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MartinV  Suspended Member (Idle past 5828 days) Posts: 502 From: Slovakia, Bratislava Joined: |
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Author | Topic: Descent of testicles. | |||||||||||||||||||||||||||||||||||||||||||||
MartinV  Suspended Member (Idle past 5828 days) Posts: 502 From: Slovakia, Bratislava Joined: |
Introduction:
Evolution is a directed process in which the neodarwinian forces of random mutation and natural selection play no role. Evolution is a predetermined process established by spirit and directed by internal forces of unknown characters. Materialistic biology has only a restricted capacity to solve the great mystery of evolution. Great scientists of the past coined the term "orthogenesis". The only scientists nowadays who continues in their work is professor John Davison with his "Evolutionary Manifesto". I would like to extend and support his ideas of "evolution governed by law" by some interesting thoughts about evolution of descent of testicles. This is the partial problem of evolution where on my opinion neodarwinism hasn't offered a coherent and plausible explanation. Obviously behind the descent of testicles are evolutionary forces that govern beyond "natural selection", and we are facing some evolutionary forces with their own rules. Mammalian species are often characterised by having testicles outside their bodies. Evolution of descent of testicles outside body has been a puzzle for evolutionary biology for a long time and the most common and accepted explanation for many years has been it was due to "cooling sperma". The history and enumeration of concepts explaining descent of testicles are to be found in the article by doctor Myers at Pharyngula:
What I want to stress is that the most common explanation is probably only a hypothesis with no scientific backing, because it is untestable:
A plausible, though at present untestable, scenario is that in the course of the evolution of mammalian endothermy, core body temperatures eventually reached levels at which spermatogenesis was disrupted I think it is not only untestable, but utterly dubious neodarwinian explanation. The problem cannot be solved by "cooling sperma" explanation, because:
We should take into the consideration that having testicles outside the body is a very dangerous place. The whole phenomenon can be observed in females too - descent of ovaries during evolution. But of course it is not as aparent and manifest as in males. What we observe is increasing structuring of mammalian bodies and their functions in the two poles. The head pole - responsible for individual orientation towards the world (here are almost all senses: vision, taste, hearing, smell) and the opposite pole responsible for reproduction. So the evolution of the descent of testicles into dangerous places outside of the body is directed by evolutionary forces that stand above random mutation and natural selection and cannot be reduced to them. It cannot be explained by neodarwinian formula "form follows fuction" either.
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AdminModulous Administrator Posts: 897 Joined: |
Thread moved here from the Proposed New Topics.
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subbie Member (Idle past 1254 days) Posts: 3509 Joined: |
Okay, darwinian evolution can't explain it, so you resort to some sort of directed process to explain descended testes. What, then, does a preference for descended testes tell us about the implied "director?" I posit that it tells us one of three things. The director is either:
a. a blithering idiotb. a woman, or c. a comedy writer. Those who would sacrifice an essential liberty for a temporary security will lose both, and deserve neither. -- Benjamin Franklin We see monsters where science shows us windmills. -- Phat
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Larni Member (Idle past 164 days) Posts: 4000 From: Liverpool Joined: |
Testicles being in a dangerous place is indead very odd.
But it is much more odd for them to be in such a dangerous position in a directed version of evolution, don't you think?
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nwr Member Posts: 6408 From: Geneva, Illinois Joined: Member Rating: 5.1 |
2. Birds often have temperatures of 42o Celsius and do not have "cooling spermatozoa" problems either:
I'm not currently persuaded that this is very relevant. Birds have taken a different evolutionary path than mammals, and this could include other changes in the reproductive system that make bird sperm able to withstand higher temperatures. I have not yet looked at the examples of mammals with internal testes. I'm not sure what you mean by "evolutionary forces that stand above random mutation and natural selection" (particularly the "stand above" part of that). If that "stands above" is intended to refer to an intelligent designer, then your own observeration that "having testicles outside the body is a very dangerous place" would seem to argue against such intelligent design. Let's end the political smears
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Granny Magda Member Posts: 2462 From: UK Joined: Member Rating: 4.0 |
Martin, you say;
The whole phenomenon can be observed in females too - descent of ovaries during evolution. But of course it is not as aparent and manifest as in males. If the process was directed (and you neglect to mention who your director might be, but I think I get the hint) then why lower the ovaries at all? Why not descend the testicles and leave the ovaries where they were? Of course, if the whole business evolved, it might make sense... Mutate and Survive
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macaroniandcheese  Suspended Member (Idle past 3927 days) Posts: 4258 Joined: |
i don't know anything about testicles, but i did do a science fair project about cetaceans and deep diving. when whales and dolphins dive into deep water for long periods of time, their blood nearly boils from the pressure and so forth. this is fine for the cetaceans, but dangerous for their fetuses. they have specific adaptations to protect their fetuses from the damaging effects of boiling hot blood. god help me it's been a long time ago, but look into it. maybe that'll give you some answers.
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Modulous Member Posts: 7801 From: Manchester, UK Joined: |
You mention two categories of counter-example.
Would you agree that if the animals that have internal testicles had either an alternative way of cooling their sperm, or had sperm that was not damaged by their body temperature then the cooling hypothesis still stands? The paper cited by PZ is quite interesting. The most parsimonious explanation for the pattern of scrotumless mammals is that the adaptation came no earlier than the common ancestor of golden moles and elephant shrews, with some independent adaptations in the monotremes and one group of tenrecs. Thus, as you say: external scrota is not the best solution...unfortunately it was the best one mammalian ancestors had. Evolutionary pressures are decreasing the numbers of mammal species with this less than perfect solution. There are many examples of less than perfect solutions, and I don't see how a paper that gives evidence of less than perfect solutions being replaced by better solutions helps your theory that this is not neodarwinian in nature.
What we observe is increasing structuring of mammalian bodies and their functions in the two poles. The head pole - responsible for individual orientation towards the world (here are almost all senses: vision, taste, hearing, smell) and the opposite pole responsible for reproduction. We also observed increasing structuring of mammalian bodies in areas that you have not designated 'poles'. How does observing an increase in structure contradict neodarwinian evolutionary predictions?
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jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
One thing that we tend to forget is that the filter is "was it good enough to live long enough to reproduce?"
That's it. Was it good enough to live long enough to reproduce? Fini! Often mutations can result in really dumb traits, pointless traits, ones that make you scratch your head in wonder. But that's just how it is. At some time in some species some mutation led to testicles descended. Did those species continue to reproduce? Was the mutation one that kept the individual from reproducing? The answer is "No, they reproduced." And that's it. The topic title begins with an implied fallacy, that some feature had to confer some advantage. That is simply a false assumption. The way the filter works is, anything goes unless it confers some disadvantage that is so severe that it prevents the critter reproducing. "Was it good enough to live long enough to reproduce? Yes!" Immigration has been a problem Since 1607!
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sidelined Member (Idle past 5908 days) Posts: 3435 From: Edmonton Alberta Canada Joined: |
MartinV
I think it is not only untestable, but utterly dubious neodarwinian explanation. The problem cannot be solved by "cooling sperma" explanation, because: 1. Some mammalian species have testicles inside their bodies and obviously haven't "cooling spermatozoa" problems.t 2. Birds often have temperatures of 42o Celsius and do not have "cooling spermatozoa" problems either: From this site http://www.ossh.com/birds/budgies/gensystm.html we get this explanation.
In common with their reptilian ancestors, the body temperature of birds fluctuates; it is believed that when it falls at night, sperm production can then proceed. From another site Picture Gallery - Infertile Felines | Fooling With Nature | FRONTLINE | PBS we get this interesting bit of information.
Florida's panthers are in serious trouble. And some scientists see unsettling parallels between these large cats and other mammals, including humans. Already an endangered species, Florida's panthers are plagued by low sperm counts, abnormal sperm, undescended testicles, thyroid problems, depressed immune function, and congenital heart defects. Only 30 to 50 of the large cats survive. Until recently, inbreeding was blamed for their fertility problems. But many scientists think that manmade chemicals, like pesticides, are the real culprits. The panthers' reproductive problems are the most severe of any cat species studied. Panthers have the lowest sperm counts, the lowest semen volume, and the highest number of abnormal sperm on record. In fact, over 90% of their sperm are abnormal. Most of the males also suffer from "cryptorchidism", meaning that one or both testes remain lodged in the abdomen. These undescended testes can contribute to sperm defects. They produce less sperm, and more defective sperm, than testes that descend properly into the scrotum. As a result of the defects, several of Florida's panthers are completely sterile and are unable to impregnate a female. These fertility problems are eerily similar to reports of undescended testicles and plummeting sperm counts in humans. By some estimates, although the science is controversial, human sperm counts have dropped 50% over the last fifty years. What's more, a study in England showed an approximate doubling in the rate of undescended testes in three-month old boys between the 1950's and 1980's. Similar increases in cryptorchidism have been reported in Scotland and Denmark, although not in the U.S. Since evolution does not require that our hypothesis be correct and only that the observed phenomena {undescended testicles} have no deleterious effects on the reproduction capabilities of the species. It may be dangerous but I do not think that there is much in the way of evidence that danger has ever slowed down the human capacity for sexual fitness. Edited by sidelined, : No reason given.
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MartinV  Suspended Member (Idle past 5828 days) Posts: 502 From: Slovakia, Bratislava Joined: |
I'm not currently persuaded that this is very relevant. Birds have taken a different evolutionary path than mammals, and this could include other changes in the reproductive system that make bird sperm able to withstand higher temperatures.
I have two points. I. If such changes were possible in reproductive system of birds I see no reason why such changes in reproductive system would not have been possible in mammalian lineages too. It is only speculation that it was somehow impossible. II. I think that the concept of sperms withstanding this or that temperature has two explanation. Either yours or the opposite one - sperms adapted to lower temperature in external scrotum. Now you consider sperms seeking lower temperature to be the source of their descent. The opposite view - their lower temperature as adatation on environment is also possible. I would say the second explanation is more in accord with the spirit of neodarwinism than the first one, but it is only my personal opinion.
I'm not sure what you mean by "evolutionary forces that stand above random mutation and natural selection" (particularly the "stand above" part of that). If that "stands above" is intended to refer to an intelligent designer, then your own observeration that "having testicles outside the body is a very dangerous place" would seem to argue against such intelligent design.
Not at all. We have two poles. The evolutionary "polarization force" do not care for survival advantage of species or for selfish gene's opinion. It do it job regardless of natural selection and do not care if it's outcomes are fittest or not. Maybe in some periods fittest were reptilians, dinos etc, but mammalians went their way. I do not deny "natural selection" but is only force removing extremities.
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Modulous Member Posts: 7801 From: Manchester, UK Joined: |
The way the filter works is, anything goes unless it confers some disadvantage that is so severe that it prevents the critter reproducing. That's not right, really. The critter and its descendants have to reproduce at a rate at least the same as the other critters in its deme, otherwise the proportion of critters with the mutation will decrease over time. The only exception to this is if the deme has not reached its maximum size with respect to its environment. If the deme has little competition for resources and can grow, then minor disadvantages are less likely to be penalized as much. However, once competition kicks up again, when there are limited numbers who get to successfully reproduce...any disadvantage relative to your deme-mates will tend to lead to the extinction of that disadvantage. A descent of testicles may well increase fecundity, an advantage in a competitive world and so it could spread as long as the accompanying survival disadvantage was not too severe. There may be better ways of increasing fecundity but scrota got there first, and once we had it we'd have to wait until a better solution came along. That seems to have happened to some mammals, but not all of us.
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jar Member (Idle past 394 days) Posts: 34026 From: Texas!! Joined: |
That's not right, really. The critter and its descendants have to reproduce at a rate at least the same as the other critters in its deme, otherwise the proportion of critters with the mutation will decrease over time. Sure, but there is still no purpose and is just the next iteration of the process. As long as they reproduce they continue. If eventually they become so small a minority that they cease to exist, then that is simply the way things went. Immigration has been a problem Since 1607!
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MartinV  Suspended Member (Idle past 5828 days) Posts: 502 From: Slovakia, Bratislava Joined: |
Granny Magda
If the process was directed (and you neglect to mention who your director might be, but I think I get the hint) then why lower the ovaries at all? Why not descend the testicles and leave the ovaries where they were? Of course, if the whole business evolved, it might make sense...
I don't see your point. The process of polarization involved both sexes.
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sinequanon Member (Idle past 2864 days) Posts: 331 Joined: |
Total speculation, but has the following been ruled out?
An external scrotum presents more direct health cues (size, smell etc.) for females wishing to reproduce. This would increase the probability of healthy offspring. Perhaps such an adaptation becomes more likely in animals with a longer reproductive cycle. I'm not a biologist, so if the above is garbage, a one line explanation would be enough. Thanks.
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