Write evolutionary history of modern man
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Evolution of modern humans
The origin of modern humans has probably been the most debated issue in evolutionary biology over the last few decades.
Where did we come from?
“
The exact origin of modern humans has long been a topic of debate.
Our evolutionary history is written into our . The human genome looks the way it does because of all the genetic changes that have affected our ancestors. The exact origin of modern humans has long been a topic of debate.
KEY FACT
Modern humans originated in Africa within the past 200,000 years and evolved from their most likely recent common ancestor,Homo erectus.
Modern humans (Homo sapiens), the that we are, means ‘wise man’ in Latin. Our species is the only surviving species of the genusHomo but where we came from has been a topic of much debate. Modern humans originated in Africa within the past 200,000 years and evolved from their most likely recent common ancestor, Homo erectus, which means ‘upright man’ in Latin. Homo erectus is an extinct species of human that lived between 1.9 million and 135,000 years ago.
Historically, two key models have been put forward to explain the ofHomo sapiens. These are the ‘out of Africa’ model and the ‘multi-regional’ model. The ‘out of Africa’ model is currently the most widely accepted model. It proposes thatHomo sapiens evolved in Africa before migrating across the world.
On the other hand, the ‘multi-regional’ model proposes that the evolution of Homo sapiens took place in a number of places over a long period of time. The intermingling of the various populations eventually led to the single Homo sapiens species we see today.
“
Current genomic evidence supports a single ‘out-of Africa’ migration of modern humans.
This is still very much an area of active research, however, current genomic evidence supports a single ‘out-of Africa’ migration of modern humans rather than the ‘multi-regional’ model. Although, studies of the of the extinct hominids Neanderthals and Denisovans suggest that there was some mixing of genomes (1-3 per cent) with humans in Europe and Asia. This interbreeding between two previously separated populations is called ‘admixture’ and results in a mixing of between the populations.
‘Out of Africa’: what’s the evidence?
‘Mitochondrial Eve’
KEY FACT
There is more genetic diversity in Africa compared with the rest of the world put together.
Genetic studies tend to support the ‘out of Africa’ model. The highest levels of in humans are found in Africa. In fact there is more genetic diversity in Africa compared with the rest of the world put together. In addition, the origin of modern in the mitochondria (the ‘powerhouses’ of our cells) has been tracked back to just one African woman who lived between 50,000 and 500,000 years ago – 'Mitochondrial Eve'.
Our genomes are a combination of DNA from both our mother and father. However, mitochondrial DNA (mtDNA) comes solely from our mother. This is because the female egg contains large amounts of mitochondrial DNA, whereas the male sperm contains just a tiny amount. The sperm use their small amount of mitochondria to power their race to their egg before fertilisation. Once a sperm merges with an egg, all the sperm mitochondria are destroyed.
KEY FACT
Your mitochondrial DNA is almost exactly the same as your mother’s and her mother’s.
As a result, mitochondrial DNA is described as being matrilineal (only the mother’s side survives from generation to generation). So, your mitochondrial DNA is almost exactly the same as your mother’s and her mother’s. Mitochondrial DNA has been extensively used by evolutionary biologists, as it is easier to extract than DNA found in the and there are many copies to work with.
However, Mitochondrial Eve wasn’t the first or only woman on Earth at that time. She was simply the point from which all modern generations of human appear to have grown. Evolutionary biologists think the most likely reason for this is that an evolutionary ‘bottleneck’ occurred during the time Eve was alive. This is when the majority of a species suddenly dies out, perhaps due to a sudden catastrophe, bringing it to the brink of extinction. If Mitochondrial Eve was one of the few women to survive then this could explain why her ‘matrilineal’ mitochondrial DNA ended up being passed along so many generations.
Similarly, DNA from the Y is only passed on from fathers to sons and a evolutionary tree relating all present day male individuals also supports the ‘out of Africa’ model.
“
The origin of modern humans has probably been the most debated issue in evolutionary biology over the last few decades.
Where did we come from?
“
The exact origin of modern humans has long been a topic of debate.
Our evolutionary history is written into our . The human genome looks the way it does because of all the genetic changes that have affected our ancestors. The exact origin of modern humans has long been a topic of debate.
KEY FACT
Modern humans originated in Africa within the past 200,000 years and evolved from their most likely recent common ancestor,Homo erectus.
Modern humans (Homo sapiens), the that we are, means ‘wise man’ in Latin. Our species is the only surviving species of the genusHomo but where we came from has been a topic of much debate. Modern humans originated in Africa within the past 200,000 years and evolved from their most likely recent common ancestor, Homo erectus, which means ‘upright man’ in Latin. Homo erectus is an extinct species of human that lived between 1.9 million and 135,000 years ago.
Historically, two key models have been put forward to explain the ofHomo sapiens. These are the ‘out of Africa’ model and the ‘multi-regional’ model. The ‘out of Africa’ model is currently the most widely accepted model. It proposes thatHomo sapiens evolved in Africa before migrating across the world.
On the other hand, the ‘multi-regional’ model proposes that the evolution of Homo sapiens took place in a number of places over a long period of time. The intermingling of the various populations eventually led to the single Homo sapiens species we see today.
“
Current genomic evidence supports a single ‘out-of Africa’ migration of modern humans.
This is still very much an area of active research, however, current genomic evidence supports a single ‘out-of Africa’ migration of modern humans rather than the ‘multi-regional’ model. Although, studies of the of the extinct hominids Neanderthals and Denisovans suggest that there was some mixing of genomes (1-3 per cent) with humans in Europe and Asia. This interbreeding between two previously separated populations is called ‘admixture’ and results in a mixing of between the populations.
‘Out of Africa’: what’s the evidence?
‘Mitochondrial Eve’
KEY FACT
There is more genetic diversity in Africa compared with the rest of the world put together.
Genetic studies tend to support the ‘out of Africa’ model. The highest levels of in humans are found in Africa. In fact there is more genetic diversity in Africa compared with the rest of the world put together. In addition, the origin of modern in the mitochondria (the ‘powerhouses’ of our cells) has been tracked back to just one African woman who lived between 50,000 and 500,000 years ago – 'Mitochondrial Eve'.
Our genomes are a combination of DNA from both our mother and father. However, mitochondrial DNA (mtDNA) comes solely from our mother. This is because the female egg contains large amounts of mitochondrial DNA, whereas the male sperm contains just a tiny amount. The sperm use their small amount of mitochondria to power their race to their egg before fertilisation. Once a sperm merges with an egg, all the sperm mitochondria are destroyed.
KEY FACT
Your mitochondrial DNA is almost exactly the same as your mother’s and her mother’s.
As a result, mitochondrial DNA is described as being matrilineal (only the mother’s side survives from generation to generation). So, your mitochondrial DNA is almost exactly the same as your mother’s and her mother’s. Mitochondrial DNA has been extensively used by evolutionary biologists, as it is easier to extract than DNA found in the and there are many copies to work with.
However, Mitochondrial Eve wasn’t the first or only woman on Earth at that time. She was simply the point from which all modern generations of human appear to have grown. Evolutionary biologists think the most likely reason for this is that an evolutionary ‘bottleneck’ occurred during the time Eve was alive. This is when the majority of a species suddenly dies out, perhaps due to a sudden catastrophe, bringing it to the brink of extinction. If Mitochondrial Eve was one of the few women to survive then this could explain why her ‘matrilineal’ mitochondrial DNA ended up being passed along so many generations.
Similarly, DNA from the Y is only passed on from fathers to sons and a evolutionary tree relating all present day male individuals also supports the ‘out of Africa’ model.
“
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Explanation:
The evolutionary history of modern man:
•Approximately 7 crore years ago, the dinosaurs disappeared completely.
•At that time, monkey-like animals appeared from more or less similar to the modern lemurs.
•Tail of these monkey-like animals disappeared about 4 crore years ago. Due to enlargement of brain and improvement in their hands, ape-like animals were evolved and then later they evolved into gibbon and orangutan.
•From gibbon and orangutan, gorilla and chimpanzee evolved about 2.5 crore years ago.
•About 2 crore years ago first human-like animals evolved who had erect posture and able to use their hands.
•Ramapithecus ape recorded as first human-like animal. Afterwards, this ape grown up in size and became more intelligent.
•About 20 lakh years ago skilled human developed and about 15 lakh years ago evolved human with erect posture and walking.
•Neanderthal man was considered as the first wise-man.
•About 50 thousand years ago the Cro-Magnon man evolved and afterwards, this evolution had been faster than the earlier.
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