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NCEA | Walkthrough GuideLevel 3BIOLOGY

HUMAN EVOLUTION

Introduction 3

Human Biological Evolution 4

Classifications and Background Stuff 4Hominin Evolution 5Bipedalism 9Structural Features in Bipeds and Quadrupeds 11Advantages and Disadvantages of Bipedalism 17Effects of Bipedalism 18

Human Cultural Evolution 21

Defining Cultural Evolution 21Tools 22Fire 24Farming 25Behaviour 26

Human Origin and Dispersal 28

Mitochondrial DNA and Y Chromosome Analysis 28What is Dispersal? 31Replacement Theory (Out of Africa Theory) 32Multiregional Theory 34

Key Terms 36

Level 3 Biology | Human Evolution Walkthrough Guide

Level 3 Biology - Human Evolution | © Inspiration Education Limited 2017. All rights reserved.3

INTRODUCTIONThis standard is all about you!

Well, kind of. This standard is all about the evolution of us, humans. Don’t worry, we aren’t going to start from the origin of life and explain all the steps to get to humans, we’ll jump forward to the evolution of primates.

Join us on this journey of self-discovery, exploring the origin of us.

What will you learn in this cram guide?

First, we’ll look at the evolution of bipedalism – a pivotal point in the evolution of humans. We’ll look at all the features that evolved to let us walk on two legs and compare these structures to those in apes who are stuck walking on all fours.

Next up, is cultural evolution - which includes things like tools, fire, farming and speech. Just like with bipedalism, we’ll explore how these things changed throughout the evolution of hominins and compare between different species.

Finally, we’ll end things by looking at the question, “where did we come from?” This final section explores the two main theories: “Out of Africa” and “Multiregional”. We’ll explore the evidence for and against each theory.

A word on exam strategy.

Unfortunately, some students go to exams thinking that this external topic is all about memorising the features of different hominins or remembering the details about each model of human dispersal. The key to acing this paper is to understand the “why?”. That is, understanding why the physical features of humans help us to walk upright or why the physical features of apes make them better suited to walking on all fours. So, linking structure to function. And, it’s about understanding why we came up with the two models of human dispersal from the evidence. In this case you’ll need to understand the implications of different pieces of evidence. Don’t just memorise the facts, think “why” these are the way things are.

Here at StudyTime, we’re pretty much GCs (good citizens), so to help you out, we’ve made this guide in plain English as much as we can. We’ve also included a glossary for some of the key terms that you’ll need to master for your exam.

4 Level 3 Biology - Human Evolution | © Inspiration Education Limited 2017. All rights reserved.

Level 3 Biology | Human Evolution

However, the language we use isn’t always something you can directly write in yourexam. When this is the case, we offer a more scientific definition or explanation (in ahandy blue box) underneath. These boxes are trickier to understand on your first read through, but contain language you are allowed to write in your exam. Look out for them to make sure you stay on target!

HUMAN BIOLOGICAL EVOLUTIONThe evolution of bipedalism in hominins is a very important aspect to this paper. You are required to discuss the selective pressures for the evolution of bipedalism, as well as the structural features which evolved as a result.

To tackle this section, make sure that you understand:

The difference between hominins and hominids. The basic course of hominin evolution up to modern humans. Why hominins went from swinging through the trees to waltzing across the African plains. What structural changes occurred as a result of walking on two legs. The advantages and disadvantages of walking on two legs. How walking on two legs accelerated cultural evolution.

Classifications and Background Stuff

Humans are primates, and therefore when we want to consider where we came from, we need to consider the evolution of primates.

There are lots of different types of primates and they can be grouped into:

Prosimians (includes the lemur) New World monkeys (includes the spider monkey) which are primates who walk on all fours, only live in the trees and have a prehensile tail – a tail that can grab onto things.Old World monkeys (includes baboons) which are primates that also walk on all fours, sometimes move around on the ground as well as amongst the trees, and have a non-prehensile tail.Great apes (includes gorillas, chimpanzees, orangutans and gibbons) who walk on all fours but mainly live on the ground. Hominins (includes modern humans!) which are primates that walk on two legs, have a large brain, reduced canine teeth and have little body hair with no tail.



Hominins and the great apes are closely related and make up the hominid group – an annoyingly similar term to hominins, we know.

The hominin group refers to all the members leading to humans after they split from chimpanzees in the evolutionary history.

In this external we will focus on the evolution of hominins…

…this can be described as “humans and their most recent ancestors”, as well as looking at some differences between different hominids.

Because we are budding scientists here we need a more complicated way to refer to humans.

Humans are called Homo sapiens

What this tells us is that we belong to the Homo genus, which also includes our now-extinct ancestors, and are the “sapiens” species within the genus.

Technically, we are Homo sapiens sapiens as we are the “sapiens” subspecies within the “sapiens” species.

So, what other species are in the hominin group?

Not only does the hominin group include the Homo genus, beginning with Homo habilis and Homo erectus, but there is also the Australopithecus genus, beginning with A. anamensis and includes the first bipedal (walking on two legs) hominin, A. afarensis.

STOP AND CHECK:

Turn your book over and see if you can remember:

The difference between hominids and hominins. Examples of primates. The scientific name for humans.

Try to explain it in your own words.



Hominin Evolution

There’s a whole bunch of hominin species throughout the evolution of modern humans

Millions of years ago

commonancestors ofhumans andgreat apes

Homini

9 8 7 6 5 4 3 2 1 0

GoriliniAfrican great apes

chimpanzee

Australopithecusafricanus

Australopithecusafarensis

Sahelanthropustchadensis

Ardipithecusramidus

Homo habilis

Homo erectus

Homoheidelbergensis

bonobo

gorilla

Homo sapiens

Homo neanderthalensis

This external topic isn’t about memorising each one, but instead you’ll be introduced to key features of particular species throughout the Walkthrough Guide.

In this section, we’ll briefly run through the hominin timeline and finish with a reference table with all the species.

The first in the Australopithecus genus was A. anamensis

But we’re not too interested in this guy, instead A. afarensis is a whole lot more fascinating.

Often called Lucy, A. afarensis, was the first bipedal hominin ancestor who lived 3-4 million years ago

They lived in the savannahs of Africa and were most likely scavengers, but they didn’t



use tools. They moved around in groups, but unlike later ancestors, didn’t use speech to communicate.

There were a few more Australopithecus species, like A. africanus, A. boisei and A. robustus.

40 cm12 inches

The Homo genus burst into existence with the evolution of Homo habilis

This species lived from 2.4 to 1.5 million years ago.

They were the first hominin handymen using simple stone tools (Oldowan tools). They were also the first to have speech, but it was most probably simple grunts similar to those made by a moody teenager in the morning.

With tools, they were able to hunt animals, and with this extra protein in their tummies there was better brain development.

40 cm12 inches

A wee while later, existing from 1 million to 300,000 years ago, Homo erectus – the “upright man” – was the first to use fire

Fire was a wonder for them, allowing them to cook their food, making it safer and easier to digest, and provided them a source of light and warmth, allowing them to

Australopithecus afarensis

Homo habilis



venture out of Africa to new locations. Their tools were more advanced than H. habilis, their brains were further developed and they had a bigger population.

Even more advanced was H. heidelbergensis, popping up 300,000 years ago all over Africa, Europe and Asia.

40 cm12 inches

Next to consider are the “cavemen”

“Cavemen” isn’t the technical term, but instead it typically refers to Homo neanderthalensis (also called Neanderthals).

They lived between 230,000 and 28,000 years ago and were relatively intelligent and had advanced cultural practices, like burying their dead and performing rituals. Their tools were advanced and served many purposes.

It is expected Neanderthals lived in caves and dressed in clothes made of animal hide. DNA analysis has shown that Neanderthals and humans interbred early on.

40 cm12 inches

Homo erectus

Homo neanderthalensis



Homo sapiens came onto the scene 160,000 years ago…

…and, at the time of this Walkthrough Guide being written, are still ruling the planet.

Hopefully you know what humans are like, considering you are one.

These are not the only hominin species, but are considered the key players, each having some sort of significant advancement over the others. For example, Homo floresiensis is an extinct species, having a very small height (1.1 metres tall), living exclusively in Indonesia.

Keep referring to this table throughout the guide:

Hominin Time Period Brain Size Tool Culture Advancements

A. afarensis4 – 3 million years

ago (mya)380 – 450 cm3 No tools Fully bipedal

H. habilis 2.4 – 1.5 mya 500 – 800 cm3 OldowanFirst to make stone tools

H. erectus 1 – 0.3 mya 800 – 1100 cm3 Oldowan + Acheulean

First to use fire

H. neandertha-lensis

230,000 – 28,000 years ago

1200 – 1750 cm3 Mousterian

First to care for elderly and

bury dead

H. sapiens160,000 years ago –

present day1200 – 1700

cm3

Upper Palaeolithic

Current hominin species

STOP AND CHECK:


The main hominin species in the evolution of humans. The special features of each of the main hominin species stated above.




Bipedalism

Bipedalism is just a smart way of saying “walking on two legs”

It’s what all the cool hominids, like Homo sapiens (us humans), have been doing for the past 5 million years.

Other hominids, like modern day chimpanzees, are quadrupedal.

“Quad” means “four” and “ped” means “foot”, so quadrupeds move around on all four limbs.

Quadruped Biped

The ancestors of hominins were arboreal

What this means is that they chilled out in the trees.

But, somewhere around 5 million years ago, the African climate became cooler and drier. The dense forests became the savannah – the sprawling, dry plains – we associate with Africa today. The savannah is a grasslands with the occasional tree.

This change in climate placed heavy selection pressure of hominids

Bipedalism was selected for because it allowed the hominins to walk around. This was necessary, as they couldn’t move around amongst the trees anymore.

Before After



In the next few sections we’ll have a look at the different structural features between bipeds and quadrupeds that allow them to do their thing.

STOP AND CHECK:


The difference between bipedalism and quadrupedalism. The likely reason that bipedalism evolved.


Structural Features in Bipeds and Quadrupeds

If we compare the structural features of apes, such as gorillas and chimpanzees, with humans we can associate these changes with bipedalism. So, we’re about to compare the skull, spine, pelvis, femur and feet of apes and humans.

Skull:

At the bottom of the skull there is a rather large hole called the foramen magnum

Don’t be alarmed, this hole allows the spinal cord to descend from the brain and down through the spine.

In humans and other bipedal species, the foramen magnum is centrally located

By being centrally located, it places the skull directly on top of the spine, requiring less muscular energy to hold the head up – you don’t want the face facing down when you’re walking on two legs.

This also means that the nuchal crest – where the neck muscles are attached to the skull – is small in humans and other bipedal species.

The foramen magnum isn’t in the same place in apes

In apes, like gorillas and chimpanzees, the foramen magnum is found at the back of the underside of the skull to position the head appropriately when on all fours.

To prevent the head facing directly downwards – they kind of need it facing straight in front of them – the quadrupedal species require big muscles. Therefore, the nuchal crest in apes is large.



Ape

Foramenmagnum

NuchalArea

NuchalArea

Foramenmagnum

Human

STOP AND CHECK:


The purpose of the foramen magnum. What the nuchal crest is. The difference in the foramen magnum and nuchal crest between bipeds and quadrupeds.


Spine:

It’s hard to see what your spine looks like with pesky flesh in the way…but if you stand up straight and follow it along with your hand you might notice you’ve got some curves.

In humans, and in all bipeds, the spine is S-shaped

The S-shape of the spine keeps the body weight above the hip joints.

This allows us to stand and walk upright without too much stress on the legs.



The S-shaped spine also acts as a shock absorber.

Apes also have a curved spine, except theirs is C-shaped

In this case, the shape of the spine counterbalances the force of the organs pushing downwards when walking on all fours.

STOP AND CHECK:


The advantage of an S-shaped spine in bipeds. The advantage of a C-shaped spine in quadrupeds.

Try explain it in your own words.

Pelvis:

We know that bipeds stand up straight. So, what do they require?

In order to reduce the stress placed on the pelvis from the weight of the upper body when standing upright, bipeds have a bowl-shaped pelvis which is short and wide.

This also supports the internal organs and allows for females to give birth to offspring with relatively large skulls, such as the skulls found in humans.

Let’s think about what walking on all fours would require:

For starters, they would need large leg muscles. These large leg muscles will attach to the pelvis and so there needs to be a large enough surface area.



Therefore, apes have a long and narrow pelvis which supplies that surface area for large leg muscle attachment.

Chimpanzee Human

STOP AND CHECK:


The difference between the pelvis of bipeds and quadrupeds.


Femur:

Most of biology is just using big words to describe simple things:

A valgus angle is what we call an angle that’s away from the midline.

When looking at the femur, humans have a valgus angle where the femur is angled in relative to the pelvis.

This gives us the knock-kneed stance that we have and brings the knees directly under the pelvis.

Why is this good?

It positions the body weight through the middle of the pelvis when walking.

Apes, on the other hand, lack the valgus angle. Instead, their short, stubby femurs hang directly vertically from the hip.

This allows for the swinging motion they use when moving from tree to tree.



Gorilla Human

Valgusangle

Centre ofgravity

STOP AND CHECK:


What the valgus angle is. The advantage of having the femur angle inwards from the pelvis.


Foot:

Last structural feature to go!

The feet of humans and apes are quite different

In humans, the big toe points forwards like the other toes, whereas the big toe in apes sticks out.

Also, the human foot is arched, while the ape foot is flat.

So, why the difference?

Bipeds need to have forward thrust when walking, and therefore need to minimise the damage to the joints in the leg and feet when travelling long distances.

The forward-facing big toe helps provide this forward thrust, while the arch of the foot acts as a shock absorber when walking and running, allowing us to walk for relatively long distances.



What about apes?

If we think about the apes, they swing through the trees, gripping branches with both their hands and feet.

The big toe of apes is similar to the thumb of humans…

In other words, it is opposable. It allows them to grab stuff with their feet, like branches and food.

They don’t require the forward-facing toe as they don’t need to produce a powerful forward thrust.

Since they’re not on their feet often enough they also don’t need much shock absorbance, explaining the absence of a foot arch.

Gorilla footHuman foot

STOP AND CHECK:


The purpose of a forward-facing toe in the foot. The purpose of an arch in the foot. The difference between the feet of humans and apes.


The following table summarises the structural features of humans and apes, which help allow the individual to either walk on two legs or to walk on all fours:

Structural Features Humans (Bipedalism) Apes (Quadrupeds)

Skull Central foramen magnum and small nuchal crest

Foramen magnum right at the back and a large nuchal crest



Spine S-shaped spine C-shaped spine

Pelvis Bowl-shaped (short and wide) pelvis

Long and narrow pelvis

Femur Valgus angle (femur angled inwards)

No valgus angle (femur hanging vertically downwards)

H. sapiensForward-facing big toe and presence of arch in the feet

Opposable big toe facing outwards and no arch in the feet

Advantages and Disadvantages of Bipedalism

There are a number of advantages of being bipedal – turns out it was quite useful in the evolution of hominins and eventually humans.

Before we even go into the advantages, walking up on two legs allowed hominins to travel easily in the savannah. With the loss of dense forest and the transformation to flat, grassy plains, the arboreal lifestyle was no longer a good option.

The main advantage of bipedalism is that it frees up the hands

This allow the hands to be used for carrying things: infants are able to be carried in the hands, tools were able to be crafted and used, and larger amounts of food were able to be carried.

Nowadays, being bipedal lets us drive cars, and spend hours on our phones.

But to the delight of the first bipedal hominins there were a few more surprises

Imagine the burning sun, high above the African savannah, you’d want to keep as cool as possible. When standing upright there is less sun shining on you, preventing excessive heat.

The upright stance allowed early hominins to see further than they would on all fours. This means that both predators and food could be spotted from far away, as well as appearing more intimidating some predators.

Mother Earth giveth, and Mother Earth taketh away

If you’re on all fours, most of your body is at the same level, making it no trouble



for blood to flow around. Standing upright makes it harder for blood to move from the legs to the heart, making varicose veins – those enlarged, twisted veins in some people’s legs – more likely to form.

We’ve already said that bipeds have arched feet to act as shock absorbers, but the problem is, that in some people the arch of the foot isn’t as ‘arched’ as it should be, known as flat feet. This makes walking harder and painful over longer distances.

Lastly, back problems are much more common with standing upright. For one, the discs between the vertebrae can become damaged, resulting in what is referred to as a ‘slipped disc’.

STOP AND CHECK:


Some examples of the upside to bipedalism. Some examples of the downside to bipedalism.


Effects of Bipedalism

With the hands free, tools were able to be crafted and used for killing prey and cutting up food.

The ability to start fires allowed food to be cooked, making it easier to eat and digest. As a result, the diet changed because of bipedalism.

When the diet changed this put selective pressures on other structural features

Large teeth and large jaws were no longer required, nor were the large muscles and muscle attachments, such as the sagittal and nuchal crest.

Humans have smaller teeth and a U-shaped jaw, while apes have large teeth and a rectangular jaw.

Ape

Diastema

Human



Apes have large brow ridges above the eyes to support the skull from the stresses resulting from chewing difficult-to-eat foods. Humans have a much less pronounced brow ridge.

Ape

Brow ridge

Brow ridge

Human

Similarly, apes have prominent zygomatic arches (the fancy way of saying cheek bones) which are thicker and wider than in humans. The zygomatic arch is where the jaw muscles pass through; apes require larger jaw muscles, while the humans have smaller ones.

Ape

Zygomatic arch

Zygomatic arch

Human

Believe it or not, bipedalism ultimately led to humans becoming an intelligent species

The crafting of tools and the eventual hunter-gatherer lifestyle of early humans, due to the development of bipedalism, led to increasing intelligence, facilitated by increasing cranial capacity.

One of the developments associated with brain development was speech developing, allowing early humans to communicate more complex ideas with one another.



The Broca’s area is responsible for organising sounds into sequences that make sense, and the Wernicke’s area is responsible for interpreting these sounds that are heard.

STOP AND CHECK:


The consequences of bipedalism – what did it lead to? The difference between the jaw, brow ridge and zygomatic arches between humans and apes.


Quick Questions

Have a look at the following skeletons:

On the left is a human skeleton, in the middle is “Lucy” (Australopithecus afarensis), and on the right, is a chimpanzee skeleton.

Explain how the skeletons of humans and “Lucy” tell us that they most probably spend most of their time walking on two legs, while the skeleton on chimpanzees tell us they walk on all fours or spend their time among the trees.

Discuss the survival advantages and disadvantages Lucy would have had due to being bidepal. Make sure you consider the changing climate and the selection pressures for bipedalism.

?



HUMAN CULTURAL EVOLUTIONCultural evolution involves passing on knowledge from one generation to another

As new ideas are built on old ideas that have been passed on, the culture changes. Tool use is an example of cultural evolution. Homo habilis is thought to have been the first species to use stone tools.

Other examples of cultural evolution were the use of fire, the burial of dead (exhibited first by Neanderthal), and art forms. So, what's in stock for this section?

Can’t really discuss cultural evolution without defining it first. Look at the four types of tools used by hominins throughout their evolution. How hominins came across fire and why it was such a wonderful thing. How farming changed the lives of hominins.Finally, we’ll finish by looking at things like language, rituals, art forms and intelligence.

Defining Cultural Evolution

Cultural evolution is simply the passing on of knowledge from one generation to another, not through DNA or biological means, but by social interactions.

As new ideas are built on old ideas that have been passed on, the culture changes. Cultural evolution involves a wide variety of things, ranging from beliefs (such as religion), knowledge, customs, language and skills.

Like biological evolution, cultural evolution can still be thought of as a Darwinian evolutionary process, with selection pressure selecting for certain cultural changes that enhance survival in the current environment.

STOP AND CHECK:


The difference between cultural and biological evolution. Examples of what cultural evolution may involve.




Tools

Tool use is a good example of cultural evolution

Homo habilis is thought to be the first species to use stone tools.

The first stone tools don’t even look like tools

Imagine Homo habilis threw a stone at the wall, it chipped, and they thought “wow, this is going to be so useful”.

That’s because these tools, called Oldowan tools, were basically just stones that had been chipped on one side.

They were sharp enough to cut meat and to work wood, though.

cm

0 4

Oldowan tools were replaced by Acheulean tools approximately 1.5 million years ago

They are often associated with Homo erectus, but were also used by Homo heidelbergensis.

These tools were flattened handaxes that were made by chipping off at either side.

These tools were symmetrical and had multiple purposes, such as cutting up carcasses, cutting wood, and scraping or cutting hides. So, they were quite handy!



Just like with technology today, Acheulean tools soon became obsolete with the unveiling of Mousterian tools.

These sleek, stylish and functional tools belonged to the Neanderthal (Homo neanderthalensis).

These tools were more carefully shaped and were often used with other materials. So, there might have been a stone arrowhead bound to wood to create a spear, for example.

We end with the upper Paleolithic tools used by both Neanderthals and Homo sapiens

As usual, the tool making techniques became more refined allowing for more precise functions.

These upper Paleolithic tools weren’t just made of stone but other materials as well: bones from animals and plant fibres were often incorporated.

Not only were there cutting-type tools, but there were ropes, nets and needles, even allowing for the creation of tents and clothes.



Tool use is an example of cultural evolution. This is because the knowledge used to create and advance tools was passed down from older generations through to younger generations.

The use of tools allowed hominins to hunt different prey, allowed them to work together – enhancing communication and language – and increased their survival.

STOP AND CHECK:


The name of 4 tool types. The first hominin species to use tools. The hominin species which used each tool type. How tool shape and function changed over time.


Fire

Our love of fire began 1 million years ago with Homo erectus. These hominins were likely the first to use fire, with the primary uses being to cook food and keep warm.

Imagine what it would be like to eat a slab of raw meat…

…chances are it’d be quite tough to bite and rip apart and there’s a good chance you’ll get sick from all the microbes chilling out on the meat.

So, fire did wonders: it softened the food, making it easier to eat and digest, and killed all the microbes, making it safer to eat.

Therefore, fire enabled meat to remain a part of our diet.

By starting a few fires, Homo erectus was able to stay warm even in the winter months

This source of warmth allowed Homo erectus to venture out in the big, wide world to new areas. Without fire, Homo erectus would never have been able to leave Africa.

Not only does fire provide warmth, but it provides light

A source of light extended the effective day length allowing hominins to have more time to gather and hunt food, make tools and basically have more free time for social interactions.



All of these contributed to the growing rate of cultural evolution.

Finally, fire even helped construct tools, with the heat being used to harden certain materials.

STOP AND CHECK:


The first hominin species to use fire. The advantages of fire for hominins.


Farming

Hominins began as scavengers, with Australopithecus scavenging meat, catching some small prey, and eating things like nuts and fruits. As tools developed, hominins were able to hunt and kill larger animals and eat their meat. With the capability of starting fires, meat became safer to eat – microbes were killed by the fire – and was easier to eat and digest.

Often, migration of hominins was linked to resources

Hominins relied on the food present in the environment, and when the population grew or when resources ran out, they moved to a new location.

Farming became vital to the proliferation of early humans

Animals such as dogs, sheep and pigs became domesticated, and plants like wheat, rice, beans and cotton, were grown and cultivated by humans.

By setting up farms there was a constant source of food for the early humans, allowing for the development of villages with permanent locations and larger populations.

So, what were the advantages of farming?

If we consider the advantages of farming, it made food easier to obtain and was more dependable, with less risk of disappearing. As a result, fewer people died of starvation and fewer individuals were needed to go out hunting or gathering for food.

The development of farms advanced cultural evolution, with new skills and tools developing as a result. As well as this, less time spent gathering food meant more time available for other things like arts and crafts.



Ultimately, farming and agriculture gave rise to the Industrial Revolution in the 18th and 19th centuries. Commerce, politics and transport came out of this agricultural industry.

But farming came with some disadvantages

The biggest one was that the diet became restricted and was based on what they could grow. The growth of crops and health of domesticated animals also depended on the weather.

With the creation of large villages and more dense populations, disease became more common.

Finally, farms lead to fighting for animals, resources and land.

STOP AND CHECK:


The advantages of farming. The disadvantages of farming.


Behaviour

The evolution of abstract thought is also important to consider

This involves things like communication (language), art, and rituals.

Many processes in cultural evolution are related to the increasing intelligence of hominin species.

As a general rule, the closer the hominin species is to humans in evolutionary history the more intelligent they were.

Intelligence correlates pretty well to the brain size of human ancestors according to the fossil records:

Earlier hominins had small brains (Australopithecus afarensis had a brain size of 380 – 450 cm3 and Homo erectus had a brain size of 800 – 1100 cm3) Later species had much larger brains (H. neanderthalensis and H. sapiens had brains bigger than 1200 cm3 and up to 1700 cm3).



Homo sapiens

Homo neaderthalensis

Homo erectus

Homo habils

Australopithecus

Sahelanthropus

An interesting hominin species is the Neanderthals

Archaeologists have shown that they buried their dead, suggesting they looked after their elderly and had much stronger social bonds. Amongst the dead were things like tools and flowers, sometimes with red ochre decorations. This indicates a ritualistic behaviour and could suggest Neanderthals had some belief in an afterlife.

Homo sapiens are the most evolved culturally

For one, we were the first species to use art. This is evident from cave paintings found in many different locations across the globe. And as you know, modern humans are very creative.

Finally, let’s consider communication

It is likely that Homo habilis were the first to have speech. But based on fossil records they didn’t have a voice box so it would have been grunting sounds only. However, the larger brain and presence of a Broca’s area does indicate they were capable of speech.

Homo erectus had an even larger brain and so likely had more advanced speech, though still not complete sounds.

It wasn’t until Homo neanderthalensis and Homo sapiens that proper sounds were made.

It is important to note that, although speech wasn’t always present, ever since



Australopithecus afarensis, hominins lived and moved in groups, likely having social structure.

STOP AND CHECK:


Which hominin was the first to bury their dead? What evidence suggests that Neanderthals believed in an afterlife? How language evolved in hominins.


Quick Questions

Identify and describe the tool culture associated with Homo habilis. Explain how the tools would have been used and how it helps us to understand the behaviours of Homo habilis.

Explain how fire may have affected both cultural and biological evolution. Several thousand years ago, many Homo sapiens populations changed from the life of hunting and gathering to using agriculture. Discuss how this change led to an increase in cultural evolution. What were the key pros and cons of agriculture for these populations?

HUMAN ORIGIN AND DISPERSALThere are two main models of the origin and dispersal of modern humans

Although the Replacement theory (Out of Africa model) is the most widely accepted by scientists, you must be able to explain the idea behind both the Replacement theory and the Multiregional theory, including the evidence for each.

Before we jump into dispersal we’ll look at the types of genetic evidence that scientists used to come up with theories of dispersal. We’ll look at what dispersion of humans involved. Finally, we’ll explain the basics of both dispersal models and look at the evidence for and against each one.

Mitochondrial DNA and Y Chromosome Analysis

Before we jump into the juicy stuff, we need to think about what types of evidence

?



scientists look at to support different theories.

The first piece of evidence is the fossil record

This is pretty straightforward: animal dies, leaves behind its skeleton, sometimes the skeleton gets fossilised, enthusiastic archaeologist catches a break and digs it up.

The fossil record can tell us when and where these organisms were from, and what they might have looked like.

In more recent times, fossils have gone out of fashion and genetic analysis has become the new fad.

Two types of genetic analysis have been used to explain where and when humans originated and where they explored:

1. Mitochondrial DNA analysis2. Y chromosome analysis

Wait, mitochondrial DNA?

By now you’ll know that DNA is present in the nucleus of cells and is the genetic information that encodes for the characteristics and traits of the organism.

What you may not know is that the mitochondria – the powerhouses of the cell – are hiding a few thousand base pairs of their own DNA, which encodes for many of the proteins within the mitochondria.

Now this ain’t your regular old DNA though, this is circular double-strand DNA which replicates separately from the rest of the cell, and is inherited from your mum only.

Mitochondria

Mitochondrial DNA

Cell



Mitochondrial DNA is inherited a little bit differently…

Since mitochondrial DNA is only passed on from mother to child it doesn’t get altered by things like crossing-over.

There is a steady rate of mutation which allows scientists to determine how long two species, or even two individuals, shared a common ancestor by comparing their mitochondrial DNA.

Nuclear DNA is inheritedfrom all ancestors

Mitochondrial DNA is inheritedfrom a single lineage

Y chromosome analysis can be used in a similar way to mitochondrial DNA; it has the same purpose

While mitochondrial DNA is passed down from mother to child, Y chromosomes are only passed down from father to son.

Just like mitochondrial DNA it doesn’t get altered by things like crossing over during meiosis.

Y

Y

Y

Y



By using both mitochondrial DNA and Y chromosome analysis you can basically map out the dispersal of humans – Homo sapiens – out of Africa. We’ll look at dispersal in more detail in the next sections.

STOP AND CHECK:


Why mitochondrial DNA and Y chromosomes are used in genetic analysis. The differences between mitochondrial DNA and regular nuclear DNA (DNA found in the nucleus of the cell).


What is Dispersal?

Regardless of how it happened exactly, Homo erectus and Homo sapiens moved out of Africa and ventured in the big, wide world.

Based on fossil records, all previous hominin species were found exclusively in Africa, and since not all humans currently live in Africa they had to leave at some point in time.

This is the idea of “dispersal”.

So, why did they leave the cosy nest of their African home?

It’s thought that dispersal was linked to climate change.

Around 1-2 million years ago, the climate changed and the landscape dramatically changed. Sea levels dropped, new land was exposed, forests shrunk and grasslands, or savannahs, popped up.

This wasn’t ideal and it is expected that late hominins left and explored to find food

Populations who stayed put were either too lazy to leave or, more likely, were either better adapted to the new climate and/or food sources or were geographically isolated and unable to leave.

Travellers were able to explore the corners of the globe as climate change resulted in lower sea levels exposing more land.



There are two main models to do with the origin and dispersal of humans:

Multi-regional Theory: Some Homo erectus gapped it while others stayed behind. Homo sapiens evolved from Homo erectus in different locations around the globe. Out of Africa: Homo erectus first evolved into Homo sapiens while still in Africa, and then some Homo sapiens gapped it and left Africa to explore and colonise the rest of the globe.

STOP AND CHECK:


What is meant by the term “dispersal”. The two main models of human dispersal. The possible reason that lead to dispersal.


Replacement Theory (Out of Africa Theory)

20.000 yr

13.000 yr

40.000 yr

100.000 yr67.000 yr

40.000 - 60.000 yr

Remember, around 1-2 million years ago, some Homo erectus decided to gap it and test their luck outside of Africa.

Well, according to the Out of Africa mode, their luck ran out and those that left Africa died out. This is likely due to the not-so-ideal conditions at the time. But, those who were smart enough to stay in Africa eventually evolved into Homo sapiens.



The Out of Africa model suggests that all Homo sapiens originated in East Africa

What this means is that they evolved from previous Homo erectus populations already present.

Modern humans are thought to have evolved 200,000 years ago, leaving Africa between 125,000 and 65,000 years ago.

Once modern humans left Africa they replaced earlier hominins, including Homo neanderthalensis, with little interbreeding.

DNA analysis has shown that 1-4% of European DNA is “Neanderthal DNA”. This would have resulted from interbreeding between Homo sapiens and Homo neanderthalensis during a period of overlap of time and location.

So, why should you believe the Out of Africa model?

First of all, according to the Out of Africa model, every single person who isn’t of African descent originated from a small group of 200 people who left Africa.

Genetic analysis also has shown that current African individuals are more genetically diverse than Asian and European populations. This indicates Africa populations are much older than European and Asian, suggesting Homo sapiens originated in Africa first and then left.

Although the genetic similarity across all races suggests a common ancestor.

The Out of Africa model is also supported by fossil evidence

For one, the oldest Homo sapiens fossils are almost 200,000 years old, while Homo sapiens fossils found outside Africa are not nearly as old. This suggests an African origin of Homo sapiens.

If you were hoping for Multiregional Theory you’d be expecting similar-aged Homo sapiens fossils in all areas: Africa, Asia and Europe.

STOP AND CHECK:


How dispersal occurred according to the Out of Africa model. The evidence which supports the Out of Africa model.




Multiregional Theory

Let’s show some love to this neglected theory:

Years agoMultiregional

African Asians AustraliansEuropeans African Asians AustraliansEuropeans

African origin for Homo erectus

Spread of Homo erectusthroughout the World

Spread of Homo erectusthroughout the World

African origin for Homo erectus

Out of Africa

Modern humans

50.000

100.000

150.000

2.000.000

Homo erectus

Homo habilis

The Multiregional theory suggests that Homo erectus left Africa and formed different populations in different geographical areas before eventually evolving into modern humans.

It is suggested that these isolated populations adapted to their particular environments, which resulted in some of the phenotypic differences between different human races.

But there was some gene flow between these populations so that they all evolved into the same species – gene flow prevented the different populations from forming different species.

Basically, Homo sapiens evolved simultaneously in Africa, Asia and Europe

Because high levels of gene flow would be required it just seems unlikely that this is what occurred. Recently genetic analysis has also put further doubt on this model. Remember, DNA across all humans is very similar, with really only African populations being more genetically diverse.

However, if the Multiregional theory was true you’d expect a whole lot more genetic variation than there really is.



Multiregional theory has one saving grace:

This is because there have been a few transitional fossils – not quite Homo sapiens – found in places like Asia which fits in with the Multiregional theory, where older Homo sapiens evolved simultaneously in different locations.

Remember, there will usually always be evidence that supports and evidence that doesn’t support a theory.

It’s about considering all the evidence and thinking what is most likely to be true.

STOP AND CHECK:


How dispersal occurred according to the Multiregional model. The evidence which supports the Multiregional model. What you’d expect if the Multiregional model was true.

Try explain it in your own words.

Quick Questions

Consider the following scientific findings:

In 2010, Neanderthal specimens were analysed and their DNA was sequenced. It showed that they share as much as 4% more of their genome with non-Africans than with Africans.

In 2010, Denisovans (an extinct hominin) were found to share 4-6% of its genome with living humans from Melanesia (Vanuatu, the Solomon Islands, Fiji and Papua New Guinea), but not with any other living group.

In 2011, all living males were found to have descended from an ancestor that lived around 60,000 to 140,000 years ago in Africa. This was determined from Y-chromosomal analysis.

Discuss how well these pieces of evidence support the theories of human dispersal: Out of Africa and Multiregional Model. Make sure you start by explaining how each of the two models describes human dispersal.

?



KEY TERMSAcheulean Tools:

An advancement of Oldowan tools resembling flattened handaxes, first used by Homo erectus.

Arboreal: Refers to tree-dwelling, or spending most time above the ground amongst the trees.

Bipedalism: The act of walking upright on two legs, or two limbs.

Cultural Evolution: The passing on of knowledge from one generation to another through means other than DNA, such as social interaction.

Foramen Magnum: The hole in the bottom of the skull that allows the spinal cord to pass through.

Hominids: The group of primates made up of hominins and the great apes, such as gorillas, chimpanzees, orangutans and gibbons.

Hominins: The group of primates made up of humans and our most recent, closely related, ancestors.

Mitochondrial DNA: The small, circular DNA found in the mitochondria of cells, which replicates independently on nuclear DNA.

Mousterian Tools: Carefully shaped stone tools often combined with other materials, first used by the Neanderthals.

Multi-regional Theory: The model of dispersion whereby Homo sapiens evolved from Homo erectus simultaneously in different locations around the globe after Homo erectus left Africa.

Nuchal Crest: The part of the skull where the muscles of the neck attach.



Oldowan Tools: The oldest tools used by hominins, first used by Homo habilis, made from stones with chips on one side.

Out of Africa Theory (Replacement Theory): The model of dispersion whereby Homo erectus first evolved into Homo sapiens while still in Africa, and then some Homo sapiens left Africa and colonised other locations around the globe.

Quadrupedalism: The act of walking on four legs, or four limbs.

Upper Paleolithic Tools: Advanced tools made from a variety of materials, such as animal bone and hide, used by Neanderthals and Homo sapiens.

Valgus Angle: An angle which points away from the midline.

Zygomatic Arches: Cheek bones.



NOTES

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