It is now commonly accepted that human life originated in East Africa.

Question

It is now commonly accepted that human life originated in East Africa. There is less agreement as to whether the humans that left Africa in a final exodus as recently as 100,000 years ago replaced all other hominids (thus becoming ancestors to everyone now alive) or humans evolved independently in geographically separated regions. Recently, the replacement scenario, as it is sometimes called, has been lent support from genetic research.

Genetic investigations into the origins of human life most often focus on mitochondrial DNA. As opposed to nuclear DNA, mitochondrial DNA is transmitted only from the mother. This allows for the tracing of mutations that arise independently of changes that occur because of the combining of the mother’s and father’s DNA. As useful as this is, the high mutation rate of mitochondrial DNA allows scientists a look at only relatively recent prehistory. Nuclear DNA, on the other hand, has a low mutation rate, making it ideal for looking into the more distant past. Studying the nuclear DNA of fossils now shows a substantial decrease in population size in Europe and Asia approximately 50—80 thousand years ago. No such decrease happened in Africa. This supports the idea that migrants from Africa replaced all previous humans, and did not interbreed with earlier migrants.

Other research shows less genetic diversity the farther human populations are located from Africa. This difference in diversity, which continues to the present day, also supports the hypothesis that modern human life came from Africa and gradually spread throughout the world. It is worth noting that there is no discontinuity in the decrease of diversity as one travels from Africa; this points to less distinct ethnic and racial divisions than is popularly thought to be the case.   1 
 1. Which of the following is the primary purpose of the passage?

(A) To present statistical evidence that points to a new hypothesis
(B) To illustrate the ways in which new forms of scientific research can bring about surprising results
(C) To offer evidence that supports one of two competing theories
(D) To cast doubt on the reliability of premises that underlie a conclusion
(E) To describe a model that can be applied to a variety of scientific undertakings

2 
 2. According to the passage, which of the following is NOT characteristic of mitochondrial DNA?

(A) Transmission comes from the mother only.
(B) It can be used to trace the origins of human life.
(C) It is used more frequently than nuclear DNA to study the origin of human life.
(D) It can be used to investigate distant prehistory.
(E) It has a relatively high mutation rate.

3 
 3. Which of the following most strongly argues against the replacement scenario?

(A) Mitochondrial DNA from a human skeleton found in East Africa matches the DNA found in a known route taken by migrants from Africa to Europe.
(B) Remains have been found of humans in Southeast Asia that developed independently of humans in Central America.
(C) The DNA from human specimens taken in China and Spain are nearly identical.
(D) No evidence can be found to support the idea that the first Africans to leave Africa bred with the second group to make the trip.
(E) DNA from a Neanderthal—an early hominid—shows some similarity with modern human DNA.

4 
 4. According to the passage, which of the following can be inferred about genetic diversity among humans?

(A) It is easier to detect through the examination of nuclear DNA than through the study of mitochondrial DNA.
(B) It is affected only by an individual’s mother’s DNA.
(C) It has gradually diminished since about 100,000 years ago.
(D) It is not as ambiguous as most people think.
(E) The amount of diversity within an existing population can be predicted by its geographic location.

Kurtosis · Accepted Answer

First paragraph discusses origin of human life from Africa. Proposes 2 models and accepts replacement model.
Second paragraph supports replacement model by suggesting nuclear DNA is better than mitochondrial DNA to trace the evolution.
Third paragraph supports replacement model by taking diversity into consideration.

Which of the following is the primary purpose of the passage?

(A) To present statistical evidence that points to a new hypothesis - Incorrect. Statistical evidence is not presented.
(B) To illustrate the ways in which new forms of scientific research can bring about surprising results - Incorrect. Out of scope.
(C) To offer evidence that supports one of two competing theories - Correct.
(D) To cast doubt on the reliability of premises that underlie a conclusion - Incorrect. The premise is not doubted anywhere in the passage.
(E) To describe a model that can be applied to a variety of scientific undertakings - Incorrect. Out of scope.

Answer: C

According to the passage, which of the following is NOT characteristic of mitochondrial DNA?

(A) Transmission comes from the mother only. - Incorrect. True.
(B) It can be used to trace the origins of human life. - Incorrect. Yes it can be used but its not a very efficient one.
(C) It is used more frequently than nuclear DNA to study the origin of human life. - Incorrect. True.
(D) It can be used to investigate distant prehistory. - Correct. It cannot be used.
(E) It has a relatively high mutation rate. - Incorrect. True.

Answer: D

Which of the following most strongly argues against the replacement scenario?

(A) Mitochondrial DNA from a human skeleton found in East Africa matches the DNA found in a known route taken by migrants from Africa to Europe. - Incorrect. DNA analysis to diversity cannot be inferred to argue against the replacement scenario.
(B) Remains have been found of humans in Southeast Asia that developed independently of humans in Central America. - Correct. Weakens the replacement scenario.
(C) The DNA from human specimens taken in China and Spain are nearly identical. - Incorrect. Does not answer the evolution from Africa. If anything, this option strengthens the replacement scenario as they have similar diversity.
(D) No evidence can be found to support the idea that the first Africans to leave Africa bred with the second group to make the trip. - Incorrect. Out of context.
(E) DNA from a Neanderthal—an early hominid—shows some similarity with modern human DNA. - Incorrect. Out of context.

Answer: B

According to the passage, which of the following can be inferred about genetic diversity among humans?

(A) It is easier to detect through the examination of nuclear DNA than through the study of mitochondrial DNA. - Incorrect. Out of scope. No correlation is presented between DNA and diversity in the passage.
(B) It is affected only by an individual’s mother’s DNA. - Incorrect. Out of scope.
(C) It has gradually diminished since about 100,000 years ago. - Incorrect. Out of scope.
(D) It is not as ambiguous as most people think. - Incorrect. It may be ambiguous. Out of scope.
(E) The amount of diversity within an existing population can be predicted by its geographic location. - Correct. Since diversity supports replacement scenario, this option has to be true.

Answer: E

varun325 · Answer

The main points of the passage para wise are as follows:

1st Para:
a)Two theories for the origin of the humans is given.

2nd Para:
a)Two Techniques for studing the origins of human are discussed.
b)The result the study, Humans in Africa replaced all other human and didn't inter breed with humans of other parts of the world.

3rd Para:
a) The results of another study which states that humans are originated from Africa are discussed.

In all the author s convinced that the replacement theory is true and all humans has originated from Africa , East Africa to be precise.

06:38

1. Which of the following is the primary purpose of the passage?

(A) To present statistical evidence that points to a new hypothesis. 
First of all No statistical data is given anywhere in the passage.Moreover a new hypothesis is not proposed rather one of the two hypothesis is accepted as true. 
(B) To illustrate the ways in which new forms of scientific research can bring about surprising results. OUT OF CONTEXT
(C) To offer evidence that supports one of two competing theories( Absolutely correct)
(D) To cast doubt on the reliability of premises that underlie a conclusion. 
The studies are discussed and results are accepted .
(E) To describe a model that can be applied to a variety of scientific undertakings.
Two techniques are discussed for studing the origing of human. This also occupies a small portion of the passage and is mentioned as premise in the second para to support the conclusion that Replacement theory is True.

00:28

2. According to the passage, which of the following is NOT characteristic of mitochondrial DNA?

Before looking at the answer choices , we ll try to remember all the characterstics of MITO DNA we have studied while reading the passage.This will warm up our mind and will save us from looking abck at the passage.moreover
The characterstics mentioned were:
1.Comes from mothers only
2. Independent o changes that comes from mutation of Mothers and Fathers DNA.
3. High mutation rate
4.Shows only recent history.

(A) Transmission comes from the mother only. True
(B) It can be used to trace the origins of human life. True
(C) It is used more frequently than nuclear DNA to study the origin of human life. Can't Say
(D) It can be used to investigate distant prehistory.( Opposite ) Correct 
 I remember from the passage that Nuclear DNA is used for distant prehistory.
(E) It has a relatively high mutation rate.True.

04:56

3. Which of the following most strongly argues against the replacement scenario?

(A) Mitochondrial DNA from a human skeleton found in East Africa matches the DNA found in a known route taken by migrants from Africa to Europe.
(B) Remains have been found of humans in Southeast Asia that developed independently of humans in Central America.(Correct)
"It is worth noting that there is no discontinuity in the decrease of diversity as one travels from Africa "
In the last passage author states that the DNA diffrence is constatnt and increases as someone travels from Africa. So it means that there has to be some similarity in the DNA/REMAINS/HUMANS ( whatever) as the origin place is same.

(C) The DNA from human specimens taken in China and Spain are nearly identical.Means some differences are present in line with the replacement theory.
(D) No evidence can be found to support the idea that the first Africans to leave Africa bred with the second group to make the trip. No idea what it has to do.
(E) DNA from a Neanderthal—an early hominid—shows some similarity with modern human DNA.

01:49
4. According to the passage, which of the following can be inferred about genetic diversity among humans?
"It is worth noting that there is no discontinuity in the decrease of diversity as one travels from Africa "
Author in the last passage has stated that the genetic diversity is less among humans. & It is worth noting that there is no discontinuity in the decrease of diversity as one travels from Africa

(A) It is easier to detect through the examination of nuclear DNA than through the study of mitochondrial DNA.
(B) It is affected only by an individual’s mother’s DNA.
(C) It has gradually diminished since about 100,000 years ago.
(D) It is not as ambiguous as most people think.
(E) The amount of diversity within an existing population can be predicted by its geographic location.(Correct)

poojakhanduja3017 · Answer

Got 3/4 Correct in the first go

Time to read : 3 Mins. 
 Question 1 : 1 min 22 sec. Answer is C. 
A) To present statistical evidence that points to a new hypothesis :  Humans originated from Africa is not a new hypothesis. It is well accepted. And statistical evidence is not given 
(B) To illustrate the ways in which new forms of scientific research can bring about surprising results.  The results are not surprising, they go with the accepted notion 
(C) To offer evidence that supports one of two competing theories Correct.  
(D) To cast doubt on the reliability of premises that underlie a conclusion   Instread of casting doubt, the para tries to promote the reliability of premises 
(E) To describe a model that can be applied to a variety of scientific undertakings.   There is no model described here

Question 2: 1 Min : Answer is D  : 
Para 2 Line 7 :  As useful as this is, the high mutation rate of mitochondrial DNA allows scientists a look at only relatively recent prehistory

Thus D is not the characteristic.

Question 3: Well, for me it was between B and E, and the correct answer is B

(A) Mitochondrial DNA from a human skeleton found in East Africa matches the DNA found in a known route taken by migrants from Africa to Europe.  This proves the replacement theory as people migrated from there.  
(B) Remains have been found of humans in Southeast Asia that developed independently of humans in Central America. Well, correct 
(C) The DNA from human specimens taken in China and Spain are nearly identical. They are identical means they could have come from the same source  
(D) No evidence can be found to support the idea that the first Africans to leave Africa bred with the second group to make the trip.  This supports the theory instead of negating it 
(E) DNA from a Neanderthal—an early hominid—shows some similarity with modern human DNA.   Well i am confused about this one, so i won't just answer for the sake of answering

Will edit once i am clear about this one.

Question 4: The correct answer is E

(A) It is easier to detect through the examination of nuclear DNA than through the study of mitochondrial DNA. Opposite is mentioned in Para 2 
(B) It is affected only by an individual’s mother’s DNA. :  Opposite is true 
(C) It has gradually diminished since about 100,000 years ago.  It has not  gradually  diminished If there is replacement theory 
(D) It is not as ambiguous as most people think. :  This option is also ambiguous 
(E) The amount of diversity within an existing population can be predicted by its geographic location.

mariatoledoo · Answer

Don't understand Q3, would somebody explain me please each option?? Thank U

bM22 · Answer

Hi  mariatoledoo ,

3. Which of the following most strongly argues against the replacement scenario?

This is more of strengthen/weaken question.
The replacement theory that the author talks about in the 1st para is: There is less agreement as to whether  the humans that left Africa in a final exodus as recently as 100,000 years ago replaced all other hominids (thus becoming ancestors to everyone now alive) or humans evolved independently in geographically separated regions. . Now we need to look for an option that goes against this theory.

Incorrect, as it clearly strengthens the argument above and shows strong support for the replacement theory.

Now this option mentions something that does not agree with the replacement theory. What this option says is that remains of humans have been found in Southeast Asia that developed independently of humans in Central America, now if all the humans that left Africa replaced all other hominids, this scenario is not possible and if option B were to be true, it would weaken the replacement theory, implying that option B is clearly correct.

Incorrect, because if the Africans replaced all other hominids, the DNA from human specimens taken in China and Spain would be identical.

Again, incorrect, as it provides support for the replacement theory.

Incorrect, reasoning similar to option C.

Hope This Helps.
Thanks.

VerbalBot · Answer

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It is now commonly accepted that human life originated in East Africa.

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It is now commonly accepted that human life originated in East Africa.

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