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Genetically Engineered Mouse is Not Scared of Cats
Gary writes "A team from the University of Tokyo has genetically engineered a mouse that does not fear cats. By tweaking genes to disable certain functions of the olfactory bulb (the area of the brain that receives information about smells directly from olfactory receptors in the nose) the researchers were able to create a 'fearless' mouse that does not try to flee when it smells cats, foxes and other predators. 'The research suggests that the mechanism by which mammals determine whether or not to fear another animal they smell -- and whether or not to flee -- is not a higher-order cerebral function. Instead, that decision is made based on a lower-order function that is hardwired into the neural circuitry of the olfactory bulb.'"
I can't find myself fearing fearless mice. Why? Because there was most likely a very good reason for the mice that they are afraid of cats and large things that can eat them... I just can't seem to worry about these things getting loose and breeding in the wild.
It's sort of like the fear of spiders, snakes, bears, and large cats. There are very valid reasons for humans to be naturally afraid of things that can kill/harm and maybe eat us.
Well, I think that it's interconnected; there are certain smell receptors in a mouse that are hardwired to the "oh shit, run" response. They have disabled that in these mice, either by breaking the connection or disabling/removing the smell receptors more directly. The result is that the behavior is not present anymore.
That's really the interesting thing, here: they have found a genetic variation that produces a very definite, high-level behavioral change. That's pretty cool.
Although it's clear that many animals have a lot of behaviors that are 'instinctive' and must be carried genetically (which you can test by bringing an animal up in an environment that's devoid of other animals and monitoring it's behavior), it's not terribly clear exactly how they work and are transmitted. This might be one small step towards understanding a part of that.
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i\hbar\dot{\psi}=\hat{H}\psi
It's sort of like the fear of spiders, snakes, bears, and large cats. There are very valid reasons for humans to be naturally afraid of things that can kill/harm and maybe eat us. It's not the mice I'm afraid of, it's the supersoldier program to which this could be applied.
Of course, I'm not entirely sure they took out the mice's fear as much as their ability to detect the smell... maybe that's in TFA, I'll go see.
You can't take the sky from me...
Maybe someone pointed this out already, or perhaps I am just a bozo...
If a mouse's sensorium is determined a great deal by its sense of smell... and you disable that sense of smell... its "higher-order cerebral functions" would be impaired because they would not be getting the input they require to make decisions. How can you conclude that fear in mammals is related to the oflactory sense? Other mammals may use other senses to a larger degree.
To me, this seems like the old joke about the bad scientist who concluded that a frog with all its legs removed becomes deaf because it doen't jump when he yells at it.
It seems the only way evolution could explain this is by saying that the vast-majority of mice without this gene were promptly eliminated by cats and taken out of the gene pool.
Not at all.
Consider a population of pre-mice, without the gene, that are reasonably adept at avoiding predators for other reasons -- camouflage, fast, good hearing, whatever. Then some sub-population of these critters acquires this gene. Said sub-population becomes much more adept at avoiding predators, and tend to out-survive (and hence, out-reproduce) those without it. Perhaps later, since that gene is so effective, the biological cost of the other avoidance factors (camouflage, hearing, speed etc) outweighs the advantage they confer, and they fade from the population, or perhaps not. Probably in the pre-smell avoidance gene days, cats and other predators were on average slower, and the predator population slowly gets faster as the quick ones outcompete the slow ones.
Likewise for the smell of other predators. But that would imply that there was initially an enumerated list of odors
Not at all.
This assumes that not only do all predators smell different, but that the odor-causing chemical in each species is completely unrelated to all others. This is highly improbable. More likely the odorant chemical is identical or very nearly so in mouse-predator species, probably some byproduct of digesting and metabolizing mouse (and other rodent) proteins. (Consider also that there are only a few different families of mammalian rodent predators - felis, canis, mustelidae - and this smell aversion probably doesn't work for snakes or owls.)
-- Alastair
Well, dogs seem to take delight in chasing cars, as an example, so I wouldn't be surprised if you're right. The run response is something I've noticed myself, time and time again. Bears, dogs, cats...If you stand still, they stop chasing.
I've never had the misfortune of being menaced by a bear in an aggressive situation, and they're not very aggressive in general, so a little loud noise and some raised arms will usually send them lumbering off, while they may chase you a bit if you run.
Dogs...I used to run competitively, and I have more "being chased by dogs" experience than a half dozen normal people. Generally, if you stop, the dog will stop. Doesn't hold for a really aggressive dog who is after you because he specifically wants to kill YOU, but it works fine for any kind of dog that's just excited by the whole idea of running prey.
Cats...Well, I've never been chased by a big cat. But I've led little cats around with all manner of shiny cat distractions. They are excited by movement and bored by stillness.
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