I always had this question in mind. I think, If humans find answer to it then we can trigger the next evolution of human specie.

What is the mechanism or structure responsible for evolution ? I don't mean the nucleus and the genetic code. because it's the consequence (the result) of evolution.

I mean all that I found right now as studies materials, treat only the consequences of the evolution, similarities between ancestors and descendants..etc

But what process triggers this evolution ? For example, the birds ancestor (which couldn't fly ), how did his cells generate genetic code to build new proteins needed to build new protein structures and organs and also to keep this evolution's result for next generations ?

Is there any current research on this matter ?

Thank you All for your explanation, but they treat only the case when there is only a certain length ADN chain and this chain will change in time to produce let's say "more effective population ".

but if we say that all the species came from one cell. than this cell had necessarily less ADN then we have now (for ex: it doesn't have yet ADN to code for hemoglobin and other complex proteins)

So my question was Where did the new ADN came From ?

This question came to me, when we were studying bacteriology and one bacteria had all my attention, it's the staphylococcus, they produce a coagulase that trigger the coagulation process to stop the blood stream so the phagocytes and immune cells can't reach there position.

Random mutations ? well random process can have some result in variation and deletion of existing species, but not in building new ADN chains.

don't tell me that the staphylococcus acquired the ability to produce this protein randomly, because if we do some math, the ADN is a base 4 code (there is 4 bases) and to produce an amino acid we will need 3 bases, so for 30 A.A protein we have only one chance in 4 power 90 without adding the random length and the random 3 dimensional structure, I know, even if there is billions of staphylococcus that will mutate all the time there will be nearly 0 chance to produce a protein that can action exactly with the prothrombin.

that's only for one protein.

I Know I have moderate knowledge in biology but I don't believe that errors in a code (mutations) can make it "better" or produce functioning mechanisms that can interact with other organisms, because if we say so, then we are just insulting our intelligence as human being, because we are saying that random process is making organisms that we, with our brain can't reproduce, the proof is we are still using antibiotics and didn't make our immune system more effective.

  • $\begingroup$ On a cellular level, Meiosis is the mechanism that creates genetic diversity in gametes. Sexual reproduction, though, is the largest contributing factor to diversity and the catalyst of evolution. $\endgroup$
    – MG_MD
    Commented Feb 12, 2016 at 16:59
  • $\begingroup$ Thank you for your comment MG_MD, I agree with you that Meiosis and Sexual reproduction contribute to diversity. But not necessarily to evolution because we all know that these two processes use what's already existing of genetic material (from parent cells), but a new specie need new genetic code to evolve. so My question is, what mechanism or structure that builds or generate this new code ? $\endgroup$
    – Allad1n
    Commented Feb 12, 2016 at 17:11
  • $\begingroup$ The mechanism is simply random changes. If the changes are neutral or beneficial, they stick around. If they are seriously detrimental, the changed creature doesn't survive to pass on the changes. $\endgroup$
    – jamesqf
    Commented Feb 12, 2016 at 18:33
  • 1
    $\begingroup$ Evolutionary biology is a large field of research that investigate the mechanism that dictate evolutionary processes. There are hundreds of papers published each month on evolutionary biology and the question is therefore way too broad. $\endgroup$
    – Remi.b
    Commented Feb 12, 2016 at 19:10
  • 1
    $\begingroup$ @Allad1n Your questions are very very basic questions in evolutionary biology (no offense) and you will get all the info you need by following the links I gave you. It will take you a few hours and you will have a much better understanding of what evolution is about (and about the role of mutations in evolution). Your question for the moment is just too broad for a StackExchange post. $\endgroup$
    – Remi.b
    Commented Feb 13, 2016 at 1:52

1 Answer 1


I strongly advice to have a look at an introductory source of information on evolutionary biology (such as Understanding Evolution by UC Berkeley). It will give you much more information.

Locus and Allele

Here are two definitions to start with:

  • A locus is a location on a chromosome. This location can be of any size. It can be a single nucleotide, a codon, a whole gene or even longer.

  • An allele is one variant at a given locus. When considering relatively short loci (say 1 nucleotide or 1 base pair (bp)), then the majority of loci have only one allele.

What is evolution?

Evolution is defined as any change in allele frequency in a population over time.

There are a number of "forces" that affect evolutionary processes. I picked the 3 most commonly considered: Mutations, Natural Selection and genetic drift

Natural Selection

Natural Selection is the process by which variants of genes called alleles are selected and therefore increase in frequency. This selection result from a differential reproductive success.

Natural selection occurs whenever the three following conditions are respected

  1. Individuals in a population varies in terms of a given trait
  2. This trait has some (additive) heritability. Here is one of the several posts that explain the concept of heritability. It might be slightly a post that is a bit advanced for you though but shortly speaking it means that offspring are more similar to their parents more than they are to other non-kin individuals in the population.
  3. The fitness varies (not necessarily linearly) as the trait varies.

Simple example:

  1. In a population, there are blue pens and red pens
  2. Reproduction is asexual and blue pens create other blue pens while red pens create other red pens.
  3. blue pens make more offspring than red pens.

In such situation natural selection occurs yielding the frequency of the blue pens to increase in the population while the frequency of red pens will decrease.

You may want to have a look at this post (although it might be too advanced) to understand the concept of heritability.


In the broad sense mutation is any change in the DNA sequence. Some changes are more likely to happen that other but in any case the likeliness of these changes to happen is not dependent on the consequence they will have on the phenotype (shortly speaking, phenotype is how an individual looks like) and on the reproductive success. So mutations occur randomly and the specific mutation that would be needed in the population may not occur. Therefore saying, if a trait is needed (in the sense of "if a trait would be beneficial"), then a mutation will occur to make this trait existing is wrong. Note that most mutations are deleterious (decrease the reproductive success) while few of them are beneficial (increase the reproductive success) and those that are beneficial are more likely to raise in frequency in the population.

Mutations can be a simple a "small change" such as nucleotide substitution, an nucleotide insertion and deletion or can be a "bigger change" such as a chromosomal duplication/deletion, a whole genome duplication and the duplication/deletion of a long sequence.

Mutations create the genetic variance on which natural selection selects the best variants. As a consequence natural selection decreases the genetic variance while mutations increases genetic variance.

Genetic drift

If the change in frequency of mutations would depend exclusively on natural selection, then I would not have said before that a beneficial mutation is more likely to raise in frequency but I would have said that a beneficial mutation will raise in frequency deterministically. An intuitive explanation of what is genetic drift can be found on this post. It will also allow you to understand why small population undergo more random change in frequency of their genes than are big population.


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