geb@dsl.pitt.edu (Gordon E. Banks) (01/29/90)
>In article <12900@cbnewsd.ATT.COM> kja@cbnewsd.ATT.COM (krista.j.anderson) writes: >Then again, in view of the fact that *most* mammals don't >kill their rivals, > >1. that most mammals have an instinct that forces them to halt >aggressive behavior in response to submissive gestures and >postures. (If such an instinct were not part of the animals' >brain organization, the species would have failed to survive.) And do you suppose humans are any different in this regard (otherwise, WE would also have failed to survive!)? Learning about these submission gestures can help a lot in confrontations with persons in a position of dominance over you (such as when a cop has stopped you for a traffic violation). Fights in which a human is killed when our natural weapons (feet, fists, and teeth) are used are very very rare. The problem is we have equipped ourselves with unnatural weapons over which our instincts have less control (clubs, knives, guns, nuclear weapons...). See Kubrick's 2001 for a film dissertation on the subject. Unfortunately, our technology has run faster than our instincts can evolve to keep up with it. Our only hope is that we can use our intelligence to survive in spite of this.
rowe@pender (Mickey Rowe) (01/30/90)
In article <2440@leah.Albany.Edu> ms361@leah.Albany.Edu (Mark Steinberger) writes: >In article <31315@shemp.CS.UCLA.EDU>, frazier@oahu.cs.ucla.edu (Greg Frazier) writes: >> There are many species of fish and reptile which prey upon >> their own young. >But apparently felines do prey on their own young. I've heard it say >about housecats, but can't give you a quote. But I do know >that it is explicitly stated in the National Geographic special on >tigers that tigers will prey on tiger young, and will also fight >to maim over one another's kills. (Maiming can easily cause death >in the wild.) > >--Mark I'm afraid that I didn't see the National Geographic special in question, but I kind of doubt that these are the same things. Many mammals do indeed kill the young of their own species, but usually only under certain conditions; particulary when the infanticide will give the killer another opportunity to reproduce. As it happens, I just read an article about this (Watts, David, P., 1989, "Infanticide in Mountain Gorillas: New Cases and a Reconsideration of the Evidence", _Ethology_, 81(1):1-18.), and it seems that it occurs almost exclusively when a female and her young have recently lost their mate/father. In fact, female lions may take their cubs and live in isolation from all other lions as a means of protecting those cubs if the mate has been killed. This is very different from animals randomly eating the young of their species (as many fish and reptiles do) as though they were just another source of food. It is also very different from the infanticide by the female chimpanzees that were discussed to start this thread. As for humans and the war/peace thing, it turns out that in many mammals (but not mountain gorillas) infanticide follows when a male or group of males from one group attacks and kills the males from another group. Certainly there is a selective advantage for males that wipe out the genetic contribution of other males and then contribute their own genes in their place. But this is grisly, and I don't even want to think about it. Please, no follow-ups. Mickey Rowe (rowe@pender.ee.upenn.edu)
barbara@Gang-of-Four.Stanford.EDU (Barbara Chapman) (01/30/90)
In article <31315@shemp.CS.UCLA.EDU> frazier@oahu.UUCP (Greg Frazier) writes: >In article <1283@oravax.UUCP> ian@oravax.odyssey.UUCP (Ian Sutherland) writes: >+In article <12900@cbnewsd.ATT.COM> kja@cbnewsd.ATT.COM (krista.j.anderson) writes: >+I believe (correct me if anyone knows I'm wrong) that there are species >+(not mammals, but species) which have no such "instinct". If so, what >+permits such species to get along without such instincts? > >There are many species of fish and reptile which prey upon >their own young. A prime example of this is the American >alligator. This is a positive trait in the alligator, because >it is at the top of the food chain in its biosphere. Not that >this has any direct bearing upon mammals in general, or chimps >in particular, but it does show how aggression/predation >against an animal's own species can be a postitive trait. On >the other hand, it raises questions such as why don't mammilian >carnivores such as bears exhibit this behavior? I realize that >bears are omnivores and actually get most of their calories from >vegetation, but since they were at the top of the food chain, >did they really rely upon disease and starvation to limit their >population? Or have there always been enough human beings around >to limit their numbers sufficiently? > >Greg Frazier >........................................................... >"They thought to use and shame me but I win out by nature, because a true >freak cannot be made. A true freak must be born." - Geek Love > >Greg Frazier frazier@CS.UCLA.EDU !{ucbvax,rutgers}!ucla-cs!frazier Reptiles, amphibians and fishes tend to have a very different reproductive strategy from that of birds and mammals. The lower vertebrates generally expend a great deal of energy producing young, and little or no energy ensuring the survival of the babies. That is, reptiles, amphibians and fishes produce huge numbers of eggs (at sometimes severe metabolic detriment to the mother) and are often not even around when the eggs hatch. Higher vertebrates, on the other hand concentrate their energies on ensuring the survival of the few offspring they produce, spending weeks to years (or even decades in the case of some humans :) feeding and protecting their progeny. Hence it may be reproductively efficient for an alligator to eat some of her tens to hundreds of children under some circumstances, whereas it is unlikely for it to be efficient for a mother bear to eat one of her one or two cubs unless there is a very good reason why she will not be able to raise the cubs to adulthood (in such a case, for example a birth defect in the cub, or a season of famine for the mother, the mother is likely to eat the babies.) Barbara Chapman barbara@gang-of-four.stanford.edu
J.M.Spencer@newcastle.ac.uk (J.M. Spencer) (01/30/90)
In article <2440@leah.Albany.Edu> ms361@leah.Albany.Edu (Mark Steinberger) writes: >In article <31315@shemp.CS.UCLA.EDU>, frazier@oahu.cs.ucla.edu (Greg Frazier) writes: >> There are many species of fish and reptile which prey upon >> their own young. ... On >> the other hand, it raises questions such as why don't mammilian >> carnivores such as bears exhibit this behavior? > >But apparently felines do prey on their own young. I've heard it say >about housecats, but can't give you a quote. But I do know >that it is explicitly stated in the National Geographic special on >tigers that tigers will prey on tiger young, and will also fight >to maim over one another's kills. (Maiming can easily cause death >in the wild.) > >--Mark When a nomadic lion defeats a lion that owns a pride (by biting the spine of the defending lion) his next act is to kill all the cubs (because they are not carrying *his* genes). The lionesses then flirt greatly with the new lion and will also abort their current pregnancies. [BBC television documentary on the African Lion c. 1988] This isn't preying on their own young in the true sense.
kja@cbnewsd.ATT.COM (krista.j.anderson) (02/01/90)
<> Well, I decided to get a little more information about animal aggression. I knew, really, that the idea that "animals never kill" is outdated. Here's some further info, from the Encyclopedia Americana (1989) and Academic American Encyclopedia (1981). Instinct is unlearned, inherited and species-common. Closed instincts cannot be modified. Open instincts can be modified. An example of a closed instinct is that certain fish and birds will respond aggressively to a red belly or chest and that behavior cannot be extinguished. An example of an open instinct is nest-building in some birds. The instinct is to pick up any material to build the nest. But as the bird learns, it ignores materials in the area that did not work well and picks up only those materials that have worked well. Aggression and territoriality are not necessarily related. Some advantages of territoriality: 1. Territorial species will have flexible dimensions of each individual's or group's territory, depending on the amount of food available each year. These species have less fluctuation in population densities than non-territorial animals. 2. Being more spread out lends protection against diseases and parasites. 3. Group defense cooperation leads to social organization. In lower animals, aggression is inherited and laboratory rats can be bred to be more docile or hostile. In higher animals, including humans, learning plays a role in aggression-looking behavior. 13 types of aggression have been identified and each is elicited by different stimuli and each is associated with different neural and endocrine bases: 1. predatory - in response to presence of prey 2. anti-predatory - in response to presence of predator 3. territorial - in response to intruders 4. dominance - in response to challenge to rank or possessions 5. maternal - in response to threat to offspring 6. weaning 7. parental discipline 8. sexual 9. sex-related 10. intermale - in response to presence of competitor 11. fear-induced - in response to being confined or cornered 12. irritable - in response to signals such as red belly 13. instrumental - change in environment making any of above more likely On the one hand, the encyclopedia says that threats of aggression and withdrawal are much more common than actual fighting. On the other hand, langurs will kill the offspring of other males. Also, male lions will go as far as to kill one another when they are fighting for possession of a pride, and if the challenger wins, he might kill the cubs sired by the deposed male. The encyclopedia points out that a certain amount of aggression can give a breeding advantage to individuals, which then passes on the level of aggression to the offspring. On the other hand, too much energy spent in aggressive behavior can be a disadvantage, for instance, in the case of birds whose time would be better spent caring for the young. Hence, a balance is maintained for each species and probably for a particular environment. Well, this is grisly stuff, as Mickey said. Personally, I think humans can do better than nature in the sense of putting justice and compassion into practice. Nature is competitive. Sorry if this is a depressing topic. Then again, how do we know that the chimps, gorillas and lions that killed did not feel unusual pressures due to the presence of humans? If lions and apes have been killing all along, why didn't someone notice it sooner? Weren't the "Born Free" people studying lions for a long time (before they got murdered)? There are certain mechanisms I've heard of that take effect under crowded conditions. Lemmings go nuts and run into the sea in their panic. Mice will have spontaneous abortions or the males may eat the offspring, I seem to recall. Guppies will eat newborns under crowded conditions, I've heard. And as Barbara said, the alligators can afford to eat the young because there are so many compared to the area available. I'm not sure where these mechanisms would fit into the 13 types of aggression above. "Instrumental", I guess. Apologies if this is too depressing or grisly. -- Krista A. HONOR Our Neighbors' Original Rights!