This commentary argues that, ontrary to Crow's (2000) two-step saltationist hypothesis -- that Homo sapiens suddenly appeared as a mutant endowed with cerebral asymmetry, and the newly acquired lateralised brain allowed the sudden evolution of language -- the empirical data suggest that both the evolution of language and the linguistic use of the resources of the left hemisphere have been gradual processes.
1. If I understand it properly, Crow's (2000) line of argument is the following: language is a specific feature of modern humans; linguistic functions are lateralised; therefore the genetic changes that produced lateralisation in humans could explain the speciation of Homo sapiens. Moreover, since language is assumed - by some - to have appeared suddenly, Crow argues that the genetic changes that are needed for cerebral lateralisation can be given a saltationist explanation. Indeed much of the paper is about his saltationist explanation of hemispheric asymmetry.
2. I cannot comment on the saltationist nature of the advocated changes. I hope the evolutionary biologists and geneticists in the readership will comment on this part. In her commentary Annett (2000) has already expressed strong reservations about making the speciation of Homo sapiens depend on a gene for cerebral asymmetry. From my linguistic vantage point, I would like to discuss two points: the allegedly sudden appearance of language, and the lateralisation of linguistic functions.
3. It is said that if you repeat something long enough, people will start believing it. The idea that language has appeared suddenly in a steady state form is one of those gratuitous statements that has been repeated, without anyone ever presenting any supporting evidence. The lame justification that is given is that today's languages are all complex systems (see Lewontin 1990 for the vacuity of this argument). That today's languages are complex is undeniable, but it is also undeniable that when we observe the history of languages over a few millennia, we recognise definite evolutionary trends (cf. Bichakjian 1999), and if we project these trends back in time, we may surmise a developmental sequence stretching from an improvised set of implements to ever more advanced systems.
4. There is also no empirical support for Bickerton's alleged caesura between "protolanguage" and language. The historical record clearly shows, and the projection of the observed trends clearly suggests, a continuity from rudimentary to ever more developed systems. The continuity is similar to that observed in the evolution of organisms, which developed from prokaryotes to humans, or in the evolution of organs such as the brain, which started with the accumulation of a few nerve cells at one end of the nerve cord and gradually developed to become the powerful command centre of our physical and mental activities. For as long as we can observe language and linguistic features, evolution is there to be recognised, and the process is continuous.
5. The partially observed and, for the rest, putatively surmised existence of the continuous evolution of language raises the question of the starting point. Where is the beginning of the continuum? Biologists have a rich array of palaeontological data to trace the evolution of humans; linguists, unfortunately, have a big gap. They can study the communicative skills of bonobos and surmise those of human ancestors some five or more million years ago. Sue Savage-Rumbaugh has argued that "the most parsimonious view of the language competency gap between ape and man is that it results from differences in information processing capacity, memory, and voluntary control over the vocal mechanism rather than from a lack of innate linguistic structures" (1990:617). But how did those ancestral skills develop during the ensuing millions of years?
6. The presence of possible language areas in the brain of Homo habilis suggests that roughly halfway through the evolution from an apelike ancestor to modern humans, at least some of the biological correlates of speech had developed. Phillip Tobias has long advocated "that the endocast markings, especially those representing Broca's area and Wernicke's area, coupled with the cultural evidence point to the likelihood that articulated speech, albeit rudimentary, was within the capacity of Homo habilis" (1991:71). In the last two years, two other biological indicators have been uncovered. A team of scientists from Duke University has observed that the canal housing the nerve that controls tongue movement is considerably larger in humans, Neanderthals and archaic Homo sapiens than in apes, australopithecines, and Homo habilis. Since the age of fossil bones suggest that the enlargement had occurred more than 300,000 years ago, and since the size increase of the hypoglossal nerve can only be correlated with the tongue's acquisition of a speech function, the authors conclude that "human-like speech capabilities may have evolved much earlier than has been inferred from the archaeological evidence for the antiquity of symbolic thought" (Kay et al. 1998:5419; see also DeGusta et al. 1999). A comparable study was conducted by Ann MacLarnon and her associate, who focused their attention on the size of the vertebral canals housing the nerves that control the contraction of the thoracic muscles and thence the finely-tuned breathing necessary for speech. Their findings are in line with those of the hypoglossal study humans and Neanderthals have enlarged canals, while early Homo erectus and older species do not display increased innervation in the thoracic region. The direct interpretation of these results is that the change must have occurred at some time between 1,600,000 and 100,000 BP, but the authors argue that the expansion of the thoracic canals must be older than the common ancestor of Neanderthals and that the "increased innervation [probably] evolved to enable enhanced breath control, and the most likely functional reason for this was the evolution of speech" (1999: 358-60).
7. While the thoracic study does not pinpoint the exact time when the larger size canals first appeared, nor when the increase began, the combined data from possible language centres and from tongue and thorax innervation do suggest that the development of the central and peripheral speech organs spanned hundreds of millennia. Moreover, since it would be highly unlikely for these size increases to have occurred in a single burst, the evolution must be concluded to have been a gradual process, probably driven by the mutual fertilisation of the biological "hardware" and the linguistic "software".
8. The software did not fossilise, but when one contemplates the Acheulean industry and surveys its evolution, one is prompted to draw a parallel between the evolution of industry and that of language (cf. e.g. the Acheulean-like handaxes recently found in China's Bose Basin and dated to 803,000 BP; Yamei et al. 2000; reproduced in Figure 1).
FIGURE 1. Acheulean-like handaxes recently found in China's Bose Basin and dated to 803,000 BP
Both language and artefacts are not constants, but as variables they vary, essentially in time, from the more rudimentary to the more sophisticated. Like industry, language started as a rudimentary system in our faraway hominid ancestors and steadily developed to become today's complex systems. This is also the view of Marian Annett, who in her commentary wrote that 'the many levels of intelligence, between the 2 year old equivalent of the chimpanzee and an intelligent adult ..., must have evolved through several stages in various types of hominid ancestor. The development and use of intelligence at all these stages would have been aided by an efficient speech system' (2000, par.12).
9. The evidence from the evolution of linguistic features from the earliest reconstructed prototypes to their modern derivatives, coupled with the palaeontological data and the archaeological example, pleads against the view that language suddenly emerged as a steady state entity, or abruptly jumped from a primitive "protolanguage" to linguistic plenitude; instead, they suggest that language, starting in distant ancestors, gradually developed to become what we speak today, and, like our organism, our behaviour, and our technology, will go on evolving.
10. The idea that a rapidly spreading genetic mutation produced a lateralised brain, and the availability of a language-suitable hemisphere triggered the prompt emergence of language also constitutes a scenario that seems at variance with what we observe in, and could deduct from, language evolution. When one scans the history of linguistic features, one notices that the ancestral languages made use of vowel length, pitch accent, consonants produced with increased subglottal pressure, perceptual notions such as agent and patient, and holistic grammatical structures, whereas modern languages use instead sound quality distinctions, dynamic accent, supraglottal points of articulation, conceptual notions such as subject and object, and syntactic structures that lend themselves to serial processing (cf. Bichakjian 1999a and b for a detailed presentation).
11. Since the older features are more in line with the workings of the right hemisphere, while the modern ones correspond better with the modus operandi of the left brain, the observed pervasive shift would suggest that language was not triggered by lateralisation, but gradually adapted its features to make an increased use of the more advantageous capabilities of the left hemisphere. This also seems to be the assessment of Terrence Deacon, who from his neurological vantage point argues that "the structure of languages has probably evolved to take advantage of intrinsic subtle biases in developing brains", and concludes that "lateralisation is probably ... not a cause or even precondition for language evolution" (1997:309 and 310).
12. The puzzle of human speciation remains unsolved. Did the successive hominid species, if species they all were, gradually grade into one another? Or did they evolve by jumping from one plateau to the next?. From their vantage point, linguists are not in a position to answer those questions, but, if they have carefully observed and correctly interpreted the historical record, they are in a position to submit sufficient data suggesting that language evolution has always been and continues to be a gradual process.
Annett, M . 2000. No Homo Speciated on Cerebral Dominance Psycoloquy 11 (020) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/2000.volume.11/ psyc.00.11.020.language-sex-chromosomes.2.annett http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?11.020
Bichakjian, B.H. 1999a. Language Diversity and the Straight Flush Pattern of Language Evolution. Target article with discussion. Jazyk i rechevaja dejatelnost (Language and Speech Activity. The Journal of the Linguistic Society of St. Petersburg). 2. 18-44.
Bichakjian, B.H. 1999b. Language Evolution and the Complexity Criterion Psycoloquy 10 (033). ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/1999.volume.10/ psyc.99.10.033.language-complexity.1.bichakjian http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?10.033
Crow, T.J. 2000. Did Homo Sapiens Speciate on the y Chromosome? PSYCOLOQUY 11(001) ftp://ftp.princeton.edu/pub/harnad/Psycoloquy/2000.volume.11/ psyc.00.11.001.language-sex-chromosomes.1.crow http://www.cogsci.soton.ac.uk/cgi/psyc/newpsy?11.001
Deacon, T.W. 1997. The Symbolic Species. The Co-Evolution of Language and the Brain. New York: W.W. Norton and Co.
DeGusta, D., Gilbert, W. H. & Turner, S.P. (1999) Hypoglossal canal size and hominid speech. Proceedings of the National Academy of Sciences, USA 96:1800-04.
Kay, R. F., Cartmill, M. & Balow, M. (1998) The Hypoglossal Canal and the Origin of Human Vocal Behavior. Proceedings of the National Academy of Sciences, USA 95: 5417-19.
Lewontin, R. C. 1990. How much did the Brain have to Change for Speech? Behavioral and Brain Sciences 13: 740-41.
Savage-Rumbaugh, E. S. 1990. Language Acquisition in a Nonhuman Species: Implications for the innateness debate. Developmental Psychobiology 23: 599-620.
Tobias, P. V. 1991. The Emergence of Spoken Language in Hominid Evolution. Cultural Beginnings: Approaches to Understanding Early Hominid Life-Ways in the African Savanna, ed. J. D.Clark. Bonn: Habelt, pp. 67-78.
Yamei, Hou, Potts, R., Yuan Baoyin, Guo Zhengtang, Deino, A., Wang Wei, Clark, J., Xie Guangmao, & Huang Weiwen. 2000. Mid-Pleistocene Acheulean-like Stone Technology of the Bose Basin, South China. Science 287: 1622-1626.