| Near-extinction Evolution Theory |
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Information AboutNear-extinction Evolution Theory |
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Futurist writer Allan Silliphant produced a television documentary in 1996 titled " Near Extinction, The Core of Evolution" which proposed and explained his concept of a central mechanism of mammalian, primate. and even human Evolution . The theory points to the mis-conception that large, complex creatures exist in populations of many thousands They seldom do. Most Great Ape s, including early Homo Sapiens existed, through most of their biological development, with a world-wide total population of less than 100,000 animals or men, perhaps as low as a few thousand or so, with no real threat to their species survival. Only when breeding numbers get down to just a few hundred in an entire region, and the population density is also very low, is the Species truly at risk. The thesis stresses that evolution works most effectively, at a point in time, when the largest cohesive breeding group of a species finds itself poised at the edge of extinction. There might be only as few as a half dozen breeding females, in an entire species Gene Pool . This "near miss" could change the physical traits of the population through random genetic drift, and it will automatically mirror the genetic makeup of the most active breeding male. The survival of that breeding male over time might depend on a few or even just one random trait. In this way, for example, a light coated Brown Bear , can greatly contribute to the emergence of a more "arctic adapted" carnivore like the Polar Bear . This might require five or six "near extinction" threats over a few hundred years, or a few thousand years at most. With large populations, the process is slowed by perhaps a thousand fold. World-wide species like many sharks can live unchanged for millions of years Certain animals, like Shark s, who have few natural enemies and can move without impediment over vast distances, seldom change and remain the same for tens of millions of years. In all probablility, there have always been several million living members of most common shark species. This is expressed in Biology as " Species Equilibrium ". Isolation is frequently the crucible Land mammals, especially Primate s and Carnivore s tend to live in discrete areas of geographical isolation, since they neither fly nor swim long distances, and are likely to find themselves in "island-like" territories where game (for carnivores), or mixed foraging food supply (for primates) or both (in the case of humans and their forebears) is adequate. They frequently must remain within a limited "island" territory. That "island" may be a "highland forest" area, surrounded by desert, or a more conventional island. In that isolation, population shrinkage can trigger rapid evolution. Brown Bear into Polar Bear example A highly evolved land animal, like a Brown Bear, might find itself locally reduced to a few dozen specimens on an arctic island. That likely happened as the last Ice Age came to an end, and the Bering Land Bridge receded into the sea. In that circumstance, a beneficial trait appearing in an Alpha Male or two may change the color, size, swimming ability, cold resistance, or aggressiveness of the group in just a few generations, assuming the traits are effectively passed on. Inbreeding can destroy a local sub-species, or trigger a new one The risk of inbreeding causing loss of genetic vigor can either terminate a line, or gradually stabilize after contact is made again with viable breeders not from the isolated "close call group". Just a little added genetic variety can save a weakened species, and keep the recent physical "change" in the genetic mix. A species of higher animal may only last a hundred thousand years or less without transitioning into a different closely related species. But the animal " Family " level of genetic traits might go on for several tens of millions of years. This "Near-Extinction evolution theory" is perfectly consistent with Darwin , and the modern concept of Punctuated Equilibrium but stesses the great importance of micro-sized populations permitting accidental traits to become a "a change in a useful direction" for the stressed group. In the crunch of "near-extinction", the changes are speeded by an exponential factor. It is a kind of genetic " Russian Roulette ", make or break, depending on the luck of the draw. HARD TO CONCEIVE HOW LARGE MAMMALS CAN EXIST IN SUCH SMALL NUMBERS The complexity of a highly evolved bird or mammal, like a California Condor , or the Florida Panther (a sub-species of Puma ), is difficult to fully reconcile to a million year species history when there are only 50 living members of a population of that animal group, but, in fact, that is the present reality. Unfortunately, most of this survival and evolution of large animals may end soon, as most large non-human animals that have constituted wildlife seem to be in a short terminal end-game status. Extinction may be as little as a generation away for at least 100 well known species. ACTUAL EXAMPLE, WRANGEL ISLAND MAMMOTHS For 6000 years all the living Wooly Mammoth s in the world, probably existed on a single small island, Russia 's Wrangel Island , where they rapidly became reduced in size by 70% from sheer food supply stress, managing to survive on very limited resources. These smaller mammoths hung on until civilization flourished in the time of King Tut , in Egypt (about 3500 years ago), 6000 years longer than elsewhere, and then finally, at their reduced size, passed into extinction about the time of the Eskimo s' discovery of the island. This suggest that the Eskimos may have been a major factor in the final extinction. SPECIES GO EXTINCT FREQUENTLY... GROUPINGS OF SOMEWHAT SIMILAR SPECIES, THAT ARE WIDESPREAD, TEND TO LAST FAR LONGER Central to understanding this mechanism of evolution, is the fact that all Vertebrate creatures share a common fundamental design. That basic design goes back to the first " Chordate " animals that became Cartilaginous Fish , Bony Fish , Amphibians , Reptiles , Dinosaurs , Birds and Mammals . Most of the complexity in the highest vertebrates, such as man, developed over hundreds of million years, by slow evolution involving billions upon billions of individual vertebrate creatures. But once that super complex genetic structure was evolved, the next stages in evolution were far less profound. These changes were related only to details and refinement. A Mouse , which is a generalized small mammal, is only slightly different from a man in basic body plan though quite different in detail and scale. Both are members of the Class Mammalia . Closely related species are much more similar than mice and men. Species at this highly evolved level come and go. They may only have to change 1/10th of 1 % of their genetic code to become a "new" species. Under stress conditions, they can easily be represented by just a few living members clinging to existence in a remote or unfriendly habitat. Larger groupings, such as Classes of vertebrate animals, like birds, mammals, etc. have never gone totally extinct. The dinosaur line which was long considered to be reptilian, is now merged with birds, and renamed "dinosauria". So even that group is no longer considered extinct by most authorities, as the term "dinosaur" is now a "Class" that lumps the dinosaurs together with the birds. The "Near Extinction" theory of evolution primarily applies to the " Species " level of Taxonomic Classification . The larger classification groups would tend not to go extinct unless a catastrophic geological, ecological, disease born, or planetary impact event were to occur. Any of these could cause a mass extinction of many species, on a near global scale. Even so, Near-extinction can greatly effect change in whatever surviving species re-populate the region, or the planet. One of the key factors in the rapid development of mankind, is that his numbers were always very small, and "Near Extinction" risk situations probably occurred hundreds of times in hundreds of local, or remote populations. This "Serial Extinction Threat" could bring about some noticeable change that might improve survival probability, of those with the new traits. Conversely, by not changing in a truly useful way, the same stress factors may deliver the Coup De Grace in the final extinction of that species. POPULATION BOTTLENECK CONCEPT This phenomenon has been characterized in a broad theoretical sense as the "Population Bottleneck" concept. The term "Near-Extinction Evolution", perhaps, better associates the concept to biological evolution in a more self-explanatory way. SEE ALSO |
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