#86- From Cells to Cities - Dogs

 
scotia
 
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scotia
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16 July 2017 07:31
 

Hi all,
I’ve yet to read GW’s book - can anyone expound on the following: why do small dogs live longer than large dogs?  (e.g. a Great Dane on average lives half as long as a Jack Russell Terrier while weighing almost an order of magnitude more).  This fact flies in the face of the “economies of scale” theory.
Perhaps one of the limits to the theory constrains it to naturally selected organisms.  However, Canis lupus lives on order of magnitude less than humans while weighing in at half.
Perhaps this aspect of the theory doesn’t bear scrutiny.
Scott

 
Twissel
 
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Twissel
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16 July 2017 07:47
 

Plenty of animals violate the economics of scale theory, like giant tortoises (long) or chameleons (short).
The theory is a rough guide, but exceptions exist.

 
 
scotia
 
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scotia
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22 July 2017 18:00
 

After listening to the end of the podcast I was glad to hear when Sam brought up the same questions.  Unfortunately after a good 3 minutes of stammering there was really nothing of substance said regarding the exceptions where he obviously missed the opportunity to describe non-domesticated dogs (i.e. wolves).  Anyone who claims (as GW did) that his “law” is accurate to about 80% should relish the exceptions and describe them in detail.
Anyway I’m halfway through “Triggered” and surprised that for someone who bangs on about “confirmation bias” so much Adams can’t see his own.

 
Probus
 
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Probus
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24 July 2017 15:04
 
scotia - 16 July 2017 07:31 AM

Hi all,
I’ve yet to read GW’s book - can anyone expound on the following: why do small dogs live longer than large dogs?  (e.g. a Great Dane on average lives half as long as a Jack Russell Terrier while weighing almost an order of magnitude more).  This fact flies in the face of the “economies of scale” theory.
Perhaps one of the limits to the theory constrains it to naturally selected organisms.  However, Canis lupus lives on order of magnitude less than humans while weighing in at half.
Perhaps this aspect of the theory doesn’t bear scrutiny.
Scott

I’m only halfway through, so these issues might be addressed later in the podcast. A related observation. What did not become clear to me is to what extent it matters if organisms belong to a similar species, kingdom or even domain. For example with regard to metabolism. Does the scaling work just as well between vastly different organisms like plants, fish, reptiles, birds and mammals… or does it matter what domain, kingdom, niche or even species we are talking about? In other words, if I were to look at an adequate sample size of plants, fish and mammals that all have an equal mass. Would the estimated metabolism be the same for all organism, regardless of whether we are talking about a tree, horse or a human?

They talked a lot about mammals, which perhaps suggests that it matters what type of organism we are talking about. Geoffrey West mentioned that the scaling works to estimate the metabolism (or was it life span) of a generic elephant. At the same time, the scaling seems to work just fine with regard to the length of an aorta and the trunk of a tree. So, I’m a bit confused. Perhaps it does not matter what kind of organism we are talking about when when estimating basic characteristics like metabolism or the the length of “tubing” (in lack of a better more scientific term). But it matters when estimating more complex characteristics, like life span.

With regard to your question. If the scaling works just as well between vastly different organisms then that would answer your question. You can’t look at just dogs with a certain mass, but you would have to look at all mammals or even all organisms with a certain mass. Then you could estimate with 80 percent accuracy the life span of a generic organism with that specific mass. If it on the other hand matters how closely related (in evolutionary terms) organisms are, then your observation seems to be a problem. Perhaps it could have something to do with natural selection versus artificial selection, but that would seem strange to me. In theory, there isn’t really a difference between artificial and natural selection. Yes, we can achieve results faster by sculpting the environment to guide the selection process in a given direction. That said, artificial selection is really just a controlled form of natural selection. It’s not like we are actually driving the process. We are merely guiding it, in a desired direction.

EDIT: Yes, there is an important difference between artificial and natural selection. My explanation was a bit sloppy. The difference is of course that we are active in the selection process, that mother nature otherwise selects for us. One can of course argue, that humans are merely an extension of nature itself and thus artificial selection is a form of natural selection. But, that is going too far in this context. My point is that it is still a form of natural biological evolution. The artificial part, is giving it a push in a desired direction.

[ Edited: 24 July 2017 18:08 by Probus]