Human Brain Evolution: The Influence of Freshwater and Marine Food Resources
Book file PDF easily for everyone and every device.
You can download and read online Human Brain Evolution: The Influence of Freshwater and Marine Food Resources file PDF Book only if you are registered here.
And also you can download or read online all Book PDF file that related with Human Brain Evolution: The Influence of Freshwater and Marine Food Resources book.
Happy reading Human Brain Evolution: The Influence of Freshwater and Marine Food Resources Bookeveryone.
Download file Free Book PDF Human Brain Evolution: The Influence of Freshwater and Marine Food Resources at Complete PDF Library.
This Book have some digital formats such us :paperbook, ebook, kindle, epub, fb2 and another formats.
Here is The CompletePDF Book Library.
It's free to register here to get Book file PDF Human Brain Evolution: The Influence of Freshwater and Marine Food Resources Pocket Guide.
Prior to that, in his book, Water, Weather and Prehistory, Robert Raikes described in how, in his hydrological surveys in Baluchistan and the eastern Mediterranean, he learned to read the antiquity or recency of fresh water springs from the adjacent presence or absence of suitably ancient stone tools! Water is also essential for keeping cool. Third, as this book makes abundantly clear, water is a source of aquatic plant and animal foodstuffs.
Waterways have been both deterrents to, and facilitators of, the dispersal of humans throughout Africa, across the Old World, and even into the New World. When much water was bound up on land in the Ice Ages, sea levels were lower than they are today. Previously submerged land bridges and insular stepping-stones appeared. As noted by Morwood et al. The presence of hominid remains in Iberia, both northern and southeastern Spain, certainly at 1 mya Aguirre and Carbonell, and possibly at 1.
It has been estimated that at times of lower sea levels, with the emergence of a few islands that are at present submerged, and of a small peninsula hanging off the southern shelf of Iberia, the maximum required water crossing would not have exceeded 5 km! In this context, I propose that swimming has been a hominid activity for over a million years.
The presence of Stegodon along with stone tools in Flores across the deep strait of the Wallace Line, and the occurrence of the Algerian elephantid Mammuthus in Iberia of the early Pleistocene, raise this question: when one considers the close and intimate relationship that exists between elephants and their mahouts in the Indian subcontinent in recent centuries, it is interesting to speculate as to whether a relationship existed between the movement of early humans and early elephantids across such straits as that between the Sunda Shelf and Flores.
If man and mammoths or man and Stegodon had a close relationship over a long period of time, it is not impossible that in some way, the Stegodon might have facilitated the crossing by humans of the Flores Straits , years ago. Moreover, could those North African mammoths have been associated in any way with the crossing by humans, from Ceuta and Morocco into Iberia, as long ago as 1.
Until recently, the evolution of early hominids in the savanna has been a strongly held, prevailing hypothesis. Yet some of these human characteristics would have made us hopeless savanna dwellers. On the other hand, a number of our features align us with marine mammals, even including face-to-face copulation. Hence the suggestion by Hardy and others was, modestly, that human ancestors must have spent more time in the water in the early days of human evolution.
Under these circumstances, it was proposed, humans lost most body hair, developed the layer of subcutaneous fat, and other features. In sum, it is widely accepted that the competing savanna hypothesis is no longer tenable, since I amassed much evidence against it at University College London in Therefore, I believe that scientists now have a duty to re-examine the evidence for a closer link between hominids and aquatic environments. We need new investigations such as by fresh, open-minded research students and post-doctoral fellows. Research on those traits should be updated.
I hereby express my personal tribute and admiration to them for conceiving and editing this volume. As always my warm thanks are extended to Mrs. Felicity Krowitz. Phillip V. Early human expansions into Eurasia: The Atapuerca evidence. Quaternary International — Gibert, J. Human Evolution 29— Hardy, A. Was man more aquatic in the past?
The New Scientist — Horrobin, D. London: Bantam Press. Morgan, E. The Aquatic Ape. London: Souvenir Press. The Scars of Evolution. The Aquatic Ape Hypothesis. Morwood, M. Fission-track ages of stone tools and fossils on the east Indonesian island of Flores. Nature — Stringer, C. Coasting out of Africa. Nature 24— Tobias, P. South African Archaeological Bulletin — Evolution of brain size, morphological restructuring and longevity in early hominids. In Principles of Neural Ageing, eds. Dani Su, A. Hori, and G. Walter, pp.
Amsterdam: Elsevier. Water and human evolution. Out There — Human Evolution — Verhaegen, M. Aquarboreal ancestors?
Trends in Ecology and Evolution — It is not until about 2. Much has been written about the high energy requirements of the human brain, and the need for high-quality food sources to fuel the adult brain. In fact, to insure normal growth of the fetal and infant brain, human babies need two dietary long-chained polyunsaturated fatty acids PUFA : DHA and arachidonic acid AA. Edible fats in the soft tissues of mammals and other land-based animals are less accessible, contain much lower amounts of long-chain PUFA, and are not consistently available.
Otherwise, it seems empirically evident that what limits human brain development and function today would surely also have limited its evolution. Others have also argued that hominins evolved in an aquatic, wetlands, or shorebased environment e. However, they have focused more on morphological and physiological adaptations to aquatic environments and have said little about the implications of such an environment for the hominin brain.
Most of the research studies dealing with the modern human brain and its high energy requirements have been published in journals and books focusing on metabolism or nutrition. Similarly, the morphology, ecology, and behavior of early hominins are not common topics in biochemical publications. Louis, Missouri. The hope was to further stimulate this interdisciplinary crossover, thereby fostering a better understanding of the essential prerequisites for evolution of the human brain. The papers presented at that meeting by Ian Tattersall, Michael Crawford, Stephen Cunnane, and Kathlyn Stewart are published here, along with those of other experts in these disciplines.
In Chapter 1 of the volume, Ian Tattersall provides the conceptual underpinning for the volume with an overview of the evolution of the hominin brain and, more particularly, the development of human cognitive thought. He indicates that the emergence of human cognition was a process of long adaptive stasis interrupted by short periods of cognitive advance. These cognitive advances were not linear and directed, but were acquired indirectly as part of changing human behaviors; in other words, through the process of exaptation.
One of these exaptive changing behaviors was the move toward consuming a higher quality diet. In particular, Tattersall links the emergence of Homo sapiens and the capacity for symbolic thought with evidence of opportunistic exploitation of coastal marine resources. Michael Crawford in Chapter 2 discusses the role of lipids, in particular DHA and AA, in brain development, focusing on the evolution of the eye and neural systems in vertebrates.
Crawford indicates how variety in lipid structure, with literally thousands of options when the various fatty acids are paired up in structural lipids, helped support evolutionary diversity. Nevertheless, DHA is the one constant in the visual and nervous systems in all organisms, attesting to its singular importance for signal transmission in these systems. In mammals consuming a terrestrial diet low in DHA and AA, as body size increased from very small rodents to massive savanna herbivores, with just one exception, relative to the rest of the body, brain size did the reverse — it shrank.
The exception is humans. The question is why. Stephen Cunnane Chapter 3 suggests that the cognitive abilities of the human brain were able to evolve because hominins not only accessed a reliable long-term supply of brain-selective nutrients, but because body fat evolved in the fetus and infant. Among primates, neonatal body fat is unique to humans.
Infant body fat not only provides a store of fatty acids for energy metabolism in general but is also an important reserve of DHA. Infant body fat is crucial as a source of fatty acids converted to ketones used by the brain whenever glucose is less available. Crawford, Cunnane, Brenna, and Muskiet and Kuipers have all provided arguments for the need for brain-selective nutrients, particularly DHA and iodine, for normal development of the neonatal and infant brain, for maintenance of the adult brain and, by association, for human brain evolution.
But what mechanism s actually triggered the encephalization process? They also point to the important role iodine plays in defending fragile lipid molecules such as DHA and AA from oxidation. Similar to other studies Crockford, , , they suggest that thyroid hormone and iodine were important components of a biological control mechanism that could potentially coordinate a suite of physiological, morphological, and behavioral changes, including the encephalization process.
These chapters provide persuasive evidence of the importance of brain-selective nutrients, particularly DHA and AA, in the successful development of the human brain and, by inference, the encephalization of the hominin brain. However, through morphological and behavioral analogy with extant apes, the diet of the earliest hominins is usually reconstructed as being based primarily on fruits and leaves.
The chapters by Erlandson, Stewart, Shabel, and Parkington provide data and inferences on the shift from a plant-based diet to aquatic and marine foods, which are much more abundant in brain-selective nutrients. Non-archaeological and archaeological evidence alike increasingly points to the use of coastal and freshwater; see Chapter 8 dispersal routes used by hominins. Dispersal along these routes implies exploitation of the available aquatic foods.
Stewart suggests that periods of aridity, increased consumption of freshwater resources, and isolation in areas of potable water produced circumstances favorable to the encephalization process. These foods all contain the brain-selective nutrients linked to encephalization. The suite of features that characterizes the skulls of the wetland durophages hard-object eaters is also exhibited by the robust australopithecines. John Parkington in Chapter 10 examines the emergence of H. He presents evidence arguing for the emergence of anatomically modern humans in southern Africa between about , and , years ago.
Almost all of these innovative assemblages are associated with shell middens near the southern African coast, indicating exploitation of coastal food resources. This volume builds on the work of others before us, and we gratefully acknowledge in particular the foundation work by Alister Hardy and Elaine Morgan.
We are also very grateful to Karen Chambers at Wiley-Blackwell for her ongoing support and enthusiasm in bringing this volume to fruition. Notwithstanding the patience and professionalism of other Wiley-Blackwell staff, we take full responsibility for errors and shortcomings. British Journal of Nutrition — Thyroid rhythm phenotypes and hominid evolution: A new paradigm implicates pulsatile hormone secretion in speciation and adaptation changes. Comparative Biochemistry and Physiology Part A — Crockford, S. Victoria: Trafford Publishing. Trends in Ecology and Evolution 17 5 — But is this a valid perspective?
There are good reasons, both theoretical and empirical, for thinking not. Let us start with the concept of natural selection itself. And natural selection can, by its very nature, only vote up or down on the reproductive success of the whole individual, and not on that of its individual features Tattersall, Still less can it focus on particular genes. Of course, some attributes may well make an absolutely critical contribution to reproductive success and may thus be individually subject to strong natural selection.
But it is entirely probable that such features are largely limited to those that directly relate to the reproductive process itself. It is, for example, very likely to be no accident that testis size is consistently greatest in those primate species with polygamous mating systems Harcourt et al. Chimpanzee males compete vigorously for females, and it is very highly plausible that their remarkably large testes result directly from a history of sperm competition.
Gorilla males, on the other hand, equally plausibly have smaller testes because an excess of metabolically expensive reproductive tissue is unnecessary where single males monopolize groups of females for extended periods of time. Similarly, most well-documented cases of sexual selection seem to be convincingly attributable to pressures for the origin and maintenance of the structures concerned. If an individual is not economically successful, it is highly unlikely to be reproductively successful and in this context, it may plausibly be argued that reproductive structures and activities are little more than a veneer imposed on the basic economic machinery.
The upshot is that natural selection of the kind that promotes population change, in contrast to population stability, probably typically acts to propagate a very large and diverse subgroup of reproductively superior individuals whose economic performance is not necessarily any more than adequate. After all, evolution is constrained in ways that preclude it from being a process of structural optimization Gould, ; and what succeeds most of the time is merely what works.
Reproductive success often will not involve being the best, but simply being good enough. If your habitat changes, you are much more likely to become at least locally extinct, or to migrate to a more congenial environment, than to adapt in situ Eldredge and Gould, Of more routine evolutionary importance, then — and certainly in promoting macroevolutionary trends and patterns — is economic competition among species as wholes.
There are, then, many reasons to suppose a priori that sustained directional change within lineages should be at least a rare evolutionary phenomenon. This expectation is borne out in the hominid case by examination of both the fossil and the archaeological records. Interestingly, despite the similarity in overall pattern, there is no synchronicity between major innovations in the biological and technological realms.
This only seems counterintuitive, though, until one realizes that it is uniquely within a species that anatomical novelties and technological inventions can occur Tattersall, The one common feature claimed for all of the very early fossil hominids is terrestrial bipedality Gibbons, But at about 2.
Solid lines show stratigraphic ranges. Many of the details of relationship are entirely conjectural, and this diagram shows most importantly that typically several different hominid species have coexisted at any one point in time. It is very much the exception that Homo sapiens is the lone hominid in the world today. The earliest stone toolmakers were, in other words, australopiths. The earliest stone toolmakers simply sought an attribute: a sharp cutting edge. But following an extended period of stasis, at about 1.
And, still wielding only crude stone tools, they rapidly spread far beyond Africa — a development made possible, it seems, by the new body form alone Tattersall, And again, this invention came a long time after a new kind of hominid had shown up in the fossil record, at about , years ago in Africa and shortly thereafter in Eurasia. There is, however, nothing in the archaeological record of these hominids that convincingly suggests they indulged in symbolic activities of any kind. Perhaps the most accomplished practitioners of prepared-core toolmaking were the Neanderthals, Homo neanderthalensis.
But while the Neanderthals had brains as large as ours, invented the burial of the dead, and probably took care of disadvantaged members of society, they too left little behind them to suggest unequivocally that they possessed symbolic consciousness Klein, These early European H. They decorated everyday objects and made notations on plaques of bone.
In short, they were us. And the material record they left behind is distinguished most notably from that of their Neanderthal contemporaries by its clear indications of a symbol-based mode of cognition. The highly characteristic bony anatomy that distinguishes modern H. Similarly, while anatomically modern H. This suggests that neither hominid species had an overall competitive advantage as long as the behaviors of both could be described as the most sophisticated extrapolations yet of the trends toward increasing brain size and cognitive complexity — in both lineages — that had preceded them.
But once H. With the advent of that phenomenon, the rules of the game changed entirely, and our species became an irresistible force in Nature, intolerant of competition from close relatives, and with the ability to indulge that intolerance. Certainly, the acquisition of modern human cognition was based on what had gone before and could not have happened without it. Despite clear evidence of sporadically increasing cognitive complexity among hominids over the last 2 million years, the nature of modern hominid cognition was not predicted by what preceded it; for, rather than being an incremental improvement, it represented a radical departure from tradition.
Various recent studies have pointed to hints in the earlier record of aspects of behavior that we commonly associate with modern humans; but very likely, these straws in the wind merely point to a complex cognition that was nonetheless not symbolic. In this context, it is important not to be misled by the undoubted increase in the average size of hominid brains over the past 2 million years or so Tattersall, This is, of course, true as far as it goes; and clearly, the extraordinary predisposition of members of the genus Homo to an increasing brain size certainly tells us something of fundamental importance about this group — something that we will have to understand before we can fully comprehend the evolutionary dynamic that was at work.
Illustration by Gisselle Garcia. What we are thus seeing in the apparently inexorable increase in the amount of metabolically expensive brain tissue over the Pleistocene is almost certainly a product of the preferential survival of larger-brained species in multiple lineages within the genus Homo Tattersall, , In any event, large brains by themselves are clearly not enough to assure symbolic consciousness.
Neanderthals had brains of modern human size; but, cognitively sophisticated as they doubtless were, they failed to leave convincing evidence of symbolic behaviors, certainly in pre-contact times. The earliest potential H. There was thus a very considerable time lag between the acquisition of modern anatomy and the expression of modern behavior patterns, putatively as long ago as 75, years in Africa, and most dramatically expressed in Europe following about 40, years ago. It has been eloquently argued that an enabling genetic change, whose effects were limited to brain activity, may have occurred and spread within H.
More likely, though, the neural capacity that underwrites the faculty for symbolic thought emerged with the substantial biological reorganization that accompanied the emergence of H. That potential must then have lain undiscovered and dormant for many millennia, until it was released by a cultural, rather than a biological, innovation.
The most plausible cultural releaser of this kind is the invention of language. Equally clearly, however, it represents a qualitative leap away from any other form of communication we know of. And it should be noted that, by the time that we have any good inferential evidence for language use, modern H. Language as we know it could never have been invented in the absence of appropriate vocal structures, but those structures had initially been acquired in another context entirely Tattersall, What is more even if it is in essence an interior conduit to thought, rather than a means of communication , language is a communal property.
This externality makes language more credible in the role of releaser than other suggested facilitators of symbolic thought, such as theory of mind Dunbar, which are internalized. Indeed, natural selection is not a creative force; it can only exert itself on variations that come into existence spontaneously. In this sense, any useful novelty has to arise not as an adaptation but as an exaptation Gould and Vrba, : as a feature that is not acquired in the context of any function to which it might eventually be put.
The vocal structures that make language possible are a prime example of this.
The bottom line here is that nothing arises for anything, and selection can only work with what is already there. Sometimes, novelties persist in populations for no better reason than that they do not get in the way. Looking at the matter from this perspective takes the origin of our vaunted human cognitive capacities out of the arena of gradual honing by natural selection, placing it instead in that of emergence Tattersall, , That is to say, an entirely new and unanticipated level of cognitive complexity was acquired as result of an entirely fortuitous coincidence of acquisitions.
The whole, in other words, is greater than the sum of its parts. Human cognition is without doubt the product of the human brain, which has had a long and accretionary evolutionary history reaching back to the very origin of the vertebrates. But although the record of vertebrate brain evolution yields a story of increasing cognitive complexity over hundreds of millions of years, nothing we know of in that history predicts symbolic thought. Evidently, at the origin of the anatomically distinctive species H. What that something was structurally is beyond my expertise to speculate; but recognizing the new capacity as a simple byproduct of the larger biological reorganization that produced morphologically distinctive H.
Indeed, a lag of this kind is entirely routine in terms of evolutionary process. Much of what I have said about the appearance of modern human cognition also applies to earlier innovations in the human lineage. And this is important, because while we are naturally fascinated by the question of what the critical addition to human brain function was that gave rise to H.
To build a complete picture, we therefore need to know not only what happened, but to understand the conditions that made it possible. The modern human brain and its normal cognitive functioning are known to be constrained by a host of dietary requirements, among them the availability of high-quality fatty acids see Chapter 4. Resources must thus have been available, and exploited, to sustain the hominid brain enlargement that substantially preceded the acquisition of symbolic cognitive processes in our own lineage.
Brain enlargement to modern size actually occurred independently in at least two hominid lineages those eventuating in H. According to Marean et al. The implication here is that under certain circumstances, the availability of resources such as those the Pinnacle Point people exploited may be vital to the survival of largebrained hominids. The case of the Iberian Neanderthals is different in one critical respect. However, at the same time, there is a complete absence of any direct cultural evidence suggesting that the hominids living at the sites were symbolic. Clearly, the existence of the energy-hungry large modern human brain, like that of the Neanderthals, must from the very beginning have been underwritten both by the availability and the exploitation of dietary sources yielding the nutritional elements necessary to sustain it see also Chapter 3.
But equally clearly, the ability to acquire such resources does not necessarily imply the possession of symbolic cognition. Les civilisations du Paleolithique inferieur en Languedoc mediterraneen et en Roussillon. In La Prehistoire Francaise, Vols. Paris: CNRS. A century of getting to know the chimpanzee. Nature — Deacon, H.
Cape Town: David Philip. Dunbar, R. Theory of mind and the evolution of language. Hurford, M. StuddertKennedy, and C. Cambridge: Cambridge University Press.
- Mystical Languages of Unsaying.
- Human Brain Evolution: The Influence of Freshwater and Marine Food Resources by Stephen Cunnane.
- The Fascination of Film Violence.
Eldredge, N. The sloshing bucket — How the physical realm controls evolution. In Evolutionary Dynamics, ed. Schuster, pp. New York: Oxford University Press. New York: W.
Punctuated equilibria: An alternative to phyletic gradualism. In Models in Paleobiology, ed. Schopf, pp. San Francisco: Freeman Cooper. Finlayson, C. On the importance of coastal areas in the survival of Neanderthal populations during the Late Pleistocene. Quaternary Science Reviews, —, doi Gould, S. The Structure of Evolutionary Theory. Exaptation — A missing term in the science of form. Paleobiology — Gibbons, A. New York: Doubleday.
- Mastering Sublime Text.
- LEGO Technic Robotics.
- The Apostolic Tradition: A Commentary (Hermeneia: a Critical and Historical Commentary on the Bible)!
- Encyclopedia of Medicinal Herbs;
- Surgery of the Ureter!
- Human Brain Evolution: The Influence of Freshwater and Marine Food Resources!
- Awful First Dates: Hysterical, True, and Heartbreakingly Bad;
Testis weight, body weight and breeding system in primates. Henshilwood, C. Middle Stone Age shell beads from South Africa.
Human Brain Evolution. The Influence Of Freshwater And Marine Food Resources
Science Science — Klein, R. The Human Career. Chicago: University of Chicago Press. The Dawn of Human Culture. New York: Wiley. Marean, C. Mayr, E. Taxonomic categories in fossil hominids. McDougall I. Stratigraphic placement and age of modern humans from Kibish, Ethiopia. Schick, K. New York: Simon and Schuster. Shubin, N. Your Inner Fish: A Journey into the 3. New York: Pantheon.
File:Human Aquatic wulaqubajixy.tk - Wikimedia Commons
Neanderthal exploitation of marine mammals in Gibraltar. Tattersall, I. Out of Africa again … and again? The origin of the human capacity. The abuse of adaptation. Evolutionary Anthropology — What happened in the origin of human consciousness? Anatomical Record New Anatomist B— An evolutionary framework for the acquisition of symbolic cognition by Homo sapiens. Comparative Cognition and Behavior Reviews — The morphological distinctiveness of Homo sapiens and its recognition in the fossil record: Clarifying the problem.
Thieme, H. Lower Palaeolithic hunting spears from Germany. Valladas, H. White, R. Current Anthropology — New York: Norton. White, T. Pleistocene Homo sapiens from Middle Awash, Ethiopia. Wood, B. The human genus. Since then and for the next 2. This vast Precambrian era was dominated by prokaryotes, the Cyanophyta blue green algae. Although photosynthetic, they show no intracellular detail.
The Vendian and Cambrian eras: Starting about million years ago, oxygen tension in the atmosphere rose above the Pasteur point, at which point aerobic metabolism became thermodynamically possible Holland, The 32 phyla we know today exploded into the fossil record in a short period of time thereafter and, in contrast to the prokaryotes, these fossils of eukaryotes provide considerable intracellular detail.
Each of these phases is an example of a change in environmental chemistry. First, chemical evolution as a by-product of the supernova became biochemistry some 3 billion years ago. This prolonged stasis is powerful evidence for two forces in evolution — natural selection and conditions of existence. There was little change in the design of the life forms despite the 2. This 2. When the Pasteur point was breached at which point oxygen metabolizing systems became thermodynamically possible, all the current 32 phyla appeared in the fossil record with a remarkable suddenness see Fig.
In eukaryotic evolution, intracellular structures appear in the fossil record. This intracellular detail is made largely of membrane lipid bilayers and their embedded proteins. The organization of cellular structures was made possible by membrane lipids. It seems likely that extensive speciation was not only a product of the rise in the oxygen tension but was also due to the cell structural complexity in which the lipids would have played an important role in generating intracellular specialization and then speciation. The state of cellular lipids leading up to the Cambrian explosion can only be a topic of conjecture.
Freshwater algae operate more anaerobically than seawater algae and synthesize little of the long-chain PUFA 20 and 22 carbons with 3—6 double bonds. Oxygen is required in the desaturation reactions converting shorter- to long-chain PUFA. The synthesis of the six double bonds in DHA requires six oxygen atoms without including the energy requirement for the chain elongations. These lipids are today used for the organization of complex cellular structures, that is, those in the reticular endothelium, mitochondrial electron transport systems, nuclear envelope, and plasma membranes that accommodate receptors, transporters, signaling systems, and antioxidant enzymes.
Oxidative metabolism brought with it the emergence of the PUFA, which would have provided a great wealth of novel architectural possibilities to evolve sophisticated organization and functional accommodation of proteins, a process not previously possible. The proteins are built with 20 words that are assembled into functional three-dimensional structures. T and p are functional determinants of the degree of unsaturation.
Moreover, a number of isomeric structures exist for several of the monounsaturated fatty acids and PUFA that give rise to an even greater variety of fatty acid combinations. In addition to the most common diacyl phosphoglycerides, there are choline and ethanolamine plasmalogens, cardiolipin, sphingolipid, and glycosphingolipid species which include the many galactocerebrosides found in neural tissue, and glucocerebrosides present in muscle and other tissues, contributing another considerable number of words to the lipid dictionary.
The language of DNA has 4 words nucleotides and that of proteins 20 words amino acids. The greater the number of words in a language, the greater the potential for expression and subtlety of meaning see Table 2. Cell behavior is known to respond to diet, temperature, and pressure. Moreover, throughout biology, the lipid composition of cells varies with temperature and pressure. With humans being homeothermic, the main variables become the diet and environment, and there is an abundance of evidence that diet, stress, exercise, drugs, and toxins affect the composition of the acyl groups, which are a major part of the alphabet of the lipid molecular species.
Membrane proteins are the receptors, signalers, and transporters. Again, there is likely to be a stoichiometric relationship between the small amount of ligand released in the free form and the membrane concentration. That stasis must say something about the stability or conservation of their DNA. So, in face of this rigidity, what caused the sudden aboutface with the creation of the 32 phyla during the Cambrian explosion? How was it that the DNA and its proteins which had done little, if anything, for 2.
One likely explanation is the enhancement of cellular energy production using oxygen. With metabolic events happening at greater speeds, there was probably more opportunity for the DNA to mutate. However, once the 32 known phyla were formed, no new phyla appear subsequently in the fossil record over the next — million years despite continued use of oxygen. The introduction of order and organization by the membrane lipids was then subject to different environmental conditions in chemistry, temperature, and pressure, thereby altering the language of the lipids, including the way they talked in domains around the proteins and other membrane structures including rafts and caveolae.
With the genome being well conserved in time and the proteins dictated by the genome, there has to be a variable to explain evolution at a chemical and molecular level. The ability of the environment to effect change can be witnessed both in the Cambrian explosion and in the very recent changes in human paradigm of shape, size and chronic disease, in one century. There can be little doubt that the lipids are just that kind of variable. This is an example of extreme conservation. The preservation of DHA in neural signaling systems which occurred despite the genomic changes over million years implies that DHA could actually have been dictating to the DNA rather than the more conventional view of evolution occurring the other way round.
Synthesis of docosahexaenoic acid involves peroxisomes. Bloom et al. The possibility that DHA has unique electrical properties not fully shared by either of the DPAs could provide the explanation Crawford et al. During evolution of the land mammals, this retention of DHA composition was associated with economy in brain size relative to the body, with a logarithmic reduction as they evolved larger bodies Crawford et al. Neural cells have a particularly high membrane content of DHA. This book documents the energy and nutrient constraints of the modern brain, highlighting the significant role of long-chain polyunsaturated fatty acids LC-PUFA in brain development and maintenance.
Human Brain Evolution. Based on studies of the modem human brain, certain prerequisites were needed for the development of the early brain and associated cognitive advances Crawford provides further emphasis for the role of essential fatty acids, in particular DHA, in brain development, by discussing the evolution of the eye and neural systems It is also an excellent selection for a grad student discussion seminar. Handbook of Polymers for Pharmaceutical. View Store.
Human Brain Evolution : The Influence of Freshwater and Marine Food Resources
Register now to get updates on promotions and. Or Download App. India's fastest online shopping destination. How can we help you? No result found for "OK". Please press enter for search. Visit Help Center. Trending Searches. Cart 0. Item s Added To cart Qty. If you are a new user Register login. Help Center.
Exchange offer not applicable. New product price is lower than exchange product price. Exchange offer is not applicable with this product. Exchange Offer cannot be clubbed with Bajaj Finserv for this product. Please apply exchange offer again. Your item has been added to Shortlist.
View All. Return form will be sent to your email Id:. Academic Texts. Humanities Books. Literature Books.