Language is a peculiar thing. In some ways it can be considered the fundamental neurological adaptation of the human species. Indisputably a cultural artifact, language is also a neurological one; speaking utilises definite neurological constructs. One of the interesting characteristics of these neurological constructs is that they are not bilaterally symmetric. While there is ongoing controversy about whether humans are the only neurologically asymmetrical primate, it seems clear that language’s neural correlates are asymmetrical. Furthermore, while modern language skills definitely require the use of hereditary linguistic ability, as the inability to teach language to primates demonstrates, it seems evident that language could have arisen as a sort of neural software in a primate that happened to have exess neural material just “lying around”. It turns out that megaencephaly in mice is only a recessive mutation away, so we have some reason to suspect that megaencephaly is the sort of evolutionary mutation that could arise and persist independent of any particular selection pressure; in other words, it could be that a significant sub-population of a H. sapiens precursor could have been megencephalic, much like a significant sub-population of modern H. sapiens is a dwarf or polydactyl today.
This sub-population of big brained freak monkeys tended to hang together, since the machiavellian intelligence of their non-mutent bretheren tended to socially ostracise them, and frankly the other monkeys were kind of boring.
Excess neural tissue doesn’t just sit there. I remember vividly seeing a child who was congenitally deaf experience his first sound through a cochlear implant at age 6 or so; he reacted with shock, and vivid discomfort. I don’t think we can quite imagine what that experience was like. Just as the auditory centers of his brain were doing something else before they were stimulated by the chochlear implant. Similarly, the novel brain tissue of these proto-humans organized itself according to its experience.
So you’re a comely proto-human lass, and you’ve got this moderately intricate series of vocalizations and gestures that let you get by pretty well in the world, and you’re looking for someone to get it on with. Now, if you go outside the dome-heads, you know you aren’t going to get any sort of gesticulation, so you look for another dome-head. Once you’ve found a worthy mate, you have another problem; your offspring are likely to be megaencephalic, which will make your reproduction more difficult, and your offspring’s larger brain will take longer to fully develop.
As a strapping young proto-human man, you could stick with sowing your wild oats, and that still pays dividends, but most of your big-brained offspring are going to require careful attention if they’re going to survive, so those boys that stick around and help out more with child-rearing are more likely to have progeny that make it to reproductive age.
These increased needs and changing reproductive strategies drive an explosion of culture like nothing else. Enhanced cultural needs imply enhanced ability to model and project our colleagues’ internal state, and this drives the improvement of not only our capacity to recognize facial expression but our capacity to make facial expressions; the development of a chin and the cheekbones enhanced our facial repoitoire and our capacity for making sounds. Being able to make a variety of interesting sounds led to pressure towards more capacity to make interesting sounds and so our larynx dropped. That making sounds was extremely important is suggested by the fact that the dropped larynx means we’re the only mammal that can choke to death while drinking water.
With all of these pressures encouraging the development of the anatomical prerequisites of modern language, pressure was active in the brain, as well. During development brains undergo a sort of evolution in miniature, where neurons that effectively participate in neural networks survive and those that do not commit apoptosis. This means that genes only have to provide a rough outline of neural structures, and the brain is capable of ‘filling in the blanks’. Nonetheless, the intense selective pressure of increased vocal ability rapidly resulted in key neurological mechanisms that give language a ready home in the human brain.
The story of the interpersonal communication’s evolution seems nearly synonymous with the emergence of humankind. The many interrelated factors that went into the development of human language as a cultural and physiological artifact both illustrate the core of what we are as a species and the sort of capacities and challenges we have to face in our individual experience of our linguistic world.