Hi everyone.

I'm so glad you've come to learn with me today.

I'm Mrs. Horan, and I'm really looking forward to learning all about a really interesting science and history crossover with you in today's lesson.

Today's lesson is part of the Evolution and Inheritance Unit.

The lesson is called Human Skulls: using evidence from the past, and we will be learning all about the evidence scientists have gathered about the way our skulls have changed over time.

The outcome for our lesson today is to describe how human skulls have changed over time and use fossil evidence to suggest reasons why.

This lesson builds on what you already know about what fossils are and how they're formed, and is part of our big learning question, why are there similarities and differences between living things? These are the key words that we are going to be focusing on today.

Prehistoric, fossil, evidence, ancestor and skull.

You might feel really confident about what some of these mean, and some might be a bit more new to you, but we'll look at each one in detail when we come to it in the lesson, so you'll be really familiar with them all by the end.

Here are some explanations of the keywords.

As I said, our new words are all gonna be explained as we come to them in the lesson, so you don't need to look too closely at them now.

They're just here in case you want a reminder of anything later on and you need to look back for a quick check.

Our lesson today is divided into two parts.

Let's get started with the first part, finding out about the past.

Scientists estimate that modern humans have been living on Earth for around 200,000 years, and the first written records were made by humans around 5,000 years ago by the ancient Egyptians.

This means that the first time humans made a record of something was about 5,000 years ago.

Often, records are in the form of written words, but they can also be pictures too.

In this case, the records were created in the pictorial form of written language the ancient Egyptians used, which we call hieroglyphics.

You can see some in the picture here.

We call the time before this prehistoric, because it is before we had a written record of history.

The prefix pre at the start of that word means before, like in the word preschool, a place you go before you start school, or even prefixed, which is something you put before a word to make a new word.

So pre-history means before history.

With no written records, how can scientists find out about prehistoric humans? So that means no writing, no pictures, nothing created by humans that explained how they lived or even what they looked like, and that's a tricky question.

Aisha says, "I think they could use fossils." Alex says, "But I think fossils are only dinosaurs and other extinct animals." Now we know humans aren't extinct, because we're sitting here right now.

So if Alex is right, there won't be any fossils of humans.

What do you think? Scientists who study prehistoric humans depend on evidence from fossils, and there are a lot of today's keywords in that sentence, so let's break it down a bit.

We already know prehistoric means the time before there were written records.

Evidence is information which helps us to find out more about something, or to prove that something is true or not true.

And fossils are the remains or imprints of living things that are sometimes preserved in rock.

So if we put all that together, we know that scientists can find out information about prehistoric humans by using evidence gathered from remains that have been preserved in rock.

Thousands of fossilised bones and teeth from humans have been unearthed by scientists, giving us lots of evidence about our ancestors.

You can see a fossilised human skeleton there, and like most fossils, the remains and imprints we have of humans usually don't have any of the soft parts of the human, like skin, eyes or organs, but they do have the hard parts, which in this case are bone.

Let's have a quick check for understanding now to see how you're doing.

Now what is the best source of evidence we have for learning about prehistoric humans? Is it A, writing done by prehistoric humans? B, human skeleton fossils? Or C, photographs of prehistoric humans? What do you think? Great, the best sources of evidence we have to learn more about prehistoric humans is B, human skeleton fossils.

What clues could we gather from this fossilised skeleton that tell us about the human when it was alive? I suggest you pause the video here to have a really good look at this skeleton, to think about what evidence we could gather, maybe even have a chat with a partner about your ideas.

Let's take a look at what fossilised human skeletons can tell us then.

Skeletons are a frame of bones for support, protection, and movement.

We can gather clues as evidence about all of these things by looking at a skeleton.

We can get a good idea of what shape and size an animal would've been by looking at its skeleton.

You can see there, a picture of a skeleton with a human shape drawn around it.

Skeletons support our otherwise squishy bodies and help 'em to keep their shape, so we can work out the shape of an animal by looking at its skeleton.

Skeletons protect our major organs, so we can use them to gather clues about the size and shape of the organs that they're protecting.

Scientists have observed that older human skeletons have larger rib cages.

They've used this as evidence to suggest that prehistoric humans had larger lungs than we do today.

Why do you think this might have been? Why do you think humans in the past had larger lungs than we do now? That's a really interesting and a really tricky question.

This is another good point to pause the video and chat about your ideas with a partner if you can.

So what did you think? Well, we don't know for sure, but some scientists think that prehistoric human ancestors had larger lungs because they needed more oxygen to fuel their taller, stockier bodies.

How interesting.

Did you have a similar idea or did you have a different theory? Now skeletons help animals to move.

This means we can use skeletons to gather information about how they might have moved.

Can you find clues as evidence for how each of these animals moved by observing their skeletons? So let's take a look at these animals.

Here's the first one.

Think about what you can see, what shape the bones are, and maybe what animals you know of that are a similar shape, that might move in the same way.

Let's take a look at a very different skeleton now.

What can you see here? How do you think this animal may have moved when it was alive? Jun and Sofia have been looking at the same pictures as you.

Let's see what they think.

Jun says, "I can see this animal has four jointed legs.

I think it moved on land and could run quite fast like a horse or deer." Did you have a similar idea? Sofia has been taking a look at the second picture.

She says, "It looks like this animal had wings, so I think it could fly.

I can see two short legs too, so I think it could walk but not very fast." Was that what you thought too, or did you have different ideas? Time for another quick check-in on our understanding of the lesson so far.

Use the evidence from the fossil to suggest how this animal might have moved.

Take a really good look at the fossil in the picture there and decide whether you think that A, it mostly swam through water, B, it mostly walked on two legs, C, it mostly walked on four legs, or D, it mostly flew through the air.

You might wanna pause the video here to get a good close look at the skeleton on screen before making your choice.

So based on what we can see, it is likely this animal mostly swam through water.

We can see it has flipper like shapes at the front for swimming, and it appears to be a streamlined shape similar to a fish or a dolphin.

We can also use fossilised teeth to tell us about what the animal's diet may have been like.

We're gonna take a look at a couple of animal fossils now.

Take a look at them and decide what kind of foods do you think these animals ate? Here's our first fossil.

So think about the shape of the teeth and whereabouts they are in the animal's mouth.

Use what you know already about teeth and different kinds of animal diets to help you come up with your ideas.

And here's another fossil.

What do you think this animal ate? If you want, you can pause the video here for a closer look and a bit of thinking time before we look at some of the ideas other children have had.

Sam says, "This animal doesn't have any sharp canines at the front of its mouth, so I don't think it caught prey.

I think it used its teeth at the sides to grind down plants." Do you agree? Alex has been looking at the other fossil and he says, "This animal has lots of sharp teeth.

I think it was a carnivore who used its teeth to catch and tear apart prey." Is that what you thought too? We can either gather evidence to suggest how the animal caught or found its food using its fossilised skeleton.

Andeep has been carefully observing this fossilised Tyrannosaurus rex skeleton, and he says, "This skeleton has long legs, short arms, and a big jaw with lots of sharp teeth.

I think it ran after its prey and caught it in its mouth." Laura has been looking at a fossil of a very different animal.

She says, "This animal has a tail and no arms or legs.

I think it swam through water and found food." Let's have one more check for understanding before we tackle a practise task.

Take a look at this statement and decide whether you think it is true or false.

The only thing we can learn from a fossilised skeleton is the shape of the animal.

Do you think that is true or false? That statement is false.

Now can you justify your answer and say why it's false? Is it because A, we can't learn what shape it was because it doesn't have any soft body parts left? Or is it false because B, we can gather lots more evidence such as how it moved and what it ate.

Great, it's false because it's not just the shape of the animal we can learn about from its fossil.

We can also gather lots more evidence such as how it moved and what it ate.

Now we've learned all about the evidence we can gather from fossilised skeletons.

Let's apply that knowledge to a practise task.

Your job is to explain how we could use a human skeleton fossil to answer the questions, one, what shape was the human? Two, what was its height? Three, how did it move? Four, how did it get its food? Five, what did it eat? So we're not looking for you to answer the questions here.

So for number one, you wouldn't describe the shape of the human.

Your job is to think about what we could do with a fossil and which bits of it we would look at to answer the questions.

So for example, thinking about question five, what did it eat? We probably wouldn't look at the animal's feet, would we? So what would we look at? What part of the skeleton would help us to answer that question? Each one of these questions can be answered using a fossil.

You just have to decide what specific part of the fossil you would look at to find that answer.

Pause the video here to have a try and come back when you're ready.

Let's have a look at some answers then, see if they match your own.

For question one, what shape was the human? We could arrange the bones and use their shape to give us an idea of the overall shape of the human.

Question two, what was its height? We could measure the bones and estimate the height.

For question three, working out how the human moved, we could look at the shape of its body and the type of limbs it had.

Question four, how did it get its food? We could answer by looking at its limbs, how it moved and what its teeth were like.

And for question five, what did it eat? We could look at the teeth themselves and the shape of its jaw.

Your answers don't need to be written in exactly the same words as these ones to be correct.

You just need to have identified the right part of the skeleton to look at for each question.

Time for the second part of our lesson now, changes to skulls over time.

Scientists can use fossils from different time periods to see how living things have changed over time.

They use evidence from fossils to make theories about prehistoric humans.

Do you think humans have changed over time or have we always been the same? That's another really interesting question.

Evidence from the skeletons of modern humans and their ancestors shows that we have changed over millions of years.

You might have spotted we have another keyword in that sentence.

We already know that evidence is information we can use to prove something is true or not true, but we haven't looked at this word, "ancestors" yet.

Your ancestor is someone who was born and lived in the past, who was directly related to you.

So your parents or your ancestors, they were born before you, as are your grandparents and your great great great great great great great grandparents, and it wouldn't even end there.

Far back as humans go, so would your ancestors.

And the evidence we have suggests that our prehistoric ancestors looked a little different to us today.

Let's take a look at some of the evidence we have.

Can you see any differences between these skeletons? First, we have a prehistoric human fossil.

That one is a picture of a real fossil that is thousands of years old, and here we have a model of a modern human skeleton.

It's obviously a lot whiter and brighter than the fossil, because it's a model made of plastic rather than real bones, but it's the right shape for a modern human skeleton.

What differences can you see between these two skeletons? You might wanna pause the video here to make some really close observations of the two of them and talk about your ideas with a partner.

So did you spot the differences in rib cages that we talked about earlier? The older skeleton has a much larger rib cage, with room for larger lungs than the modern skeleton.

You might have also noticed some differences in the other bones, like humerus bone in the arm, this one up here, and the collar bones looking a slightly different shape, collar bones are these ones you can feel here between your neck and your arms. For the rest of the lesson, we're gonna focus in on the differences in one really important part of the skeleton though, the skull.

Scientists have observed changes in the skull shape of humans over millions of years.

Skull is the last one of our keywords today, and it means the bones in the head, including the whole top part and the jaw at the bottom.

The jaw is this bit here, the bit that moves when we talk or chew food.

Can you see the differences in these skulls? So we're gonna have three to look at.

So these are three skulls from humans or human ancestors from different time periods, with the oldest being on the left and the most modern on the right, what differences can you see between them? This is a really good point to pause the video so you can make some close observations of these different skulls.

Did you spot any differences? Keep those in mind because we're going to be reflecting on them during the rest of the lesson.

So we've established that there definitely are differences between the skulls.

Do you have any theories about why they are different? You can see on screen we've got a bit more information about the skulls now, we can see how old they are.

So the first skull on the left is around 3.

5 million years old, the one in the middle is around 1 million years old, and the last skull on the right is a modern human skull, and the same shape as yours and mine.

Do you have any ideas about why they're different from each other? That's a really big question, isn't it? Hang onto your ideas for now.

Let's have a quick check on our understanding, which of these statements about human skulls is correct.

Is it A, human skull have changed shape over a very long time? Is it B, human skull have changed shape over a short time? Or is it C, human skull have always been the same shape? Which do you think is correct? Well done, it was A, human skulls have changed shape over a very long time.

The skulls in those pictures we just looked at had changed over millions of years.

The round part of the back of the skull looks quite different across the different fossils.

We can see it really clearly in this diagram here.

The oldest skull is first and they get newer as you look from left to right.

Can you see how the back of the skull has changed over time? Do you have any ideas why this might be? You might wanna pause the video again here for some thinking and discussion time.

So the first skull is from a species called Australopithecus, which lived around 3.

5 million years ago.

What a word.

Do you want to have a go at saying it? It's Australopithecus, quite a mouthful.

You can sound it out by looking carefully at the word though.

Scientists believe it's an ancestor of modern humans, so they have evidence to suggest that today's humans are descended from this species.

It only had space for a brain around a third of the size of ours today.

You can see how small the round part of the back of the skull is in the picture there.

The second skull is from a species called Homo erectus, which is much easier to say, and which lived around 1 million years ago and was another ancestor of modern humans.

It looked larger on the outside, but actually had a similarly sized space for the brain to the modern skull on the inside.

The shape of the jaw is also different for each fossil.

Did you notice that when you were making your observations? Do you have any theories about why this is? You can pause the video here if you need some thinking time for this big question.

Scientists think that the human jaw has become smaller due to changes in our diet.

In modern times, humans eat softer, more processed foods, so our jaws don't need to be as long and strong to rip and tear apart food.

You might notice there that it says scientists think, not scientists know.

Now, scientists have used all the evidence they have and carefully thought about it to come to this theory.

We probably won't ever know for certain, but we can make some conclusions about what is most likely, using the evidence we have.

This idea might change one day if we ever find more evidence that suggests something else.

That's one of the really exciting things about science, the way that ideas can change and improve as we gather more new evidence.

At the minute, this is the best idea we have.

Did you notice any other changes in the human skulls over time? Anything that we haven't talked about yet? Jun says, "I noticed that the eye sockets are smaller in the most recent skull." Sam says, "I noticed the teeth are wider in the older skulls." Maybe you noticed that as well.

Let's have a couple more quick checks for understanding before you take on the final practise task of the lesson.

Which of these statements is incorrect? So which one is wrong? Is it A, human skulls have changed shape over time.

B, human brains have changed in size over time.

C, human teeth have become smaller over time.

Or D, human jawbones have become larger over time.

You might want to pause the video here to have a think about this one, because it is quite tricky.

So the statement that was incorrect is D, human jawbones have become larger over time.

We saw in the fossils before that they have actually become smaller.

Now, why do scientists think that human jawbones may have become smaller over time? Is it A, because modern humans eat tougher, more chewy food? B, because modern humans eat more processed foods that are soft, or C, because modern humans brush their teeth? What do you think? So this one was B, scientists think human jawbones may have changed over time because modern humans eat more processed foods that are soft.

Now for a practise task, carefully observe the three skulls from different time periods and explain the differences you can see.

Think about the shapes and sizes of the different parts and how you could describe these.

Pause the video here to have a go.

Did you manage to make lots of observations about the differences in skulls? Here is what we found.

I noticed that the older skulls had larger and longer jaws, which became smaller over time.

The teeth were also wider on the older skulls, and they looked like they stuck out a bit more than they do now.

I noticed the round part at the back of the skull was much smaller on skull A than it was on the other two.

The eye sockets looked a little larger on skull B than they did on the others.

I noticed a large brow ridge over the eyes on skull A that wasn't there on the other two.

The brow ridge is this bit here, bit where your eyebrows are.

Now this task will really get you thinking.

Choose one of the differences you observed and suggest a theory for why this change might have happened.

Remember, a theory is an idea that is formed taking into account all of the evidence that we have.

We might not be able to say for certain, so your theory might be different to the ones we've looked at today, or it might be different to the people around you.

That's all okay.

What's important is that you carefully consider the evidence when you make your theory.

Pause the video now to have a go.

Welcome back.

Did you find it easy to come up with a theory or was it quite challenging? Here's what Lucas thought.

"I noticed that the eye sockets are smaller on the modern skull C, than they were on the older skull B.

I think this might be because modern humans do not have to look out for predators like prehistoric humans had to.

It might also have been to allow more light to enter their eyes in the dark, because they wouldn't have had easy access to light at night time like we do now." That brings us to the end of our lesson.

You've done some really deep thinking today, well done.

Let's recap on the key learning points from this lesson.

Scientists use fossil evidence to help them learn about how our ancestors have changed over time.

Human skulls from different time periods show changes in characteristics such as skull shape, brain and jaw size.

Modern day skulls show differences, suggested by scientists, that are linked to humans chewing softer, processed foods.

Thank you so much for joining me today to learn about how human skulls have changed over time and to think about the reasons this might be.

I hope you found this lesson as interesting as I did, and that you learned some great new facts to share with others.

I'll see you again next time.