Another possible explanation could be that animals feeded on an artificial monotonous diet and set free from predation pressure, start showing genetic/colour defects quickly. Similar colour issues happen with captive birds and fishes unless we provide extra charotenes to complete its diet. In the wild the diet is much more diverse and finding charotenes is not a problem.
Or that when the mice population increases the animals just fight more. Domestic mouse males fight and bite other males. Mother with litters will attack males also. More animals in the same place = more scars by bites, and this could easily lead to an increase on white (regrown) hair patches. A simple explanation that does not depend on human contact. Is normal in birds to create white feathers after a predation event to quickly replace missing ones and cover bald patches.
And another explanation could be that when the mice population increases, their individual size decreases because there are less food for each one (and different hormone interactions non necessarily human related). If we extract some of those mice and put it in a new cage subject to the same human manipulation but with a more diverse sources of food, would the average skull size quickly increase again? Would the animals with white patches decrease? I bet that yes.
Yes, these are all possible explanations, but the specific symptoms observed - development of spots and smaller cranial capacity - are well documented as common effects of human domestication across a broad range of mammalian species. That the same mechanism is driving the changes observed in these mice would be a simpler explanation than various disparate, piecemeal effects combining to produce them.
Domestication, like in the foxes study, needs a small genetic pool to work and a deliberate selection of the sexual reproduction by humans (killing the non-desired ones, mating only animals with desired traits). Nothing of that is happening here.
One of the problems with the article is that does not try to discard those explanations. A simple check to investigate if white spots are linked to sex or age would help. A check for scars in those patches would positively help us to understand what is happenning. It does not mean necessarily harming the mice, they could just rasurate some white patches and take a look.
We are concluding that animals sort of "deliberately increase" their "cuteness" to please humans but this conclusion is not justified. What if aggression is just being increased as response to animals being marked with strange human odour?. This kind of articles should discuss at least some of those alternative explanations.
The article claims that the animals were not exposed to selection based on their domesticity, but it includes this line "These animals are regularly provided with food and water, and investigated by the researchers."
It strikes me that that situation represents a selection pressure, because mice that are more afraid of humans, are likely to avoid a place where they are regularly present, and thus lose the advantage of the risk-free meal ticket these particular humans are providing.
Along same line. With wolves, the aggressive ones were likely shooed away or killed. Either way it’s selection or a learned then taught behavior pattern change.
"Russian scientists achieved a population of domesticated foxes that are fundamentally different in temperament and behavior from their wild forebears. Some important changes in physiology and morphology became visible, such as mottled or spotted colored fur. Some scientists[citation needed] believe that these changes obtaining from selection for tameness are caused by lower adrenaline production in the new population..."
For those interested in hearing more about phenotypic changes in domesticated mammals (many of which also apply to humans), I'd recommend "The 'Domestication Syndrome' in Mammals: A Unified Explanation Based on Neural Crest Cell Behavior and Genetics" (link: http://www.genetics.org/content/genetics/197/3/795.full.pdf).
A lot of this might be neoteny, which often occurs with domesticated animals. There are various mechanisms by which this might occur.
These younger looking animals will look less threatening, and might even have traits similar to human young (relatively larger eyes, etc.)
So it might be more that cuteness is related to neoteny which is related to domestication and other situations where animals might be seen as less threatening. Definitely doesn’t answer the whole question though.
> Often, juvenile behaviors are selected for in order to domesticate more easily a species; aggressiveness in certain species comes with adulthood when there is a need to compete for resources. If there is no need for competition, then there is no need for aggression. Selecting for juvenile behavioral characteristics can lead to neoteny in physical characteristics because, for example, with the reduced need for behaviors like aggression there is no need for developed traits that would help in that area.
One interesting aspect is the idea that more than just natural selection is at stake in the evolution of our gene pool. That some genetic features may be dropped or changed if not required anymore without the pressure of a higher death rate / lower reproduction. Another example is wisdom teeth, which aren't really useful anymore given that we cook meat. They are slowly disappearing but not as a result of natural selection. Darwinism doesn't seem to explain everything, there must be other mechanisms involved.
>That some genetic features may be dropped or changed if not required anymore without the pressure of a higher death rate / lower reproduction ... darwinism doesn't seem to explain everything
If the results of a newly-introduced selection pressure can be explained by darwinism / natural selection, then surely so can the results of a removal of selection pressure.
For example, if there are genes that result in lowered fear or agression, and that leads to fewer offspring for wild mice, they will have a lower frequency in a wild mouse population than in a population where they don't lead to fewer offspring. I'm no expert, but it doesn't seem like this particular article requires any additional mechanisms beyond natural selection.
Wow this is fascinating. I didn't realize changes in the adrenal glands could so rapidly and dramatically alter a species. What evolutionary pressure to domestic themselves would these animals have if they werent coming into contact with people regularly?
Or that when the mice population increases the animals just fight more. Domestic mouse males fight and bite other males. Mother with litters will attack males also. More animals in the same place = more scars by bites, and this could easily lead to an increase on white (regrown) hair patches. A simple explanation that does not depend on human contact. Is normal in birds to create white feathers after a predation event to quickly replace missing ones and cover bald patches.
And another explanation could be that when the mice population increases, their individual size decreases because there are less food for each one (and different hormone interactions non necessarily human related). If we extract some of those mice and put it in a new cage subject to the same human manipulation but with a more diverse sources of food, would the average skull size quickly increase again? Would the animals with white patches decrease? I bet that yes.