Interesting article in Science

[AquaEyes]

Quote:
Not only that, but also flopped over ears, which have long been associated with domesticated animals. Really neat stuff.

Yes, that led to an interesting study of the biology of behavior -- how differences in neurotransmitter levels and changes in pigmentation can be different effects attached to the same cause -- basically, the genes make proteins that are involved in several chains of reactions that overlap, and changes in one gene (or its expression) can have multiple effects down the line. This is called pleiotropy.

Huh, I totally did not know there was a term for that, or rather, what the term was. I've got to take a more in-depth look at those studies, because, to be honest, I was mainly just browsing at the time for possible pet purposes.

Fascinating studies Aqua. I'm going to have to search for those, especially the rats being raised by docile or aggressive foster parents. I don't remember that one, and was citing a different study....wonder if it was the same PI, just expanding upon what they found?​

Yes, the ear-flopping was another trait common in domesticated animals (not all breeds, but most domesticated species of mammals contain at least one breed with a bent or floppy ear, which seemed to be an unusual trait to have in common).

Pleiotropy wasn't discovered in the farm-fox study. It was known from earlier genetic studies. It's just that the farm-fox experiment offered pleiotropy as an explanation for how all the "weird" traits that domesticated mammals share that don't seem to have a particular beneficial function with regards to becoming domesticated. In other words, the selection criteria for breeding wolves with the goal of a "dog" doesn't seem to require floppy ears, curled tails, piebald coats, etc. but these traits keep popping up -- and not just in domesticated dogs. They also occur in most other species of domesticated mammals. So this study found that selection for behavioral traits can have pleiotropic consequences in body phenotype that just "tag along." When these differences in appearance "tagged along", people were able to further select for appearance in the now domesticated animals, and explains how the vast array of different physical traits can arise from small genetic changes relating to selecting for behavior in a relatively short time (the experiment turned captive-bred but still wild foxes into puppy-like domesticated foxes within the span of one man's lifetime).

Another thing to note with this study is how new knowledge arose from research that was aimed in a slightly different direction -- the original goal was to breed tamer foxes for fur farms. This is another example of why scientific studies are good, even if the initial desire for information doesn't seem to have an immediate application. For one thing, something unintended could be discovered along the way. And even if that doesn't happen, it adds verifiable information to the library, from which another researcher may later pull information for something of a more applied use. That's the benefit of basic research -- we're expanding knowledge, which is good even if we don't immediately have a use for it. Too often people say that only applied research should be funded -- but most ideas for applied research come from studying previously-done basic research, so the two work together.

Don't quote me on the "rat" study, because I'm not sure if it was rats or mice. I don't have the paper in front of me, and I haven't read anything referring to it in a year. It's just what I remember off the top of my head. But if you want to look it up, the information is out there. Try PubMed.

 

[scratch'n'peck]

Don't let the thread die now!

Another thing to bring up regarding behavioral studies is the set of four questions posed for understanding behavior, by Nikolaas Tinbergen. Each question seeks to understand the behavior from a different perspective. They are broken down like this:

1) What causes the behavior? (i.e., the set-up of stimulus --> perception --> process information --> response...explaining pieces of the behavior-machine and how they work, so to speak)
2) How does it develop? (i.e., how does the organism acquire the behavior -- is it inborn, or is it learned? If learned, what are the steps involved in learning the behavior?)

These first two are called proximate questions, because basically they are asking questions about the behavior as it is exhibited in the organism in front of you.

3) How does it function to confer an evolutionary advantage? In other words, what about engaging in the behavior increases the reproductive fitness of individuals exhibiting the behavior over individuals NOT exhibiting the behavior?
4) How did the behavior evolve? In other words, how is the behavior represented among living related species, and how does the behavior differ among species either less-related or from another family tree?

The last two are called ultimate questions, because basically they are asking questions about how the behavior came to be in a species (or group of species) over the course of evolutionary history.


Using these four questions, what could we investigate further with regards to the study in the original post?

This is helpful, Aqua Eyes. Then I wonder where hormone levels and such would fit in. Would that be considered a moderating variable?

I found that fox study really interesting, too, so I went back to take a look because I recalled that they mentioned something about cortisone levels. Here is what the study said:

After 12 generations of selective breeding, the
basal levels of corticosteroids in the blood plasma
of our domesticated foxes had dropped to slightly more than half the level in a control group. After 28 to 30 generations of selection, the level had
halved again. The adrenal cortex in our foxes also
responds less sharply when the foxes are subjected to emotional stress. Selection has even affected
the neurochemistry of our foxes’ brains. Changes
have taken place in the serotonin system, thought
to be the leading mediator inhibiting animals’ aggressive behavior. Compared with a control
group, the brains of our domesticated foxes contain higher levels of serotonin; of its major
metabolite, 5-oxyindolacetic acid; and of tryptophan hydroxylase, the key enzyme of serotonin
synthesis. Serotonin, like other neurotransmitters,
is critically involved in shaping an animal’s development from its earliest stages.

Selection and Development
Evidently, then, selecting foxes for domestication may have triggered profound changes in
the mechanisms that regulate their development. In particular, most of the novel traits and
other changes in the foxes seem to result from
shifts in the rates of certain ontogenetic
processes—in other words, from changes in
timing. This fact is clear enough for some of
the novelties mentioned above, such as the earlier eye opening and response to noises and
the delayed onset of the fear response to unknown stimuli. But it also can explain some of
the less obvious ones. Floppy ears, for example, are characteristic of newborn fox pups but
may get carried over to adulthood.

I copied and pasted a part about development, too.

Here is the link to the whole study if you want to take a look: https://johnwade.ca/attachments/article/359/russianfoxfarmstudy.pdf​

 

[AquaEyes]

Look up "neoteny." You might also be interested in "evo-devo", the relatively new science of evolutionary development studied as a result in differences in gene expression.

 

[scratch'n'peck]

Thanks for the suggestions, Aqua Eyes. I did a search on them. Although I have come across these concepts in passing when reading about epigenetics, I haven't explored them much yet. Looks interesting.

 

[punk-a-doodle]

Neoteny is a really interesting subject to me, both phenotype and genotype wise. But...I can't say I enjoy the phenotype look taken too far for my comfort levels in some domestic breeds. 'Fetal-face' syndrome occurs. X)

 

[AquaEyes]

scratch'n'peck :

Thanks for the suggestions, Aqua Eyes. I did a search on them. Although I have come across these concepts in passing when reading about epigenetics, I haven't explored them much yet. Looks interesting.

Ah, epigenetics...that "other" way for traits to be inherited. For those that aren't familiar with the term, epigenetics refers to inherited differences that are not found within the DNA sequence but affect how the DNA operates. One way to look at it is how the strand of DNA lies within the nucleus. The images you've seen of neat, bundled chromosomes is not how the DNA usually appears, but rather it gets bundled up that way only during cell division. Think of a chromosome during the process of cell division as a ball of twine. The rest of the time, the string is pulled entirely off the spool, and just sort of bunched up in random parts. How the string is bunched up will affect the level of gene expression. If one piece of the string is bunched up too tightly for a protein to attach to initiate transcription, that piece won't be expressed -- unless another process opens it up. Then there are other things, like whether other molecules attach to particular sequences of the DNA, that can affect the level of gene expression.

Imagine it this way -- our genes are like bits of information in a book. A library is the nucleus of a cell -- the entire collection of all the books arranged in a particular order. The books that are accessible can be taken off the shelf and read more readily than those that are less accessible. How the library shelves are arranged varies from cell to cell, so that while every cell has the same books, not every book is in the same "easy-access" area of every library. That's how gene expression varies from cell to cell, allowing for cellular differentiation.

Well, in epigenetics, how those books are arranged is inherited as well as the books themselves. If Dad has a gene with a protein bound to it, the sperm that fertilized Mom's egg that eventually became you also had that protein bound to the gene. During cellular division, when copies of the chromosomes are made, some of those proteins and where they are bound will also get copied. So while Dad may have the same version of a gene that Mom had, that piece of protein bound to Dad's version reduces the frequency of the gene being expressed. This can account for some of the variation found for a trait even though the genotype is the same.

Oh, and then there's methylation -- the fun way that what you eat can affect the genes of your descendents.....​

 

[AquaEyes]

scratch'n'peck :

Don't let the thread die now!

Another thing to bring up regarding behavioral studies is the set of four questions posed for understanding behavior, by Nikolaas Tinbergen. Each question seeks to understand the behavior from a different perspective. They are broken down like this:

1) What causes the behavior? (i.e., the set-up of stimulus --> perception --> process information --> response...explaining pieces of the behavior-machine and how they work, so to speak)
2) How does it develop? (i.e., how does the organism acquire the behavior -- is it inborn, or is it learned? If learned, what are the steps involved in learning the behavior?)

These first two are called proximate questions, because basically they are asking questions about the behavior as it is exhibited in the organism in front of you.

3) How does it function to confer an evolutionary advantage? In other words, what about engaging in the behavior increases the reproductive fitness of individuals exhibiting the behavior over individuals NOT exhibiting the behavior?
4) How did the behavior evolve? In other words, how is the behavior represented among living related species, and how does the behavior differ among species either less-related or from another family tree?

The last two are called ultimate questions, because basically they are asking questions about how the behavior came to be in a species (or group of species) over the course of evolutionary history.


Using these four questions, what could we investigate further with regards to the study in the original post?

This is helpful, Aqua Eyes. Then I wonder where hormone levels and such would fit in. Would that be considered a moderating variable?​

Hormone levels affecting a behavior would be a proximate cause. Depending on what you're targeting, it could be either question #1 or #2. For example, if you want to know about how seasonal hormone fluctuations alter direction of behavior, that would be #1. If you wanted to know about how hormones initiate the development of the behavior, that would be #2.

The questions are merely a way of organizing approaches to studying behavior. They don't need to all be addressed in a study -- in fact, many researchers focus on just one question, and the same behavior can be approached from all four directions by different researchers. If someone was to do an ethogram of a species, use of these four questions will aid in understanding how the animal's behaviors work.

 

[scratch'n'peck]

I like your explanation of epigenetics; it helps visualize the process.