such as a piece of wood, is slowly replaced by minerals. Over millions of years, the organic material decays and leaves behind an exact stone replica.
La Brea Tar Pits
Tap to learn moreThe La Brea Tar Pits are a famous site in Los Angeles where ancient animals, like sabre-tooth cats and dire wolves, came for a drink. They were trapped in sticky, bubbling natural asphalt, preserving their bones beautifully for thousands of years.
Sedimentary Layers
Tap to learn moreSedimentary Layers form over millions of years as tiny particles of mud, sand, and silt settle on riverbeds, lake floors, and ocean bottoms. These loose particles are called sediment. As new sediment piles on top, the weight and pressure slowly compact the lower layers and cement them into solid sedimentary rock. Because each layer formed at a different time, scientists can read them like a timeline: the deeper the layer, the older the fossil buried inside it.
Palaeontologist
Tap to learn moreA palaeontologist is a scientist who studies the history of life on Earth through the fossil record. As we saw in the episode, they use extremely delicate, careful tools to extract ancient bones from the rock without ruining them.
Trace Fossils
Tap to learn moreNot all fossils are body parts like bones or teeth! Trace fossils are records of an animal's behaviour. The dinosaur footprints Bill Nye the Science Guy measured to figure out if the dinosaur was walking or running are perfect examples of trace fossils.
Amber
Tap to learn moreAmber is fossilised tree sap! Bill Nye the Science Guy mentions how insects can get stuck in soft tree sap. Over millions of years, the sap hardens into beautiful, clear amber, preserving the organism inside perfectly so palaeontologists can study it today.
Try It: Fossil Excavation
Grab your pickaxe and dig through the sedimentary layers like a real palaeontologist! Click or tap repeatedly on each rock layer to chip away the stone and uncover the fossils hidden inside. The deeper you dig, the older the secrets you will find.
Apply Your Knowledge
Now let us see if you can connect what you have learned to real palaeontology work.
Match the Concepts
Click an object to select it, then click the matching description to place it.
Real-World Challenge
Imagine you are a palaeontologist who just found fossilised footprints of a two-legged dinosaur. The footprints are spaced very far apart. What can you conclude about the size of the dinosaur and what it was doing when it made the tracks?
What Has Changed Since This Episode Aired
This episode first aired in the 1990s. While the core science remains incredibly accurate, here are a few things that have advanced in the world of palaeontology.
Updated: Scientists have since refined this figure to be even more accurate. Based on the fossil record, it is now estimated that over 99 percent of all species that have ever lived on Earth are extinct!
Updated: We no longer have to guess! Modern palaeontologists have discovered fossilised melanosomes (pigment cells) in perfectly preserved dinosaur feathers. By looking at the shapes of these microscopic cells, we actually know the real colours of some feathered dinosaurs, like the iridescent black of the Microraptor.
Updated: Today, palaeontologists do not just say they are related; they classify birds as actual, living dinosaurs! Science now splits them into "non-avian dinosaurs" (the ones that went extinct 66 million years ago) and "avian dinosaurs" (the birds that survived and are still all around us today).
Test Your Understanding
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Results
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Reflection
If you discovered a brand new fossil in your back garden, what kind of ancient creature would you hope it belonged to? If you could travel back in time to see it alive, what is the first thing you would want to learn about how it really lived?
Episode Discussion
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