Ed Hypothesis about Coat Color

[aggle-rithm]

Semantics, apparently.

What I'm saying is that there is no reason to believe that a particular feature has been selected for to begin with.

So: the current parsimonious approach is to assume that a feature without obvious benefit was probably obtained accidentally through selection of a beneficial neighbour.

True...that's why people who study dog evolution gave up on trying to figure out why dogs have multi-colored coats. They decided that the multi-colored trait was linked to the docility trait (specifically, the trait that made them less suspicious and more trusting of humans) and thus gave them access to the excess resources of humans -- primarily food that humans considered inedible but was nutritious to wolves/dogs.

 

[aggle-rithm]

Another reason I suspect that a 'one gene for both traits' model is unlikely is that docility really comes across as a complex property.

My feeling is that this suggests multiple genes for that property alone.

How about a gene that increases the amount of available seratonin? There seems to be a correlation between this and docility.

 

[aggle-rithm]

It's very rare. You may be thinking of multiple exons per gene, which are common. The gene can produce multiple amino acid chains, which combine into a protein.

Also common: multiple genes contribute to one protein. For example: the hemoglobin protein has three subunits spread across genes on two chromosomes. More complicated is that its heme cofactor is not produced in these genes, but is the product of perhaps a dozen more enzymes in a pathway. (I'm a little rusty on my biochem)

Point is: a typical protein has multiple genes, rather than a typical gene producing multiple proteins.

Clearly, the Intelligent Designer needs to lay off the sauce.

 

[blutoski]

How about a gene that increases the amount of available seratonin? There seems to be a correlation between this and docility.

Could be. Causal directionality is relevant to understanding the correlation. I don't think we're there yet.

 

[Roboramma]

It would be an incredibly unlikely combination of events.

* gene codes two proteins (rare but not impossible) or
* single protein controls two unrelated systems (rare but not impossible)
* both features are single-gene (really hard to believe)

I suppose I don't really understand what single-gene means. Certainly if a protein is multi-gene changes in any of those genes may affect that protein, and may affect it in ways that affect the resulting phenotype. And I don't see any reason that changes in a single protein won't have affects on many different parts of the body.

I suppose it's unlikely, though, than more than one of those affects would be beneficial.

 

[little grey rabbit]

I have a hypothesis I've been thinking about recently. I saw an episode of the TV series Life on primates the other day, and it showed a species of monkey whose infants are brightly colored to allow the mothers to easily find them. As they mature, the coats turn a more drab color to make them less visible to predators.

Suppose the infant coats were drab color and the adult coats were bright?

Then the infants coat color would be to make then less visible to predators and the adults coat color would be to attract mates.

A perfect example of the evolutionary just-so concept.

I won't cover what others have done, but simply say docility is a trait which has been breed and selected for over centuries (as are attractive coats). It is also a complex genetic trait. In sheep breeding there is something known as hybrid vigour whereby pure breed sheep of a particular strain are known to be docile, while breeding sheep of two different but docile breeds will result in offspring that are more difficult to handle.
You could assume that there are multiple pathways and multiple genes to create a docile phenotype - when you mix and match between breeds it will be lacking the complete set of genetic features necessary for each particular breeds "docility" and hence be comparatively more lively.

 

[aggle-rithm]

Suppose the infant coats were drab color and the adult coats were bright?

Then the infants coat color would be to make then less visible to predators and the adults coat color would be to attract mates.

Except that we know that there is a correlation between docility and coat color, and the adult progeniters were unlikely to be docile.

A perfect example of the evolutionary just-so concept.

I won't cover what others have done, but simply say docility is a trait which has been breed and selected for over centuries (as are attractive coats).

But we know from the fox [url = "http://mammals.suite101.com/article.cfm/domesticating_the_silver_fox"]experiment[/url]that it only takes a few generations of breeding for docility that you get the coat coloration.

 

[aggle-rithm]

Except that we know that there is a correlation between docility and coat color, and the adult progeniters were unlikely to be docile.



But we know from the fox [url = "http://mammals.suite101.com/article.cfm/domesticating_the_silver_fox"]experiment[/url]that it only takes a few generations of breeding for docility that you get the coat coloration.

I screwed the pooch on that URL.

http://mammals.suite101.com/article.cfm/domesticating_the_silver_fox

 

[blutoski]

I suppose I don't really understand what single-gene means.

In this sense, I meant that the measureable trait is controlled by just one gene.

Docility appears to be a gradient trait, which strongly suggests more than one gene is involved.

Certainly if a protein is multi-gene changes in any of those genes may affect that protein, and may affect it in ways that affect the resulting phenotype. And I don't see any reason that changes in a single protein won't have affects on many different parts of the body.

I suppose it's unlikely, though, than more than one of those affects would be beneficial.

Proteins tend to be involved in a very specific role. It is possible for an enzyme's downstream effects to impact multiple systems, but the mechanism is usually pretty clear (CF or porphyria are examples) and these are often well documented already.

 

[little grey rabbit]

Except that we know that there is a correlation between docility and coat color, and the adult progeniters were unlikely to be docile.



But we know from the fox [url = "http://mammals.suite101.com/article.cfm/domesticating_the_silver_fox"]experiment[/url]that it only takes a few generations of breeding for docility that you get the coat coloration.

docility would be both a genetic based trait and learned behaviour, as you can't breed a trait over a few generations. One assumes that the development of docility in breeds of sheep would be an unconscious thing rather than directly selected for and would have taken many generations to fully develop.

To be honest, I don't know what to make of your coat color and docility linkage claim. It seems unlikely as it pre-supposes that a) they are both single gene traits and b) linked closely together on the same chromosome.

I suggest you skeptically see if alternative hypothesizes might explain your observations

 

[aggle-rithm]

To be honest, I don't know what to make of your coat color and docility linkage claim. It seems unlikely as it pre-supposes that a) they are both single gene traits and b) linked closely together on the same chromosome.

I suggest you skeptically see if alternative hypothesizes might explain your observations

Actually, that claim isn't mine. It's been pretty well established by the observations of those far more qualified than I, such as the scientist that my botched link refers to.

My hypothesis builds on the assumption that this is correct...if not, then the whole thing falls apart.

 

[blutoski]

Clearly, the Intelligent Designer needs to lay off the sauce.

Also, I'm glad I qualified my position to say that multiple-system effects of one gene are rare, rather than the indefensible position that they're "impossible".

To give credit where credit is due: [Top killers share genes]

 

[little grey rabbit]

Actually, that claim isn't mine. It's been pretty well established by the observations of those far more qualified than I, such as the scientist that my botched link refers to.

My hypothesis builds on the assumption that this is correct...if not, then the whole thing falls apart.

I have just read your link, it refers to experiments done in the Soviet Union in the 1950s. Genetics in the Soviet Union at that time was something of a joke as it struggled under the baleful influence of state sponsored Lysenkoism.

Scientists that supported Mendelian genetics could end up in the Gulag. I suggest caution in using that as a source.

 

[aggle-rithm]

I have just read your link, it refers to experiments done in the Soviet Union in the 1950s. Genetics in the Soviet Union at that time was something of a joke as it struggled under the baleful influence of state sponsored Lysenkoism.

Scientists that supported Mendelian genetics could end up in the Gulag. I suggest caution in using that as a source.

But the particular scientist who conducted this research was something of a rogue. At any rate, regardless of what his beliefs were in the mechanisms of evolution, the results of his experiment were real...unless you think he fabricated his results to support the party line.

From the link:

Although genetics was not an accepted science in the Soviet Union in the 1950s, Belyaev’s experiment showed that genetic selection for tameness could also select for other genes as well. It also showed that domestication could be a rather quick process, and that Stone Age people could have potentially created genetically tame wolves within a the truncated lifespan of a person of that time. These findings greatly shape how we understand the domestication process.

Read more at Suite101: Domesticating the Silver Fox: Breeding for Tameness Changes Animals Behaviorally and Physically http://mammals.suite101.com/article.cfm/domesticating_the_silver_fox#ixzz0m2PTaFx5

 

[aggle-rithm]

Here is a descendant of one of the silver foxes from the experiment:

The markings are very similar to that of a border collie.

These foxes were selected for temperement only, not for coat color.

A lot of research has been built on these experiments...I haven't seen anything so far that questions their validity.