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Author | Topic: Female Infanticide? | |||||||||||||||||||||||
Quetzal Member (Idle past 5872 days) Posts: 3228 Joined: |
The strategy for male rodents is to kill any young they can up until the point that they mate. Then they no longer kill. This isn't entirely accurate. Although it appears to hold for gerbils, it is inconsistent with the literature that suggests at best males will refrain from killing their own progeny, but there is no behavioral constraint in most species against slaughtering everyone else's neonates. In fact, the communal rearing strategy used by some rodents - where the females huddle in a bunch with their pups, and in some species will even suckle the pups of their sisters (consistent with kin selection) - is a defense reaction against the males. In this case, the males apparently "recognize" the nest-scent of the pups, and will refrain from eliminating them. They don't appear constrained about eliminating the pups without this nest-scent.
By Hamiltons Rule, since relatedness is nearly equal to zero, the benefit must also be near to zero as well. On average a male rodent will benefit by this tactic to pass their genes onto the next generation. Inclusive fitness dictates that the selfish genes will work the percentages from the standpoint of relatedness. I don't think it makes any difference whether the offspring are female or not. Female hyenas will kill off their litter mates in order to dominate their cohort. Right. Which renders any counterexample - the supposed gerbil, hamster, and mouse examples used by schraf, et al - somewhat problematic. Which is why I got on this subject in the first place. Moreover, the quite plain human "violation" of Hamilton's rule through maternal infanticide needs an explanation.
In humans, the practice of female infanticide is not uncommon, but this is mostly due to socio-economic reasons. Again, right. However, almost any socio-economic reason for any behavior has a natural analog. I can think of few, if any, human group behaviors that don't - including religion . The analog is what I'm reaching for here. I'm actually surprised that the theists haven't jumped on this already. Aftr all, if it can be shown that maternal infanticide has no natural equivalent or adaptive explanation, then there's a tiny bit of additional weight to their argument that humans are "special" - not simply different. Admittedly a kind of gruesome argument in this case. Genetics ultimately provides the underpinnings of behavior, although as Ehrlich describes it: "Genes do not shout commands to us about our behavior. At the very most, they whisper suggestions..." (Ehrlich, P 2000 "Human Natures: Genes, Culture and the Human Prospect", Penguin Books, New York, pg 7). Culture vs biology, again.
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John Inactive Member |
Apparently Jane Goodall reported one instance of infanticide by females.
This doesn't fit into the picture very well, but it's about chimps. All infanticide we've spoken of so far was committed by males, and this is the rule in primates and other animals. There are some exceptions, and one was documented by Jane Goodall. A female named Passion began killing and eating several of the babies in her community. Together with her daughter Pom, over a period of many years they attacked and killed infants in their group. Usually when males kill a baby, they don't eat it, but these females seemed to be after meat; they'd chase and consume the infant. They were actually seen to eat 3, chase 3 others, and there were 8 others who disappeared under mysterious circumstances. In this period, there were almost no infants weaned successfully. So this is kind of a question mark because it's only been these two individuals documented- and the daughter probably learned it from the mom- so maybe we can label this one pathological and say that it's not a part of normal chimp behavior.
No webpage found at provided URL: http://www-personal.umich.edu/~phyl/anthro/infant.html ------------------
No webpage found at provided URL: www.hells-handmaiden.com
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Speel-yi Inactive Member |
quote: It would be Trivers parent/child conflict theory. This occurs because a child "shares" 100% of its genes with itself and the mother only 50%. The child wants as much of the resources from the mother as possible, while the mother seeks to limit that investment in order to have something for her other children. So a child born to a mother while she has another that is not yet weaned, is more likely to be killed or neglected by the mother. Female infanticide occurs in some societies because males provide more of the calories and thus ensure the contributions of food to their kin more than a female would. An example of this is the Ache in Paraguay. You should consider that the strategy for an R-selected organism like a rodent will be quite a bit different from a K-selected like a human. ------------------Bringer of fire, trickster, teacher.
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Zhimbo Member (Idle past 6012 days) Posts: 571 From: New Hampshire, USA Joined: |
I could send you a .pdf of the article if you're getting hardcore about this. Send email to my yahoo.com address, username is zhimbo.
The behavior isn't direct infanticide, but is "active rejection" (the author's words) of pups. It's gender specific, and the article is about the adaptive nature of this for this species. Males will lose out on body weight, and are the first to die. It's a fine line between "deliberate neglect" which leads to death and "infanticide". Apparently "brood reduction" is pretty well documented in various birds, and the McClure article lists three citations after the claim "there are few reports of litter reduction in mammals." [This message has been edited by Zhimbo, 10-04-2003]
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bruchid girl Inactive Member |
This is in response to the original request of a mammalian example where a female kills her own offspring. I have myself been looking for examples of this, and have found it very difficult. I have yet to find a peer reviewed article documenting this occurance, but it is well known to occur in Norway rats http://www.ratbehavior.org/infanticide.htm, at least those kept in captivity. I have also heard of cases in Kangaroos where the mother (who is capable of superfetation) will remove one young from her pouch in order to allow a second to continue developing when resources are scarce. While not a mammalian example, I believe coots regularily kill a portion of their clutch. Hope that helps!
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capeo Inactive Member |
I would think human's ignoring the general foundations of Hamilton's Law needs no direct evolutionary explanation. It would seem more likely a by-product of our brains' evolution, specifically the ability to be cognizant of future socio-economic scenarios with great detail. Some the example's already stated (China, Victorian England, India...) show cultural and socio-economic selection defeating instinctive drives of kin selection.
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AdminPD Inactive Administrator |
Welcome bruchid girl and capeo,
Glad you decided to add to our diversity. We have a wide variety of forums for your debating pleasure, but I warn you it can become habit forming. In the purple signature box below, you'll find some links that will help make your journey here pleasant. Pay particular attention to our Forum Guidelines and all will go well. Again welcome and happy debating. Usually, in a well-conducted debate, speakers are either emotionally uncommitted or can preserve sufficient detachment to maintain a coolly academic approach.-- Encylopedia Brittanica, on debate Links for comments on moderation procedures and/or responding to admin msgs:
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capeo Inactive Member |
Thinking about it I wondered if PPD had been worked into evolutionary theory and it has:
http://www.anth.ucsb.edu/projects/human/ppd.pdf http://itb.biologie.hu-berlin.de/~hagen/papers/perinatal.pdf The gist of which is that PPD is not a pathology but an expressed response, which leads to me ask if similar theories have been put forth for other apes. This might lead to the answer of your original question, Quetzal. |
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capeo Inactive Member |
Thanks,
glad to be here.
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Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
There was an article about this in the NY Times last mother's day. It mentions the kangaroo example as well as touching on infanticidal, not neccessarily directly, behaviour in pigs and rabbits.
TTFN, WK
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Quetzal Member (Idle past 5872 days) Posts: 3228 Joined: |
Thanks to both of you for your replies and comments. Unfortunately, I suffer from a severe attention span deficit. The question in the OP has inevitably fallen off my personal radar screen over the past few years.
On the other hand, welcome to EvCForum! From your quality of your replies, I very much look forward to reading your input on other topics.
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macaroniandcheese  Suspended Member (Idle past 3928 days) Posts: 4258 Joined: |
btw. you do know that male offspring take more resources to raise right? in humans, there is an increase in female births to women with absent husbands (business trips included). there was a story on it on npr last year. i can find it if you like.
instances of male infanticide are easy to explain thus in times of want.
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capeo Inactive Member |
LOL... I didn't realize this post started in 2003!
Brennakimi,if you would like to the find the article I'd certainly read it. Thanks
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mick Member (Idle past 4986 days) Posts: 913 Joined: |
Hi Quetzal,
You might look up resorption of litters which is reasonably common in mammals. Here's an image of a litter being resorbed by a mother mouse:
Top left is the full litter, bottom left is the litter being resorbed at 15 days, bottom right is 18 days. The litter is genetically abnormal so (apparently) the mother recycles them. Mick
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