I just finished reading the chapter about the Loch Ness Monster in the skeptical cryptozoology book Abominable Science! by Daniel Loxton and Donald R. Prothero. I will review it here.
Overall, the chapter makes a decent analysis of several of the evidence marshaled to support the existence of the Loch Ness cryptid, including the Surgeon's Photo taken by Dr. Robert Kenneth Wilson, who was really a gynaecologist, rather than a surgeon, but, hey, I guess most people don't think of the Loch Ness Monster, but something else entirely, when they hear the phrase "Gynaecologist's Photo". I agree with the chapter's conclusions that the Surgeon's Photo is likely to be a hoax, although I am still open to the possibility that it shows either a bird or an otter, as well as the same conclusion with regard to the Stuart Photo. I should note that when I first set eyes on both of these pictures as a child, they looked off to me, in some way. I suppose my intuition wasn't too far off the mark.
I also found the connection drawn between King Kong and the sighting by the Spicers enlightening, and I am inclined to think that this is quite a plausible suggestion. I think it is quite plausible that the release of the movie King Kong created an atmosphere during the time of the Great Depression which made prospective witnesses more likely to interpret sightings of common animals and disturbances of water in the loch in the light of the film, causing it to morph into a sauropod- or plesiosaur-like entity. I might opine here that the Spicer sighting could have been a group of otters seen crossing the road, which they interpreted as a sauropod-like beast since they might have been driving home groggily after seeing the movie.
These are the good parts of this chapter, in my opinion. Overall, I found the analysis of evidence, such as photos and videos, to be mostly rational and cogent, with one exception. The digital enhancement of the Rines flipper photograph was emphasized, and the original, unenhanced version was shown next to the enhanced version, in an attempt to show how a plesiosaur-like flipper was detectable in the enhanced version, but not in the unenhanced version. However, with me, this juxtaposition of the images had the exact opposite effect as that which was intended. Indeed, I could still clearly make out the shape of a flipper, even in the original, unenhanced version, and it is much too clear to me, I think, to be a case of pareidolia on my part.
But when it came to the evaluation of the plesiosaur hypothesis and the possible entry of prospective Nessies into the loch from the ocean, I was left somewhat disappointed. I did not find the argument put forth against a plesiosaur identity being a possible one for a prospective unknown creature in Loch Ness convincing. This is because the argument overlooked key fossil finds and paleontological studies, overlooked possibilities for plesiosaur behavior and physiology which seem plausible in light of those of relatives known to be extant, and flatly contradicted other portions of the same chapter on the issue of entry into Loch Ness from the sea.
It is stated that "They [plesiosaurs] were tropical animals, unsuited for the cold waters of the loch—and most plesiosaurs were marine animals, unsuited for freshwater in general". Yet a study published three years prior to this book found evidence that plesiosaurs likely were in possession of endothermy, colloquially referred to as "warm-bloodedness". And the claim that plesiosaurs were "tropical animals" is just false. Indeed, plesiosaur fossils have been found in several Upper Cretaceous formations in Antarctica. And while it is true that Antarctica in the Upper Cretaceous was warmer than it is today, it still had a climate not too dissimilar to Southern South America today, as one article covering an Antarctic plesiosaur fossil find noted. Considering the southern tip of South America, Tierra del Fuego, lies at a latitude that is more southerly than Loch Ness is northerly, I doubt that a plesiosaur adapted to the cold climate of Late Cretaceous Antarctic waters would have much difficulty adapting to the cold climate of Holocene Loch Ness waters.
And plesiosaur fossils have also been found in regions indicative of them having lived in a freshwater environment. Indeed, considering that numerous modern species which spend some or much of their life in marine environments, ranging from seals to cetaceans to Bull sharks to both saltwater crocodiles (Crocodylus porosus) and American crocodiles (Crocodylus acutus), have been known to inhabit freshwater environments, as well as saltwater environments, it seems rather dogmatic to me to state that plesiosaurs could not have done the same.
It is also stated that "Finally, plesiosaurs were air breathers. Any plesiosaurs in Loch Ness could be photographed several times an hour, each time they surfaced to breathe." This argument is stating that, as plesiosaurs were air-breathers, they would be regularly seen far more often breaking the surface of the water to take a breathe, rendering it unlikely that they would be able to remain inconspicuous for long in a lake such as Loch Ness. However, the idea has been previously brought forth that plesiosaurs might have evolved snorkel-like appendages on their heads that they might protrude above the surface of the water to take a breathe, which would not be as conspicuous. And while it is argued that such snorkels would, nevertheless, still be detected, another option awaits in the wings. And that is the aquatic cutaneous diffusion method of respiration.
Whether plesiosaurs were entirely air-breathers, or whether they respired through water, is not something that can be directly ascertained from the fossil evidence at hand. It is, in fact, entirely plausible that plesiosaurs could have been able to supplement their oxygen intake by aquatic cutaneous diffusion of oxygen -- i.e., absorbing molecules of oxygen directly from the water through their skin. Indeed, some turtles are known to respire in this way nowadays, and it is worth noting that, additionally, all humans once respired in this manner, as well, in utero, prior to their birth. If plesiosaurs were able to respire in such a manner, it would render them far more adapted to an aquatic lifestyle and ecological niche. Indeed, considering that extant turtles, which are less aquatic than plesiosaurs probably were (there is evidence that plesiosaurs were viviparous, giving birth at sea, constituting evidence that they were supremely adapted to a nearly completely aquatic existence), have evolved this ability, it would be surprising if plesiosaurs did not, likewise, do the same. A plesiosaur respiring through water via cutaneous diffusion of oxygen would not have a pressing or urgent need to routinely come to the surface to breathe air, meaning that it could conceivably remain hidden in a freshwater lake for a long stretch of time.
When discussing possible entry of the unidentified animals into Loch Ness from the ocean, it is stated, as well, that "The rivers and canals that flow into Loch Ness can be confidently ruled out as commuter routes for large monsters, broken up by shipping locks, or some combination." While it is true that, past a certain upper limit on size, an oceangoing creature would encounter considerable difficulty in navigating these pathways to the loch, it is worth noting that it is a confirmed fact that animals as substantially-sized as seals and porpoises have managed to do so. Indeed, it strikes me as rather perplexing that the author(s) spent so much of the rest of the chapter emphasizing the fact that these known marine animals have been known to make their way into Loch Ness previously with the purpose of using their presence in the loch to explain Nessie sightings. So why the double standard here? If porpoises and seals can swim into Loch Ness from the Moray Firth through the River Ness or the Caledonian Canal, why not putative Nessies, as well?
The statement about "large monsters" not being able to enter the loch is a red herring, as it is by no means a prerequisite that the creatures must already be large at the time that they enter the loch. The creatures could have made their way into the loch from the ocean when they were juveniles, perhaps no larger than salmon, or even smaller, and remained in the loch until they grew larger, rendering them trapped in the loch.
Indeed, this allows me to segue into another issue brought up in this chapter, that of the need to maintain a breeding population of creatures in the loch for eons. It is asserted that, to have a population large enough to breed, it would necessarily follow that there would not be enough food in the loch to sustain them, and the population would be too large for them to be able to remain hidden.
However, it is entirely possible that, rather than a breeding population of creatures having been extant in Loch Ness since the end of the Pleistocene, occasional vagrants have navigated their way into the loch from the ocean, and remained trapped there for a generation or two, before dying out. This would have the additional advantage of explaining why sightings seem to pique in some years in comparison with others. This hypothesis has come to be referred to as the 'Rogue Nessie' hypothesis, and it is covered delightfully well by writer Kurt Burchfiel in this article for StrangeMag magazine: http://www.strangemag.com/roguenessie.html
Finally, it is stated repeatedly that there were no sightings of a strange, unidentified creature in the same vein as Nessie at Loch Ness prior to the 1930s in the decimal Gregorian calendar. Yet this, too, is demonstrably false. Indeed, a newspaper report from the 19th century of the decimal Gregorian calendar reporting on a sighting of what seemed to the locals to be an anomalous large fish in Loch Ness stated that the locals had been inclined to think of the existence of such a besst in the loch as a reality for years, indicating that there was already a tradition of reported sightings of strange creatures in Loch Ness by this time.
And, even if it were true that Nessie sightings made their debut in the 1930s, this would not be a big deal, as, with the Rogue Nessie hypothesis, which postulates that Nessie is an oceangoing creature which occasionally swims into the loch from the open ocean, it is entirely plausible that a small population of these creatures could have entered the loch for the first time in the 1930s.
Overall, the chapter on Nessie, the Loch Ness Monster, the fourth chapter of Abominable Science!, contributes a decent analysis of much of the evidence purported to support this alleged cryptid, while having some deficiencies in the theoretical realms, in particular, when it comes to the arguments presented against a plesiosaur identity for Nessie and those presented against the creatures being able to remain undiscovered in Loch Ness.
The truth is that the palaeontological evidence from peer-reviewed scientific journals is, at worst, indifferent to the question of whether or not a plesiosaur identity is plausible for lake monsters in general, and the Rogue Nessie hypothesis shows that the objections with regard to population size and detectability can be surmounted by certain scenarios, the plausibility of which has been borne out by documented cases of marine animals making the switch to freshwater habitats.
It is worth noting at this juncture that all of the evidence and reasoning presented here applies to most reported lake cryptids, such as Champ of Lake Champlain, Ogopogo of Lake Okanagan, Storsjoodjuret or Storsie of Lake Storsjon, Selma of Lake Seljordsvatnet or Lake Seljord, Nahuelito of Lake Nahuel Huapi, etc.
References/External Links:
Endothermy in Plesiosaurs:
http://science.sciencemag.org/content/328/5984/1379
http://news.nationalgeographic.com/news/2010/06/100610-giant-sea-reptiles-warm-blooded-science/
Polar Plesiosaurs:
http://www.bioone.org/doi/abs/10.1671/0272-4634(2003)23%5B104%3ATEPACF%5D2.0.CO%3B2
http://www.nature.com/news/2006/061211/full/news061211-4.html
Freshwater Plesiosaurs:
http://www.tandfonline.com/doi/full/10.1080/14772019.2011.634444?scroll=top&needAccess=true
Saturday, February 25, 2017
Saturday, February 18, 2017
An Additional Note On Monozygotic Twinning And Individuality In Embryos
I mentioned earlier that it now appears that, when monozygotic twinning occurs, an original embryo is formed at time of egg-sperm fusion, and then some of its cells break off at the blastula stage to form a second embryo, while the original embryo continues to exist, and can regenerate its missing cells.
Even if this picture turns out to be erroneous, and it turns out that monozygotic twinning erases the existence of the original embryo, and leaves two new embryos in its wake, this would still not prove that, before the twinning event occurred, there was not one individual embryo.
As an analogy to help demonstrate this clearly, let us consider the fact that, in principle, every single cell could be taken from an adult animal, such as an adult human's, body and a clone made from each one of them. This would have the result that there would be trillions of clones of the original adult, while the original adult would cease to exist. But by no means does this, somehow, retroactively negate the existence of the original adult as one individual organism, as opposed to merely a not-yet-individuated clump of cells, prior to its dismantlement and concurrent cloning.
When it is realized that, in any case, regardless of what happens to the original embryo when it splits to form identical twins, triplets, quadruplets, etcetera in the monozygotic twinning process, the exact same process could theoretically happen to an adult, as well, the legitimacy of this argument against the individuality of early embryos during the stage in which monozygotic twinning is possible gets effectively flushed down the toilet.
Even if this picture turns out to be erroneous, and it turns out that monozygotic twinning erases the existence of the original embryo, and leaves two new embryos in its wake, this would still not prove that, before the twinning event occurred, there was not one individual embryo.
As an analogy to help demonstrate this clearly, let us consider the fact that, in principle, every single cell could be taken from an adult animal, such as an adult human's, body and a clone made from each one of them. This would have the result that there would be trillions of clones of the original adult, while the original adult would cease to exist. But by no means does this, somehow, retroactively negate the existence of the original adult as one individual organism, as opposed to merely a not-yet-individuated clump of cells, prior to its dismantlement and concurrent cloning.
When it is realized that, in any case, regardless of what happens to the original embryo when it splits to form identical twins, triplets, quadruplets, etcetera in the monozygotic twinning process, the exact same process could theoretically happen to an adult, as well, the legitimacy of this argument against the individuality of early embryos during the stage in which monozygotic twinning is possible gets effectively flushed down the toilet.
Cryptozoology And The Whole Science Vs. Pseudoscience Debacle
It is often claimed that cryptozoology is a pseudoscience. I have written on this topic before, but I feel the need to do so once more right now, as I have encountered arguments that have made me come to realize that it would be germane of me to do so.
First, we need to define "science" and "pseudoscience". Science is a means of obtaining information by formulating ideas called hypotheses, testing them to see whether or not they match the reality at hand, and keeping or discarding them based on how well they conform to the physical evidence at hand. This process should usually be able to be repeated by others. Pseudoscience is something that has a superficial veneer of being scientific, but does not meet the key criteria of being scientific. While it is still somewhat debated what those criteria are, the two dominant schools of thought are the logical positivist, or verificationist, philosophy of science, and the falsificationist philosophy of science, particularly the latter. Verificationism means that a hypothesis needs to be able to be proven, or verified, by obtaining sufficient evidence for it to be scientific, while falsificationism means that a hypothesis needs to be able to be disproven, or falsified, by obtaining sufficient evidence against it to be scientific.
Cryptozoological assertions meet both of those criteria. If I assert that "a large undiscovered hominoid species is inhabiting North America", this could potentially be verified by finding a body of this hypothetical unknown hominoid. Meanwhile, it could also potentially be falsified by painstakingly searching every square centimeter of North America and failing to find one scrap of evidence, one measly little body part, to support the assertion.
There is the issue that many self-proclaimed cryptozoologists insert intrinsically unfalsifiable supernatural assertions into the field, such as asserting that a given cryptid is a noncorporeal entity, such as a ghost or a phantom. Indeed, critics of cryptozoology often use the ubiquity of such supernatural-seeming reports of cryptids in the archives of cryptozoology to imply that the cryptids in question are inherently connected to the supernatural, and, thus, it makes sense to lump in cryptozoology with the study of paranormal phenomena, such as parapsychology. Yet this is a grave error. This is because many known animals have been associated with supernatural phenomena, as well, just as frequently, if not more so, than cryptids. From superstitions of black cats being associated with bad luck to reports of spectral hounds to reports of cows being abducted by aliens, all of the same criticisms that are leveled at reported hypothetical unknown species investigated by cryptozoology could equally be applied to known species whose existence is unquestioned, and, thus, render the entire field of zoology pseudoscientific due to its association with the supernatural.
So cryptozoology deals in hypotheses that are potentially both verifiable and falsifiable, and the association of the reported creatures it investigates with the supernatural does not render it pseudoscientific any more so than the association of other, known animals with the supernatural renders "mainstream" zoology pseudoscientific.
One more argument commonly leveled in favor of classifying cryptozoology as a pseudoscience is that it has not had any successes thus far. While this statement is certainly questionable, and, indeed, I highly doubt its veracity and deem it untrue, even assuming that it was true, this would not render cryptozoology a pseudoscience any more than the fact that no extraterrestrial life has yet been discovered outside of Earth renders astrobiology (the study of life, including extraterrestrial life, throughout the Universe) a pseudoscience. Indeed, many of the same claims regarding cryptozoology being pseudoscientific could equally be applied to astrobiology. Yet astrobiology is widely recognized as a legitimate branch of biology, as opposed to a pseudoscience. So what gives? Why the apparent double standard here?
I honestly think the reason as to why cryptozoology is widely panned as pseudoscientific is because it has been marred by association with poorly-done versions of it that actually are pseudoscientific in the popular media. From true believers who fail to think critically and investigate what evidence they think they have managed to obtain to those who assert a supernatural origin for certain cryptids, it is true that most of what masquerades as cryptozoology to much of the population is, indeed, pseudoscience. Much of the real scientific work going on in cryptozoology -- such as the peer-reviewed articles in the Journal of Cryptozoology, the studies of potentially undiscovered large marine species by Naish, Shanahan, and Paxton et al., the studies of reported Yeti hairs that found them to belong to bears by Bryan Sykes, Karl Shuker's books, The Cryptozoologicon, etc. -- is obscure, and does not receive as much attention as the pseudoscience that surrounds it.
As cryptozoology is not, inherently, pseudoscientific, by bringing the actual science going on in it to the forefront and drawing more attention to it, hopefully, its reputation among the scientific community can be salvaged, and serious scientific investigations of reported cryptids can occur on a wider scale than they currently are.
First, we need to define "science" and "pseudoscience". Science is a means of obtaining information by formulating ideas called hypotheses, testing them to see whether or not they match the reality at hand, and keeping or discarding them based on how well they conform to the physical evidence at hand. This process should usually be able to be repeated by others. Pseudoscience is something that has a superficial veneer of being scientific, but does not meet the key criteria of being scientific. While it is still somewhat debated what those criteria are, the two dominant schools of thought are the logical positivist, or verificationist, philosophy of science, and the falsificationist philosophy of science, particularly the latter. Verificationism means that a hypothesis needs to be able to be proven, or verified, by obtaining sufficient evidence for it to be scientific, while falsificationism means that a hypothesis needs to be able to be disproven, or falsified, by obtaining sufficient evidence against it to be scientific.
Cryptozoological assertions meet both of those criteria. If I assert that "a large undiscovered hominoid species is inhabiting North America", this could potentially be verified by finding a body of this hypothetical unknown hominoid. Meanwhile, it could also potentially be falsified by painstakingly searching every square centimeter of North America and failing to find one scrap of evidence, one measly little body part, to support the assertion.
There is the issue that many self-proclaimed cryptozoologists insert intrinsically unfalsifiable supernatural assertions into the field, such as asserting that a given cryptid is a noncorporeal entity, such as a ghost or a phantom. Indeed, critics of cryptozoology often use the ubiquity of such supernatural-seeming reports of cryptids in the archives of cryptozoology to imply that the cryptids in question are inherently connected to the supernatural, and, thus, it makes sense to lump in cryptozoology with the study of paranormal phenomena, such as parapsychology. Yet this is a grave error. This is because many known animals have been associated with supernatural phenomena, as well, just as frequently, if not more so, than cryptids. From superstitions of black cats being associated with bad luck to reports of spectral hounds to reports of cows being abducted by aliens, all of the same criticisms that are leveled at reported hypothetical unknown species investigated by cryptozoology could equally be applied to known species whose existence is unquestioned, and, thus, render the entire field of zoology pseudoscientific due to its association with the supernatural.
So cryptozoology deals in hypotheses that are potentially both verifiable and falsifiable, and the association of the reported creatures it investigates with the supernatural does not render it pseudoscientific any more so than the association of other, known animals with the supernatural renders "mainstream" zoology pseudoscientific.
One more argument commonly leveled in favor of classifying cryptozoology as a pseudoscience is that it has not had any successes thus far. While this statement is certainly questionable, and, indeed, I highly doubt its veracity and deem it untrue, even assuming that it was true, this would not render cryptozoology a pseudoscience any more than the fact that no extraterrestrial life has yet been discovered outside of Earth renders astrobiology (the study of life, including extraterrestrial life, throughout the Universe) a pseudoscience. Indeed, many of the same claims regarding cryptozoology being pseudoscientific could equally be applied to astrobiology. Yet astrobiology is widely recognized as a legitimate branch of biology, as opposed to a pseudoscience. So what gives? Why the apparent double standard here?
I honestly think the reason as to why cryptozoology is widely panned as pseudoscientific is because it has been marred by association with poorly-done versions of it that actually are pseudoscientific in the popular media. From true believers who fail to think critically and investigate what evidence they think they have managed to obtain to those who assert a supernatural origin for certain cryptids, it is true that most of what masquerades as cryptozoology to much of the population is, indeed, pseudoscience. Much of the real scientific work going on in cryptozoology -- such as the peer-reviewed articles in the Journal of Cryptozoology, the studies of potentially undiscovered large marine species by Naish, Shanahan, and Paxton et al., the studies of reported Yeti hairs that found them to belong to bears by Bryan Sykes, Karl Shuker's books, The Cryptozoologicon, etc. -- is obscure, and does not receive as much attention as the pseudoscience that surrounds it.
As cryptozoology is not, inherently, pseudoscientific, by bringing the actual science going on in it to the forefront and drawing more attention to it, hopefully, its reputation among the scientific community can be salvaged, and serious scientific investigations of reported cryptids can occur on a wider scale than they currently are.
Wednesday, February 8, 2017
Epithelial Tissues: An Arbitrary & Artificial Grouping That Ought To Be Split Up
Epithelial Tissues: An Arbitrary & Artificial Grouping That Ought To Be Split Up
Histology is the study of the bodily tissues of organisms and their cellular structure. In histology, animal tissues are conventionally divided into no more than four main types: Muscle Tissues, Connective Tissues, Nervous Tissues, and Epithelial Tissues. Muscle Tissues constitute muscles, which allow an organism to move. Connective Tissues are tissues that connect body parts to other body parts, and include bone, cartilage, and blood. Nervous Tissues constitute the nervous system, including the brain, spinal cord, and peripheral nerves, and are utilized by organisms to sense and be cognizant of their environments. It is often asserted that these four tissue types are natural groupings that arise from common shared characteristics of the tissues grouped within them. While this appears to be the case for Muscle, Nervous, and possibly Connective Tissues, I think it is not true for Epithelial Tissues. I think Epithelial Tissues are an arbitrary and artificial grouping of several disparate tissue types that humans have lumped together, without good cytological or ontogenetic justification. This article will explore Epithelial Tissues in depth, and arrive at an explanation as to why I propose that this unnatural grouping ought to be split into several different tissue types.
To start out, it shall be noted that all tissues in an adult animal are ultimately derived from one of three original germ layers that develop in an embryo during a process known as gastrulation: the Ectoderm, the Mesoderm, and the Endoderm. If two or more tissues in the adult were derived from the same embryonic germ layer, then this furnishes a natural basis for them to be grouped together. Indeed, analogously to phylogeny, if two or more adult tissues share a common ancestor, so to speak, in an embryonic germ layer, this is the ontogenetic equivalent of sharing a common ancestor in phylogenetics, and, thus, provides good reason to group them together, with the resultant tissue group being the equivalent of a monophyletic group in phylogeny.
On the contrary, if two or more adult tissues do not derive from the same embryonic germ layer, then grouping them together would be analagous to grouping together two or more species that do not share a most recent common ancestor together in phylogeny, rendering the resultant group the equivalent of a polyphyletic group in phylogeny. A notable example of such a polyphyletic grouping is Pachydermata, including usually large mammals with thick skin such as rhinoceroses, hippopotamuses, and elephants. Pachydermata, as a group, has now been abandoned by those who study the phylogenetic relationships of these mammals, as it has now been demonstrated that elephants actually share a more recent common ancestor with manatees and hyraxes than with either of the other two, hippopotamuses share a more recent common ancestor with cetaceans than with either of the other two, and rhinoceroses share a more recent common ancestor with horses than with either of the other two.
Now here's the kicker. While all tissues classified as Muscle Tissues are derived from the mesoderm, all tissues classified as Connective Tissues are, likewise, derived from the mesoderm, and all tissues classified as Nervous Tissues are derived from the ectoderm, tissues classified as Epithelial Tissues are derived from all three of the germ layers, endoderm, mesoderm, and ectoderm, with different subcategories of Epithelial Tissues being derived from different germ layers. This makes Epithelial Tissues analogous to a polyphyletic phylogenetic grouping, such as Pachydermata. Just as polyphyletic groupings have now largely fallen by the wayside in favor of the more natural monophyletic groupings in taxonomy, likewise, it makes sense for groupings naturally derived from shared ontogenetic provenance from one of the embryonic germ layers to take precedence over artificially-derived arbitrary groupings of disparate tissues from different embryonic germ layers in histology.
Additionally, it shall be noted that at least Nervous Tissues and Muscle Tissues share common aspects of physical appearance. For example, although the exact specifications may vary between different locations in the nervous system, all Nervous Tissues are composed of the same type of cells, neurons. Meanwhile, while there is variation between striated, smooth, and cardiac types of muscles, all muscle tissue, likewise, is comprised of cells that have an appearance and structure that is, overall, mostly similar.
The same cannot be said for Epithelial Tissues. There are numerous variegated types of Epithelial Tissues, and the cells present wildly varying morphologies. Epithelial Tissues are currently divided into seven subcategories based upon the shape and configuration of their constituent cells: simple squamous, simple cuboidal, simple columnar, stratified squamous, stratified cuboidal, pseudostratified columnar, and transitional. As shown in the juxtapositions of Figure I, Figure II, and Figure III below, these different subcategories of Epithelial Tissues look vastly different, as opposed to the subcategories of Muscle Tissues and Nervous Tissues, which, overall, present a pretty similar appearance.
Additionally, unlike Muscle Tissues, which are all universally internal, and Nervous Tissues, which are all universally internal, as well, Epithelial Tissues are found both externally and internally. The tissue on such widely separated locations in the body as the epidermis of the skin and the lining of the gastrointestinal tract is said to consist of Epithelial Tissues, for example. An often-asserted commonality shared by all Epithelial Tissues is that their job is to protect the body from external substances in the environment. However, this seems like a rather arbitrarily-chosen criterion to me. For example, adipose tissue, or fat, is classified as one of the Connective Tissues, yet it also plays a role in protecting the body from various putative threats in the environment, including trauma from impacts and cold, to name two. Yet it is classified among the Connective Tissues, rather than among the Epithelial Tissues. This shows that this shared characteristic of function is not enough to group the widely differing varieties of tissues grouped under the name of Epithelial Tissues into such a broad, overarching category.
Overall, to recap, Epithelial Tissues are derived from all three of the embryonic germ layers, meaning that they lack common ontogenetic provenance, unlike the other principal tissue types, they present a wide variety of cell structures and configurations, unlike the other principal tissue types, and the proposed criterion of common function is not enough to salvage the grouping, as, if applied logically and consistently, this same criterion would subsume other tissues that are not classified as Epithelial Tissues into the category, as well.
This is why I propose that, since Epithelial Tissues seem to me to be an arbitrary and artificial grouping of several unrelated tissues together by humans, it would be beneficial for histology to drop this grouping, and split it into several different groupings, with the result that there would be more than four principal types of tissues present in animals' bodies, just as phylogeneticists have now dropped arbitrary, artificial polyphyletic groupings in favor of natural monophyletic groupings.
Fig. I: The three primary types of neurons, cells that constitute what is classified as Nervous Tissue.
Histology is the study of the bodily tissues of organisms and their cellular structure. In histology, animal tissues are conventionally divided into no more than four main types: Muscle Tissues, Connective Tissues, Nervous Tissues, and Epithelial Tissues. Muscle Tissues constitute muscles, which allow an organism to move. Connective Tissues are tissues that connect body parts to other body parts, and include bone, cartilage, and blood. Nervous Tissues constitute the nervous system, including the brain, spinal cord, and peripheral nerves, and are utilized by organisms to sense and be cognizant of their environments. It is often asserted that these four tissue types are natural groupings that arise from common shared characteristics of the tissues grouped within them. While this appears to be the case for Muscle, Nervous, and possibly Connective Tissues, I think it is not true for Epithelial Tissues. I think Epithelial Tissues are an arbitrary and artificial grouping of several disparate tissue types that humans have lumped together, without good cytological or ontogenetic justification. This article will explore Epithelial Tissues in depth, and arrive at an explanation as to why I propose that this unnatural grouping ought to be split into several different tissue types.
To start out, it shall be noted that all tissues in an adult animal are ultimately derived from one of three original germ layers that develop in an embryo during a process known as gastrulation: the Ectoderm, the Mesoderm, and the Endoderm. If two or more tissues in the adult were derived from the same embryonic germ layer, then this furnishes a natural basis for them to be grouped together. Indeed, analogously to phylogeny, if two or more adult tissues share a common ancestor, so to speak, in an embryonic germ layer, this is the ontogenetic equivalent of sharing a common ancestor in phylogenetics, and, thus, provides good reason to group them together, with the resultant tissue group being the equivalent of a monophyletic group in phylogeny.
On the contrary, if two or more adult tissues do not derive from the same embryonic germ layer, then grouping them together would be analagous to grouping together two or more species that do not share a most recent common ancestor together in phylogeny, rendering the resultant group the equivalent of a polyphyletic group in phylogeny. A notable example of such a polyphyletic grouping is Pachydermata, including usually large mammals with thick skin such as rhinoceroses, hippopotamuses, and elephants. Pachydermata, as a group, has now been abandoned by those who study the phylogenetic relationships of these mammals, as it has now been demonstrated that elephants actually share a more recent common ancestor with manatees and hyraxes than with either of the other two, hippopotamuses share a more recent common ancestor with cetaceans than with either of the other two, and rhinoceroses share a more recent common ancestor with horses than with either of the other two.
Now here's the kicker. While all tissues classified as Muscle Tissues are derived from the mesoderm, all tissues classified as Connective Tissues are, likewise, derived from the mesoderm, and all tissues classified as Nervous Tissues are derived from the ectoderm, tissues classified as Epithelial Tissues are derived from all three of the germ layers, endoderm, mesoderm, and ectoderm, with different subcategories of Epithelial Tissues being derived from different germ layers. This makes Epithelial Tissues analogous to a polyphyletic phylogenetic grouping, such as Pachydermata. Just as polyphyletic groupings have now largely fallen by the wayside in favor of the more natural monophyletic groupings in taxonomy, likewise, it makes sense for groupings naturally derived from shared ontogenetic provenance from one of the embryonic germ layers to take precedence over artificially-derived arbitrary groupings of disparate tissues from different embryonic germ layers in histology.
Additionally, it shall be noted that at least Nervous Tissues and Muscle Tissues share common aspects of physical appearance. For example, although the exact specifications may vary between different locations in the nervous system, all Nervous Tissues are composed of the same type of cells, neurons. Meanwhile, while there is variation between striated, smooth, and cardiac types of muscles, all muscle tissue, likewise, is comprised of cells that have an appearance and structure that is, overall, mostly similar.
The same cannot be said for Epithelial Tissues. There are numerous variegated types of Epithelial Tissues, and the cells present wildly varying morphologies. Epithelial Tissues are currently divided into seven subcategories based upon the shape and configuration of their constituent cells: simple squamous, simple cuboidal, simple columnar, stratified squamous, stratified cuboidal, pseudostratified columnar, and transitional. As shown in the juxtapositions of Figure I, Figure II, and Figure III below, these different subcategories of Epithelial Tissues look vastly different, as opposed to the subcategories of Muscle Tissues and Nervous Tissues, which, overall, present a pretty similar appearance.
Additionally, unlike Muscle Tissues, which are all universally internal, and Nervous Tissues, which are all universally internal, as well, Epithelial Tissues are found both externally and internally. The tissue on such widely separated locations in the body as the epidermis of the skin and the lining of the gastrointestinal tract is said to consist of Epithelial Tissues, for example. An often-asserted commonality shared by all Epithelial Tissues is that their job is to protect the body from external substances in the environment. However, this seems like a rather arbitrarily-chosen criterion to me. For example, adipose tissue, or fat, is classified as one of the Connective Tissues, yet it also plays a role in protecting the body from various putative threats in the environment, including trauma from impacts and cold, to name two. Yet it is classified among the Connective Tissues, rather than among the Epithelial Tissues. This shows that this shared characteristic of function is not enough to group the widely differing varieties of tissues grouped under the name of Epithelial Tissues into such a broad, overarching category.
Overall, to recap, Epithelial Tissues are derived from all three of the embryonic germ layers, meaning that they lack common ontogenetic provenance, unlike the other principal tissue types, they present a wide variety of cell structures and configurations, unlike the other principal tissue types, and the proposed criterion of common function is not enough to salvage the grouping, as, if applied logically and consistently, this same criterion would subsume other tissues that are not classified as Epithelial Tissues into the category, as well.
This is why I propose that, since Epithelial Tissues seem to me to be an arbitrary and artificial grouping of several unrelated tissues together by humans, it would be beneficial for histology to drop this grouping, and split it into several different groupings, with the result that there would be more than four principal types of tissues present in animals' bodies, just as phylogeneticists have now dropped arbitrary, artificial polyphyletic groupings in favor of natural monophyletic groupings.
Fig. I: The three primary types of neurons, cells that constitute what is classified as Nervous Tissue.
Fig. II: The three types of Muscle Tissue and their characteristics and functions.
Fig. III: The seven recognized types of tissue currently classified under the label of "Epithelial Tissues", and the characteristic shapes of the cells that comprise them.
Friday, February 3, 2017
Why Time Travel Does Not Violate The First Law Of Thermodynamics
Time Travel And Conservation Of Energy/Mass/Matter:
The possibility of time travel, particularly to the past, has had numerous objections raised to it over time. Perhaps one of the most seemingly difficult to grasp is the objection that time travel, particularly to the past, violates the First Law of Thermodynamics, also known as the Law of Conservation of Energy and Mass/Matter (as energy and mass are equivalent, as shown by Albert Einstein's famous equation e=mc^2). This law states that energy can never be created nor destroyed, but can only be changed from one form to another. The reason some have equated this to ruling out time travel is the following: You are probably aware that you existed in the past, for example, one week ago. Even prior to your conception, although you were not alive, the particles that would later make up your body still existed, but were just scattered around in various places until they later coalesced to form you. So every person comes from matter that already existed, and has since the beginning of the Universe. Let's say you time traveled to the Late Jurassic period. Even though it is at least 144 million years before your conception, the energy that would later constitute your body exists, as tiny particles scattered throughout the world (and possibly throughout the universe -- who knows if some of the particles that would later make up your body came to Earth from outer space?). This, according to some, constitutes a violation of the First Law of Thermodynamics, since you now coexist in the same time period alongside the particles in the past that would later form you, with the result that more energy is being added to the Late Jurassic, while energy is being simultaneously removed from the present Quaternary period, constituting a violation of conservation of energy.
This is the crux of the argument against time travel from violation of conservation of energy/mass. However, I disagree with this argument, and this article will refute this argument by probing more deeply into the logical underpinnings at work beneath it.
The Law of Conservation of Energy simply states that, in a closed system, energy cannot be created or destroyed. A closed system is defined as a system in which no input from outside of the system is received by said system. The issue at relevance here is that different time periods are emphatically, demonstrably not closed systems, due to the simple fact that entities are always, constantly moving forward in time, and, therefore, entering new time periods. Someone inevitably entered Wednesday from the preceding Tuesday; they did not just magically, spontaneously pop into existence on Wednesday. Additionally, general relativity shows that space and time are inextricably woven together, as complementary components of a single, unified system known as spacetime. Therefore, since individual time periods are not closed systems, we do not have to apply the conservation law to particular periods of time, on their own. Considering the entire spacetime continuum, altogether, to constitute a closed system, someone popping into a past time prior to their conception, and existing alongside the particles that would later make up the ovum and spermatozoon that would eventually conceive them, would not be injecting more mass or energy into a closed system, as, without time travel into the past, both the putative time traveller and the particles in the past prior to the individual's conception that would later come to constitute their body already are coexisting in the spacetime continuum -- merely at different times. Travel to the past would merely bring their locations in spacetime into greater proximity with one another, as they are now at the same time, instead of at differing times.
As a thought experiment, let us now envision a wormhole connecting the year 1733 to the year 1725, for example. A person conceived in 1721 who is twelve years old in 1733 and four years old in 1725 would exist in both time periods. Now let's say the twelve-year-old goes through the wormhole, and arrives back in time in 1725 from 1733. When this happens, the twelve-year-old disappears from 1733, and reappears in 1725. While, if we were to consider each of the times, 1733 and 1725, as closed systems, this would, indeed, be in violation of the First Law, since we know that they are not closed systems, we know that this is not a violation. If we are to consider the entire spacetime continuum, as a whole, to be a closed system, then, there is no violation of the First Law of Thermodynamics inherent in this situation, as the disappearance of the time traveller from 1733 is balanced out by his/her subsequent reappearance in 1725. It's just like how removing a peanut from a bag of peanuts does not violate the law of conservation of energy/mass, as the peanut bag is not a closed system, but, rather, part of a closed system. Energy/matter can, indeed, be displaced within a closed system. And being displaced is completely different from being destroyed or created.
Energy can be displaced from one region of a closed system and arrive at another region in its stead. There is, theoretically, no reason that a person could not coexist at the same time as the particles which would later go on to constitute their physique, instead of existing at a different time from them. Only the location of the person along the time dimension would have changed, without creating any new energy, so this would not violate the Law of Conservation of Energy, and, by extension, of Mass and of Matter.
Overall, this argument against time travel, particularly time travel to the past, seems compelling at first glance, but, upon closer examination, its faults become readily apparent. It shall be noted that one may feel tempted to accept arguments against the possibility of time travel due to the fact that time travel contradicts common sense. However, there are numerous statements made by science, some of which are facts, which contradict common sense. Common sense is not always necessarily an infallible arbiter of truth. One must always tread with caution, and think critically about any arguments one finds, and parse them logically, even if they seem to appeal to intuitive notions of common sense. This is how progress is made, and new discoveries that potentially overturn paradigms occur.
The possibility of time travel, particularly to the past, has had numerous objections raised to it over time. Perhaps one of the most seemingly difficult to grasp is the objection that time travel, particularly to the past, violates the First Law of Thermodynamics, also known as the Law of Conservation of Energy and Mass/Matter (as energy and mass are equivalent, as shown by Albert Einstein's famous equation e=mc^2). This law states that energy can never be created nor destroyed, but can only be changed from one form to another. The reason some have equated this to ruling out time travel is the following: You are probably aware that you existed in the past, for example, one week ago. Even prior to your conception, although you were not alive, the particles that would later make up your body still existed, but were just scattered around in various places until they later coalesced to form you. So every person comes from matter that already existed, and has since the beginning of the Universe. Let's say you time traveled to the Late Jurassic period. Even though it is at least 144 million years before your conception, the energy that would later constitute your body exists, as tiny particles scattered throughout the world (and possibly throughout the universe -- who knows if some of the particles that would later make up your body came to Earth from outer space?). This, according to some, constitutes a violation of the First Law of Thermodynamics, since you now coexist in the same time period alongside the particles in the past that would later form you, with the result that more energy is being added to the Late Jurassic, while energy is being simultaneously removed from the present Quaternary period, constituting a violation of conservation of energy.
This is the crux of the argument against time travel from violation of conservation of energy/mass. However, I disagree with this argument, and this article will refute this argument by probing more deeply into the logical underpinnings at work beneath it.
The Law of Conservation of Energy simply states that, in a closed system, energy cannot be created or destroyed. A closed system is defined as a system in which no input from outside of the system is received by said system. The issue at relevance here is that different time periods are emphatically, demonstrably not closed systems, due to the simple fact that entities are always, constantly moving forward in time, and, therefore, entering new time periods. Someone inevitably entered Wednesday from the preceding Tuesday; they did not just magically, spontaneously pop into existence on Wednesday. Additionally, general relativity shows that space and time are inextricably woven together, as complementary components of a single, unified system known as spacetime. Therefore, since individual time periods are not closed systems, we do not have to apply the conservation law to particular periods of time, on their own. Considering the entire spacetime continuum, altogether, to constitute a closed system, someone popping into a past time prior to their conception, and existing alongside the particles that would later make up the ovum and spermatozoon that would eventually conceive them, would not be injecting more mass or energy into a closed system, as, without time travel into the past, both the putative time traveller and the particles in the past prior to the individual's conception that would later come to constitute their body already are coexisting in the spacetime continuum -- merely at different times. Travel to the past would merely bring their locations in spacetime into greater proximity with one another, as they are now at the same time, instead of at differing times.
As a thought experiment, let us now envision a wormhole connecting the year 1733 to the year 1725, for example. A person conceived in 1721 who is twelve years old in 1733 and four years old in 1725 would exist in both time periods. Now let's say the twelve-year-old goes through the wormhole, and arrives back in time in 1725 from 1733. When this happens, the twelve-year-old disappears from 1733, and reappears in 1725. While, if we were to consider each of the times, 1733 and 1725, as closed systems, this would, indeed, be in violation of the First Law, since we know that they are not closed systems, we know that this is not a violation. If we are to consider the entire spacetime continuum, as a whole, to be a closed system, then, there is no violation of the First Law of Thermodynamics inherent in this situation, as the disappearance of the time traveller from 1733 is balanced out by his/her subsequent reappearance in 1725. It's just like how removing a peanut from a bag of peanuts does not violate the law of conservation of energy/mass, as the peanut bag is not a closed system, but, rather, part of a closed system. Energy/matter can, indeed, be displaced within a closed system. And being displaced is completely different from being destroyed or created.
Energy can be displaced from one region of a closed system and arrive at another region in its stead. There is, theoretically, no reason that a person could not coexist at the same time as the particles which would later go on to constitute their physique, instead of existing at a different time from them. Only the location of the person along the time dimension would have changed, without creating any new energy, so this would not violate the Law of Conservation of Energy, and, by extension, of Mass and of Matter.
Overall, this argument against time travel, particularly time travel to the past, seems compelling at first glance, but, upon closer examination, its faults become readily apparent. It shall be noted that one may feel tempted to accept arguments against the possibility of time travel due to the fact that time travel contradicts common sense. However, there are numerous statements made by science, some of which are facts, which contradict common sense. Common sense is not always necessarily an infallible arbiter of truth. One must always tread with caution, and think critically about any arguments one finds, and parse them logically, even if they seem to appeal to intuitive notions of common sense. This is how progress is made, and new discoveries that potentially overturn paradigms occur.
Subscribe to:
Posts (Atom)