Mrs. Darth Vader
04-24-2010, 07:10
Chapter 8 starts with a description of how fireflies attract each other for mating purposes. A moth sends out a scent that draws the opposite sex from a distance away. This chapter deals with the question of why sex is so important. Sagan then gives you a list of the plants and animals that could reproduce with out sex. Dandelions, salamanders, some lizards and some fish reproduce with out sex. This brings Sagan to ask; Why have sex since more than half of the history of life on earth asexual reproduction was how it was done? Sagan then describes how asexual reproduction is done. The cell divides in half and each half is duplicated making a whole. Instead of one, you have two. This kind of reproduction creates a spitting image of the first being. It is a carbon copy. Sort of like the many agent Smiths in the movie “The Matrix”. In asexual reproduction the monotony is hardly ever broken by mutation. This works as long as the environment is stagnant and repetitive. Evolution is slow under this form of reproduction according to the fossil evidence. From 3.5 billion years ago until 1 billion years ago evolution was slow because reproduction was done with out sex. One billion years ago sex was invented.
The introduction of sex meant instead of very slow evolution with a letter or a word here or there, you could suddenly have whole volumes. Each partner would come to the table with tried, tested and true DNA. Now the reshuffling choices were enormous. This allows for more rapid evolutionary change and adaptability. Now like a big casino many choices are available. Sexual reproduction upped the chances of survival. Now there would be more variety. In a changing environment or world, sexual reproduction is more advantageous. Sex according to Sagan goes hand in glove with Natural Selection. Sex provides the varieties. Natural Selection screens out the varieties that are best suited to survive. We even have a form of “ambidextrous” organisms that use both forms of reproduction. These organisms can do asexual and sexual reproduction. Some bacteria to aphids to aspens do both kinds of reproduction.
Sagan gives another reason that sex was invented and that is viruses and bacteria that invade a host organism could easily defeat an organism that does asexual reproduction. But with sex, the creations of antibodies can keep pace with the virus. This example could be easily compared to the cold war arms race. America invents some kind of missile defense system or a way to attack Russia (Soviet Union). The Soviet Union (Russia) finds a counter measure and a defense system to stop the would be attack by America. Hence the attack is stopped. The same is true of viruses. The virus tries to attack the host organism by mutating itself. The host defends it self by it’s antibodies who also mutate to out wit the virus. In this example sex is a preservative element. If we did asexual reproduction and each generation was the same as the last adinfinitum then eventually a virus would hit the right sequence and our number would be up. We would be wiped out. Sex randomly reshuffles the deck in the next generation which is enough to confuse the viruses. This is natures way of making sure we are not wiped out as a species.
Sagan then gives a biological explanation of the war between females and males as regard to monogamy verses many partners. In many species of reptiles, birds and mammals the female produces a small number of eggs per year. So from an evolutionary point of view it makes sense that the female is slow and picky as to choice of mates. She is devoted to nurturing both the fertilized egg and the young. The male on the other hand can have as much as hundreds of millions of sperm cells per ejaculation. A healthy male primate is able to ejaculate many times in a single day. So from an evolutionary point of view, the male strategy is to have many partners further spreading his seed. The male leans towards indiscriminate sex. The male does everything possible to get the female to comply from gentle persuasion to down right intimidation. In primates this shows up markedly. Human laws and culture tries to soften these blunt edges. Some societies are more successful than others. This does not imply this is lock step because in many species the female is the one that has many partners and it is the male who cares for the young. Birds score the highest marks for monogamy. 90% of birds are monogamous. Only 12% of monkeys and apes are monogamous. Our closest relatives did not score so high in monogamy. Wolves, jackals, coyotes, foxes, elephants, shrews, beavers, and miniature antelope are all monogamous. This monogamy means that they have a steady female that plays the role of wife. But these animals much like people have a mistress or two. They do sneak and mate on the side as well. Unlike humans this side mating does not end the “married” couple’s relationship. They both still stay together even though both the male and the female “cheat”. Sex here is portrayed as mechanistic. The whole goal is to get out the next generation and many offspring from the same parents if possible. Here the pleasure of sex is not portrayed as sinful but an evolutionary machine to tempt an organism into getting many young so when natural selection comes to bear some of your genes will survive.
Then Sagan does something interesting because sex is connotated with death. By having sex we loose immortality. Sagan tells the story of how salmon travel far against the currents in a heroic effort to get to spawning spot and in only a few hours later they die. Here Sagan says; “Nature is unsentimental. Death is built in.” And “ This is very unlike the far less dramatic asexual reproduction of beings like paramecia, where, pretty closely, remote descendants are genetically identical to their distant ancestors. The ancient organisms can with some justice be described as still alive. With all it’s manifold advantages, sex brought something else: the end of immortality.” Here Sagan sounds like many tales of Shiva who brings life, sex, love but also is the destroyer who brings death. Of course Sagan would remind us that in many myths truths are buried in murky metaphors and arrived at it quite by accident. Sagan has used mythical symbolism to make the hard science easier to understand. In the “Cosmos” series, he did the same when explaining our spherical universe being locked into a succession of births, deaths and rebirths. Sagan stood on Hindu temple grounds explaining about the “Big Bang” and the possible “Big Crunch”. Here Sagan reminds us that asexual beings in direct copying the parent and since the parent is still there when the splits occurs down the generations. They are considered immortal because death to these organism only comes from a lethal accident, getting eaten or when they run out of something like a food supply for example.
In sexual reproduction, death is built right in. The parent eventually dies leaving the world to their offspring but the offspring becomes parents leaving the world to their offspring and so on. Built in the DNA of sexual organisms is the “death gene” to say it in cliché. Sagan states how the genes are preprogrammed for your time to die. “By relaxing the extreme fidelity of it’s own replication, DNA can arrange, at the appropriate moment, for it’s own death”.
Sagan then ends the chapter by describing two things that happen in nature. One is chilling and disturbing. The other more warm and what would seem normal. The first thing Sagan describes is a form of cannibalism that is normal in nature. He describes where mothers eat their young because they are very nutritious morsels. Surprisingly this does not just occur during famines or overcrowding but at normal times. Birds and mammals for the most part do not do this but frogs and fish eat their young. Then Sagan talks about Beetles and Crocodiles who dote over their young and make sure they are put at a safe location to better their chances at survival. So here extreme cruelty in nature is shown. Next to gentle compassion.
The introduction of sex meant instead of very slow evolution with a letter or a word here or there, you could suddenly have whole volumes. Each partner would come to the table with tried, tested and true DNA. Now the reshuffling choices were enormous. This allows for more rapid evolutionary change and adaptability. Now like a big casino many choices are available. Sexual reproduction upped the chances of survival. Now there would be more variety. In a changing environment or world, sexual reproduction is more advantageous. Sex according to Sagan goes hand in glove with Natural Selection. Sex provides the varieties. Natural Selection screens out the varieties that are best suited to survive. We even have a form of “ambidextrous” organisms that use both forms of reproduction. These organisms can do asexual and sexual reproduction. Some bacteria to aphids to aspens do both kinds of reproduction.
Sagan gives another reason that sex was invented and that is viruses and bacteria that invade a host organism could easily defeat an organism that does asexual reproduction. But with sex, the creations of antibodies can keep pace with the virus. This example could be easily compared to the cold war arms race. America invents some kind of missile defense system or a way to attack Russia (Soviet Union). The Soviet Union (Russia) finds a counter measure and a defense system to stop the would be attack by America. Hence the attack is stopped. The same is true of viruses. The virus tries to attack the host organism by mutating itself. The host defends it self by it’s antibodies who also mutate to out wit the virus. In this example sex is a preservative element. If we did asexual reproduction and each generation was the same as the last adinfinitum then eventually a virus would hit the right sequence and our number would be up. We would be wiped out. Sex randomly reshuffles the deck in the next generation which is enough to confuse the viruses. This is natures way of making sure we are not wiped out as a species.
Sagan then gives a biological explanation of the war between females and males as regard to monogamy verses many partners. In many species of reptiles, birds and mammals the female produces a small number of eggs per year. So from an evolutionary point of view it makes sense that the female is slow and picky as to choice of mates. She is devoted to nurturing both the fertilized egg and the young. The male on the other hand can have as much as hundreds of millions of sperm cells per ejaculation. A healthy male primate is able to ejaculate many times in a single day. So from an evolutionary point of view, the male strategy is to have many partners further spreading his seed. The male leans towards indiscriminate sex. The male does everything possible to get the female to comply from gentle persuasion to down right intimidation. In primates this shows up markedly. Human laws and culture tries to soften these blunt edges. Some societies are more successful than others. This does not imply this is lock step because in many species the female is the one that has many partners and it is the male who cares for the young. Birds score the highest marks for monogamy. 90% of birds are monogamous. Only 12% of monkeys and apes are monogamous. Our closest relatives did not score so high in monogamy. Wolves, jackals, coyotes, foxes, elephants, shrews, beavers, and miniature antelope are all monogamous. This monogamy means that they have a steady female that plays the role of wife. But these animals much like people have a mistress or two. They do sneak and mate on the side as well. Unlike humans this side mating does not end the “married” couple’s relationship. They both still stay together even though both the male and the female “cheat”. Sex here is portrayed as mechanistic. The whole goal is to get out the next generation and many offspring from the same parents if possible. Here the pleasure of sex is not portrayed as sinful but an evolutionary machine to tempt an organism into getting many young so when natural selection comes to bear some of your genes will survive.
Then Sagan does something interesting because sex is connotated with death. By having sex we loose immortality. Sagan tells the story of how salmon travel far against the currents in a heroic effort to get to spawning spot and in only a few hours later they die. Here Sagan says; “Nature is unsentimental. Death is built in.” And “ This is very unlike the far less dramatic asexual reproduction of beings like paramecia, where, pretty closely, remote descendants are genetically identical to their distant ancestors. The ancient organisms can with some justice be described as still alive. With all it’s manifold advantages, sex brought something else: the end of immortality.” Here Sagan sounds like many tales of Shiva who brings life, sex, love but also is the destroyer who brings death. Of course Sagan would remind us that in many myths truths are buried in murky metaphors and arrived at it quite by accident. Sagan has used mythical symbolism to make the hard science easier to understand. In the “Cosmos” series, he did the same when explaining our spherical universe being locked into a succession of births, deaths and rebirths. Sagan stood on Hindu temple grounds explaining about the “Big Bang” and the possible “Big Crunch”. Here Sagan reminds us that asexual beings in direct copying the parent and since the parent is still there when the splits occurs down the generations. They are considered immortal because death to these organism only comes from a lethal accident, getting eaten or when they run out of something like a food supply for example.
In sexual reproduction, death is built right in. The parent eventually dies leaving the world to their offspring but the offspring becomes parents leaving the world to their offspring and so on. Built in the DNA of sexual organisms is the “death gene” to say it in cliché. Sagan states how the genes are preprogrammed for your time to die. “By relaxing the extreme fidelity of it’s own replication, DNA can arrange, at the appropriate moment, for it’s own death”.
Sagan then ends the chapter by describing two things that happen in nature. One is chilling and disturbing. The other more warm and what would seem normal. The first thing Sagan describes is a form of cannibalism that is normal in nature. He describes where mothers eat their young because they are very nutritious morsels. Surprisingly this does not just occur during famines or overcrowding but at normal times. Birds and mammals for the most part do not do this but frogs and fish eat their young. Then Sagan talks about Beetles and Crocodiles who dote over their young and make sure they are put at a safe location to better their chances at survival. So here extreme cruelty in nature is shown. Next to gentle compassion.