Genetically Engineered Mouse is Not Scared of Cats 286
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.'"
Fearless Mice.. (Score:4, Insightful)
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.
Re:Seems flawed... (Score:5, Insightful)
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.
Re:Smell only? (Score:5, Insightful)
Of men and mice... (Score:3, Insightful)
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.
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.
Fear of the fearless (Score:2, Insightful)
Note that experiments like this are inherently more imprecise than the way they are summarized. The whole point is not "fears cats" or "doesn't fear cats", it's "has been observed trying things it wasn't previously doing that are assumed to be out of fear of cats" and "not having been observed ...etc." I recommend not reading the words describing research outcomes too literally.
When you see a study that says
"blah causes cancer in married people over 18",
give some serious thought to whether it might not mean
"blah may cause cancer generally, but our tests only covered this group and we're
being conservative about our claims."
One way this matters is kind of like the reason that evolution proceeds primarily through behavioral pathways of things being attempted. Fear of a certain smell might keep mice from cats, but maybe cats are not their principal threat any more. Maybe this is a behavior from when there were lots of cats, and maybe most homeowners don't have freely breeding cats any more. If that's so, then this could allow a lot mice to come into areas they haven't been in before, as racoons have moved into cities.
A second and less obvious reason it may matter is that a lot of what holds animals at bay in the openness of human cities may be more a holdover of a natural fear that other animals, to include humans, would be "impolite". But humans are, comparatively, ruthlessly polite. Maybe most animals may steer clear out of us for primitive fear reasons, not for practical reasons. As they learn we are bad at wiping them out, and unwilling to use all available means, that could change. We don't need to hasten things by genetically improving their willingness to try harder.
Experimenting with the boldness aspects of behaviors may have unintended consequences. I don't think it's bad to understand this kind of thing, since it may also help to fix such problems as they come up (e.g., killer bees, and finding ways to get them to be less aggressive). But that doesn't mean one shouldn't be careful about the genes and make sure they don't leave the lab, perhaps even using strong rules similar to what we use for dangerous viruses.
Perhaps mice fear humans due to this same gene, and that's why they run away rather than running toward them and biting when they see them. Maybe this also affects that. In sufficient numbers, and there are no known ethics genes inhibiting the creation of such numbers in mice, a bunch of fearless mice could be very dangerous. In general, fearlessness is to be feared in sufficient numbers. Just look at war movies where large numbers of dedicated lives are thrown away to make a small push forward. If mice showed similar determination to take over a household, that would be formidable. There are some good horror movies on this, but we could easily turn such movies to reality through genetics.
And moreso if the recent "mighty mouse" gene [slashdot.org] got mixed in, too.
It that really the conclusion? (Score:4, Insightful)
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.
Several false assumptions, there. (Score:3, Insightful)
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.)
Re:Smell only? (Score:3, Insightful)
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.