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发表于 17-2-2012 01:37 AM
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本帖最后由 bashlyner 于 17-2-2012 02:03 AM 编辑
根据科学上的解释，是先有蛋
The theory of evolution states that species change over time via mutation and sexual reproduction. Since DNA (deoxyribonucleic acid) can be modified only before birth, a mutation must have taken place at conception or within an egg such that an animal similar to a chicken, but not a chicken, laid the first chicken eggs. These eggs then hatched into chickens that inbred to produce a living population.[12][13] Hence, in this light, both the chicken and the structure of its egg evolved simultaneously from birds that, while not of the same exact species, gradually became more and more like present-day chickens over time.
Not any mutation in one individual can be considered as constituting a new species. A speciation event involves the separation of one population from its parent population, so that interbreeding ceases; this is the process whereby domesticated animals are genetically separated from their wild forebears. The whole separated group can then be recognized as a new species.
The modern chicken was believed to have descended from another closely related species of birds, the red junglefowl, but recently discovered genetic evidence suggests that the modern domestic chicken is a hybrid descendant of both the red junglefowl and the grey junglefowl.[14] Assuming the evidence bears out, a hybrid is a compelling scenario that the chicken egg, based on the second definition, came before the chicken.
This implies that the egg existed long before the chicken, but that the chicken egg did not exist until an arbitrary threshold was crossed that differentiates a modern chicken from its ancestors. Since this arbitrary distinction cannot be made until after the egg has hatched, one would have to first find the original chicken, then from this find the first egg it laid.
但必须认清一点那就是这个基因突变是经过很多代的，也就是某个生物可能只有 10% 像今天的鸡，下的蛋孵出了 11% 像鸡的生物，然后该生物下蛋生了个 12% 像鸡的以此类推，但是这个 increment 不一定是 1%，而对鸡的定义应该是 DNA来判定的，也就是说只要 DNA 上和其他鸡一样一样就可以了，如果还要扯进其他定义我想还是一样永远争论不完，比如说上面提到先有蛋才有鸡，但是先有鸡才有鸡蛋 |
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