Immediately after fertilization, an essential life process, the unicellular embryo (the zygote) resulting from union of two gametes, male and female, is divided into halves, these two cells are divided in their turn, giving birth to four cells, after eight, sixteen, …

You noted it, we spoke of "cells which are divided" and not of "cells which divide themselves", that not to hide creative entity (operator) who manages this process.

Besides, after their birth, the cells are identical and have the same evolution potentialities ; in other words, any cell can become a neuron, a liver cell, …, or a commonplace cell of skin.
On the other hand, cells cannot be differentiated and perform completely their task, without the processes organizations and information which take into consideration, besides their environment, the happy and unfortunate experiences which have "enamelled", which "enamel" the history of the life's phenomenon and of the individual.

Therefore, there is not mutations without available potentialities for their actualization (their materialization to become realities).
Let's remind, for example, that numerous bacteria have two mutation possibilities so as to enable them to survive during dramatic environmental changes. (cf. Barry G. Hall - Spontaneous point mutations ..., Genetics, 1997).
Hall concludes that "the selective generation of mutations by an unknown process is a solution which cannot and which must not be rejected.".
John Cairns also observed that actualization rate of certain potential mutations, is more high for bacteria who need it to survive, that for those who do not need it. (cf. The origin of mutants - Nature). 

Naturally, it is not processes which manage these activities of creation, these anticipations and these actualizations. Nevertheless we can admit "realism" (the existence) of biological processes organizations which give possibility to do or not, by respecting rigorous chronologies, actualization of such or such potentiality,
and it, by taking into consideration the lived experiences and anticipations.

But then, inevitable questions,
of where these processes are they coming and who is elaborating them ?,
who is master of the "sense" and of the time (of the durations) ?

We are therefore away traditional questions, and it is not enough to answer in a simplistic way, as geneticists make it nowadays, that the biological directives emanate from genetic heritage, this great book of the life.
Let us quote one of these answers :

"Genes are representative of a great library of information and directives, which contains about forty thousand books written in a language and an alphabet common to life's phenomenon.
Letters of this great book, are molecules which compose DNA.
This library is besides contained in a tiny sphere : the nucleus ; this one is separated from cytoplasm, this immense and mysterious factory where proteins are conceived and elaborated according to singular directives emanating from DNA, of proteins which are the true actors of the cells's dynamics ....
That is the proteins produced by a cell which, collectively, determine its evolutions and behaviors ... 
Difference between two cells which belong to two distinct families, as a brain cell and a liver cell, is resulting of the fact that every family of cells consults different genetic information and thus makes different proteins. No cell can read and use totality of the genetic information contained in the genes's library common to all body's cells." (cf. Specialized literature).

Certainly, we can consider the DNA molecules as letters of the life's book, nevertheless, and it, never is said, it’s because there are electromagnetic waves inexorably associated to atoms, that these molecules are memories and vectors of the genetic language (that’s why for example, there is no structural abyss between the inert matter and the living matter).
On the other hand, the cells, proteins, genes, neurons, activators, repressors, organs, ..., are not able to recognize, to read, judge, choose, ..., decide and to act.
Therefore, elaboration and diffusion of genetic directives (according to us of processes organizations) presuppose a creative entity, of transcendent order, implicated in any state of the beings and things, and notably able to interpret characteristics of the electromagnetic waves, this universal vectors of "sense". 

Let’s beware thus to scientifical monism, in particular, to comprehension expressed, during 1980s, by James Watson, co-discoverer with Francis Crick, of the DNA's structure :
"In every cell, approximately seven percent of all DNA is used to make proteins.... It seems very improbable that activity of ninety-three percent of remaining DNA is blocked by thousands other repressor proteins.
The common sense suggests that in our cells, ..., most of proteins that control the genes, act as activators and not as repressors." (cf. Molecular Biology of the Cell). 

Let's specify moreover, contrary to what is often announced, the information and the memorized processes organizations on DNA, to potential state, were never deciphered, and they cannot be it.
Geneticists are only comparing the molecular structures which compose DNA, what is very different !
However, all these processes organizations why do they show respect of a mysterious direction ? :
towards always more complexity.

The experiment imagined by Otto Loewi during 1920s, is also rich in information as for actualization (materialization) of potentialities :
"Otto Loewi took hearts of two frogs and he made a perfusion to this hearts with a saline solution similar to corporal liquid … Then he stimulated electrically nerves of the first heart, what changed its beating rhythm … When he removed solution of the stimulated heart and injected it in the other, this one also changed frequency of its beating as if it had been stimulated too, indicating that a substance had been emitted of the first heart and transferred to the second." (Cf. Joseph Ledoux - Neurobiology of personality).

Rich in information indeed, because we can consider solution injected in second heart, as a memory and a vector of processes organizations, to potential state, which enable biological effects ; that shows, once again, the realisme (existence) of potentialities waiting for their actualization.

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With regard to impact of the environmental constraints, on actualization (materialization to become realities) of the genetic and brain potentialities, let's quote coexistence of the Neanderthal men and Cro-Magnon men, two men types who are descended from the Homo erectus who is appeared in Africa more than 1,5 million years ago.
According to what is today recognized, we know that Neandertal man (Homo neanderthalensis) has evolved for about 170 000 years in Europe, less in the Middle East, for to disappear suddenly and mysteriously, approximately 30 000 years ago ; so, he lived probably for 5 000 years, with Cro-Magnon man, our direct ancestor who arrived in Europe here is 35 000 years.

Scientifical discoveries enable also to believe that the small morphological differences which characterize them, are old of 600 000 years, and that their adaptation power concerning extreme climatic conditions that they have known, reveales brain potentialities comparable to ours, notably faculties which enable previsions.
So much facts which show that these two men kinds, have been fruits of different actualizations of similar genetic potentialities, concerning body and psyche,
different actualizations, evidently, on account of specific environmental constraints and of distinct social conditions.
Thus, we understand better why apparently similar individuals can be more or less creative !

Why for example, shape of the stones hewed by the Neandertal men to make tools, has little changed it seems, during  thousands years, while for that the Cro-Magnon men ceaselessly were innovating.
If we consider the jewels, difference is even more revealing ; oldest known human ornaments would belong to Cro-Magnon men (some specimens of extremely rudimentary jewels, some fragments of flints and bones marked by regular streaks or chevrons, are nevertheless attributed to neandertal men).
Observe that jewel has no functional value, it’s a sense vector that presupposes abstraction capacities since it is made to bring to light a social status or an idea which we have of us.

Other numerous evolutions of our ancestors's psyche, although they seem commonplace, are also remarkable ; let's quote only two examples :

- Researchs, in Middle East, showed that about 12 000 years ago, tribal populations have acclimatized some plants until then wild, and gradually have "improved" their production.
Certainly this new behaviors was necessary for satisfying vital needs, however they would not have been possible without a wide range of brain potentialities which allow to observe, recognize, judge, …, to anticipate and create. 

- On both sides of the Atlantic Ocean, in different epochs and distinct places, some civilizations having no contact, showed of similar actualizations of alike brain potentialities ; it has been so for pyramids construction in Africa and in Mesoamerica.
Let's quote the resemblances between most old Egyptian pyramids, and pyramid with floors built, about 4600 years ago on the site of Caral, in coastal desert of Peru (discovered in 1994).
The Mayan pyramids, more recent, were also preceded by wooden modest graves, similar to Egyptian ancient graves at Abydos. 
Evidently, these resemblances don’t depend on hazard (chance), it would be only because all these pyramids reveal common presentiment of a life after death.

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