Some draft notes on some ideas about evolution:
In sexually reproducing species where genes can be exchanged and where partial solutions to problems dispersed in a population can come together in some individual, evolution should not be thought of as a linear process.
Instead, evolution may be viewed as co-evolution of genes within a species. Just like in a symbiosis, varieties of the organisms taking part in it will select each other if they fit together to produce an overall system that works well, the genes within a species may be seen as co-evolving species if the species has sexual reproduction, enabling those genes to be combined in different ways. An organism can thus be viewed as a simbiosis of on-gene-species that co-evolve.
Even single genes might be the result of coevolution if a process of crossing over, as the analogue of sexuality on the level of single genes, allows them to exchange bits of genetic sequences that code for different domains of proteins.
For a new feature to evolve, what is needed then is an initial coupling of co-operating genes. This initial coupling, i.e. their co-operation in producing some functionality in the phenotype, might be very weak. But as soon as it is there, mutual selection of gene variants that fit together might set in, resulting for the population to quickly “zoom in” or “converge” on an optimized version of the new feature. One can think of this as a process of mutual filtiering of gene variants.
For example, in a wind-polinating plant species, there is a co-evolution between the genes controlling the properties of the pollen and the properties of the pollen-catching organs of the female flower. While in this example, you literally have some “mutual filtering” of genes, the idea can be applied much more widely.
As a result of a co-evolution of genes starting with simple genes, new features may evolve very quickly, within a few generations, while the resulting forms might then be stable for long times since “aberrations” (diverging from the optimal cooperation) will be selected away by the other genes belonging to the group of co-operating genes. The whole group of genes forms part of the evolutionary environment of every gene takeing part. This stability will last as long as the environmental conditions remain stable or until a genetic innovation creates a new coupling of features that will drive the process somewhere else.
New genes might be included into the process even if they offer only tiny optimizations. It is even possible that pieces of genetic material that at one point where non-coding, like introns, become coding, even if their protein products have only very tiny effects initially, and then develop into important genes by being “guided” in a co-evolutive process of mutual filtering of gene variants.
The co-operating and co-evolving genes will together form some aspect of the phenotype. As a result, in many instances properties of organisms will not be controlled by a single gene but by a multitude of genes.
The genes coding for a feature might be replaced by others in such a cooperation. Some genes might be drawn into a cooperative complex and others disappear from it. As a result, similar phenotypical features in closely related species might have a very different genetic basis (comparable to the reimplementation of a feature in a software system where the surface remains similar although the implementation might become completely different). If a feature is lost in evolution due to an environmental change, but the overal structure remains, it might be redeveloped later on the basis of other genes (e.g. secondary shells in some sea turtles).
In organisms that have a culture, i.e. learned behavior that is passed from one generation to the next (e.g. migratory birds learning a route of migration by following the flock), this learned behavior can become part of a genetic coupling as if there was an underlying gene causing it. One could think of it as a virtual gene becoming part of the coupling of a group of genes or even starting a new coupling. In this way, invented and culturally transmitted behavior can trigger new spurts of evolution (and as a result, the behavior might become genetic by the selection of genes that make its learning easier).
In the evolution of humans, such processes might have played a role in driving the development of the human brain. However, the direction taken by evolution here was not towards the development of specialized behaviors but towards de-specialization, through alternating increases in the complexity of culture (including language) and in the cognitive capacity of the brain. The trigger might have been a rather unspecialized body with a versatile hand that enabled the development of a large diversity of behaviours.
Language development might have started only based on general intelligence (plasticity) without any language-specific adaption in the brain or in any other structure (note that all the organs involved have another function initially (the tongue, lips, teeth etc.). Even the glottis, although already used for communicative sound production in apes, initially might just have had a function in coughing, i.e. cleaning the bronchial tubes. Secondary adaption to language lead to a more elaborate fine motor skills of the speech organs, higher resolution of the auditive system in the range of language frequencies and volume, and probably a higher processing capacity of some brain areas. There might also have been some specific adaptions to handling complex grammar, but I guess these are overestimated in classical Chomskyan linguistics. In any case, language was invented first and then the neural system, auditive system and speech organs adapted to it. It did not emerge at once as a fully developed whole by a single genetic mutation. In any case, there might have been a co-evolution of a group of genes optimizing the language skills and thus the bandwidth of communication. The culturaly invented language might have played the role of the phenotype of a virtual gene (or a piece of environment) in this coupling of cooperating genes.
(The picture, showing an old anatomical drawing of the human larynx, is from https://commons.wikimedia.org/wiki/File:Gray960.png)