Post by Admin on Sept 14, 2020 21:01:14 GMT
Published: September 10, 2020
What Our DNA Can Tell Us About the History of Humans
ABSTRACT
Almost every cell in our bodies contains DNA. DNA is a molecule that stores the instructions for how our bodies work and it is passed on from parents to their children. In this article, we show you how DNA can be used as a time machine, taking us back many thousands of years and revealing stories of our ancestors. For instance, we can find out about the ancient history of humans, and tell where and with whom our ancestors likely lived. DNA can also tell us about a country’s recent history, uncovering stories of how ordinary people lived or moved about.
INTRODUCTION
Our DNA Molecule that stores the instructions for how our bodies work. It is passed on from parents to their children, and sometimes mutates, causing small differences in the DNA of present-day people. Its full name is deoxyribonucleic acid. is like a long diary of human history, passed down from generation to generation. This diary contains many fascinating stories of our ancestors, with each new generation adding its small contribution. Using mathematics, statistics, and computers, scientists can uncover these stories by making sense of small differences in our DNA. These can be stories about ancestors of Homo sapiensThe name of the only remaining human species to which we all belong. who lived hundreds of thousands of years ago, or they can be about our ancestors over the last few thousand years.
Let us start with where our DNA Molecules. These are the chemical building blocks of our bodies and much of the living world. They are made up of multiple tiny particles called atoms that stick very tightly together. come from. We each inherited a unique combination of DNA from our parents. This is why we look different from our siblings, except for identical twins, whose DNA is the same. Each chunk of DNA can be traced to one of our four grandparents, and because they all have different ancestors themselves, each chunk of DNA tells a slightly different part of the story of the past.
Chunks of our DNA have been passed on through our ancestors over thousands of years. Let’s imagine looking back in time to trace our ancestral lines. Ancestral lines describe which ancestors we inherited our DNA from (for instance, through mum—grandad— greatgrandma and so on). We inherit many chunks of DNA, each from a different ancestral line. Interestingly, only a few of your distant ancestors passed on their DNA to you, just by chance. This is because a parent can only pass on half of their DNA to each child, and so over many generations of halving, halving, and halving again, not all of their descendants will end up receiving a chunk of their DNA. for each chunk (red and blue lines in Figure 1A). When two people share an ancestor, their ancestral lines meet. For people who are closely related (like cousins), these ancestral lines can meet very recently, but for people who are not closely related, ancestral lines meet much further in the past. Ancestral lines form DNA family treesThey describe how and when the ancestral lines of different people meet back in time, and can tell us how we are related to each other over many thousands of years., showing how people’s DNA are related to each other. Each chunk of DNA is inherited through different ancestors, so the DNA family tree can be different for different chunks (Figure 1B). The same two people can be closely related in some DNA family trees and distantly related in others. In fact, for some chunks, the closest DNA ancestor of you and your cousin can go back millions of years to the very origin of human-like apes.
Figure 1 - (A) We show two different chunks of DNA in red and blue and how they were passed through our ancestors.
As they are passed from one generation to the next they sometimes mutate, so that there are small differences between the chunks inherited by present-day people. (B) DNA family trees are different for the red and blue chunks, which can be seen by tracing back who each chunk was inherited from in (A). Scientists can reconstruct these trees using the idea that chunks with fewer differences are more closely related than chunks with more differences.
Scientists have worked out ways to reconstruct DNA family trees by looking at the small differences in the DNA between people living today [1, 2]. Typically, the further back in time two people share an ancestor, the more genetic differences there will be between those two people.
In this article, we will tell you three different stories contained in these DNA family trees. The first story is about how we can uncover the ancient past, including when our ancestors settled in different parts of the world. The second story looks at our recent history and what we can learn from the DNA of people living in the same country today. The third story is about how groups of people have moved and merged, and how we are all really a mixture of many ancestral populations.
UNCOVERING THE ANCIENT PAST USING DNA FAMILY TREES
Written records only go back a few thousand years. They cannot tell very ancient stories but, amazingly, our own DNA can. To understand how scientists read the stories from DNA, let us consider you and a friend. If you are both in a small room with a few other people, you will easily find your friend. If you are in a larger room full of hundreds of people, it might be much harder to find your friend. We can think about your ancestors using similar reasoning. At any given time in the past, if there were only a small number of humans alive or if your ancestors inhabited the same geographic region, then the chance that you share an ancestor with your friend at that time is high. On the other hand, if the number of humans living at that time was large or if your ancestors lived far away from each other, the chance of sharing an ancestor at that time will be small.
How often you and your friend shared an ancestor at different times in the DNA family trees can tell us whether your ancestors lived close to each other, how they moved about, and how many other humans occupied our world back then.
Today, almost 8 billion humans live on our planet, spread widely across all continents. Until relatively recently, humans were a much rarer species, and going back as far as 200,000 years ago, humans were mostly living on the African continent. DNA family trees indicate that a relatively small number of people migrated out of Africa and settled in other parts of the world. At that time, some distant relatives of ours, most famously NeanderthalsA distant relative of Homo sapiens, who lived across Eurasia long before Homo sapiens did. When Homo sapiens started to populate Eurasia (migrating out of Africa), they mixed with Neanderthals, so that most people with non-African ancestry carry a small amount of Neanderthal DNA. Neanderthals went extinct around 40,000 years ago., were already living in Europe and Asia. For a long time, we did not know how Neanderthal people were related to us. Only when scientists compared their DNA to ours, and used the idea of DNA family trees, did they discover that humans who migrated out of Africa mixed with Neanderthals [3].
What Our DNA Can Tell Us About the History of Humans
ABSTRACT
Almost every cell in our bodies contains DNA. DNA is a molecule that stores the instructions for how our bodies work and it is passed on from parents to their children. In this article, we show you how DNA can be used as a time machine, taking us back many thousands of years and revealing stories of our ancestors. For instance, we can find out about the ancient history of humans, and tell where and with whom our ancestors likely lived. DNA can also tell us about a country’s recent history, uncovering stories of how ordinary people lived or moved about.
INTRODUCTION
Our DNA Molecule that stores the instructions for how our bodies work. It is passed on from parents to their children, and sometimes mutates, causing small differences in the DNA of present-day people. Its full name is deoxyribonucleic acid. is like a long diary of human history, passed down from generation to generation. This diary contains many fascinating stories of our ancestors, with each new generation adding its small contribution. Using mathematics, statistics, and computers, scientists can uncover these stories by making sense of small differences in our DNA. These can be stories about ancestors of Homo sapiensThe name of the only remaining human species to which we all belong. who lived hundreds of thousands of years ago, or they can be about our ancestors over the last few thousand years.
Let us start with where our DNA Molecules. These are the chemical building blocks of our bodies and much of the living world. They are made up of multiple tiny particles called atoms that stick very tightly together. come from. We each inherited a unique combination of DNA from our parents. This is why we look different from our siblings, except for identical twins, whose DNA is the same. Each chunk of DNA can be traced to one of our four grandparents, and because they all have different ancestors themselves, each chunk of DNA tells a slightly different part of the story of the past.
Chunks of our DNA have been passed on through our ancestors over thousands of years. Let’s imagine looking back in time to trace our ancestral lines. Ancestral lines describe which ancestors we inherited our DNA from (for instance, through mum—grandad— greatgrandma and so on). We inherit many chunks of DNA, each from a different ancestral line. Interestingly, only a few of your distant ancestors passed on their DNA to you, just by chance. This is because a parent can only pass on half of their DNA to each child, and so over many generations of halving, halving, and halving again, not all of their descendants will end up receiving a chunk of their DNA. for each chunk (red and blue lines in Figure 1A). When two people share an ancestor, their ancestral lines meet. For people who are closely related (like cousins), these ancestral lines can meet very recently, but for people who are not closely related, ancestral lines meet much further in the past. Ancestral lines form DNA family treesThey describe how and when the ancestral lines of different people meet back in time, and can tell us how we are related to each other over many thousands of years., showing how people’s DNA are related to each other. Each chunk of DNA is inherited through different ancestors, so the DNA family tree can be different for different chunks (Figure 1B). The same two people can be closely related in some DNA family trees and distantly related in others. In fact, for some chunks, the closest DNA ancestor of you and your cousin can go back millions of years to the very origin of human-like apes.
Figure 1 - (A) We show two different chunks of DNA in red and blue and how they were passed through our ancestors.
As they are passed from one generation to the next they sometimes mutate, so that there are small differences between the chunks inherited by present-day people. (B) DNA family trees are different for the red and blue chunks, which can be seen by tracing back who each chunk was inherited from in (A). Scientists can reconstruct these trees using the idea that chunks with fewer differences are more closely related than chunks with more differences.
Scientists have worked out ways to reconstruct DNA family trees by looking at the small differences in the DNA between people living today [1, 2]. Typically, the further back in time two people share an ancestor, the more genetic differences there will be between those two people.
In this article, we will tell you three different stories contained in these DNA family trees. The first story is about how we can uncover the ancient past, including when our ancestors settled in different parts of the world. The second story looks at our recent history and what we can learn from the DNA of people living in the same country today. The third story is about how groups of people have moved and merged, and how we are all really a mixture of many ancestral populations.
UNCOVERING THE ANCIENT PAST USING DNA FAMILY TREES
Written records only go back a few thousand years. They cannot tell very ancient stories but, amazingly, our own DNA can. To understand how scientists read the stories from DNA, let us consider you and a friend. If you are both in a small room with a few other people, you will easily find your friend. If you are in a larger room full of hundreds of people, it might be much harder to find your friend. We can think about your ancestors using similar reasoning. At any given time in the past, if there were only a small number of humans alive or if your ancestors inhabited the same geographic region, then the chance that you share an ancestor with your friend at that time is high. On the other hand, if the number of humans living at that time was large or if your ancestors lived far away from each other, the chance of sharing an ancestor at that time will be small.
How often you and your friend shared an ancestor at different times in the DNA family trees can tell us whether your ancestors lived close to each other, how they moved about, and how many other humans occupied our world back then.
Today, almost 8 billion humans live on our planet, spread widely across all continents. Until relatively recently, humans were a much rarer species, and going back as far as 200,000 years ago, humans were mostly living on the African continent. DNA family trees indicate that a relatively small number of people migrated out of Africa and settled in other parts of the world. At that time, some distant relatives of ours, most famously NeanderthalsA distant relative of Homo sapiens, who lived across Eurasia long before Homo sapiens did. When Homo sapiens started to populate Eurasia (migrating out of Africa), they mixed with Neanderthals, so that most people with non-African ancestry carry a small amount of Neanderthal DNA. Neanderthals went extinct around 40,000 years ago., were already living in Europe and Asia. For a long time, we did not know how Neanderthal people were related to us. Only when scientists compared their DNA to ours, and used the idea of DNA family trees, did they discover that humans who migrated out of Africa mixed with Neanderthals [3].