The theory is that the structures (phonology, lexicon and
syntax) of language in general, and of particular languages, are
directly modelled on the neural systems for controlling motor
action. But languages differ widely from each other in these
aspects said to be modelled on the neural motor system. There are
many different phonemic systems (the distinctive speech sounds
used in different languages, including phonemic use of tones),
obviously very large differences in lexicons (the words used in
different languages), and equally large differences in syntaxes
(word order, the use of inflections, the formation of compound
words, agreement between different parts of speech, gender). If
all languages are said to have the same origin, that is, by
modelling on neural motor systems, how is it that languages
differ so much from each other?
The first step in attempting to reconcile the motor theory
with observed diversity of language is to examine the nature of
the diversity. What is the extent and nature of the differences
between languages. What is the orthodox or most common
explanation of the differences between present-day languages? How
satisfactory are the existing explanations? We have to recognise
that the diversity of languages must come from somewhere, either
from their first origin (whatever that may have been) or if their
first origin was single and uniform from processes of change in
language, which led to the multiplication of different languages,
to arrive at the state that we see today.
Languages are strikingly similar as well as strikingly
different. They are similar in their very general structure:
a. the speech sounds of any single language are selected from
a restricted set; the speech sounds of all languages can be
analysed in uniform ways in terms of the anatomy and functioning
of the vocal organs; for most speech sounds (possible exceptions
tones and clicks) people belonging to different language
communities can produce good enough examples even of unfamiliar
sounds.
b. as regards lexicon, whilst each language has a distinctive
collection of words peculiar to it, there is extensive similarity
of words between languages, a very great amount of borrowing of
words between languages, and of course great similarity between
the things, actions, etc, for which words are available in
different languages. A large part of traditional historical
linguistics has been concerned with the similarities in lexicon
between languages
c. grammatical structure has something in common in all known
languages, particularly at the deeper levels of grammar. All
known languages have words or word-like elements combined in
accordance with rules into sentences; all known languages
distinguish in some way nounlike and verblike sentence
components. As regards syntax more specifically, there is
variation only within certain broad types, and languages have
been classified in terms of their syntactic similarities.
Languages which may be widely different in their lexicons and
phonology may have syntactic systems which are similar, e.g.
Chinese and English.
But although there are these considerable similarities,
particularly phonological, which themselves call for explanation,
the differences between present-day languages are even more
considerable, particularly in lexicon, and demand an explanation,
whether in traditional terms or in relation to any biological
theory of language origin (such as the motor theory).
How are the differences currently explained? One line of
explanation is that there was only one original language
(monogenesis), and all other languages, however different they
now appear, were derived from it. On this account, differences
in
phonology and syntax between different languages resulted from
processes of language change over immense periods of time; even
if lines of descent and relation are difficult to construct or
hypothesise for many modern languages, language change must be
the explanation, and the residual unexplained differences
represent the end results of language 'evolution' (in a general
sense) so extended that the links can no longer be found between
different languages. Note that this line of explanation, that all
languages are related by descent and change, has been applied
most vigorously to phonology and syntax, and that the difficulty
is greater in suggesting how the lexicons of different languages
can have diverged so much. For differences between lexicons, an
ancillary explanation often put forward is that the words
individual languages have chosen to represent experience of the
world are arbitrary, that is, they are mere chance patterns of
sound which at some stage in a language's development from its
original source have been adopted by the group or community
speaking the particular language.
Another explanation - or perhaps it should be described as
the ultimate pessimistic account of language diversity - is that
everything in language is in origin arbitrary; the words found
in
the lexicon, the syntax - systems of inflection, gender, etc. -
and the choice of phonemic sets in particular languages is
totally arbitrary. Whilst some relationships between individual
languages are recognised, e.g. Indo-European, apart from a few
broad families like this everything is the result of chance, not
the product of order. This view probably accepts that components
of a language originally totally arbitrary in origin can undergo
more systematic processes of language change, e.g. the
transmutation of Latin CANIS into French CHIEN, but once the root
form has been found in the particular protolanguage, there is no
point in attempting to go any further back to explain why the
particular protoform was adopted.
How satisfactory are these more orthodox explanations for
language diversity? The second explanation, the arbitrary
character of differences between languages, really amounts to no
explanation. It says no more than that there are differences and
no account can be given of the causation of the differences. Any
assertion that some event or process, in linguistics or any other
field of science, is arbitrary, provokes the question: How do you
know that it is arbitrary; how do you know that there was no
chain of causation; how have you been able to exclude all
possible causative explanations? Please give some example of the
arbitrary selection or creation of a particular word in a
particular language, of an inflection, of a syntactic rule, e.g.
that a given preposition takes a given case, of selection of a
particular phoneme in a given language.
The more usual explanation, that diversity of current
languages is the result of processes of language change affecting
an earlier language or earlier languages, is also less
satisfactory than it sounds. It asserts that languages change -
as obviously they must have; it suggests that certain types of
change have taken place, e.g. phonological, lexical or syntactic,
but it does not explain the process of change; it simply relates
present diversity to past diversification. Language and languages
have changed (so far as there are records of earlier forms of
languages) but why have languages changed? How have languages
changed? What is the process of change which produces the
diversity? What is the source of the specific change?
On the assumption of monogenesis, the current diversity of
languages coupled with the diversity of languages over time
(languages have fallen out of use and apparently earlier forms
of
existing languages have been replaced) reduces to the question
of
the nature, causes, direction, of language change.
The alternative to monogenesis for the origin of language is
polygenesis, i.e.that language originated in human evolution at
a
number of distinct points. If polygenesis is assumed, then the
different protolanguages would have developed independently and
led over millennia to the diversity of the descendant languages
found at the present day. However, the assumption of polygenesis
only thrusts the problem of language diversity further back. Why
should there have been different protolanguages? By what process
were the different protolanguages formed? How was selection made
of the various phonemic systems, lexicons and syntaxes
constituting the protolanguages and distinguishing them from each
other? And, of course, even with polygenesis as one's assumption,
the question of language change over time still remains, since
the multiple protolanguages clearly developed and changed to
produce the diversity of their descendant languages now found.
If we could explain what drives and directs language change,
then we could start to explain language diversity, present and
past. This explanation could be either in the context of orthodox
linguistics or in relation to a neurological/physiological
(essentially biological) account of language origin. The next
step is to look at what is known about language change and what
has been suggested as the causation and process of language
change. To fix our thoughts, some extracts are introduced here
(in order of date) from a number of linguists on the issue of
language change:
What supports the necessity for change? ... How
do differences that result in the most varied dialectal forms
originate? What pattern does their evolution follow?... An
explanation that has been favoured for several years attributes
change in pronunciation to our phonetic education during
childhood ... What prompts a generation to retain certain
mistakes to the exclusion of others that are just as natural is
not clear. From all appearances the choice of faulty
pronunciation is completely arbitrary, and there is no obvious
reason for it. Besides, why did the phenomenon break through at
one time rather than another? ... [Alternatively, linguists have
suggested a variety of general causes for language change]
Climatic influence, racial predisposition, tendency towards least
effort are all permanent or lasting. Why is it that they act
sporadically, sometimes on one point of the phonological system
and sometimes on another? A historical event must have a
determining cause, yet we are not told what chances in each
instance to unleash a change whose general cause has existed for
a long time. This is the most difficult point to explain. The
blind nature of the evolution of sounds... Time changes all
things ; there is no reason why language should escape this
universal law. (Saussure 1966: 77, 149-150, 199, 231)
Are we not imputing to this history a certain mystical
quality? Are we not giving to language a power to change of its
own accord over and above the tendency of individuals to vary the
norm? .. Language exists only in so far as it is actually used..
What significant changes take place in it must exist, to begin
with, as individual variations .. random phenomena, like the
waves of the sea, moving backward and forward in purposeless
flux. The linguistic drift has direction.. The drift of a
language is constituted by the unconscious selection on the part
of its speakers of those individual variations that are
cumulative in some special direction. (Sapir 1921: 154-155)
Every conceivable cause [for language change] has been
alleged: 'race', climate, topographic conditions ... No permanent
factor can account for specific changes .. theories of this kind
are confuted by the fact that when sound-change has removed some
phonetic feature, later sound-change may result in the renewal
of
just this feature... Although many sound-changes shorten
linguistic forms, simplify the phonetic system or in some other
way lessen the labor of utterance, yet no student has succeeded
in establishing a correlation between sound-change and any
antecedent phenomenon. The causes of sound-change are unknown.
(Bloomfield 1933: 385-386)
The fundamental cause of linguistic change and hence of
language diversification is the minute deviations occurring in
the transmission of speech from one generation to another. These
changes are mostly very gradual in their operation, becoming
noticeable only cumulatively over the course of several
generations. But, in some areas of vocabulary, particular words
closely related to rapid cultural change are subject to equally
rapid and therefore noticeable changes within a generation or
even within a decade. Grammatical and phonological structures are
relatively stable and change noticeably over centuries rather
than decades. (Robins 1979: 652, 660-662)
For centuries, men have speculated about the causes of
language change. The confusion and controversies surrounding
causes of language change ... some reputable linguists have
regarded the whole field as a disaster area, and opted out
altogether. Children are unlikely to initiate change, since
change is spread in social groups, and babies do not have
sufficient influence to persuade other people to imitate them.
Change is likely to be triggered by social factors, such as
fashion, foreign influence, and social need. However, these
factors cannot take effect unless the language is 'ready' for a
particular change. They simply make use of inherent tendencies
which reside in the physical and mental make-up of human beings.
Continual language change is natural and inevitable ... there is
no evidence that language is either progressing or decaying ..
[or] that languages are moving in any particular direction from
the point of view of language structure ... Finally, it is always
possible that language is developing in some mysterious fashion
that linguists have not yet identified. Only time and further
research will tell. There is much more to be discovered.
(Aitchison 1981: 111-112. 168, 190, 234)
These extracts show how puzzling most linguists have found
the diversity of languages and the problem of language change.
Language variation is the product of change, but the variation
is
much more extensive than simply the distinction between different
languages: each language contains within it extensive variation
in the form of dialect areas and dialect features, which show an
even more complicated distribution than language diversity. Once
one recognises that the variation is not only between languages
but within languages, the problem becomes even greater, and the
explanations even more tenuous and less satisfactory.
But if in traditional linguistic terms, the problems of
language diversity and language variation receive no very
convincing solutions, consider what the approach to these issues
might be on a biological theory of language origin and function.
Let us take some specific examples of language and dialect
variation and change so as to be able to judge more concretely
what the relevance of a biological approach might be:
Dialectal variation - Within a single language, there can be
major dialectal variation in typology, syntax and morphology, as
well as differences in lexicon. The position in Serbo-Croat and
Slovene is an extreme example of this structural variation:
dialects are found with synthetic declensions (case endings, as
in Latin) and analytic declension (use of prepositions and word
order, as in English). In addition, there are among these
dialects complex systems of verbal tenses contrasting with simple
ones, as well as dialects with or without the dual number or the
neuter gender. The dialects of Serbo-Croatian and Slovene also
exhibit almost every type of prosodic structure (e.g. tone,
stress, length) found in European languages. Some dialects
differentiate long and short vowels or rising and falling
accents, while others do not; and in some, but not all of them,
stress fulfils a grammatical function. Of the several dozen vowel
and diphthong sounds that occur in these dialects, only five are
common to all of them; all the rest are restricted to relatively
small areas. (Ivic 1979)
Similarities across language frontiers - Languages which are
spoken in the same general geographical region tend to have
phonetic features in common even if they are not closely related
historically. Examples: some assimilation in the sound systems
of
Spanish and Basque (Swadesh 1972); Bushman and Zulu both have
clicks, even though racially and linguistically, the two are
judged to be unrelated; on the northwest coast of North America
most of the American Indian languages have a glottalised series
of sounds and a proliferation of sounds produced in the back of
the mouth, in addition to other similarities; Indo-Aryan
languages have cerebral or retroflex speech-sounds unknown
otherwise in their language group - these sounds are found in
Dravidian (an unrelated language family, though spoken in the
same area as the Indian languages); Swabian dialects of German
are found with nasalised vowels quite unlike German generally;
the dialects are spoken in proximity to French, which makes
abundant use of nasalised vowels. How are we to explain these and
hundreds of similar phonetic convergences?(Sapir 1921). Tonal
languages are not only extremely widespread through Southeast
Asia and China, they also show remarkable similarities to one
another ... the tonal systems of Chinese, Miao-Yao and Tai have
developed in almost identical fashion. (Norman 1988)
Diversity associated with different groupings but also cutting
across groupings - Similarities across language frontiers are not
restricted to phonology. Isoglosses can be drawn for many
linguistic features which bear no relation to language frontiers.
The best known linguistic area in Europe is undoubtedly the
Balkans. The languages spoken in this area, particularly
Romanian, Bulgarian, Macedonian, Albanian and Greek, are not for
the most part closely related but nevertheless show striking
resemblances to one another in many respects. The most striking
example of the similarity is the fact that four of the languages,
Albanian, Bulgarian, Macedonian and Romanian, all have a
postposed definite article. This feature does not occur in
[non-Balkan] languages which are historically related to the
Balkan languages (Chambers and Trudgill 1980: 184-185). There
does not seem any adequate linguistic explanation for this sort
of distribution which cuts across the accepted groupings of
languages.
Australian and Papuan languages: These are of special interest
because (particularly in the case of the Australian languages)
they have undergone virtually no external influences for tens of
thousands of years. The following account of the Australian
languages is drawn from a number of sources (Dixon 1980, Kaldor
1982, Wurm 1972, Vazsolyi 1976, O'Grady et al. 1966). There are
some 200 Australian languages spoken by about 600 tribes. No
relationships have been shown to exist between Australian
languages and any outside languages. All but 2 or 3 of the
languages belong to one language family (Pama-Nyungan) which
occupied 7/9ths of the entire land area. Each tribe has or had
something of the order of 500 members on average. The multi-tribe
Western Desert language community is the largest, with 6000
speakers spread over perhaps half a million square miles.
Phonology: Australian languages show remarkable similarity
throughout the continent in the structuring of their speech
sounds, a surprising phonemic uniformity, unparalleled anywhere
else in the world. Most Aboriginal languages have only three
vowels I A U close to Italian vowels. Diphthongs are non-existent
or atypical. Most Australian languages do not distinguish
consonantal sounds from each other on the basis of voicing .The
effect of this (coupled with the restricted set of vowels) is
that, for example, speakers of Western Desert languages have
difficulty in distinguishing BIT BEET PIT PET PEET BID BED BEAD.
A large number of consonants are absent. They do not have F
"fish", V "van", TH "thin", TH "this", S "sun", SH "shoe", Z
"zero", ZH "pleasure", CH "child", DZ "joke", H "hat". No (or
very rare) consonant clusters, e.g. "kin" for "skin". Typically
they have an extended range of stop consonants and nasals. A
striking uniformity in the languages is that the number of linear
distinctions made among oral stops in a given language is
identical with the number of linear distinctions made among
nasals. The few phonologically aberrant languages in the North
are the result of external influences, probably from New Guinea,
which also manifest themselves in racial features in the same
areas.
Syntax: Most of the languages are suffixing but there is a
smaller group of prefixing languages. The suffixing languages
show long strings of suffixes, agglutinative in type. The
prefixing languages form a geographically solid block. Word order
is very flexible with the generally preferred order being SOV.
Adjectives often follow nouns. A typical syntactic feature of
Australian languages is the presence of ergative case markers.
The ergative marker expresses the exclusive function 'subject of
a transitive sentence' (but not 'subject of an intransitive
sentence').
Lexicon: Except for pronouns which are similar across the
continent and the limitation that there are only two or three
numerals, the most striking lexical feature of Australian
languages is the fewness of cognates between languages which
otherwise seem closely related. Two languages may share
grammatical properties and similarities in speech sounds but
hardly share any vocabulary items. A curious feature is that a
few cognates have been found to be shared by languages at
opposite ends of the continent with no intervening cognates.
Linguists comment that something special seems to be going
on
in Australia which presents a challenge to accepted methods in
comparative linguistics. There seems to be a contradiction
between the results of shared vocabulary counts and the results
of comparison of other aspects of language viz: that of speech
sounds and of abstract grammatical/semantic properties. This
contrasts not only with other language groupings in the same
general geographical region eg. Austronesian (where phonology,
syntax and lexicon appear to have a more systematic relation) but
also very strikingly with the situation in Papua/New Guinea.
There one also finds a great diversity of languages for a small
population. However, in New Guinea the languages differ
phonologically, lexically and grammatically from each other.
Papua/New Guinea is said (Foley 1986) to be the
linguistically most complex area in the world. There are around
750 Papuan languages (nearly 20% of the world's total). The
Papuan languages are not all genetically related but belong to
at
least sixty different language families; no Papuan language
family has been demonstrated to have any genetic affiliation
outside the immediate New Guinea area. Given the relatively small
area, and the small total population (approximately four
million), they present an unparalleled picture of linguistic
diversity. The Papuan languages provide a different but even
greater challenge than does the Australian language situation,
for accepted approaches to the problems of language diversity and
language change.
In historical linguistics, terms drawn from biology have been
freely used. Linguists speak about the genetic relationships of
language, about language descent, language families and language
drift. Some linguists have tended to look upon an individual
language as an organism: the evolution of language is a
frequently used concept;some linguists talk about the 'life' of
particular languages: "the invisible and impersonal drift that
is
the life of language" (Sapir 1921: 171), their readiness to
change in certain directions and even their fitness to survive.
One of the criticisms directed against the comparative method is
that it is based upon a misleading genealogical metaphor: "There
is obviously no point in time at which it can be said that new
languages are 'born' of a common parent language.. It is easy
enough to recognise the inappropriateness of these biological
expressions".(Lyons 1979: 1009)
The trouble comes from adopting a limited and wrong analogy
from biology. Rightly used, biology in its modern form provides
an instructive model or analogy for language and an account which
can be directly explanatory of the phenomena of language. This
was most fully developed by Stevick (1963): The new biological
model is different from the older one that we properly reject.
..
Biological models for variation in the rate of linguistic change
are to be found ... in the study of population structure. .. If
complexity is a criterion, evolutionary biology more than
qualifies as a model for language history ... Linguistic and
biological histories are closely similar particular examples of
the general evolutionary model.(160-162, 168-169) He demonstrates
this convincingly by paraphrasing key sections of Dobzhansky
(1951) substituting language and language-related terms for
Dobzhansky's references to species, races, populations etc. Both
language and species continue, modify, and diversify. Hence both
language and biology distinguish variation and change.
Population genetics can provide not only a model or an
analogy but also an explanation for language variation and
language change. To see how this is possible it is necessary to
give some brief account of the main themes in the biology of
populations. The issues in population genetics, as in language,
are those of variation and change.
Individual variation: Individuals within any population
usually show variations in almost all characteristics. The
differences that exist between individuals in a population are
so
many that any individual is likely to be distinct and possibly
unique.
Group (deme) variation: Population sub-division seems to be
almost as common as individual variability. There is considerable
evidence that most populations can be subdivided into
semi-isolated demes.
Population or community variation: A population is a
collection of individuals that can freely interbreed. It is a
cohesive genetic unit within which alleles are freely
interchanged. It is often referred to as a collective gene pool
out of which alleles are drawn at random during each
reproduction. A much higher level of heterogeneity occurs in
natural populations than used to be thought possible.
Race variation: The notion of race is statistical and
describes the characteristics of populations. A race is a
breeding population characterised by frequencies of a collection
of inherited traits that differ from those of other populations
of the same species. Genetically, races differ with respect to
allele frequencies rather than in the possession of unique
alleles. Natural races tend to be separated by intergrading zones
rather than by sharp lines of demarcation.
Species variation: A species typically consists of a number
of
partially overlapping populations showing various intergradations
of morphological or physiological characters. Recent applications
of recombinant DNA techniques have uncovered much more variation
than previously imagined both within and between species.
The process of evolution consists essentially in transforming
individual variation within species into variation between
species. Variations are maintained in the population by local
demic differentiation. Because the demes are small, genetic drift
contributes significantly to altering allele frequencies between
demes. Small populations will be subject to large fluctuations.
A
series of small populations formed from a single large one will
inevitably diverge, even if they were initially identical.
Genetic drift is the effect of the sampling process that
occurs in reproduction. A special case of the sampling effect
occurs when a small number of individuals from an originally
large population become founders of a new population. The allele
frequencies of the new population will be those of the founders,
which may or may not be representative of the original
population. Founder effects are often invoked as an explanation
for differences in allele frequencies among different human
ethnic groups.
New species may arise subsequent to the interruption of gene
flow in part of an original species' range. There are many ways
in which gene flow may be interrupted. The most widely recognised
is that of geographic isolation due to physical barriers such as
mountain ranges, rivers,the sea. Some geneticists place a great
deal of emphasis on the founder effect and genetic drift in small
populations as mechanisms for producing rapid genetic
differentiation and hence the formation of new species. Intrinsic
isolating mechanisms such as the formation of social groups in
many mammals, including humans, tend to reduce genetic exchanges
between groups and to encourage genetic differentiation. There
is
a special problem of the amount of racial variation that exists
in modern human populations. Berry (1977) suggests that hunting
groups must have had all the possibilities of differing widely
from each other through the repeated operation of the founder
effect and the greater variety of habitats to which they would
have had to respond in different parts of their range.
The essence of the motor theory is that each main aspect of
language, the phonological, the lexical and syntactic, depends
upon the integration of action and perception organisation with
language, that phonemes, words and syntactic rules are derived
from motor organisation in specific ways. That is, language
directly reflects or expresses neural organisation, the system
of
neuronal connections which constitute motor programs and result
in articulatory movements. But the reality of neural organisation
is that each brain differs from every other brain, the patterns
of neural connection vary from individual to individual; not only
this but the conformation of vocal organs varies from individual
to individual, the musculature varies, and obviously enough the
quality of the voice which results varies from individual to
individual. These differences between individuals are the product
of differences in the genetic control operating in development
and interacting with the environment.
From population genetics, it is clear that every individual
is genetically unique. And also that, on any technique of
measurement, genetic variation is great within populations. Any
population whilst embracing a great degree of variability also
has uniformities which characterise the gene pool of the
population. These uniformities exert a uniform (statistically
averaged) effect over the physical and mental constitution, brain
and body development of the population. They mean that certain
features of brain and body development are found more frequently
in one population than in another. The obvious extent of
morphological differences between populations and between races
makes it impossible to believe that non-observable features of
sensory and cerebral organisation will not also reflect differing
gene frequencies (Baker 1974). In population genetics, the
propositions of individual variability within populations and
variation in gene frequencies between populations and even more
between races. are generally accepted. There are also
well-established accounts of how, given individual variation
within a population, factors can operate to increase and
consolidate differences between populations and between subgroups
within the populations. These factors take the form of migration,
geographic separation, founder effects, environmental forces
(providing the setting for expression of genes in the gene pool)
and so on. Population genetics thus indicates how change in
cerebral and bodily organisation, brain wiring and morphological
features (particularly those affecting the organs of
articulation) can occur. The whole account in population genetics
of the processes of race and species formation bears a close
resemblance to the accounts given by linguists of the processes
by which linguistic variation within a community can develop into
differentiation of dialects and later of separate languages, by
very similar processes of geographic separation, migration,
isolation - with reproductive isolation in the case of the
development of races and species being paralleled by
communicative isolation in the case of dialects and languages.
The next step in the reconciliation is that in the same way
as the expression of the genome in bodily development is the
product of interaction with the environment, so the development
of a language is the result of interaction between the
genetically controlled cerebral, anatomical and physiological
features of the population (reflecting the relative gene
frequencies within the population) and the environment within
which the development of the language takes place. The importance
of the environment derives from the reality that language cannot
be an individual-centred capacity but has to be an
inter-individual or group product. Such a group product will be
biassed towards the aspects of language most compatible with the
cerebral and bodily articulatory organisation prevailing in the
group within which the language is to be used. A relation will
be
apparent between the phonemic system adopted in the group and the
physical conformation most prevalent within the group. So far as
basic and original lexicon is derived from integration of
articulation with perceptual and motor organisation, the words
found in the group will have their structure determined (within
the limits set by the phonology preferentially adopted) by neural
organisation governing perception and the planning of motor
action, Similarly, in the origin of a language the structure of
the motor system will have a dominant influence on the basic
syntactic features of the language of the group.
Given conditions prevailing throughout most of human history
(barriers to communication, small and scattered populations etc),
this account of the link between gene frequencies in the group
and the characteristics of language in the group leads easily on
to explanation of processes of dialect development, language
splitting, language change etc. Dialectal variations will tend
to
develop as a result of changes in controlling gene frequencies
within a local area, or the transmission of gene variations by
intermarriage across dialect divisions. By the same process,
genetic effects on articulatory morphology, and cerebral motor
organisation, can explain the tendency for phonological
characteristics to be spread across language borders, such as the
cerebrals found in both Dravidian and Indo-Aryan languages, and
many other examples. Similarly, over time within any language
community, the characteristics of the language, its
sound-complement, its lexicon and syntax, will tend to reflect,
though with a considerable drag, changes in the gene frequencies
for factors controlling articulatory morphology and cerebral
organisation for perception and movement. Gene frequencies may
change within a population for a variety of reasons, most
obviously as a result of inward migration from other communities
with different gene frequencies, as a result of change in the
relative size of different subgroups within the population, and
also as a result in smaller populations of fluctuations in gene
frequencies which occur as a sampling effect. This link between
changing gene frequencies and changing, particularly
phonological, features can explain the apparently erratic
character of some sound changes, where features disappear from
a
language and later reappear.
But how can changing gene frequencies, affecting articulatory
morphology and cerebral organisation, actually have an impact on
the characteristics of a language which already exists and
appears to be preserved by its function of being a uniform medium
of communication within the group? The relevant changes in gene
frequencies may be taking place, must be taking place, all the
time, but at what point does language also change to reflect
them? Part of the problem is linguists' idealised conception of
an individual language as a uniform system spread over a language
community. In fact, any language as actually used in a community
as a spoken medium (reliance on written versions of a language
can be misleading) is an immense collection of local,
occupational, class, register, variations. A language changes
when some variation becomes more widely used and others become
less widely used. So the question reduces partly to how the range
of variation is generated within the community, and how change
in
gene frequencies affecting articulatory and cerebral organisation
is translated into language variation.
This leads one back to the development of language by
children. Regardless of their genetic inheritance, children learn
the language of the community in which they grow up. Nevertheless
changes in gene frequencies affecting articulation and cerebral
organisation for perception and motor control translate most
directly into changes in the physical and neural development of
children. At this stage one needs a physiologically-based theory
of the process of development (not just acquisition) of a
language by children. A plausible account starts from research
into the acquisition of behavioural characteristics by birds and
other animals, of a kind where the behaviours acquired have to
be
related most appropriately to the environments in which the birds
or animals find themselves and will spend their adult lives. The
topics here are imprinting, the acquisition once and for all of
a
particular cerebral set, and the somewhat different idea of the
critical period, the period of plasticity in cerebral and
behavioural organisation that many young animals experience.
Moulding in the critical period for a human infant, a bird or a
monkey, is the result of interaction between the genetic
endowment of the infant and the environment to which it is
exposed. If the genetic endowment changes (as a result of changes
in gene frequencies) then the product of interaction between that
endowment and the environment will also necessarily be different.
If gene frequencies alter significantly in a population over a
period, then the tendencies and preferences of the children
developing in that period will also alter. This will, insofar as
the genes concerned are those affecting relevant physical or
cerebral organisation for language, constitute a force tending
towards language change. Even though children as such have no
important influence on speech patterns and preferences, the
tendencies and preferences changed in them as a result of changes
in gene frequencies will continue to exist when they grow up into
adults and it will be at the adult stage that the force deriving
from population change in gene frequencies will start to have an
impact on the phonological, lexical or syntactic features of the
languages.
Supporting argument and evidence can be presented at various
levels. The broad plausibility of the idea of a genetic basis for
language (in a strict biological sense) is the very obvious
parallelism between the analysis and findings of population
genetics and the phenomena of language differentiation, language
variation, dialectal features, language spread, etc. The second
broad line of argument derives from the motor theory as such,
that is from the theory that there is a specific neural basis for
language derived from pre-existing cerebral organisation.
Once it is accepted that cerebral and articulatory
organisation have direct significance for language, and that
'genetic' factors in a strict biological sense have a controlling
influence on these within and between populations, then there is
ample more detailed evidence from mainline population genetics
for the circumstances in which gene frequencies may change
between populations, within populations and between individuals
and groups within a population. Authoritative accounts of this
are given eg. by Dobzhansky (1951), Berry (1977) and many others.
That is, the variation in the relevant genetic aspects both over
space and over time is available from which language patterns and
changes may be determined. Differences between gene frequencies
relevant for language would extend not only to physical aspects
dealt with above but also to neural organisation.
More specific evidence bearing directly on variation within
populations and between populations which can be relevant for the
character and development of languages is drawn from various
sources. There is evidence for differences between individuals
both in brain organisation and in articulatory organisation.
Relevant evidence can be presented under three heads: evidence
for differences between individuals and between populations and
races in aspects of brain and body relevant for speech and
language; evidence of correlation between measurements of genetic
distance and language differences between human communities,
evidence bearing on the transmission of changes in language via
the process by which children develop their language capacity.
There have been some studies of the extent to which there is
correlation between language and genetic (biological) groupings.
Given the linguistic peculiarities in Australia and Papua/New
Guinea, results of research there are of special interest. In
Papua/New Guinea, Bougainville was chosen for study because of
the remarkable diversity of indigenous languages (19 languages
for 45000 people). The researchers were interested in physical
differences between the various groups in Bougainville and how
they related to language relationships and patterns of
intermarriage. They found that the morphological differences
encountered were genetically rather than environmentally
determined; the pattern the villages made in the discriminant
analysis was a 'neat reflection' of language group discreteness,
with consistent clustering of villages from the same language
area. The role of the language group as morphological (physical
conformation) unit was apparent (Friedlaender 1976).
Similar studies with Australian aboriginals produced rather
similar results. The Australian aboriginal has physical features
which differentiate him clearly from all other races but at the
same time there is considerable regional variation and there is
little doubt that physical differences exist between populations
of Aborigines. The results of the analysis using a variety of
measures of genetic distance (seven genetic marker systems
including blood groupings) suggested that for large parts of the
Australian continent, linguistic differentiation has been
proceeding in a similar manner to genetic differentiation. Four
tribes were studied in depth: statistical analysis showed genetic
distances between the tribes similar to the order of
relationships given by linguistic studies (Sanghvi et al. 1971,
Balakrishnan et al. 1975).
This kind of work is still at an early stage. There can be
argument about the best measures of genetic variation and genetic
distance (blood-groupings, protein complexes or polygenic
characters such as observable morphology); morphological
variation seems more relevant than single-gene characters.
Nevertheless, the findings so far are consistent with a direct
relation between genetic diversity and language diversity in the
particular areas studied. Interestingly, similar studies have
been carried out on the relation between genetic variation and
song variation in birds. The object was to see if any genetic
variations coincided with a boundary between two dialects of
birdsong. It was found that the dialects of the group of birds
studied, a subspecies of white-crowned sparrow, formed a kind of
genetic mosaic, with enough differentiation for each song-dialect
area to constitute a deme or selective unit (Bright 1984).
The next issue is the suggestion that changes in population
and deme gene frequencies take effect by way of their impact on
children's development of their language and act through altering
the biases, tendencies and preferences which those children
subsequently experience when they become adults, and which at
that time start to cause language change. The evidence relevant
for this is drawn from general work on neural and behavioural
development in infants and animals. The most useful evidence
relates to birds. This is important for two major reasons: first,
neural organisation is similar across the range of vertebrates;
the basic elements, neurons, synapses, neurotransmitters, are the
same, and if certain processes are found in birds or other
vertebrates, then there is no reason why one should not look for
parallel processes in human beings. The second reason is that
birds are vocal animals like human beings, and if the neural
control of vocalisation is found to take particular forms in
birds (despite the different anatomy of articulation) then this
has a direct relevance for human vocalisation. Research findings
described in Bright (1984) offer a significant pointer: whilst
the period of learning or moulding of vocalisation comes in a
limited period of the bird's early life, the effects are only
expressed when the bird becomes adult; the moulding of neural
connections made in the infant period is necessarily carried
through into the adult period. The suggestion that genetic
changes in a human population are carried through into language
in a similar way is speculative but plausible; Meillet (1937),
VendryÖs (1902) and other linguists had speculated along much the
same lines long before progress in neurology and ethology could
offer any evidence. If in fact this is how language change
occurs, then it overcomes the valid counter-argument of Saussure
that language is not transmitted discontinuously from generation
to generation, and also Aitchison's (1981) comment that children,
as children, can exert no powerful influence on current language.
The process of dialectal differentiation has been described
for birdsong along the following lines (Purves and Lichtman 1985
summarising work of Thorpe, Marler,Nottebohm, Konishi and
others). Chaffinches are born with an innate but imperfect idea
of what they are to sing but the fully formed song must be
learned from conspecifics during a limited (critical) period in
early life. When they reach sexual maturity, they proceed to
reproduce this type of song. This results in considerable
variations between the songs of different flocks of the same
species: each has its own self-perpetuating dialect. Dialect-like
differences on this view are an accidental by-product of song
learning. A young bird, within the first year of life, hears
other chaffinches singing. The following spring it starts to sing
itself, matching its own output to its memory of what it has
previously heard, producing near-perfect copies six to eight
months later. In song learning birds make mistakes; as a result,
song is almost certain to change, though slowly. Swamp sparrows
in the phase of plastic song generate far more song material than
is needed for normal adult song production; the excess song
components get winnowed out until the mature repertoire is left.
Much of the work on neural plasticity has been done with cats.
The development of the visual system of cats also takes place
during a critical period. The final organisation of pattern
detecting neurons in the visual cortex of a cat is fundamentally
determined by the kitten's early visual experience; the effect
appears to be that the feature-detecting system is optimally
matched to the animal's visual environment.
From these ethological studies a main conclusion is that
various behaviours can only be learned during a restricted
(critical) period, e.g. birdsong in some species must be learned
during a limited time in the first season, and socialisation in
monkeys must occur during early life or be forever abnormal.
Neural connections can be modified only within a certain age
range. The studies of birds, cats and monkeys are in accord with
a growing body of neurobiological evidence that confirms that
experience can modify innate behaviour in a more or less
permanent way. One reason for the intense interest in these
results is the notion that the purpose of critical periods is to
allow the outside world to influence cortical connectivity. The
goal of neural development is appropriate behaviour. Central
patterns of neural organisation are present very early in
embryonic development. Many receptive field properties are
established prior to any experience. Neonatal neurons are less
sharply tuned than their adult counterparts, but the basic wiring
that subserves these various aspects of adult responsiveness is
largely present at birth. Although many aspects of connectivity
depend on intrinsic mechanisms, other aspects of connectivity
remain malleable at birth. As a result of further postnatal
maturation, experience can influence the final pattern of
connections. (Purves and Lichtman 1985, Atkinson, Barlow and
Braddick 1982)
The neural and anatomical basis for change as a result of
genetic factors is most plausible for phonology of a language,
which is least likely to be affected by passing fashion. Radical
changes in phonology occur rarely and when they do affect a wide
swathe of the language, e.g. the German soundshifts and the
English vowel shift. Nevertheless, the most frequent argument
against any physiological basis for diversity or change in
language has focused on phonology. Saussure's comment has been
repeated with little variation by later linguists:
Does the phonational apparatus vary from one race to the
next? No, scarcely more than from one individual to the next. A
newborn Negro transplanted to France speaks French as well as a
native Frenchman (Saussure 1966: 147).
The powerful objection to all hypotheses which posit a
mutation in the vocal organs or a modification of the cerebral
centres is the simple fact that young children or refugee
children learn the language of adoption with no trace of
imperfection (Lord 1966: 83).
There seem to be no physiological differences between the
races which are reflected in speech. Although the Chinese and
other Mongoloid peoples have differently shaped incisors, a
Caucasoid child brought up in China among the Chinese will speak
Chinese as a native speaker, even if both the child's parents
spent their whole lives in Chicago (Davis 1983: 3).
Apart from the fact that there are anatomical and
physiological differences between individuals and races capable
of affecting the articulatory system, such arguments are based
on
views of race, inheritance and development which are out of date.
Brosnahan deals with the point effectively:
It is the preoccupation with the individual which on the
linguistic side has led to the obfuscation of the whole problem
with largely irrelevant and non-cogent arguments, such as whether
a given individual can or cannot learn perfectly a language other
than that of his parents. Experience seems to show that this is
quite possible but far from this being an argument against
genetic factors in language, it would seem indeed only possible
because all languages have been developed by human beings of
basically similar genetic structure, and because human beings
inherit a potential plasticity of development with regard to
sound production and speech. (Brosnahan 1961: 30)
Meillet and Vendryes, both eminent historical linguists, saw
no difficulty in linking phonological change with physiological
change. So Vendryes (following Meillet):
Every sound change has a natural cause; the regularities in
the transmission of sounds results from changes in the
articulatory system; it is in the passage from one generation to
another that an articulatory system is ordinarily modified.
[Sound changes] depend on the physiological makeup of the brain
and oral cavity. Every sound change can then be considered as the
result of deep-seated and hidden forces, for which the term
tendency is suitable enough. It is these tendencies that
continually modify the structure of language ...They are linked
intimately to the physiological aspect of the speech organs and
determine, consequently, in a perfectly natural way, the normal
evolution of language ... Each individual .. by the very fact
that he differs from his contemporaries, carries the germ of new
tendencies. Within each group, a kind of mean is established and
the resemblance of the whole is sufficient, so that one can
abstract the tendencies of detail... If the identity of
tendencies is the cause of the homogeneity of dialects, inversely
it is the difference of tendencies that creates the diversity
among dialects (Vendryes 1902: 112,117).
This account of the matter is close to that put forward by
Darlington (1947) which was developed later in detail by
Brosnahan (1961). Jakobson also emphasised the biological aspect
of phonology: the universal sound patterning of speech is "the
most enrooted in the psychobiological nature of humans"; the
sound patterns of single languages are "varying implementation
of
universal invariants".(Jakobson and Waugh 1987: 64, 236) More
recently, Lieberman has commented, in a phonological context,
that "the presence of genetically distinct subgroups in the human
population who may differ with respect to some of the neural
mechanisms that determine the perception of speech offers an
explanation both for the diversity of human language and for
linguistic change". (Lieberman 1986: 106)
Changes in gene frequencies within a population, a language
community, a dialect group, do not explain sufficiently why new
words are added to the lexicon, or old words drop out, or
different words replace established words as and when they do.
The rate at which the lexicon changes is faster than can
plausibly be ascribed to changes in population gene frequencies.
But there is an important point that should be made in this
regard. Given that language and dialect variation reduce to
language change, nevertheless it is not the case that all
language change has to be treated as directly genetic in timing
as well as in origin.
In the case of phonology and syntax, the implication of the
motor theory is that neural and anatomical factors restrict the
range of possible systems in any language and that diverging gene
frequencies within language communities over time affect the
balance of preference between the different possibilities, that
is, the change in gene frequencies does not alter the total set
of phonemes or the total set of syntactic patterns which are
possible but the system of phonemes or syntactic patterns which
are actually chosen by a particular community.
In the case of the lexicon, the approach is the same. Motor
and perceptual organisation limit the range of words potentially
appropriate for objects or actions and the lexicon of any
language represents a selection made from the set of possibly
appropriate words. There are two separate questions, how the
range of possible words is limited - what is the generating
mechanism for the forms which words for particular objects,
actions, etc. may take. Secondly, how, given a range of possible
words for a particular object or action, a particular community
currently makes use of one form of the possible words rather than
any other. The range of possible words in a language is limited
in the first instance by the phonological system of the language;
for example, English cannot readily adopt words which depend on
phonemic tone; Australian languages cannot adopt words which
depend on the voicing distinction. But within this phonological
limitation, a number of different wordforms may be possible
within a language to refer to a particular object, action, etc.,
and there may be wordforms already existing in other languages
which are phonologically possible for borrowing into another
language community. What determines which wordforms will actually
be available and actually be used in a given language community?
The argument in the motor theory as developed earlier was
that words are neural programs, formed from the subprograms of
which the phonemes consist, and that the structures of the
wordforms derive from perceptual and motor organisation involved
in the objects, actions, etc. for which words are required. It
is
argued that there is no necessarily unique wordform for a
particular object or action, in the same way as there can be
variation in action organisation to achieve a given end or there
can be variation in modes of perception between individuals,
scanning patterns for objects, and order of analysis of complex
scenes. The original formation of a particular word structure for
a particular object or action will have been derived from the
object, action, etc., under the influence of the particular
perceptual and motor organisation of the individual first to use
the word; at this level, the word used is a selection made from
a
number (but not unlimited number) of appropriate wordforms,
governed by the individual's neural and anatomical structures
subserving motor and perceptual organisation, i.e. ultimately the
genetic endowment for motoric and perceptual organisation as it
has interacted with the individual's developmental environment.
Thus all the words found in a language, and in all languages,
have their origin in the physiological/neurological organisation
of individuals in the different communities, and to the extent
that genetic endowment and perceptual/motoric organisation differ
between individuals and on average between communities, different
words may be formed as appropriate in different language
communities.
The separate question is why, once wordforms have been
generated in this essentially genetic way, they should be adopted
by a particular group, deme, population, etc., at a particular
time. At this point, two sorts of influence may operate: the
first is the extent to which the group has gene frequencies
harmonious with those of the originating individual, i.e. an
'identity of tendencies' (to use VendryÖs' phrase) that
predisposes the community to treat the word as appropriate for
the particular object or action, etc. The second, assuming that
there is a selection of possibly appropriate words within that
community, or readily available by borrowing from another
community, depends on the extent of use of the word by classes
or
groups or individuals within the community, questions of
prestige, effective use and so on. What makes rapid change in
lexical items possible is the previous existence of variant
lexical forms within a community, which can extend their range
of
use, as a particular variant becomes associated with a larger or
smaller group, or a more prominent group, or a group with more
effective use of the word.
Syntax is a term which is used variously but here is taken
to
mean everything in language not covered by the terms phonology
and lexicon. There are, however, several distinct segments of
syntax: perhaps the most basic is syntax as ordering of words in
the utterance; the next connects with ideas about the 'parts of
sentence' - subject, object,predicate etc.; the next is concerned
with 'parts of speech' - classification of words in terms of the
regularities governing their use in the sentence (nouns, verbs).
An important broad classification is into function and content
words. Function words can be subdivided into those which are
essentially syntactic and those which are concerned with other
types of relation, e.g. positioning in time or space.
Diversity and change in syntax can affect any of these
categories or classifications of what is covered by the term
syntax. More specifically:
- variation in word order: SOV or SVO, the positioning of
attributes and nominals, of prepositions or adverbials.
suffixing, infixing and prefixing - or the ordering of clauses;
-
variation in the components of the sentence: subject, object,
indirect object, verb, predicate, particles; - variation in the
functional categories of words: presence or absence of
prepositions, conjunctions, subject, object or ergative markers,
or more generally of function words; - variation in type:
analytic, agglutinative, fusional (inflective), poly-synthetic;
-
variation in classificatory systems: declensions and
conjugations, gender, consonantal and vowel harmony, measures,
concord, etc.
Given this wide range of types of diversity in syntax, the
issue is how the diversity may have originated and how change in
the various types of syntactic structures may have come about.
The simplest way to approach this is to make a broad distinction
between syntactic features (in the narrow sense of ordering
regularities) and lexical aspects of syntax (that is, operations
of syntax which depend upon the existence of particular words (or
subwords), e.g. the availability of conjunctions, prepositions,
case endings, adverbs of time or space and so on.
The specifically syntactic aspects, i.e. ordering
regularities, are in the motor theory derived from ordering
regularities in the neural sub-structure for motor control and
perception (ordering regularities in visual perception and in the
execution of bodily actions). These very basic features of any
individual's neurological/physiological system are most likely
to
be affected by genetic factors in development but least likely
to
change rapidly. Given the extent of individual variation, in
brain, morphology and physiology generally, it is not surprising
that there should be a considerable range of possible modes of
organisation to serve as the base for a large number of different
syntactic processes. The general arguments about the effects of
relative gene frequencies, and changes over time in gene
frequencies, between populations and races are likely to apply,
so that different communities may readily have developed
different syntactic processes, reflecting genetically based
tendencies and forces prevailing in the particular community,
population or race. These very basic syntactic processes are
least likely to be the subject of any conscious alteration or any
change in response to fashion or prestige; the history of
syntactic change in this segment then would be more likely to
resemble that for changes in phonology, i.e. slow rates of
change, widespread in their effects on any language. Historical
linguistics shows that this is in fact the picture. Changes from
SOV to SVO proceed slowly but eventually operate widely over a
particular language use.
The position is somewhat different in the case of the
'lexical' aspects of syntactic diversity and change. The
distinction between 'ordering' function words and other
relational function words is important. One would expect
processes of change, e.g. in the availability of articles, in the
use of the dual, in the existence of a gender or other
classification, to proceed more slowly than changes, e.g. in
relational terms for time and space. An important category is
that of subwords which form the basis of inflectional systems and
which, in function, cover much the same ground as prepositions
or
conjunctions. It is difficult to avoid thinking that the
emergence of a preposition, for example: BY, constitutes a
conceptual advance over an inflectional system in which the idea
conveyed by BY is merged in each separate content word. The
preposition represents a higher level of abstraction than the
inflected form, the conjunction than the use of a simple sequence
of sentences. The change would have been the result of
intellectual advance, in the analysis not only of the perceived
world, but also of the individual's thought and language
processes.
How does this bear on syntactic diversity and change? If the
move to analytic forms is the result of intellectual progress,
evolution of the whole syntactic system would be expected to
proceed slowly but in a definite direction. The forms which
prepositions and conjunctions take would certainly not be the
result of any conscious or arbitrary choice by any community or
group, but be the result of unconscious preferences and
tendencies. The history of prepositions and conjunctions is
obscure but there is evidence that many of them derived from
previously existing words falling into other word categories; so
in Chinese, prepositions appear to have developed from verbs,
such as 'gei' (a verb meaning 'give') used as the preposition
'to'(Norman 1988). In English, prepositions, conjunctions and
adverbs often have a common origin.
Writers such as Labov (1984) have attempted to research, on
the ground, current language change (mostly for limited aspects
of usage or pronunciation in restricted geographical areas or
social groups). His work, he would claim, supports a view of the
social causes of language change, meaning by this that variant
forms found in particular groups are spread more widely for
reasons of prestige or as part of attempts by one group to
differentiate itself from another group. However, Labov's
approach (as Aitchison 1981 has pointed out) deals only with a
superficial aspect of language change.
This paper starts from the motor theory of language origin
that language was modelled on the structures and processes of the
neural motor system. A problem which any biological theory has
to
tackle is why, if there was a strictly biological origin for
language, such a great diversity of languages developed. The
proposal is that language changes and diversifies as a result of
genetic change over long periods of time. Language in the human
has an obvious biological base: speech depends on the anatomy of
the articulatory apparatus, on the specialised organs for hearing
and most importantly on the neural systems which make speaking
and hearing possible. Genetic change over time can affect these
physiological and neurological substrates of language.
At first sight this seems to assume that language as
currently used is derived directly from the physical and neural
organisation of the individuals composing a language community.
This is obviously not the case. Children with differing genetic
inheritance acquire the language of the local community, not the
language of the community to which they are genetically related.
If language change is a consequence over time of genetic change,
then the process by which genetic change is translated into
language change must be more subtle. Whilst variation in genetic
make-up will be expressed directly in the phenotype, in the body
and brain of the individual, variation in genetic factors
affecting the substrates for language in a population confront
an
established inter-individual system of language, which depends
not simply on each individual but on uniformities in language
behaviour between members of the group or population.
The approach adopted to reconcile a biological theory of
language origin and evolution and the diversity of languages
actually found starts from recognition of the many parallels
between variation and change in a strict biological sense (the
physical characteristics of populations) and variation and change
in language over long periods of time. Many of the phenomena
analysed in modern population genetics have close parallels in
the findings of historical linguistics. Both systems display
great diversity and continuing change within and between
populations. The next step is that the processes of biological
and linguistic change and variation are not simply fortuitously
similar but there may be causal links between them. There may not
only be a biological model for language change but also a
biological explanation. Over long periods of time, there must be
changes in the average genetic composition of populations
(changes in gene frequencies) which affect the substrates for
language of the population and prepare the ground for changes in
language forms to reflect differences of the current population
from earlier populations in which a language originally
developed.
Changing gene frequencies within a population will be
manifested in the genomes of children born into the community.
To
the extent that the gene frequencies differ, then children will
be born with physiological and neurological substrates for
language which differ from those in earlier populations. These
differences take effect, not at the stage where the child is
developing its language capacity - it can only learn the local
language - but at the stage when the child becomes an adult. The
speech preferences of a community depend on the tendencies
existing within the members of the community, which are derived
from their physiological and neurological make-up. When children
with genetic differences relevant for language grow up, their
tendencies and preferences will go to modify the prevailing
tendencies and preferences within the community. If over a period
such changed gene frequencies become sufficiently widespread,
then they will alter the linguistic preferences and tendencies
of
the adult community and exert an influence on the selection of
the language forms actually used. So far as the language of a
community is taken to be that form which is most widely accepted,
then changing gene frequencies will have operated to bring about
change in the language.
Changes in gene frequencies within a population affecting the
substrates of language come about in a number of ways described
in general terms earlier in the paper: the separation off, and
isolation, of a particular segment of the population, e.g. the
foundation of a colony, inward migration from another population,
the suppression within a community of a distinct segment of the
population. To make the idea more concrete, events in British
history such as the regional pattern of settlement of Angles,
Saxons and Danes, the dominance of French-speaking rulers after
the Norman Conquest, the Black Death (when a third of the
population died), the rise of London to be by far the major
centre of population, the formation of colonies in the United
States and Australia, the Industrial Revolution with a huge
inward migration from Ireland, obviously could have major effects
on gene frequencies, that is on the composition of the gene pool.
Such major changes will have carried with them the possibility
of
altered gene frequencies relevant for the anatomic, physiological
and neural substrates of language. There are obvious historical
parallels elsewhere (notably throughout Europe). The major
changes in gene frequencies resulting from them could have
provided the motive force and explanation for the recorded
changes in languages and dialects.
Nature of the diversity
The problem of language change
Biological change as a model
Biological variation -
Biological change -
Biological change as an explanation
Supporting argument and evidence
Physical variation relevant for
language diversification
Genetic distance and language
groupings
Transmission of language change
Genetic basis for changes in
phonology, lexicon and syntax
Phonology
Lexicon
Syntax
Conclusion