How are parasites able to imitate other animals?

  • Thread starter mark!
  • Start date
  • #1
128
12

Main Question or Discussion Point

The green-banded broodsac, a parasitic flatworm, is said to parasitise the eye stalks of snails, and through imitating a caterpillar attracts the attention of a bird. But how does it know what a caterpillar looks like, if it doesn’t even possess complex eyes?

Flatworms have primitive eyespots with a single type of photoreceptor on its head that can detect the intensity of light. So how then is it able to imitate a caterpillar in the way birds (and humans) would observe a caterpillar? Why is this kind of behaviour generally accepted to be an example of 'aggressive mimicry'?
 

Answers and Replies

  • #2
gleem
Science Advisor
Education Advisor
1,632
999
We often ascribe human characteristics to animals and their behavior. But these should not be taken literally. Organisms come into this world with enough capabilities that permit them to thrive. The capabilities are created by trial and error. When sufficient characteristics emerge that allow them to survive and thrive you have a viable specie. They will continue to exist as long as the environment remains compatible with their characteristics and tolerances. Think of the countless creatures that have been produced that failed because they were not compatible with their environment.
 
  • #3
BillTre
Science Advisor
Gold Member
1,462
3,169
Just as visio is not necessary for a visual trait to evolve (you might consider flower patterns as visual attractants for bees and birds), there are many other examples of things evolving beyond the awareness of the organism evolving a new trait.

Some Examples:
  • colonial insects evolving castes, reproductive specialization and function of colonies.
  • birds evolving feathers: "how did they know this would be useful?"
  • animals evolving hormones (inside their bodies, unseeable, can have subtle effects on their bodies)
The real explanation is that things evolve because their offspring forma greater part of the population in each succeeding generation. Eventually successful changes predominate in a population.
In the case of the parasite you mentioned, it has to develop the instinct to migrate to the right part of the snail at the right time in its life cycle, and become colorful. These traits lead to the snails predators finding and eating the unfortunate snail, which allow the parasite to continue its complex life cycle in the snail's predator.
There are lot of parasites like this. See the book Parasite Rex.
In addition, many changes evolved in domesticate plants and animals are done unconsciously by the humans in charge of them.

from here:
Darwin's The Variation of Animals and Plants Under Domestication (6) offers a litany of facts and examples of artificial selection in action at the hands of plant and animal breeders. Darwin felt that an understanding and appreciation of the depth of artificial selection was fundamental to the acceptance of natural selection. In Variation, Darwin wanted to expand on this artificial mechanism of evolution beyond examples in Origin, where he describes familiar and tangible results of husbandmen in his argument that selection by the analogous natural means-survival of the fittest—was not just plausible or possible, but probable. Darwin considered any variety, breed or subspecies, no matter how it was derived, as an incipient species, irrespective of the particular selective mechanism driving the group's evolution (6). He sought to illustrate that tremendous changes can be wrought through the “gradual and accumulative force of selection,” but he also emphasized that evolution by selection of any type can only work where variation is present; “The power of selection … absolutely depends on the variability of organic beings” (6). Thus, genetic differences between domesticates and their wild counterparts substantially reflect the native genetic variation (i.e., standing variation) present in the wild population before any selection (natural or artificial) for tameness, and the secondary effects of isolation (6).


Through the plethora of examples laid out in Variation, Darwin was making a case that the consequences of artificial selection are similar in spirit to those of natural selection, but, moreover, that artificial selection (whether methodical or unconscious) was practiced a very long time ago. Darwin further suggested that there had been little need for humans to understand the mechanism of artificial selection, so long as the process operated effectively and produced tangible results.
Random inbreeding changes (the random sorting out of genetic traits among offspring in small breeding populations) many also result in either adaptive nor non-adaptive traits.
 
  • #4
128
12
We often ascribe human characteristics to animals and their behavior. But these should not be taken literally.
So you also think it shouldn't be called 'aggressive mimicry' then, because it's a misleading term?

There are lot of parasites like this. See the book Parasite Rex.
Yes, I've read that book, great book! I learned many things from it, like why so many parasites end up in the liver, of all the possible body organs. Many examples of many different parasites are given in that book, but no other examples of parasites are mentioned that seem to actually imitate the shape another animal. But, a part from this book, there's another example, take for instance the bee orchid. How would a plant be able to imitate the morphology, size and color of an insect? How does a plant know how an insect looks like?

The question is now how mimicry works, but rather how mimicry works...through the eyes of another organism. So if there's no way for you to define an organism's shape, how can you imitate that shape? It seems so paradoxical to me. It's like a human being producing a high pitched noise that a bat is able to hear, even though that person isn't able to hear that voice himself. I really don't understand how you could have produced that sound in the first place, if you don't even possess the senses to know what it is that you've just produced, because a human being is not a bat.
 
Last edited:
  • #5
DrClaude
Mentor
7,337
3,516
So if there's no way for you to define an organism's shape, how can you imitate that shape?
There is no "imitation" going on, in the common usage of the term.

What is needed is a mechanism for random variations coupled with differential breeding. Any favourable characteristic, like "looking slightly more like another organism," gets amplified (higher probability of surviving/breeding = more offspring with the same characteristic) over generations, until the mimicry is "perfect."
 
  • Like
Likes BillTre
  • #6
128
12
There is no "imitation" going on, in the common usage of the term.

What is needed is a mechanism for random variations coupled with differential breeding. Any favourable characteristic, like "looking slightly more like another organism," gets amplified (higher probability of surviving/breeding = more offspring with the same characteristic) over generations, until the mimicry is "perfect."
Interesting! Is this your own hypothesis (which sounds very reasonable), or can you support that claim as well? If random variations did indeed gradually develop towards perfect mimicry (without even knowing you're mimicking something), then do we observe this gradual change anywhere in parasites? Are there any transitional parasitic species that haven't perfected their "mimicry" just yet? Are there in-between-parasites, just like Lucy was a transitional genus within the hominins, or Tiktaalik between fish and tetrapods on land? And if there's no transitional animal to be seen anywhere, how can you be so sure about its evolution?
 
  • #8
128
12
Interesting article, but this is yet another example of mimicry in nature. It does not answer my question.

One passage in this article in particle is quite interesting:
"Many previous studies of insects such as butterflies suggested that mimicry is a stable evolutionary endpoint. Once the mimic acquires a coloration that protects against predation, that color pattern is retained indefinitely, the insect studies suggested".

But does this suggest that mimicry is actually a total lack of intention or purpose? Don't you think that cuckoo birds first must have observed, visually processed, the eggs of the bird before it starts to imitate them? Or what about the cuckoo caterpillar then? The large blue butterfly larva first utilizes chemical mimicry to gain access to the nest, and then uses acoustic mimicry of a queen ant to elevate their status among the ants. Am I to believe that there was no intention behind this, and that random changes lead to the end point of the exact sound of a queen ant?
Example: If I start to make a random sound, and nothing happens, but then I change the pitch of that sound a little bit, and I start to see a smile on your face and I receive a reward from you, so I change it again, and you like it even more, and you reward me again for it, how probable is the chance that, ultimately, I'll reach the melody of a Beethoven's violin concerto in D major, your favourite composition? In other words: does randomly changing the pitch of a sound ultimately reach the exact melody that a queen ant produces?

Isn't it much more plausible to assume that a caterpillar must first be aware of what a certain sound means for ants, and what it potentially could lead to if it would be able to make that sound too, and then processes that sound, in order to then imitate it, and perfect it?
 
Last edited:
  • #9
BillTre
Science Advisor
Gold Member
1,462
3,169
Why would you think that intention is involved in what an insect or a fluke are doing in evolution (which is a population level event not an individual organism event). Insect brains are pretty small to think they have any intent at all and flukes nervous systems are even smaller and simpler.

The default hypothesis would be that intent is not involved and it would be up to you to show it is present and coordinated among a breeding population over many generations.
Occam's razor would favor the simpler hypothesis of not intent was involved. The perception of the naimals being tricked (or maybe the animals being messed with (taken advantage of)) are the ones whose perception is being taken advantage of in the situation. If the the caterpillar's predator can be convinced to eat the predator (due to random mutations in the parasite) then the parasite's offspring will increase in the next generation of the parasite.
There is no requirement for the parasite to know what;s happening. It just happens because the caterpillar's predator eats it. The perceptual part is on the predator.
The variation is among different parasites. Those that get eaten by the predator survive and breed again. Even if they don't know what;s happening.
 
  • #10
128
12
Why would you think that intention is involved in what an insect or a fluke are doing in evolution
Why would any organism start investing energy into mimicking anything if it's not evolutionary adaptive? It must have been cognitively aware, already beforehand, what reward would be at the end, if it manages to do so. Organisms work backwards, from a reward at the end, back to behavioral changes at the beginning. Changes are applied when it gradually leads to a reward, not the other way around. Organisms don't just start changing their ways without any reason, and then all of a sudden there's an unexpected reward at the end.
 
Last edited:
  • Skeptical
Likes BillTre
  • #11
gleem
Science Advisor
Education Advisor
1,632
999
So you also think it shouldn't be called 'aggressive mimicry' then, because it's a misleading term?
No, just that one should not interpret it as if the organism planned its particular behaviors.
 
  • Like
Likes BillTre
  • #12
128
12
No, just that one should not interpret it as if the organism planned its particular behaviors.
Can you support your argument?
 
  • Sad
Likes BillTre
  • #13
gleem
Science Advisor
Education Advisor
1,632
999
I am not sure what you think my argument is.
 
  • #14
128
12
I am not sure what you think my argument is.
Well, if you argue that mimicry is not intended, it must have occurred by chance, spontaneously, randomly, and not as a strategy, right? Sure, the black and white moths example clearly shows that random mutation is the driving force of evolution, no white moth ever intended to be white, but mimicry is something very different. Have you read my queen ant example in post #8? Those white and black moths were already there, and then one became favoured over the other. In the case of caterpillars mimicking the sound of a queen ant, no, they were not already there. There were no caterpillars who already mimicked that sound, some better than the other, and the ones that did best remained, and those who's mimicking capabilities weren't so good simply went extinct. That doesn't make any sense to me, the only thing that makes sense to me is that they have gradually learned to produces that sound. Not by chance. Changes by any organism are applied when it gradually leads to a (bigger) reward. Organisms don't just start changing their ways without any reason, and then all of a sudden there's an unexpected reward at the end. Can you explain why you think that mimicry developed NOT as a strategy, NOT intentionally? (If that is indeed your argument). I'm not saying I believe in the intentionally-hypothesis, but I don't yet reject it, and I haven't heard anything convincing that sounds reasonable to presume the opposite, to be honest. Maybe you could provide me something, because I really would like to understand the process behind it.
 
Last edited:
  • Skeptical
Likes BillTre
  • #15
gleem
Science Advisor
Education Advisor
1,632
999
An organism (a specie) comes into existence with some inherent capacities, characteristic or traits. If these are amenable to its environment that is if it has a niche in which to survive and reproduce it will produce a population. This population will have certain characteristics inherent to its species. But individual will in some small way be different e.g. color and size. They are not exact clones of one another. Spontaneous mutations occur most of which are either detrimental or irrelevant as to how the species remains in existence.

Occasionally a mutation occurs that gives a small number of individuals an advantage over the parent population. These individuals are more "fit" than the general population. A fortuitous change in coloration for example may protect these individuals from predation allowing them to increase their number relative to the parent population. They compete with the parent population for food and mates. Over time their population grows and the parent population dwindles and is replaced. Another scenario is that some individuals have traits that are of no advantage until their environment changes enough to make these traits necessary for their survival. Why do some animals "adapt" to human incursion while others can not; they do not have the inherent ability to do so.

Most likely your snail loving flatworm did not just pop up one day to infect snails. There are thousands of flat worm species all with different traits, traits that continually albeit slowly can make their continued survival better or even worse. Our attention is called to some remarkable and unusual traits that are so different from our experiences that they seem planned or the result of some mystical intervention. Consider the Polysphincta wasp which lays an egg on a spider host. The egg hatches and the baby wasp begins to devour the spider but also injects a substance that causes the spider to do something unusual before it dies and is consumed. It spins a cocoon in which the wasp can pupate. Nature does strange and awesome things.
 
  • Like
Likes BillTre
  • #16
jim mcnamara
Mentor
3,905
2,292
Hmm.

You seem to want to learn about the evolution of behavior, labelled Sociobiology. Ants are a good model.
From E O Wilson's book of the same name, 'Sociobiology':
A single worker ant has an absolute, fixed set of responses. She does not "think" or "perceive". She responds to and produces more chemicals we call pheromones. Collectively, ants behave as more than the sum of thousands of individuals. This has been the result of Natural Selection. Only. Consider that the result of Natural Selection for 99.9999% of species has been extinction. Do you suppose that every species has the intention going extinct? Probably not.

Anthropomorphism is the attribution of human traits, emotions, or intentions to non-human entities. It is considered to be an innate tendency of human psychology.

Your questions and point of view have that bent. IMO. For example, intention implies future knowledge. Ants and all of the parsites we know about do not have that behavior pattern. Rather they exhibit a lot of useful completely pre-programmed behaviors. Virus particles "fake out" immune systems to be successful.

You can counter with any claim about humans, but we perfectly fit the model. Complexity of our hypersocial behaviors was developed solely by Natural Selection. Not intention.

Try this:

Assuming you can code, try Conway's game 'Life'. The point is that a starting, incredibly simple set of pre-programmed rules will exhibit complex 'behaviors'.

Java example, click the download the source code button when it first appears. Or search on your own.
 
  • Like
Likes BillTre
  • #17
128
12
Thanks everybody for your extensive answers, especially @gleem and @jim mcnamara, this is the reason I come to this forum. You’re both providing me with theories about complex behaviour that, to me, still don’t seem to be automatically also applicable to mimicry as well. I simply don’t see the direct relation between those two very different processes of nature.

Why would humans have intentions, but (lower) animals not? Watch this video of a squirrel thinking multiple steps ahead.

Occasionally a mutation occurs that gives a small number of individuals an advantage over the parent population. These individuals are more "fit" than the general population. A fortuitous change in coloration for example may protect these individuals from predation allowing them to increase their number relative to the parent population.
Yes, but some coloration patterns can be understood as intentional, if you consider the purpose they fulfill, just like the big eyes on the wings of the owl butterfly. Or think of walking sticks, do you suppose that their shape is not in any way the result of the shape of twigs and leafs that are present all around them in their habitat, that have been 'processed' by the organism? In both cases the purpose is clear: not to be eaten. It seems far-fetched to me to assume that it didn’t have anything to do with it, and just random mutations causes their body shape to change, and magically and accidentally mimicked their surroundings, without any own active strategic internal reorganisations.

Rather they exhibit a lot of useful completely pre-programmed behaviors.
True, but many parasites complete their life cycle in birds, which appeared when dinosaurs appeared, even though these parasites already existed long before that. Hence, even pre-programmed animals seem to learn/adapt. In other words: they seem to be able to reprogram their pre-programmed behaviour.

Virus particles "fake out" immune systems to be successful.
Take the viruses ebola and measles, as well as the protozoan Toxoplasmosis Gondii, they use dendritic cells as a trojan horse. This leads to their spread and survival, an end goal all animals pursue. Rabies makes dogs want to bite, and they manipulate humans to have intensive cravings for sex because, again, that's how the virus can spread. The raspberry leafmottle virus manipulates plant volatiles to attract aphids, which spreads the virus, influenza seems to make humans more sociable. In other words, all these organisms (or the non ‘living’ units of life viruses) have the same end goal.

Or take cancer, something we are pretty sure about it isn't 'alive' or has 'intentions':
In cancer tumors, one of the first things to happen is demethylation of the silenced genes. It limits the amount of MHC receptors on the surface, which would otherwise be recognized by NK cells. Cancers frequently exploit the wound-healing side of the immune system for their own ends. They can masquerade as damaged tissue to receive help from the immune system. Tumors induce blood vessel growth (angiogenesis) by secreting various growth factors (e.g. VEGF) and proteins. The migrating cell secretes the proteases required to break down the extracellular matrix proteins. Cancer cells enter the bloodstream after undergoing EMT induced by TGF-β released from platelets. Once in the bloodstream, metastatic cancer cells recruit platelets for use as a physical barrier that helps protect these cells from elimination by immune cells. Cancers can escape immune destruction by suppressing the anti-cancer immune response through maintaining a relatively low pH in their micro-environment. After metastasis, it then bores a hole through the tissue with metalloproteases to reach a particular organ to make colonies.

My point:
These hallmarks of cancer (and more) are not simply analogous to spontaneous events, like throwing a deck of cards off the roof, and expect them to all land straight onto each other. It's possible, but in what universe? Cancer is like not simply 'uncontrolled cell division' that can simply be explained by random mutations alone. It's not simply like tipping over the first domino tile, because of open window that caused the wind to come in, just an accidental occurrence that caused it all, no, this is more like 1) an open a door, 2) walking to a new room, 3) put the key in, 4) turning the door knob, 5) walk towards the dominos and then 6) tip a domino tile over in that room. I can’t find a better word to describe these behaviours better than ‘intentional’. These are sequential steps taken by a biological organism, not unlike an animal. A cell 'wants' to survive'. I call this 'intentions' although it's possibly the wrong word, I hope you know what I'm trying to say. If not, sorry, but this is the best I could.

So, in short, based on the counter evidence I have been provided by allof you, I’m not convinced… yet. So I’m not disagreeing with you , I’m just not yet agreeing with the fact that cognition, awareness, and ‘ideas’ could not have been the reason behind some of these mimicry features in nature. I just don't get your explanations. That doesn't mean I think that you are wrong. But thanks again for taking the time to respond to my question, I really appreciate it!
 
Last edited:
  • #18
gleem
Science Advisor
Education Advisor
1,632
999
It seems far-fetched to me to assume that it didn’t have anything to do with it, and just random mutations causes their body shape to change, and magically and accidentally mimicked their surroundings, without any own active strategic internal reorganisations.
What is the saying "A leopard can't change its spots". No matter how much it might "want to ' IF it could want to. Humans can change behavior to adjust to various situations but they cannot change their physical characteristics at will. Do you believe in shape shifters?

If you look at any organism and its structure and function you have to be amazed at how these things can come about without "someone" designing them, BUT they do or don't you believe that.

With this post I resign from this thread.
 
  • Like
Likes BillTre
  • #19
BillTre
Science Advisor
Gold Member
1,462
3,169
I commiserate with @gleem.
This is an infuriating combination of arrogance and lack of knowledge.
It's more like you looking for a rationalization and don't want to undertake the effort to get to a real explanation.

You are holding tight to several misconceptions that, to me, look a lot like vitalism.
In some ways like Lamarckism (a pre-Darwinian idea).
Empowering living things with special properties to explain things that you think are not normally explainable, when in fact they are.
In biology, these ideas were rejected 100-200 years ago.

Modern biology, which is quite successful, explains most things within its domain without these kinds of considerations. It does this by making good reasonable explanations with in largely mechanistic processes.

You have presented many poorly thought out ideas that should not remain unchallenged:

Why would humans have intentions, but (lower) animals not?
Because of the lack of the necessary neurological substrates for deep thought in lower animals.
Flukes and small worms are particularly poorly endowed neurologically speaking.
The almost microscopic nematode worm C. elegans (a giant of the biological research world) has only about 300 neurons. You probabaly have more in most of your autonomic ganglia.
These small sized of nervous systems run behaviors on simple reflexes and neural pattern generators.
Humans, on the other hand, have something like 50-100 billion neurons. This allows them to have vastly more complex behavior , internal thoughts, and long term goals.
In between, some of the more complex nervous systems are considered to have similar internal states to those of humans (but generally to a lessor degree). These would be other vertebrates (similar brain structure, fewer neurons that humans (in most cases), but still have lots of neurons), some molluscs (squids, octopi, and cuttlefish). These are the kind of animals that are most protected by research animal care regulations, which are largely made by vets (among those who work most closely with a variety of animals).

Yes, but some coloration patterns can be understood as intentional
No, it can't.
There is no way within the scope of modern science that this si supported. This is bad information to distribute on the internet!
You should support this statement, rather than making it an assumption. Needs a reference or a good explanation for this this makes any sense (like what mechanism is connection an animals intent with it causing a change in its offspring's color pattern), as well as why normal mechanistic processes can not explain this.
The field of pattern formation is big in developmental biology, with a long distinguished history.
If you want to seriously present that idea, you have to explain how a mental intention will effect the molecular-cellular mechanisms that have been shown to underlie this developmental process.

consider the purpose they fulfill, just like the big eyes on the wings of the owl butterfly
This mechanism of development has been completely explained by cellular and molecular processes and have good evolutionary explanations.

Or think of walking sticks, do you suppose that their shape is not in any way the result of the shape of twigs and leafs that are present all around them in their habitat, that have been 'processed' by the organism? In both cases the purpose is clear: not to be eaten.
Yes, the walking stick is the result of imitating the shapes in its surroundings, but the awareness of involved in the evolutionary process here is in that of their predators and whether they are fooled and don't eat them, thus allowing more of their offspring in the next generation.

It seems far-fetched to me to assume that it didn’t have anything to do with it, and just random mutations causes their body shape to change, and magically and accidentally mimicked their surroundings, without any own active strategic internal reorganisations.
This just sounds like some kind of anti-Darwinist stuff.
You should review natural selection.

True, but many parasites complete their life cycle in birds, which appeared when dinosaurs appeared, even though these parasites already existed long before that. Hence, even pre-programmed animals seem to learn/adapt. In other words: they seem to be able to reprogram their pre-programmed behaviour.
Most parasites are very poorly endowed neurologically.
Evolution depends upon variation (already existing or arising through mutation).
There is not reason not to think it is possible over evolutionary (geological) time periods.
Your argument is meaningless.

Take the viruses ebola and measles, as well as the protozoan Toxoplasmosis Gondii, they use dendritic cells as a trojan horse. This leads to their spread and survival, an end goal all animals pursue. Rabies makes dogs want to bite, and they manipulate humans to have intensive cravings for sex because, again, that's how the virus can spread. The raspberry leafmottle virus manipulates plant volatiles to attract aphids, which spreads the virus, influenza seems to make humans more sociable. In other words, all these organisms (or the non ‘living’ units of life viruses) have the same end goal.
They all have the same goal (of survival and reproduction) because the whole goal of biological evolution is doing survival and reproduction better, because what evolves is what ends up being the most in the next generation.
That is exactly what evolution uses to drive the evolution of organisms.
So, your examples actually support that an evolutionary conclusion, not yours.

Or take cancer, something we are pretty sure about it isn't 'alive'
Wrong again.
There are even cancers that have been transmitted for generations in dogs and Tasmanian devils.

These hallmarks of cancer (and more) are not simply analogous to spontaneous events, like throwing a deck of cards off the roof, and expect them to all land straight onto each other. It's possible, but in what universe? Cancer is like not simply 'uncontrolled cell division' that can simply be explained by random mutations alone. It's not simply like tipping over the first domino tile, because of open window that caused the wind to come in, just an accidental occurrence that caused it all, no, this is more like 1) an open a door, 2) walking to a new room, 3) put the key in, 4) turning the door knob, 5) walk towards the dominos and then 6) tip a domino tile over in that room. I can’t find a better word to describe these behaviours better than ‘intentional’. These are sequential steps taken by a biological organism, not unlike an animal. A cell 'wants' to survive'. I call this 'intentions' although it's possibly the wrong word, I hope you know what I'm trying to say. If not, sorry, but this is the best I could.
It doesn't sound like you have a very good understanding of the varieties of cancers and the current ideas about how it arises. It complex, I not going there. You should try finding out more before you go making blanket statements about all cancers.
Cells don't have mental intentions (not sure what you are actually talking about here, but cells don't think).
How cancer arises, though series of mutations accumulating in cells is actually pretty well supported.

I’m just not yet agreeing with the fact that cognition, awareness, and ‘ideas’ could not have been the reason behind some of these mimicry features in nature.
You probably meant idea or something like that, not fact.
If its accepted as a fact, then you really should be accepting it as real (kind of the definition of a fact).
You may not be agreeing, but you really have no explanation of why.

Your basic intellectual problem is not understanding natural selection.
This is actually easy to overcome. I understood natural selection by the fourth grade (about 9 years old).
Please go do that.
Here is a page of links on the subject.
 
  • Like
Likes gleem
  • #20
128
12
This is an infuriating combination of arrogance and lack of knowledge.
I’m merely pointing out what my conclusions are so far, based on the information that I have. That doesn't mean that if you're right about something, I should therefore agree with you, even though I don't understand it. I never said that I'm sure that I was right about anything, or that I thought that I was more right than anyone else on this forum, and I also never said you, or anyone else, was wrong about anything. I don't think I've deserved your negative ad hominem remarks, because I'm only here to express my thoughts, and I am open to learn from others, to learn from new facts, other facts, facts that make other facts irrelevant, facts that are more true.

In some ways like Lamarckism (a pre-Darwinian idea).
Empowering living things with special properties to explain things that you think are not normally explainable, when in fact they are.
In biology, these ideas were rejected 100-200 years ago.
I don't reject all parts of the basic idea behind Lamarckism. It has never been proven why a giraffe or a brontosaurus evolved a long neck (although I don't have a more plausible alternative than to reach for the leaves higher up in the tree), but one can't ignore 'epigenetics', which, even though it's not exactly synonymous to Lamarckism, has proven that environmental changes can affect an organisms genome, and these adaptations can be transmitted to the next generation. (See the ‘dig deeper’-part halfway this page)

Your basic intellectual problem is not understanding natural selection.
I don't understand what makes you think that natural selection can explain everything. What about sexual selection?

I said: "Why would humans have intentions, but (lower) animals not?" to which you replied:
Because of the lack of the necessary neurological substrates for deep thought in lower animals.

Humans, on the other hand, have something like 50-100 billion neurons. This allows them to have vastly more complex behavior , internal thoughts, and long term goals.
Konrad Lorenz (a zoologist who studied instinctive behavior in animals) concurred, suggested that evolutionary continuity exists between protozoa and humans. Similar claims might also be made about bacteria. Since all behavior involves information processing, all behavior would, under this theory, involve 'cognition'. Others take a different tack, defining cognition as the adaptive regulation of states and interactions by an agent with respect to the consequences for the agent’s own viability. With both such moves, all organisms, including protists and bacteria, are cognitive creatures. (An excerpt from this book).

You're making the assumption that human intentional behaviour is part of the complex, cerebral, cortex, the outer layer of our brain, but our motivations lie deep down, in the sub cortical brain area, the sometimes called 'reptilian brain'. The ventral striatum and basal ganglia have remained basically unchanged for over 500 million years, and it contains the mesolimbic pathway, dopamine, which is what motivates us in goal directed cognition, what helps us thinking and behaving towards an end, it’s the neurotransmitter that motivates us to do things that help us survive. The animal brain is processing historical events, learns from them, in order to better predict the future. Throughout evolution we’ve actively processed all kinds of different options, and then decide to execute that which suits us best.

In short: we’re basically still animals. The neocortex is just an extra layer on top of our animal brain. There's no clear boundary between humans and animals, because if there would be one, when do you suppose this hypothetical boundary arose, 2 million years ago? 100,000 years ago? No, creative, goal directed thinking evolved gradually, and that implies that it must have existed always, at least to some degree, all the way back to the time of single celled organisms.

When I said: "Or take cancer, something we are pretty sure about it isn't 'alive'", you replied:
Wrong again.
There are even cancers that have been transmitted for generations in dogs and Tasmanian devils.
I'm arguing that no cancers are alive. You're contradicting that by saying I'm wrong. Are you hereby making the statement that some cancers are in fact alive?
 
  • #21
BillTre
Science Advisor
Gold Member
1,462
3,169
I’m merely pointing out what my conclusions are so far, based on the information that I have. That doesn't mean that if you're right about something, I should therefore agree with you, even though I don't understand it. I never said that I'm sure that I was right about anything, or that I thought that I was more right than anyone else on this forum, and I also never said you, or anyone else, was wrong about anything. I don't think I've deserved your negative ad hominem remarks, because I'm only here to express my thoughts, and I am open to learn from others, to learn from new facts, other facts, facts that make other facts irrelevant, facts that are more true.
You came here asking why something was happening, you have been given many exampels of good explanations, you don't show any effort to comprehend what you're told and instead create your own fantasies.
This is not what PF is here for.

I don't reject all parts of the basic idea behind Lamarckism. It has never been proven why a giraffe or a brontosaurus evolved a long neck (although I don't have a more plausible alternative than to reach for the leaves higher up in the tree)
More plausible explanations have already been made (selection from the genetic variation with a breeding population.
You don't seem capapble to understanding it.

I don't understand what makes you think that natural selection can explain everything. What about sexual selection?
Sexual selection is a subset of natural selection schemes!


Konrad Lorenz (a zoologist who studied instinctive behavior in animals) concurred, suggested that evolutionary continuity exists between protozoa and humans.
Concurred means he agrees with me.
An evolutionary continuity does exist between protozoa and humans.
What's the point.

Since all behavior involves information processing, all behavior would, under this theory, involve 'cognition'.
This makes no sense. Does the information processing in some machine mean it involves cognition?

Others take a different tack, defining cognition as the adaptive regulation of states and interactions by an agent with respect to the consequences for the agent’s own viability. With both such moves, all organisms, including protists and bacteria, are cognitive creatures.
So this means a bacteria or a flower has cognition? Few people are going to agree with this without a pretty convincing argument. Cognition (as most people commonly understand it) requires a functioning nervous system.

You're making the assumption that human intentional behaviour is part of the complex, cerebral, cortex, the outer layer of our brain, but our motivations lie deep down, in the sub cortical brain area, the sometimes called 'reptilian brain'.
No I am not making this assumption. IT is quite different about how I think about these things.
Its the whole thing working together.
But thanks for speaking up for me! :oldsurprised:

No, creative, goal directed thinking evolved gradually, and that implies that it must have existed always, at least to some degree, all the way back to the time of single celled organisms.
This is a bad argument.
By this logic, flight which evolved gradually in birds and therefore it must have existed always all the way back to singled celled organisms.

I'm arguing that no cancers are alive. You're contradicting that by saying I'm wrong. Are you hereby making the statement that some cancers are in fact alive?
I can't believe you are saying this and want to be taken seriously.
What makes you thing cancer cells are not alive?
 
  • #22
128
12
So this means a bacteria or a flower has cognition? Few people are going to agree with this without a pretty convincing argument. Cognition (as most people commonly understand it) requires a functioning nervous system.
Those aren't even my words, so if you don't agree with it, you're not disagreeing with me, but with a renowned neuroscientist. What do you think of the nerve net of a cnidarian? It's really not so different from the behaviour of bacteria and protozoa, which is similar to how the human brain works. There's a different level of complexity, but the basic information processing system has remained exactly the same over the course of evolution. Taxic behaviors are initiated when receptors detect attractants or repellents. Some receptors are sensitive to the concentration of chemicals in the environment (chemoreceptors) while others are sensitive to light (photoreceptors). Behaviors guided by chemicals are called chemotaxic responses and those by light phototaxic responses. Tumbling is dependent on a bacterium’s momentary situation. When an attractant is detected, less tumbling occurs, resulting in running, which moves the bacterium closer to the substance. If a repellent is present, tumbling increases, changing the direction of motion, with the result being withdrawal. Whether tumbling or running occurs depends on the molecular output signals of the bacterium’s receptors; the strength of these responses is dependent upon the concentration of the stimulus (chemical or light). That's comparable with the pleasure principle in human psychology: dopamine incentivises us to repeat a behaviour that helps us survive, while pain motivates us to not repeat something, because it is a threat to our survival. These positive and negative reinforcers have remained basically the same for billions of years, and you can't really draw a boundary between human and lower animals, all the way back to single celled organisms, before multicellularity arose.

What makes you thing cancer cells are not alive?
So you are saying that cancer cells are alive. Can you please elaborate? This is a very interesting subject to me, since cancers are not on the tree of life. If you're saying that cancer is alive, you're saying that one individual cancer cell is alive (even though it is detached and no longer part of the body in the way the other cells are). Many of the strategies that cancers possess (see post #17) are shared with viruses (downregulating MHC expression, suppressing interferon signalling, inhibiting apoptosis etc.), so what's your perspective on viruses, are they also alive, just like cancer cells? And if not, how then would you explain their shared traits?
(Btw, should we start a new topic on this?)
 
Last edited:
  • #23
BillTre
Science Advisor
Gold Member
1,462
3,169
What do you think of the nerve net of a cnidarian? It's really not so different from the behaviour of bacteria and protozoa, which is similar to how the human brain works. There's a different level of complexity, but the basic information processing system has remained exactly the same over the course of evolution. Taxic behaviors are initiated when receptors detect attractants or repellents. Some receptors are sensitive to the concentration of chemicals in the environment (chemoreceptors) while others are sensitive to light (photoreceptors). Behaviors guided by chemicals are called chemotaxic responses and those by light phototaxic responses. Tumbling is dependent on a bacterium’s momentary situation. When an attractant is detected, less tumbling occurs, resulting in running, which moves the bacterium closer to the substance. If a repellent is present, tumbling increases, changing the direction of motion, with the result being withdrawal. Whether tumbling or running occurs depends on the molecular output signals of the bacterium’s receptors; the strength of these responses is dependent upon the concentration of the stimulus (chemical or light).
The bacterial behavior you are talking about (but provide on references or links for) has been analyzed at molecular detail. No aspect on intent or awareness have been shown to be involved, or are in anyway required for a reasonable explanation of it (postulating these features one of the original cause for your wandering arguments about how things evolved). Back to Occum's razor.

So you are saying that cancer cells are alive. Can you please elaborate?
Why waste my time with your stupid idea?
It's your extraordinary claim, you support it!

This is a very interesting subject to me, since cancers are not on the tree of life. If you're saying that cancer is alive, you're saying that one individual cancer cell is alive (even though it is detached and no longer part of the body in the way the other cells are).
A) Cancer cells are in fact on the tree of life. They branch off from the species in which they arose and chart their own independent evolutionary lineage (usually with the body of their original host) for a period of time before the host organism dies and they go extinct.
However, there are exceptional cases (one of which I have cited above and you conveniently ignored) where the cancer cells can be transmitted to other organisms in the same species (Tasmanian Devil face cancer, transmitted by fighting and a cancer passed among dogs via sex). These can LIVE for thousands of years.
NOT DEAD! NOT NON-LIVING!

B) Viruses can be considered alive by some definitions and non-living by others.
If you want to include in the definition of alive as being able to provide your own metabolic energy for growth and reproduction, then viruses would not be considered alive. They parasitize cells for their metabolic energy to do their reproductive thing.
On the other hand, viruses can be thought of as living entities that find a nice environment (inside of an appropriate cell for them) and grow and evolve their, while when not in the cell, they have a form evolved for transmitting them in a cell in which to reproduce (similar to a rather inert seed).
 
  • #24
DrClaude
Mentor
7,337
3,516
Time to close the thread.

Thanks to all that have participated.
 

Related Threads on How are parasites able to imitate other animals?

  • Last Post
Replies
8
Views
8K
  • Last Post
Replies
3
Views
15K
  • Last Post
Replies
6
Views
4K
Replies
1
Views
2K
  • Last Post
Replies
4
Views
12K
Replies
14
Views
5K
Replies
1
Views
2K
Replies
2
Views
2K
Top