自然选择的含义并不难掌握。如果一个物种中每个个体的基因不同，这种区别会影响每个个体在其环境中的生存和生殖能力，在下一代中，带“好的”基因的个体就会比带“不太好的”基因的个体要多。随时间的推移，生物的群体就逐渐变的越来越适应其环境，有益的基因产生并传播到生物的群体，而有害的基因产生被清除掉(Coyne 2009)。
这个新达尔文的自然选择理论到底错在哪里，我在本书以后的章节中会谈到。但读者从上文中可以看出，达尔文理论中生物因资源相对不足而产生的为生存而竞争在新达尔文的自然选择理论中以无影无踪了。就是说新达尔文理论已经放弃了达尔文理论的关键部分。
谁听说过新牛顿定律？新欧姆定律？新达尔文理论就意味原来的达尔文理论不行了，它是要修改的一个理论。而不断修改一个理论，就是说明这些后来的理论也不成，漏洞太多，就像一件破衣裳一样补来补去。到了目前，这个新达尔文理论连错误的可能性都不存在，成为了伪科学。为什么这么说，我会在以后《为什么说新达尔文主义是个伪科学？》一文中再详细讨论这个问题。
1.综合理论的基本内容包括：（1）种群是生物进化的基本单位；进化机制的研究属于群体遗传学的范围。（2）突变、选择、隔离是物种形成及生物进化中的3个基本环节。这里理论认为，突变是普遍存在的现象，突变不仅能产生大量的等位基因，还可以产生大量的复等位基因，从而大大增加了生物变异的潜能。随机突变一旦发生后就受到选择的作用，通过自然选择的作用，使有害的突变消除，而保存有利的基因突变。其结果便造成基因频率的定向改变，这才使新的生物基因类型得以形成。群体的基因组成发生改变以后，如果这个群体和其他群体之间能够杂交就不能形成稳定的物种，也就是说，物种的形成必须通过隔离才能实现。
文献参考
Behe，M.J.(2007).The edge of evolution ：the search for the limits of Darwinism.New York，Free Press“Random mutation，natural selection，common descent ——three separate ideas welded into one theory.Because of the welding of concepts，the question，Is Darwinism true？has several possible answers.One possibility，of course，is that those separate ideas ——common descent，natural selection，and random mutation ——could all be completely correct，and sufficient to explain evolution.Or，they could all be correct in the sense that random mutation and natural selection happen，but they might be inconsequential，unable to account for most of evolution.It‘s also possible that one could be wholly right while the others were totally wrong.Or one idea could be right to a greater degree while another is correct to a much lesser degree.Because they are separate ideas，evidence for each facet of Darwin’s theory has to be evaluated independently.Previous generations of scientists readily discriminated among them.Many leading biologists of the late nineteenth and early twentieth centuries thought common descent was right，but that random mutation/natural selection was wrong.”Coyne，J.A.(2009).Why evolution is true.Oxford ；New York，Oxford University Press.
The idea of natural selection is not hard to grasp.If individuals with a species differ genetically from one another，and some of those differences affect an individual's ability to survive and reproduce in its environment，then in the next generation the “good”genes that lead to higher survival and reproduction will have relatively more copies than the “not so good”genes.Over time，the population will gradually become more and more suited to its environment as helpful mutations arise and spread through the population，whiledeleterious ones are weeded out.Ultimately，the process produces organism that are well adapted to their habitats and way of life.“Darwin，C.T.H.Huxley，et al.(1983).Autobiographies.Oxford Oxfordshire ；New York，Oxford University Press”In October 1838，that is，fifteen months after I had begun my systematic inquiry.I happened to read for amusement “Malthus on Population，”and being well prepared to appreciate the struggle for existence which everywhere goes on from long—continued observation of the habits of animals and plants，it at once struck me that under these circumstances favorable variations would tend to be preserved and unfavorable ones to be destroyed.The result of this would be the formation of new species.Montagu，A.and I.Asimov，Eds.(1984).Science and creationism.A Galaxy book.Oxford Oxfordshire ；New York，Oxford University Press.