4.b.2.c) Dominant and recessive genes

The example of the evolution of the brakes is fascinating because it makes one reflect on the real nature and instrumental behavior of dominant and recessive genes.

Regarding the molecular mechanism in which dominant genes work, we wonder whether the character of dominant or recessive genes is adequately understood, or we are talking about an old-fashioned and rather basic concept which should be further defined based on, for example, its function within the framework of genetic evolution.

Concerning the Mendelian genetics examples, we have always speculated which of the genes would express if genes of both parents were dominant or recessive.

Example of technological evolution
Gene expression and significativity

We should bear in mind that the concept of dominant gene implies discrimination against a character in the new being. Therefore, we must examine the possible causes of this discrimination, which will finally lead to a better, faster, or safer evolution.

Let us consider the next intuitive example of the mendelian significance of dominant and recessive character. We have used mechanics in the evolution of cars as an analogy:

  • Two types of genes exist for a particular characteristic of our vehicle: gene type B and gene type B+A

  • Gene type B contains the technical specifications for the car's essential brakes.

  • Gene type B+A also incorporates, as well as the car's essential brakes, the technical specifications for ABS brakes (from now on referred to as ABS t.s.)

Regarding the significance and genetic expression of the genes, the possible Mendelian combinations of the two types of genes would be the following.

  1. The dominant genes are the less evolved ones

    Let us assume that in the event of faulty ABS t.s. brakes, neither of the brake systems would work (not even the essential one). However, it is imperative to guarantee the commercial reliability of the new car –including the avoidance of accidents– that the brakes must always work –either the basic or the basic + ABS.

    Thus, when installing ABS brakes, one must be entirely convinced that the technical specifications are correct. Only comparing the technical specifications in both gene sources can ensure this. If they coincide, we can be sure that practically no fault exists, as it would be difficult for them to coincide in one particular flaw.

    If one of the genes does not include ABS t.s. or if ABS t.s. appears in both genes but is not identical in both sources the result will be a lack of ABS brakes. Therefore, in case 1 the dominant gene is type B because its presence forces essential brakes to develop.

    Note that gene type B is the least evolved of the two in our example.

  2. The dominant genes are the modern ones

    Now let us consider case 2 where, in the event of faulty ABS t.s., the ABS brakes cease to function, but the essential brakes are not affected. Now, to guarantee the commercial reliability of the new vehicle the presence of ABS t.s. is not critical in both genes, as any fault would not harm the essential brakes or the car.

    Consequently, if B+A gene type exists in only one source, the car would be manufactured with ABS brakes, as if they are operational, it is just advantageous and poses no risk.

    In this last case, the dominant genes are type B+A; because if it is present, it will always manifest itself, and it is still more evolved (modern) than type B.

    As we can see, the dominant genes from the first case have become recessive genes, and the recessive genes have become dominant genes. It implies that a dominant or recessive character is relative to the functionality of the coupled source.

Now we add a new gene type B+A+M. This gene type has a more modern (powerful) technical specifications than ABS. In the example at case 1, we would find that gene type B+A would be a recessive gene compared with type B and a dominant gene with type B+A+M. On the other hand, for case 2, gene type B+A would be dominant linked with type B and recessive with type B+A+M.

In the development of a new being, a genetic sign –mark– is necessary to establish the kind of behavior. In other words, a particular DNA chain is compulsory. An example of a molecular mechanism that allows the incorporation of this genetic mark could be histones –pieces of ADN– studied by modern molecular biology.

Now let us discuss whether the dominant genes compensate for the recessive genes, or solely the dominant genes express. Here we faced the same dilemma - the answer is that it depends. In case 1, due to the character of type B, the result is primary brakes and if both sources are type B+A and no mistake is detected when verifying the technical specifications, the sources with recessive character type B+A could develop both essential and ABS brakes.

In case 2, the dominant character of gene type B+A develops two kinds of brakes and the recessive trait of gene type B, only primary brakes if it is present in both sources. Either way, we assume that nature has come across all kinds of cases.

All the above explanation is straightforward, although not as naive perhaps as the old-fashioned concept of the dominant or recessive gene. Moreover, much less simplistic than co-dominant and co-recessive, which continue not giving any argument about why genes are dominant or recessive under different conditions.

Do not forget that nowadays the academy is that the evolutionary process depends on a combination of random mechanisms and natural selection. This argument could apply to the evolution of insects, bearing in mind that millions and millions of baby insects are born in short periods; and although they have been evolving for millions of years, their evolution has not been particularly significant.

In fact, the evolution of man has just been the opposite. There have been only 2000 generations of human descendants (if one accepts that modern humans have only existed for 40000 or 50000 years); although few children are born per generation, the evolution of the human brain has been enormous.


The discovery of various pieces of ochre carved with geometric motifs in a South African cave over the Indian ocean leads us to believe that modern human behavior originated at least 77,000 years ago during the African stone age.

Examples of the oldest artistic activity known until now, the cave paintings in Spain and France, were much more modern but also more convincing.

El País 11-01-2002. Science / Journal of Human Evolution

How many combinations of direct descendants would be necessary for the Windows 3.11 code to evolve into the Windows 95 code using an evolutionary process based on random mutations?

How many combinations would be necessary for the technical specifications of essential car brakes to convert into ABS brakes in the evolution of cars?

We believe that we should change our philosophical ideas surrounding genetics and evolution. This minor change would lead to recognition of the intrinsic dynamics of genetic development of vital impulse systems.