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I believe that the answer to this question would be that we cannot tell for certain that there were multiple origins of life. In order to determine that there were multiple origins of life, we would almost certainly need to look into the molecular biology side of these organisms, since convergent evolution makes it extremely likely that these differently ...


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It is interesting that all forms of life use the same genetic code. The nucleotides composing DNA and RNA are universal. Eric Lander, geneticist from Harvard/MIT cites this as evidence for evolution from a single ancestor. I think your instructor may be saying that it's possible alternative adaptations for initiation of life may have occured and perhaps not ...


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From jzx's answer, I thought of a possible answer to my own question. Maybe not producing identical twins all the time is a paradoxical evolutionary stable strategy for the following reason: Until recently in evolutionary history, the population remained constant when parents only had enough food to feed 2 children. Siblings didn't evolve to be fully ...


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What you describe could have happened under the right conditions. However, there are a few things you haven't considered. Because humans are especially altricial, always having twins would double the cost of children on parents. The benefit of sexual reproduction is immune diversity. So a population like this could be far more vulnerable to disease. So ...


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If we produced identical twins all the time then we'd completely lose genetic diversity which would, I assume, overwhelmingly compromise our adaptive capabilities. Don't forget, those identical twins then need to reproduce with other identical twins of others families. Moreover, and this is the more obvious explanation, as a consequence deleterious recessive ...


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Regarding the reference to Lynch, actually reading this paper is illuminating (http://www.pnas.org/content/107/3/961.full). What Lynch is saying with regards to degeneration is that he and others feel that modern technological advances may relax selection pressures, thus allowing the survival and reproduction of many who would otherwise be selected against, ...


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A small addition to what March Ho has mentioned in their answer. Fitness is not absolute; it is dependent on the present environment. Fitness has no meaning when the selection factor is not defined. You can consider a commonplace example: Can you, by just looking at an individual say how fit they are (of course I am not talking about those who are ...


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If I understand the question correctly, you are asking why random mutations (most of the non-silent ones are deleterious) cannot create information and improve the overall fitness of the organism. This is a common creationist statement, and has been shown to be incorrect in many different ways. The best way this can be shown to be false is by simply ...


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Change in genetic variance From what I have been taught, Natural Selection (or even Artificial Selection) is great for panning favorable genes from a species and bringing them to the fore, however, it does not introduce new genetic changes. Yes, you are pretty much right. In a given population, directional selection will ultimately reduce genetic ...


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You're right that the mutation must be in a germ cell in order to be passed on. Most errors are introduced during DNA replication (at a rate of around 10-10), which occurs a number of times between the zygote stage and mature gametes. This book estimates that there are 24 divisions between zygote and egg and 23n+34 divisions between zygote and sperm, where n ...


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There are indeed massive evolutionary control systems integrated into DNA. They constitute the major force for efficient change in living beings. Random DNA mutations are not as beneficial as controlled ones, you can see random single gene mutations at work in medical books: Anemia, cancer, cheese smelling sweat, no sweat glands, skin conditions, scales, ...



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