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Author | Topic: Genuine Puzzles In Biology? | |||||||||||||||||||||||||||||||||||||||||||||||||||
Blue Jay Member (Idle past 3019 days) Posts: 2843 From: You couldn't pronounce it with your mouthparts Joined: |
Hi, Stephen.
Stephen Push writes: I assume you are referring to extant species. While your evidence is suggestive, it doesn’t rule out the possibility that our ancestors encountered more dangerous species that are now extinct. Agreed. But, I'm still skeptical that any species of spider has ever been a major selective agent on any species of mammal larger than a small rodent. The possibility is there, and I won't deny it outright, but I doubt it. -----
Stephen Push writes: In fact, it is possible that a genetic predisposition to learn to fear spiders and snakes started with mammalian ancestors that predated the first primates. Well, I've argued for the evolution of a genetic predisposition to learn fear: I'm only arguing that a genetically-determined fear specifically of spiders is difficult to explain evolutionarily. I would also suggest that pushing the origin further back in mammal evolution would make it less tenable from an evolutionary standpoint, because it would imply that natural selection has maintained the specific fear for a much longer period of time. Alternatively, it might imply that arachnophobia is atavistic or on its way out. -----
Stephen Push writes: LoBue’s paper provides the first evidence of enhanced visual detection of spiders in young children. I haven't really researched the topic at all from a psychological or behavioral point of view, and I don't have institutional access to the journal of the spider paper, so I haven't prepared a proper rebuttal. I would argue that this study doesn't really distinguish between learned and genetically-determined fear. -Bluejay (a.k.a. Mantis, Thylacosmilus) Darwin loves you.
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Stephen Push Member (Idle past 5181 days) Posts: 140 From: Virginia, USA Joined: |
Bluejay writes: I would argue that this study doesn't really distinguish between learned and genetically-determined fear. As I understand it, the environmental threat hypothesis doesn't assume that fear is genetically determined. Rather it proposes that we are genetically predisposed to notice and learn to fear some stimuli more than others. I appreciate your skepticism about spiders as an evolutionary threat. But the psychological research seems sound, based as it is on a numerous studies conducted by several different researchers working with several different species. Other than the evolutionary threat hypothesis, I can't think of why humans and monkeys should be more visually attentive to things that look like spiders and more likely to learn to fear spiders than other stimuli. Perhaps the evolutionary threat was scorpions and the visual processing system didn't distinguish between scorpions and spiders. The only problem I have with that idea is I would think scorpions would be easily distinguished from spiders.
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Stephen Push Member (Idle past 5181 days) Posts: 140 From: Virginia, USA Joined: |
herebedragons writes: Is this the type of consciousness that you are refering to ... being aware of our impact upon other organisms and a feeling of moral and ethical responsibilities to those impacts? I agree that kind of consciousness is probably unique to humans. But there are other kinds of consciousness that may be present in non-human animals:
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herebedragons Member (Idle past 1179 days) Posts: 1517 From: Michigan Joined: |
I was asking in context of your original question which you proposed as a biological puzzle:
message 69 writes: Are animals conscious? I wasn't so much making a point that humans are the only moral agents but trying to understand what your question was. You also stated
message 74 writes: Definitions are part of the problem. Researchers in this field often have different definitions of what they mean by consciousness. So I was trying to clear up how you were defining consciousness. If consciousness means "show a difference between wakefulness and sleep, coma, etc." ... not much of a puzzle. Self-awareness is more of a challenge. Does simply recognizing one's self in a mirror constitute awareness? I would personally think that to be considered "aware" and conscious it would require not only recognizing your own image, but using that recognition to make an assessment of one's self such as "Man, I'm having a bad hair day!" or "All this hair sure makes me look fat!" I guess that would be "aware they are aware"? I find it difficult to imagine how anyone could make a reasonable argument against free will. But I suppose people imagine all sorts of other ridiculous and nonsensical ideas. Wouldn't just the idea of speculating and reasoning about the presence of free will support the presence of freewill? But regardless, even if we have no free will, we at the least have the illusion of being moral agents, which pretty much makes us moral agents. We can make decisions about what we believe to be "good" behavior and "bad" behavior. And even though that decision is very subjective, I would say that to be able to distinguish between the two makes us moral agents. I like my "definition" of consciousness. It is not just being aware of self, but being aware of self in context of the world around you and how you fit into that world. So, when you ask "Are animals conscious?" what are you meaning by conscious? And do you think it is a puzzle because we have difficulty defining it or because we have difficulty understanding why we have consciousness at all?
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Tupinambis Junior Member (Idle past 4977 days) Posts: 18 Joined: |
I don't believe that a fear of anything beyond tormenting pain and death can really be genetically encoded. A fear of snakes is, more likely than not, attributed to learned behavior and individual personality than genetics. I think people react more to certain attributes of snakes than the actual snakes themselves; I.E. hissing.
Present a small child with a baby corn or hognose snake and they'll probably be enamored by it. Present them with an adult King Cobra as it flairs its hood, hisses, and lunges at them and they'll probably be filled with an overwhelming sense of terror. From my casual observations most animals capable of hearing react very strongly to anything that sounds like hissing. It seems to be one of the best ways for different species to communicate their antagonism with one another. Imagine a Pomeranian aggressively approaching an adult monitor/iguana/tegu/whatever, barking and doing all that other annoying crap that I hate Pomeranians for. Lizard responds by facing the little dog, flaunting its teeth (which are barely visible), and hissing. Little dog runs away in terror.Why should this be? The dog's wolf ancestors [probably] never encountered big lizards in its natural habitat. Unless the lizard in question was a perentie or a crocodile monitor none of them would have posed a threat to the wolf either (both species are Australian, and thus would probably not have been encountered). Now, the little dog clearly did not have a pre-disposed fear of the giant lizard itself even though it was clearly large and strong enough to kill and eat it. If it did it wouldn't have approached in the first place. It did have an immediate reaction to it hissing though. I imagine this originates from it's (and our) ancestors' encounters with venomous and constricting snakes. Many people don't initially fear snakes until they've learned to do so; either by being taught so by their parents or experiencing one hissing and lunging at them. As for spiders... I have no idea. Perhaps our ancestors would commonly seek food hiding in crevasses and would get a less-than-pleasant surprise when it stuck its hand in. Of course, that would probably have also lead to a pre-disposed fear of land crabs which we don't have. Land crabs also make me skeptical of the scorpion idea. A crab can look very much like a spider, especially the small ones, yet when a person encounters a crab in their yard or even their house they're probably not going to have as strong a reaction as if it were a giant spider.
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Tupinambis Junior Member (Idle past 4977 days) Posts: 18 Joined: |
bluegenes- I'm going to give my best shot at this one. The reason there are no truly green mammals is because, with one exception, there are no mammals which really require being green to aid in their survival. You get green lizards and snakes because it helps them camouflage and, more importantly, tree-dwelling snakes and lizards (well, the bigger ones anyway) cannot effectively run away from an approaching threat while in the trees. Reptiles much prefer to hide and not move opposed to running; much more so than mammals. Ground dwelling mammals hide in burrows and tree dwelling ones are fast enough to escape. The sloth gets green algae on it, so it may not be green itself but it gets the job done.No mammal can also change its color like a chameleon or an anole can.
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Livingstone Morford Junior Member (Idle past 5095 days) Posts: 28 From: New Mexico Joined: |
So would anyone like to add to the list? What is genuinely puzzling in biology --- what are the questions that need answers and don't yet have them?
Whether or not genetic equidistance is the result of epigenetic complexity of organisms or whether it is the result of genetic drift et al. I argue for the former.
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Dr Adequate Member Posts: 16113 Joined: |
Whether or not genetic equidistance is the result of epigenetic complexity of organisms or whether it is the result of genetic drift et al. The meaning of this sentence is obscure. However I suspect that if and when you ever elucidate your meaning, this will turn out not to be a genuine puzzle in biology but rather a question to which every biologist knows the answer. Edited by Dr Adequate, : No reason given.
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nwr Member Posts: 6490 From: Geneva, Illinois Joined: |
Livingstone Morford writes:
I'm not a biologist, but it sure seems pretty obvious that it is the result of genetic change, rather than epigenetics. The measurement of genetic distance is done by comparing protein structure of different species, and the protein structure is encoded in the DNA.
Whether or not genetic equidistance is the result of epigenetic complexity of organisms or whether it is the result of genetic drift et al. Livingstone Morford writes:
You didn't actually argue anything. You just asserted.I argue for the former. If you believe that you have a good argument, start a thread on the question. I expect that the biologist members will be be able to refute your argument in pretty short order. Jesus was a liberal hippie
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Taq Member Posts: 10385 Joined: Member Rating: 5.8 |
Whether or not genetic equidistance is the result of epigenetic complexity of organisms or whether it is the result of genetic drift et al. I argue for the former. You seem to have confused your terms. Epigenetics refers to DNA methylation and histone packaging. Genetic comparisons use the actual DNA sequence, as does genetic drift. Perhaps you meant to refer to DNA regulation as a function of DNA sequence instead of epigenetics?
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Wounded King Member (Idle past 354 days) Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
I think he may be using epigenetic in a more archaic sense, if you can call terms from the 1940s archaic, which essentially means developmental. So the phrase would probably be more easily understood as developmental or morphological complexity. Alternatively it may be used to refer to all non-genetic factors influencing development, but I'm not sure how this would fit.
Or it could be something else entirely. TTFN, WK
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Taz Member (Idle past 3613 days) Posts: 5069 From: Zerus Joined: |
Tupinambis writes:
Actually, it's just not the fear of snakes that's deeply ingrained in us. It's pretty much fear of anything that doesn't look like us. The farther away in appearance the thing is to us, the more "scary" it looks to us. I don't believe that a fear of anything beyond tormenting pain and death can really be genetically encoded. A fear of snakes is, more likely than not, attributed to learned behavior and individual personality than genetics. I think people react more to certain attributes of snakes than the actual snakes themselves; I.E. hissing. This is why people instinctively fear harmless things like certain kinds of arthropods. Take the spider for example. It looks totally alien compared to us, and there are more arachnophobes out there than we can count. Would you want to hold something like this in your hand?
Snakes look alien to us because there's no limbs. And before nitpickers come snooping around, yes I am aware of the vestigial limbs. But generally speaking, the snake is a total alien to us, which is probably why we instinctively fear it.
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Livingstone Morford Junior Member (Idle past 5095 days) Posts: 28 From: New Mexico Joined:
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"The meaning of this sentence is obscure. However I suspect that if and when you ever elucidate your meaning, this will turn out not to be a genuine puzzle in biology but rather a question to which every biologist knows the answer."
The genetic equidistance phenomenon suggests that the number of different residues between two organisms is largely determined by the amount of time since the two species diverged [Margoliash, 1963]. This view not only presupposes that a neutral mutation in a given organism is also neutral in all other organisms, but it also assumes that the epigenetic complexity of an organism does not impose a restraint on the amount of genetic diversity that organism can tolerate. Taft et al. (2007) propose that organismal complexity may be defined as the number and different cell types in that organism, as well as the amount of cellular organization. If the epigenetic complexity of an organism does impose a restraint on the number of mutations that organism can tolerate, then the phenomenon of genetic equidistance would still be manifested, even if all species diverged at the same time. This is because different species can tolerate different levels of mutations, since different organisms have different numbers of cell types. It is difficult to determine whether the phenomenon of genetic equidistance is the result of the amount of time that has passed since two or more species diverged, or whether this phenomenon is the result of the epigenetic complexity of the organisms imposing restraints on the number of mutations tolerated. This is because the number of cell types in organisms has, in general, increased as evolutionary history progressed [Valentine et al., 1994] . I am proposing that this is a genuine problem in biology. I would be more than willing to elaborate on this if I am somehow still being obscure. References: Margoliash E. Primary Structure And Evolution Of Cytochrome C. Proc. Natl. Acad. Sci. U.S.A. 50: 672—9 (1963). Taft, R.J., Pheasant, M. and Mattick, J.S. (2007) The relationship between non-protein-coding DNA and eukarotic complexity. BioEssays 29:288-200. Valentine James W., Collins Allen G., Meyer C. Porter. Morphological Complexity Increase in Metazoans. Paleobiology, 20(1994):2:131-142.
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Livingstone Morford Junior Member (Idle past 5095 days) Posts: 28 From: New Mexico Joined: |
"I'm not a biologist, but it sure seems pretty obvious that it is the result of genetic change, rather than epigenetics. The measurement of genetic distance is done by comparing protein structure of different species, and the protein structure is encoded in the DNA."
It's obviously the result of genetic change, but the question is not if it is the result of mere change at the molecular level (since that is very, very obvious). With the observation of the genetic equidistance phenomenon there emerges a paradox: how do we know that this phenomenon is the result of the amount of time that has lapsed since the divergence of two organisms, or whether it is the result of the epigenetic complexity of the organisms imposing a restraint on the number of mutations tolerated in a given protein, since as time progresses, the number of cell types increases. "You didn't actually argue anything. You just asserted." I never suggested, implied, or proposed that I argue for the former in this forum. However, I have argued for the former in other places. Also, you might want to consider not nitpicking on semantic details. Just a thought. "I expect that the biologist members will be be able to refute your argument in pretty short order." You shall see what you shall see. Biology rocks!
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Dr Adequate Member Posts: 16113 Joined: |
But what is being suggested here is not that "epigenetic complexity" causes "equidistance" but rather that it limits it. The cause of the (neutral) divergence would still be drift.
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