Case studies of Physics graduates' personal theories of evolution

Asia-Pacific Forum on Science Learning and Teaching, Volume 6, Issue 1, Article 6 (Jun., 2005)
Ke-Sheng CHAN
Case studies of Physics graduates' personal theories of evolution

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Results of the interviews

Transcript of interview A

Interviewer: Have you ever seen real giraffes before?

Student A: Sure!

Interviewer: Have you noticed that most giraffes have very long necks?

Student A: Sure!

Interviewer: Have you thought about it? I mean why do you think they have such...(interrupted by A)

Student A: Well...uh, I have looked at the...the...science magazine said things like that.

Interviewer: Excuse me. Please make sure to tell me only what you really believe out of what you have read in these magazines.

Student A: Well, it is very possible that, you see giraffes...uh...lived in parts of Africa where you have little grass on the grounds and trees and something like that. Might be because of evolutionary pressures that...uh...long necks let the animals feed off the trees.

Interviewer: You talked about evolutionary pressure, can you explain more clearly about what you mean by that? I’m not quite sure about that.

Student A: OK, what I am trying to say is the following. Uh, modern time giraffes are found in parts of Africa where, uh, it’s essentially a dry area, where there is little grass on the grounds but a good number of trees which have most of the foliage on the top parts. (the interviewer nodded and said: OK!) So, uh, it is conceivable that maybe...uh...maybe...uh...you know giraffes may have started out with shorter necks, but because they have to adapt to living in the place with little grass and tall trees, they need long necks so that they can get to the leaves.

Interviewer: You said something about giraffes adapt to the living environment, can you tell me in more detail how that happens?

Student A: That’s what I have been saying. It’s a question of evolution. It is very possible that giraffes may have started out with shorter necks, but since the climate change and the land is dried, they found the need to live on the leaves of the trees. They started slowly developing longer necks.

Interviewer: Can you say more about how they develop the longer necks you’ve talked about?

Student A: Well, because they need longer necks to reach their food, they...uh...somehow managed to use their necks to reach the trees. Gradually their necks became longer and longer over each generation.

(talking about Chinese food and Indian food while eating our lunch)

Interviewer: Have you heard about cheetahs before? Or have you seen them on TV? It’s a big African cat.

Student A: Uh, I guess so but I am not sure. How do you spell it?

Interviewer: C-h-e-e-t-a-h.

Student A: Right! I think it’s the fastest animal in the world, right?

Interviewer: That’s right. I’ve seen them on a TV program called Nature. According to Nature, they can run as fast as 60 miles per hour when chasing prey.

Student A: Yeah, I have read about that somewhere.

Interviewer: My question is: is it possible its ancestor...their ancestors can not run as fast, say they can only run 30 miles per hour?

Student A: Uh...well, that’s a...that’s an interesting question. (smiling)

Interviewer: Is it possible?

Student A: Well, it depends...I mean...well, maybe!

Interviewer: OK, if we assume it is possible, how do you think this could happen? I mean, do you have any idea about how today’s cheetahs could develop the ability to run as fast as 60 miles per hour?

Student A: Uh...that’s a good question. Uh-ha (smiling)...uh...uh...well, I guess to...to...to...uh...chase the prey I guess. Uh...uh...I guess to chase the prey.

Interviewer: OK, you told me they need to run fast to survive, can you tell me how could they do that? How do they develop such ability?

Student A: Well, how do they get such ability? Well, again if you if you...uh...there is something in the theory of evolution it says that something about acquired characteristics and something like that. That is...uh...that is...uh...if an organism finds that it has to do something...then...uh... then...uh...because of certain environmental pressure and stuff like that, it develops characteristics which is slowly over a period of time which is almost negligible. I mean, it’s...went back to our business of giraffes...uh...uh...it’s like they had to adapt to the situation where less grass was on the ground and more trees and...uh...they slowly developed the characteristics in order to survive.

Interviewer: So they run faster and faster each generation?

Student A: Right, something like that maybe.

Interviewer: Are you saying that because of the environmental pressure, they will acquire the characteristics they need to survive?

Student A: Right! I mean it's again I mean it's...the...the...basic example to explain that would be the fact that...uh...something I've seen in a movie...uh...I'm not sure about the time...uh...something like 20 years ago. The world health organization claimed that they had eliminated malaria from all parts of the world. (the interviewer nodded and showed much interest) Because they came up with all sorts of chemicals which...uh...would kill out the mosquitoes, the larva and things like that. But, then...uh...in the middle eighties, there have been outbreaks of small epidemic of malaria in parts of Asia and Africa. Biologists and medical people who have gone to study the bacteria for the malaria, they found that these are essentially new strands of bacteria, which are completely resistant to the chemicals which used to kill them out before.

Interviewer: Very interesting! How do you think this could happen?

Student A: Well, they claimed that, people who worked in the team, they claimed that it's again because of this...uh...because of the essential underlying philosophy of the theory of evolution. That an organism finds it has to...there is something which is affecting its uh...its normal mode of living, it will do something to get around it. And that's essentially what the bacteria have done, they develop some characteristics which enable them to completely defy these chemicals which used to kill them out before. Since the bacteria is like a single-cell creature, it takes a short period of time to change. But for infinitely more complicated organisms, like giraffes and cheetahs, this process of change will take a long period of time. So that in a finite lifetime of ours, one could not tell the difference it has made. It might take thousands of years for this to happen.

(Chatting and eating)

Interviewer: The next question is unusual but interesting. (showing student A a picture of cave salamanders along with a brief description in a dictionary) Cave salamanders today are blind. They have eyes but their eyes are not functional. According to biologists, their ancestors used to be able to see. Can you explain how blind salamanders today evolved from their ancestors?

Student A: Well, again you see...uh...sometime in the past ancestors of salamanders...uh... there is something in the evolution biology that...uh...if organism because of change of situation finds itself in a situation in which it really doesn't need a part of its body, then...uh...I mean the physical thing might be there it may just not use it anymore.

Interviewer: OK, you just said they don't need the eyes, but how do they become blind?

Student A: Again, as I said, there is something in evolution biology that tries to explain this and said that over a period of time, an organism finds that it really doesn't need an organ of its body and...uh...physically that organ might be there but the organism might just not use it. Like in this case, we have the eyes but the eyes are useless and become blind.

Interviewer: It's really nice talking to you. Thanks a lot for your time.

Transcript of interview B

Interviewer: Have you ever seen giraffes before?

Student B: Yes, I have.

Interviewer: Have you noticed that most giraffes have very long necks?

Student B: Right.

Interviewer: Have you thought about how giraffes developed such long necks?

Student B: Uh...perhaps it's because...(pause)...giraffes may started out being not as tall, they had mild temperament and not equipped to fight with other animals for food, they didn't have horns, sharp teeth or something like that. Maybe because of this, most of the grass on the ground was occupied by other animals, in order to survive, they managed to stretch their necks to reach the leaves on the trees. My argument is based on the theory of evolution. I think maybe it is for this reason that giraffes' necks became longer and longer.

Interviewer: You have just told me why giraffes have long necks and also touched on how they did that. But you said very little about "how", can you explain more clearly about how giraffes got their long necks?

Student B: Uh...(a short pause)...perhaps giraffes didn't have such long necks in the beginning, they may have somehow stretched their bodies to reach the trees because they needed to. Notice that giraffes not only have long necks but they also have long legs. (the interviewer nodded) They tried hard to stretch their bodies towards higher trees, as a result, their necks became longer and longer over each generation.

Interviewer: OK. Have you ever heard about cheetahs or seen them on TV?

Student B: No.

Interviewer: OK. Let me show you what they look like (showing student B a picture of cheetahs along with a brief description in a dictionary). They said cheetahs are the fastest animals in the world. They can run as fast as 60 miles per hour when chasing prey. My question is: is it possible their ancestors long ago can only run 30 miles per hour?

Student B: Yes, it's possible.

Interviewer: If this is true, do you have any ideas about how today's cheetahs could develop the ability to run so fast?

Student B: Because...this is similar to the giraffe's case. In fact, the human beings are similar, too. For instance, the Olympic records in sports keep improving. Since everyone wants to break the world records, people receive intensive training and force themselves to overcome the obstacles. Of course, it will become more and more difficult to break the records because there is a limit to it. In cheetahs’ case, there is a pressure forcing them to run fast in order to survive. They did their best to run fast in order to catch the prey, and slowly they developed the ability to run faster and faster over each generation.

Interviewer: The next question is about an interesting creature called cave salamanders. (showing student B a picture of cave salamanders along with a brief description in a dictionary) Cave salamanders today are blind, though they have eyes they can not see. However, biologists said their ancestors used to be able to see with their eyes. How would you explain how today's blind cave salamanders evolved from their ancestors?

Student B: Uh...it's again a question of the theory of evolution. All these cases are similar. We know human beings evolved from the ape, however, the tails of the apes disappeared in the process. Since human beings left forests, we no longer needed the tails. Similarly, cave salamanders always lived in the caves, they didn't need their eyes anymore. Uh...this is also evolution, only in an opposite direction. Because they didn't need the eyes, the eyes disappeared.

Interviewer: But their eyes are still there, right?

Student B: Right. Since they didn't need to see, they almost never used their eyes. After a long time, their eyes gradually lose their function. But their eyes are still there, it's just that they can not see things. Perhaps, after a few thousand years, even their eyes will disappear. (giggling)

Interviewer: Interesting! Have you ever used aerosol insecticides to kill mosquitoes before?

Student B: Yes.

Interviewer: Did you notice that at first they were very effective in killing mosquitoes, but they became less and less effective after you used the same insecticides for a long time?

Student B: Yes, I did.

Interviewer: Can you explain why and how this could happen?

Student B: This is the effect of immunity. When sprayed by the insecticides, a small number of mosquitoes received very little of them and may survive. They were also influenced by the insecticides, but the effect was not strong enough to kill them. Somehow these surviving mosquitoes then became immune to the insecticides. Once they had the immunity, their offspring soon inherited the ability and became resistant to the insecticides.

Interviewer: Do you mean the immunity to insecticides can be passed on to the next generation?

Student B: Right. Because something in their cells have been changed and the change can be inherited by their offspring.

Interviewer: But how did this change happen in the first place?

Student B: Uh...(pause for a moment)...uh...I don’t know...to explain this requires detailed knowledge about the structures of the specific creature and things like that. This is beyond my current understandings of biology.

Interviewer: That’s fine. Let me ask you a final question. You have mentioned the theory of evolution several times today, can you tell me what is the theory of evolution in your understanding?

Student B: Uh...all creatures want to survive, in order to survive they need to adjust themselves to adapt to their living environments. If the outside environments change, they must change accordingly, otherwise they will become extinct. Of course, not all creatures can successfully develop the change they need to survive. For instance, dinosaurs didn't develop the necessary change when environments changed and became extinct.

Copyright (C) 2005 HKIEd APFSLT. Volume 6, Issue 1, Article 6 (Jun., 2005). All Rights Reserved.

Interviewer:	Have you ever seen real giraffes before?
Student A:	Sure!
Interviewer:	Have you noticed that most giraffes have very long necks?
Student A:	Sure!
Interviewer:	Have you thought about it? I mean why do you think they have such...(interrupted by A)
Student A:	Well...uh, I have looked at the...the...science magazine said things like that.
Interviewer:	Excuse me. Please make sure to tell me only what you really believe out of what you have read in these magazines.
Student A:	Well, it is very possible that, you see giraffes...uh...lived in parts of Africa where you have little grass on the grounds and trees and something like that. Might be because of evolutionary pressures that...uh...long necks let the animals feed off the trees.
Interviewer:	You talked about evolutionary pressure, can you explain more clearly about what you mean by that? I’m not quite sure about that.
Student A:	OK, what I am trying to say is the following. Uh, modern time giraffes are found in parts of Africa where, uh, it’s essentially a dry area, where there is little grass on the grounds but a good number of trees which have most of the foliage on the top parts. (the interviewer nodded and said: OK!) So, uh, it is conceivable that maybe...uh...maybe...uh...you know giraffes may have started out with shorter necks, but because they have to adapt to living in the place with little grass and tall trees, they need long necks so that they can get to the leaves.
Interviewer:	You said something about giraffes adapt to the living environment, can you tell me in more detail how that happens?
Student A:	That’s what I have been saying. It’s a question of evolution. It is very possible that giraffes may have started out with shorter necks, but since the climate change and the land is dried, they found the need to live on the leaves of the trees. They started slowly developing longer necks.
Interviewer:	Can you say more about how they develop the longer necks you’ve talked about?
Student A:	Well, because they need longer necks to reach their food, they...uh...somehow managed to use their necks to reach the trees. Gradually their necks became longer and longer over each generation.
(talking about Chinese food and Indian food while eating our lunch)
Interviewer:	Have you heard about cheetahs before? Or have you seen them on TV? It’s a big African cat.
Student A:	Uh, I guess so but I am not sure. How do you spell it?
Interviewer:	C-h-e-e-t-a-h.
Student A:	Right! I think it’s the fastest animal in the world, right?
Interviewer:	That’s right. I’ve seen them on a TV program called Nature. According to Nature, they can run as fast as 60 miles per hour when chasing prey.
Student A:	Yeah, I have read about that somewhere.
Interviewer:	My question is: is it possible its ancestor...their ancestors can not run as fast, say they can only run 30 miles per hour?
Student A:	Uh...well, that’s a...that’s an interesting question. (smiling)
Interviewer:	Is it possible?
Student A:	Well, it depends...I mean...well, maybe!
Interviewer:	OK, if we assume it is possible, how do you think this could happen? I mean, do you have any idea about how today’s cheetahs could develop the ability to run as fast as 60 miles per hour?
Student A:	Uh...that’s a good question. Uh-ha (smiling)...uh...uh...well, I guess to...to...to...uh...chase the prey I guess. Uh...uh...I guess to chase the prey.
Interviewer:	OK, you told me they need to run fast to survive, can you tell me how could they do that? How do they develop such ability?
Student A:	Well, how do they get such ability? Well, again if you if you...uh...there is something in the theory of evolution it says that something about acquired characteristics and something like that. That is...uh...that is...uh...if an organism finds that it has to do something...then...uh... then...uh...because of certain environmental pressure and stuff like that, it develops characteristics which is slowly over a period of time which is almost negligible. I mean, it’s...went back to our business of giraffes...uh...uh...it’s like they had to adapt to the situation where less grass was on the ground and more trees and...uh...they slowly developed the characteristics in order to survive.
Interviewer:	So they run faster and faster each generation?
Student A:	Right, something like that maybe.
Interviewer:	Are you saying that because of the environmental pressure, they will acquire the characteristics they need to survive?
Student A:	Right! I mean it's again I mean it's...the...the...basic example to explain that would be the fact that...uh...something I've seen in a movie...uh...I'm not sure about the time...uh...something like 20 years ago. The world health organization claimed that they had eliminated malaria from all parts of the world. (the interviewer nodded and showed much interest) Because they came up with all sorts of chemicals which...uh...would kill out the mosquitoes, the larva and things like that. But, then...uh...in the middle eighties, there have been outbreaks of small epidemic of malaria in parts of Asia and Africa. Biologists and medical people who have gone to study the bacteria for the malaria, they found that these are essentially new strands of bacteria, which are completely resistant to the chemicals which used to kill them out before.
Interviewer:	Very interesting! How do you think this could happen?
Student A:	Well, they claimed that, people who worked in the team, they claimed that it's again because of this...uh...because of the essential underlying philosophy of the theory of evolution. That an organism finds it has to...there is something which is affecting its uh...its normal mode of living, it will do something to get around it. And that's essentially what the bacteria have done, they develop some characteristics which enable them to completely defy these chemicals which used to kill them out before. Since the bacteria is like a single-cell creature, it takes a short period of time to change. But for infinitely more complicated organisms, like giraffes and cheetahs, this process of change will take a long period of time. So that in a finite lifetime of ours, one could not tell the difference it has made. It might take thousands of years for this to happen.
(Chatting and eating)
Interviewer:	The next question is unusual but interesting. (showing student A a picture of cave salamanders along with a brief description in a dictionary) Cave salamanders today are blind. They have eyes but their eyes are not functional. According to biologists, their ancestors used to be able to see. Can you explain how blind salamanders today evolved from their ancestors?
Student A:	Well, again you see...uh...sometime in the past ancestors of salamanders...uh... there is something in the evolution biology that...uh...if organism because of change of situation finds itself in a situation in which it really doesn't need a part of its body, then...uh...I mean the physical thing might be there it may just not use it anymore.
Interviewer:	OK, you just said they don't need the eyes, but how do they become blind?
Student A:	Again, as I said, there is something in evolution biology that tries to explain this and said that over a period of time, an organism finds that it really doesn't need an organ of its body and...uh...physically that organ might be there but the organism might just not use it. Like in this case, we have the eyes but the eyes are useless and become blind.
Interviewer:	It's really nice talking to you. Thanks a lot for your time.

Interviewer:	Have you ever seen giraffes before?
Student B:	Yes, I have.
Interviewer:	Have you noticed that most giraffes have very long necks?
Student B:	Right.
Interviewer:	Have you thought about how giraffes developed such long necks?
Student B:	Uh...perhaps it's because...(pause)...giraffes may started out being not as tall, they had mild temperament and not equipped to fight with other animals for food, they didn't have horns, sharp teeth or something like that. Maybe because of this, most of the grass on the ground was occupied by other animals, in order to survive, they managed to stretch their necks to reach the leaves on the trees. My argument is based on the theory of evolution. I think maybe it is for this reason that giraffes' necks became longer and longer.
Interviewer:	You have just told me why giraffes have long necks and also touched on how they did that. But you said very little about "how", can you explain more clearly about how giraffes got their long necks?
Student B:	Uh...(a short pause)...perhaps giraffes didn't have such long necks in the beginning, they may have somehow stretched their bodies to reach the trees because they needed to. Notice that giraffes not only have long necks but they also have long legs. (the interviewer nodded) They tried hard to stretch their bodies towards higher trees, as a result, their necks became longer and longer over each generation.
Interviewer:	OK. Have you ever heard about cheetahs or seen them on TV?
Student B:	No.
Interviewer:	OK. Let me show you what they look like (showing student B a picture of cheetahs along with a brief description in a dictionary). They said cheetahs are the fastest animals in the world. They can run as fast as 60 miles per hour when chasing prey. My question is: is it possible their ancestors long ago can only run 30 miles per hour?
Student B:	Yes, it's possible.
Interviewer:	If this is true, do you have any ideas about how today's cheetahs could develop the ability to run so fast?
Student B:	Because...this is similar to the giraffe's case. In fact, the human beings are similar, too. For instance, the Olympic records in sports keep improving. Since everyone wants to break the world records, people receive intensive training and force themselves to overcome the obstacles. Of course, it will become more and more difficult to break the records because there is a limit to it. In cheetahs’ case, there is a pressure forcing them to run fast in order to survive. They did their best to run fast in order to catch the prey, and slowly they developed the ability to run faster and faster over each generation.
Interviewer:	The next question is about an interesting creature called cave salamanders. (showing student B a picture of cave salamanders along with a brief description in a dictionary) Cave salamanders today are blind, though they have eyes they can not see. However, biologists said their ancestors used to be able to see with their eyes. How would you explain how today's blind cave salamanders evolved from their ancestors?
Student B:	Uh...it's again a question of the theory of evolution. All these cases are similar. We know human beings evolved from the ape, however, the tails of the apes disappeared in the process. Since human beings left forests, we no longer needed the tails. Similarly, cave salamanders always lived in the caves, they didn't need their eyes anymore. Uh...this is also evolution, only in an opposite direction. Because they didn't need the eyes, the eyes disappeared.
Interviewer:	But their eyes are still there, right?
Student B:	Right. Since they didn't need to see, they almost never used their eyes. After a long time, their eyes gradually lose their function. But their eyes are still there, it's just that they can not see things. Perhaps, after a few thousand years, even their eyes will disappear. (giggling)
Interviewer:	Interesting! Have you ever used aerosol insecticides to kill mosquitoes before?
Student B:	Yes.
Interviewer:	Did you notice that at first they were very effective in killing mosquitoes, but they became less and less effective after you used the same insecticides for a long time?
Student B:	Yes, I did.
Interviewer:	Can you explain why and how this could happen?
Student B:	This is the effect of immunity. When sprayed by the insecticides, a small number of mosquitoes received very little of them and may survive. They were also influenced by the insecticides, but the effect was not strong enough to kill them. Somehow these surviving mosquitoes then became immune to the insecticides. Once they had the immunity, their offspring soon inherited the ability and became resistant to the insecticides.
Interviewer:	Do you mean the immunity to insecticides can be passed on to the next generation?
Student B:	Right. Because something in their cells have been changed and the change can be inherited by their offspring.
Interviewer:	But how did this change happen in the first place?
Student B:	Uh...(pause for a moment)...uh...I don’t know...to explain this requires detailed knowledge about the structures of the specific creature and things like that. This is beyond my current understandings of biology.
Interviewer:	That’s fine. Let me ask you a final question. You have mentioned the theory of evolution several times today, can you tell me what is the theory of evolution in your understanding?
Student B:	Uh...all creatures want to survive, in order to survive they need to adjust themselves to adapt to their living environments. If the outside environments change, they must change accordingly, otherwise they will become extinct. Of course, not all creatures can successfully develop the change they need to survive. For instance, dinosaurs didn't develop the necessary change when environments changed and became extinct.