Mrs. Darth Vader
05-20-2010, 22:12
Chapter thirteen starts out describing a successful evolution of a species. Sagan uses the example of “what if” you are part of this particular species that evolved so well that you are “fat and sassy”. Any mutations here would be considered detrimental but natural selection continues to weed out mutations because these ones die or are eaten. Sagan paints this picture of this organism that is well suited in it’s stable environment but suddenly a catastrophe happens like asteroids hits this planet and the rising particles cools this planet freezing the lake you swim in or volcanoes spew up so much gas that it causes extreme green house effect so the planet warms and a pool of water is now where your nice desert environment used to be. May be some biological change has suddenly happened, like the food you eat has learned to camouflage itself so it is harder for you to find them or those that eat you have adapted to eat more of you. A germ comes and wipes many of you out. Here Sagan is giving examples of how a stable environment can suddenly change. The sudden change would change who is now better suited to the new environment. A once successful gene could suddenly be phased out by natural selection and a sequence that used to be considered a failure could be the new successful gene allowing you to survive. Natural selection would then favor the new mutation. Here nature plays the role of revolutionary because the once favored gene is replaced by the one that was the out caste during the stable times.
Sagan then talks about how every adaptation has a trade-off. Sagan then gives examples of different animals whose adaptive abilities has helped to solve one problem but got a new problem. Just that the new problem was less of a threat than the one solved.
“The ptarmigan’s white feathers provide superb camouflage in the Artic snows; but in consequence it absorbs less sunlight and greater demands are placed on its thermoregulatory system. The peacock’s gorgeous tail makes him nearly irresistible to the opposite sex, but also provides a conspicuous luncheon advertisement for foxes. The sickle-cell trait confers immunity to malaria, but condemns many to debilitating anemia. Every adaptation is a trade-off.” Page 242 “Shadows Of Forgotten Ancestors” by Carl Sagan.
From here Sagan explains why organisms specialize. Animals like penguins are excellent swimmers but they can not fly. Those that run well like the ostrich also can not fly. It seems that choices have to be made. The engineering for flying seem to conflict with those for swimming or running. It seems that natural selection forces a species in one direction or the other. Species never have the ability to do it all, like run fast, swim well and fly. Here real life is not like the movies when James Bond has Q make a car that does it all, swim (Submarine), drive, be a tank and fly. Over generalization of a species leads to extinction because usually the organism can only do each thing a little. On the other extreme of the spectrum, which is over specialization, is also just as bad, this too leads to extinction. When an organism is too narrowly specialized surviving in a restrictive environmental niche, they become extinct. They flourish for a short time but when things change they are unable to adapt and die. Sagan compares these organisms to a buggy-whip tycoon when the automobile came out.
Sagan then talks about how nature strikes a balance between the short term and the long term good of a species. So a species has to be generalized enough to allow for change and adaptation to take place. At the same time a species must be specialized enough to be good at specific tasks. The genes need to mutate often enough so that when the “right” mutation can come along that will improve the species. Since most mutations are harmful, the dice needs to be rolled enough times to get the “right” mutation to come up. This balance is a safeguard against extinction for the most part. If changes are of a more minor degree these mutations are enough to spare the species. The fact that we do sexual reproduction rolls the dice enough to keep up with most changes. No species can escape extinction of major catastrophes like many asteroids and comets hitting the earth at once. This kind of catastrophe is too fast and wide spread for any evolutionary process to survive.
Sagan then fallows the testosterone gene in a group of monkeys to illustrate why this gene must be in balance. Sagan then gives the example of these monkeys. If there is too little of the testosterone gene in the population, the monkeys might not be vigilant enough about defending themselves against predators. The monkeys might be too peaceful and passive to survive. On the other hand, Sagan gives the example if there is too much of the testosterone gene in the population of monkeys, they kill themselves off in dominance combat. Interestingly enough this balance issue comes often when talking about all facets of nature. The testosterone seems to be the most volatile and ticklish because of the severe consequences.
Nature tries to balance. If you have much testosterone to chase away strangers and predators, you need a lot of peace loving genes for keeping the peace and unity with in the group. Aggression is best used out ward. In ward it is destructive. These examples makes me think of current recent human history and today’s America. Why, because Africa has in recent history been riddled with warring factions so much that they are loosing and have lost populations so fast that one can ask; are they extinguishing themselves. I remember Bangladesh as a child and those very sad pictures of Africans with distendation. Now modern pictures of Bangladesh show a totally different group of people living there Indians from India. Where did the Africans go? Sadly the answer is they died. Was there too much testosterone among their problems? America is another country where people do not see themselves as a country or group. We see our selves as isolated individuals. Each American is very aggressive and see the other American as a competitor. Do we have too much testosterone? Will we extinguish our selves when there is no police to stop our aggression? Sagan reminds us of the balance in nature between the genes need to mutate to keep up with changes in the environment and too much mutation is lethal. So slow mutation is favored but not too slow.
Sagan then changes the subject to in breeding and incest. He goes into detail why it does not work. Even our protective knee jerk in society to hate it and call it sin and why this knee jerk genetically works in our best interest. The infant death rate skyrockets when siblings mate. John Paul Scott and John L. Fuller performed breeding experiments on pure breed dogs. Their findings proved that the pure breeds have more deformities and crippling defects than mixed breeds. The deformities were more severe when it was in the purebreds than the mixed breeds. This is based on rates and percentages. Obviously mixed breeds can suffer maladies to. It is just that the pure breeds have it happen more often. Charles Darwin said the same thing, that inbreeding leads to more defects. Here the lab results proves that it is better to have genes from different parents. This proves that the racists are wrong with evolutionary evidence from the lab. Sagan here like Darwin answers the racists claim of superiority of breeding with in the same race. This chapter shows that here people who are not racists are correct to not be. Evolution prefers many gene in puts from many choices. Sagan here does an excellent job of dispelling old myths about perfect pure breeds and master races. The lab is objective proof favoring neither side emotionally but it answers factually and dispassionately.
Sagan in this section deals with small group populations. Here Sagan explains why a female will cross into a strangers zone and mate overcoming the usual adversity to stranger tribes. Here the DNA in charge gives the urge to cross breed to prevent inbreeding with in a small group. This is how nature attempts to reconcile the tendency to inbreed when groupings are small. For any non-racist this is an excellent read so you are not silenced by Nazi breeding logic. Sagan is the scientist to come to your aid. Darwin does as well but Sagan speaks to the lay person.
Sagan then talks about how every adaptation has a trade-off. Sagan then gives examples of different animals whose adaptive abilities has helped to solve one problem but got a new problem. Just that the new problem was less of a threat than the one solved.
“The ptarmigan’s white feathers provide superb camouflage in the Artic snows; but in consequence it absorbs less sunlight and greater demands are placed on its thermoregulatory system. The peacock’s gorgeous tail makes him nearly irresistible to the opposite sex, but also provides a conspicuous luncheon advertisement for foxes. The sickle-cell trait confers immunity to malaria, but condemns many to debilitating anemia. Every adaptation is a trade-off.” Page 242 “Shadows Of Forgotten Ancestors” by Carl Sagan.
From here Sagan explains why organisms specialize. Animals like penguins are excellent swimmers but they can not fly. Those that run well like the ostrich also can not fly. It seems that choices have to be made. The engineering for flying seem to conflict with those for swimming or running. It seems that natural selection forces a species in one direction or the other. Species never have the ability to do it all, like run fast, swim well and fly. Here real life is not like the movies when James Bond has Q make a car that does it all, swim (Submarine), drive, be a tank and fly. Over generalization of a species leads to extinction because usually the organism can only do each thing a little. On the other extreme of the spectrum, which is over specialization, is also just as bad, this too leads to extinction. When an organism is too narrowly specialized surviving in a restrictive environmental niche, they become extinct. They flourish for a short time but when things change they are unable to adapt and die. Sagan compares these organisms to a buggy-whip tycoon when the automobile came out.
Sagan then talks about how nature strikes a balance between the short term and the long term good of a species. So a species has to be generalized enough to allow for change and adaptation to take place. At the same time a species must be specialized enough to be good at specific tasks. The genes need to mutate often enough so that when the “right” mutation can come along that will improve the species. Since most mutations are harmful, the dice needs to be rolled enough times to get the “right” mutation to come up. This balance is a safeguard against extinction for the most part. If changes are of a more minor degree these mutations are enough to spare the species. The fact that we do sexual reproduction rolls the dice enough to keep up with most changes. No species can escape extinction of major catastrophes like many asteroids and comets hitting the earth at once. This kind of catastrophe is too fast and wide spread for any evolutionary process to survive.
Sagan then fallows the testosterone gene in a group of monkeys to illustrate why this gene must be in balance. Sagan then gives the example of these monkeys. If there is too little of the testosterone gene in the population, the monkeys might not be vigilant enough about defending themselves against predators. The monkeys might be too peaceful and passive to survive. On the other hand, Sagan gives the example if there is too much of the testosterone gene in the population of monkeys, they kill themselves off in dominance combat. Interestingly enough this balance issue comes often when talking about all facets of nature. The testosterone seems to be the most volatile and ticklish because of the severe consequences.
Nature tries to balance. If you have much testosterone to chase away strangers and predators, you need a lot of peace loving genes for keeping the peace and unity with in the group. Aggression is best used out ward. In ward it is destructive. These examples makes me think of current recent human history and today’s America. Why, because Africa has in recent history been riddled with warring factions so much that they are loosing and have lost populations so fast that one can ask; are they extinguishing themselves. I remember Bangladesh as a child and those very sad pictures of Africans with distendation. Now modern pictures of Bangladesh show a totally different group of people living there Indians from India. Where did the Africans go? Sadly the answer is they died. Was there too much testosterone among their problems? America is another country where people do not see themselves as a country or group. We see our selves as isolated individuals. Each American is very aggressive and see the other American as a competitor. Do we have too much testosterone? Will we extinguish our selves when there is no police to stop our aggression? Sagan reminds us of the balance in nature between the genes need to mutate to keep up with changes in the environment and too much mutation is lethal. So slow mutation is favored but not too slow.
Sagan then changes the subject to in breeding and incest. He goes into detail why it does not work. Even our protective knee jerk in society to hate it and call it sin and why this knee jerk genetically works in our best interest. The infant death rate skyrockets when siblings mate. John Paul Scott and John L. Fuller performed breeding experiments on pure breed dogs. Their findings proved that the pure breeds have more deformities and crippling defects than mixed breeds. The deformities were more severe when it was in the purebreds than the mixed breeds. This is based on rates and percentages. Obviously mixed breeds can suffer maladies to. It is just that the pure breeds have it happen more often. Charles Darwin said the same thing, that inbreeding leads to more defects. Here the lab results proves that it is better to have genes from different parents. This proves that the racists are wrong with evolutionary evidence from the lab. Sagan here like Darwin answers the racists claim of superiority of breeding with in the same race. This chapter shows that here people who are not racists are correct to not be. Evolution prefers many gene in puts from many choices. Sagan here does an excellent job of dispelling old myths about perfect pure breeds and master races. The lab is objective proof favoring neither side emotionally but it answers factually and dispassionately.
Sagan in this section deals with small group populations. Here Sagan explains why a female will cross into a strangers zone and mate overcoming the usual adversity to stranger tribes. Here the DNA in charge gives the urge to cross breed to prevent inbreeding with in a small group. This is how nature attempts to reconcile the tendency to inbreed when groupings are small. For any non-racist this is an excellent read so you are not silenced by Nazi breeding logic. Sagan is the scientist to come to your aid. Darwin does as well but Sagan speaks to the lay person.