This is the original unpublished article entitled 'Homo voce – our solo choice?'. The chinese version appeared on The Hong Kong Economic Journal Monthly (V31 N5 p164-5) in August, 2007. I wonder if I would have been one of the youngest author ever to write an article in HKEJ Monthly!
A short discourse on the suitability of adopting speech as a diagnosis of human
To the Editors,
Hong Kong Economic Journal Monthly
Dear Sirs,
Contra Linnaeus (1758), who circumvented the diagnosis (or, in vernacular, definition) of human by stating 'Homo, nosce te ipsum' – human, know thyself – biologists have been keen to suggest uniqueness of humanity, albeit this being 'one of abandoned claims' (de Waal, 2005). In a review of The Talking Ape (Burling, 2005) in your esteemed journal, the author seemed to evoke the emphasis on syntactic speech as the smoking gun, asserting that Homo sapiens could be distinguished from traditional 'pongids' [1] by their uniquely enlarged brain and descended larynx, which allowed the development of syntactic speech, which in turn allowed that of culture (HKEJ Monthly, number 363, page 163-5).
None of the claims are, in reality, particularly true. Wherefore, I would seek to discuss this issue from a broader anthropological and paleontological perspective. This supplement, I hope, may further benefit your learnt readers.
Culture, for instance, is not a uniquely human phenomenon if it is not judged from a language-and-writing basis. 'The cultural label befits any species whose communities can be distinguished from one another by their unique suite of behavioral characters' – learnt and propagated through generations (de Waal, 1999). In fact, extensive, multiple behavioral pattern variations among chimpanzees have been documented in a synthesis of observation from the seven best studies of which in the field (Whiten et al, 1999).
Syntactic speech is not a prerequisite for culture, nor does it totally eclipse other behavioral and chemical signals for animal communication. Nowak et al (2000) suggested that syntax emerged as a result of human having to handle an increasing amount of signals exceeding a threshold value. That 'pongids' do not experience such a natural selection (i.e. living in habitats that demand the use of a threshold-flooding number of signals) does not speak of their incapacity of inventing syntax.
The neural and gross anatomical substrates for speech, as they turn out, preceded the origin of human (Carroll, 2003). The frontal cortex (involved in emotion and 'higher' cognitive functions) is actually not disproportionately larger in humans compared with 'pongids'. Left hemisphere-dominant communication process (required for speech production) has been demonstrated in chimpanzees, bonobos and gorillas as well. A distinct area housing the mirror-neuron system, architectonically comparable to the Broca's area for speech generation in human, has been identified in the macaque (Petrides et al, 2005). Recent discovery of the enigmatic fossil hominin Homo floresiensis, with an endocranial volume of only 380cc (e.g. Brown et al, 2004; Morwood et al, 2005) further refuted the oft-assumed correlation between brain size and intelligence [2].
Despite the initial euphoria shrouding the 'gift of gap' theory (e.g. Leakey et al, 1992; Cartmill, 1998), the descended laryngeal condition, which supposedly allows for pronunciation and speech, is fading in its uniqueness as are neural marker of humanness. It has been shown that, as in human, both the laryngeal complex descends relative to the hyoid (Nishimura et al, 2003; Nishimura, 2003) and the hyoid descends relative to the palate (Nishimura et al, 2006) in chimpanzee infants. Any proponent of the 'gift of gap' theory, in fact, must consider the truth that evolution is not purpose-driven. Laryngeal descent is more a result of facial heterochronic changes in hominins than responding to the need to produce speech. It may only be that humans have made more utilization of this resonation chamber.
It may thus be obviously concluded that the most parsimonious [3] scenario is that all neural and anatomical foundations for syntactic speech – and the corresponding trait known as culture – are present in the most recent common ancestor (MRCA) of humans, chimpanzees, bonobos and gorillas and all descendents thereof (Carroll, 2003). The assumed human uniqueness can be inferred from quantitative modification of plesiomorphic (i.e. primitive) characters rather than invoking qualitative evolution novelties!
Your article however, akin to many enthusiastic discussions on the diagnosis of human, has neglected one fundamental fault: many of the striking differences between human and chimpanzees remain valid only when extant species are considered (figure 1). Paleontology has largely put this naivety into question (Carroll, 2003). It is known that the evolution of hominins involved multiple radiations, poly-specific co-existence with the possibility of genetic and cultural exchange, and dead-end extinctions (Wood et al, 1999; figure 2). Peculiar as it may be, the mono-specific existence of Homo sapiens in the Holocene is none the norm. The implication of such a picture on the discerning of humanness is two-fold:
1 The evolution of 'modern' traits was not a linear, additive process (Carroll, 2003). Various hominins might have independently evolved an assortment of 'advanced' anatomical and behavioral characters, mostly in response to local environmental stress, which might be lost with the lineage. Any claims of 'smoking guns' must be carefully correlated with existing fossil evidence while bearing in mind that theories may have to be revised in face of new fossil findings.
A short discourse on the suitability of adopting speech as a diagnosis of human
To the Editors,
Hong Kong Economic Journal Monthly
Dear Sirs,
Contra Linnaeus (1758), who circumvented the diagnosis (or, in vernacular, definition) of human by stating 'Homo, nosce te ipsum' – human, know thyself – biologists have been keen to suggest uniqueness of humanity, albeit this being 'one of abandoned claims' (de Waal, 2005). In a review of The Talking Ape (Burling, 2005) in your esteemed journal, the author seemed to evoke the emphasis on syntactic speech as the smoking gun, asserting that Homo sapiens could be distinguished from traditional 'pongids' [1] by their uniquely enlarged brain and descended larynx, which allowed the development of syntactic speech, which in turn allowed that of culture (HKEJ Monthly, number 363, page 163-5).
None of the claims are, in reality, particularly true. Wherefore, I would seek to discuss this issue from a broader anthropological and paleontological perspective. This supplement, I hope, may further benefit your learnt readers.
Culture, for instance, is not a uniquely human phenomenon if it is not judged from a language-and-writing basis. 'The cultural label befits any species whose communities can be distinguished from one another by their unique suite of behavioral characters' – learnt and propagated through generations (de Waal, 1999). In fact, extensive, multiple behavioral pattern variations among chimpanzees have been documented in a synthesis of observation from the seven best studies of which in the field (Whiten et al, 1999).
Syntactic speech is not a prerequisite for culture, nor does it totally eclipse other behavioral and chemical signals for animal communication. Nowak et al (2000) suggested that syntax emerged as a result of human having to handle an increasing amount of signals exceeding a threshold value. That 'pongids' do not experience such a natural selection (i.e. living in habitats that demand the use of a threshold-flooding number of signals) does not speak of their incapacity of inventing syntax.
The neural and gross anatomical substrates for speech, as they turn out, preceded the origin of human (Carroll, 2003). The frontal cortex (involved in emotion and 'higher' cognitive functions) is actually not disproportionately larger in humans compared with 'pongids'. Left hemisphere-dominant communication process (required for speech production) has been demonstrated in chimpanzees, bonobos and gorillas as well. A distinct area housing the mirror-neuron system, architectonically comparable to the Broca's area for speech generation in human, has been identified in the macaque (Petrides et al, 2005). Recent discovery of the enigmatic fossil hominin Homo floresiensis, with an endocranial volume of only 380cc (e.g. Brown et al, 2004; Morwood et al, 2005) further refuted the oft-assumed correlation between brain size and intelligence [2].
Despite the initial euphoria shrouding the 'gift of gap' theory (e.g. Leakey et al, 1992; Cartmill, 1998), the descended laryngeal condition, which supposedly allows for pronunciation and speech, is fading in its uniqueness as are neural marker of humanness. It has been shown that, as in human, both the laryngeal complex descends relative to the hyoid (Nishimura et al, 2003; Nishimura, 2003) and the hyoid descends relative to the palate (Nishimura et al, 2006) in chimpanzee infants. Any proponent of the 'gift of gap' theory, in fact, must consider the truth that evolution is not purpose-driven. Laryngeal descent is more a result of facial heterochronic changes in hominins than responding to the need to produce speech. It may only be that humans have made more utilization of this resonation chamber.
It may thus be obviously concluded that the most parsimonious [3] scenario is that all neural and anatomical foundations for syntactic speech – and the corresponding trait known as culture – are present in the most recent common ancestor (MRCA) of humans, chimpanzees, bonobos and gorillas and all descendents thereof (Carroll, 2003). The assumed human uniqueness can be inferred from quantitative modification of plesiomorphic (i.e. primitive) characters rather than invoking qualitative evolution novelties!
Your article however, akin to many enthusiastic discussions on the diagnosis of human, has neglected one fundamental fault: many of the striking differences between human and chimpanzees remain valid only when extant species are considered (figure 1). Paleontology has largely put this naivety into question (Carroll, 2003). It is known that the evolution of hominins involved multiple radiations, poly-specific co-existence with the possibility of genetic and cultural exchange, and dead-end extinctions (Wood et al, 1999; figure 2). Peculiar as it may be, the mono-specific existence of Homo sapiens in the Holocene is none the norm. The implication of such a picture on the discerning of humanness is two-fold:
1 The evolution of 'modern' traits was not a linear, additive process (Carroll, 2003). Various hominins might have independently evolved an assortment of 'advanced' anatomical and behavioral characters, mostly in response to local environmental stress, which might be lost with the lineage. Any claims of 'smoking guns' must be carefully correlated with existing fossil evidence while bearing in mind that theories may have to be revised in face of new fossil findings.
2 The level of synapomorphy [4] of any candidate morphological or genetic characters must be stated in phylogenetic sense to make research meaningful. Even if a character is shown to be present in modern human (Homo sapiens) and absent in chimpanzees, it may yet be debatable whether it was present in Neanderthals, 'archaic' Homo species, australopithecines or other 'stem' hominins. In addition, characters supposed to be unique to Homo sapiens do not necessarily equate to human superiority – as Finlayson (2005) argued, the colonization by linguistic, technologically advanced Homo sapiens was not the cause of extinction of Homo neanderthalensis.
In conclusion, the qualitative evolution novelty that may provide the diagnosis of humanness remains obscure under current anthropological and paleontological evidence. While the current draft-PhyloCode (Cantino and de Queiroz, 2006) does not govern the definition of a species, future research on the diagnosis of Homo sapiens should in fact address and be conducted under the framework of hominid phylogeny. One should abandon to seek the potential difference between human and traditional 'pongids', but view ourselves (and our phenotypic traits known as speech and culture) as a quantitatively advanced species in the continuum of hominid evolution.
Yours faithfully,
Leo W Sham
Notes
[1] Pongids traditionally denote the great apes. It is an invalid paraphylectic grade (incomplete group of organism comprising an ancestor plus only some of its descendents) in current scientific understanding.
[2] The discovery of multiple specimens suggested that Homo floresiensis is unlikely a microcephalic modern human. Although its brain size is roughly that of the chimpanzee's, archeological evidence supported that it could butcher stegodons and use fire – behavior only expected of modern human.
[3] In science, the simplest hypothesis (necessitating the fewest assumptions) is preferred.
[4] In phylogenetics, only synapomorphies (shared derived characters) are considered useful in determining the uniqueness of a (group of) organism.
Figure 1: cladogram of extant hominids
Pongo pygmaeus (orangutan)
Gorilla gorilla (gorilla)
Pan paniscus (bonobo)
Pan troglodytes (chimpanzee)
Homininae (see figure 2) - Homo sapiens (human)
Figure 2: cladogram of extant and extinct hominids
'Stem hominids' (see figure 1)
Unnamed fossil chimpanzee KNM-TH 45519-45521 (McBrearty et al, 2005)
Homininae - Sahelanthropus tchadensis
Orrorin tugenensis
Ardipithecus ramidus kadabba
Ardipithecus ramidus ramidus
Kenyanthropus platyops
Australopithecus anamensis
Australopithecus bahrelghazali
Australopithecus afarensis
Australopithecus africanus
Australopithecus garhi
Paranthropus aethiopicus
Paranthropus robustus
Paranthropus boisei
Homo rudolfensis
Homo habilis
Homo erectus (including Homo ergaster)
Homo floresiensis
Homo antecessor
Homo heidelbergensis
Homo neanderthalensis
Homo sapiens
References
Brown P et al (2004). A new small-bodied hominin from the late Pleistocene of Flores, Indonesia. Nature 431: 1055-1061
Burling R (2005). The talking ape: how language evolved. Oxford University Press, 296 pages.
Cantino PD and de Queiroz K (2006). International Code of Phylogenetic Nomenclature. Version 3a Part I: clade names. http://www.ohiou.edu/phylocode/
Carroll SB (2003). Genetics and the making of Homo sapiens. Nature 422:849-857
Cartmill M (1998). The gift of gab. Discover November 1998, 56-64
Finlayson C (2005). Neanderthals and modern humans: an ecological and evolutionary perspective. Cambridge University Press, 255 pages.
Leakey R et al (1992). Origins reconsidered: in search of what makes us human. Little, Brown and Company, 375 pages.
Linnaeus C (1758). Systemae Naturae per regna tria naturae, secundum classes, ordines, genera, species cum characteribus, differentiis, synonymis, locis.
McBrearty S et al (2005). First fossil chimpanzee. Nature 437:105-108
Morwood MJ et al (2005). Further evidence for small-bodied hominins from the late Pleistocene of Flores, Indonesia. Nature 437:1012-1017
Nishimura T (2003). Comparative morphology of the hyo-laryngeal complex in anthropoids: two steps in the evolution of the descent of the larynx. Primates 44:41-49.
Nishimura T et al (2003). Descent of the larynx in chimpanzee infants. Proceedings of the National Academy of Sciences, USA 100:6930-6933.
Nishimura T et al (2006). Descent of the hyoid in chimpanzees: evolution of face flattening and speech. Journal of Human Evolution 51:244-254
Nowak MA et al (2000). The evolution of syntactic communication. Nature 404:495-498
Petrides M et al (2005). Orofacial somatomotor responses in the macaque monkey homologue of Broca's area. Nature 435:1235-1238
de Waal FBM (1999). Cultural primatology comes of age. Nature 399:635-636
de Waal FBM (2005). A century of getting to know the chimpanzee. Nature 437:56-59
Whiten A et al (1999). Cultures in chimpanzees. Nature 399:682-685
Wood B et al (1999). The human genus. Science 284:65-71
Adapted © Leo W Sham, MMVII
In conclusion, the qualitative evolution novelty that may provide the diagnosis of humanness remains obscure under current anthropological and paleontological evidence. While the current draft-PhyloCode (Cantino and de Queiroz, 2006) does not govern the definition of a species, future research on the diagnosis of Homo sapiens should in fact address and be conducted under the framework of hominid phylogeny. One should abandon to seek the potential difference between human and traditional 'pongids', but view ourselves (and our phenotypic traits known as speech and culture) as a quantitatively advanced species in the continuum of hominid evolution.
Yours faithfully,
Leo W Sham
Notes
[1] Pongids traditionally denote the great apes. It is an invalid paraphylectic grade (incomplete group of organism comprising an ancestor plus only some of its descendents) in current scientific understanding.
[2] The discovery of multiple specimens suggested that Homo floresiensis is unlikely a microcephalic modern human. Although its brain size is roughly that of the chimpanzee's, archeological evidence supported that it could butcher stegodons and use fire – behavior only expected of modern human.
[3] In science, the simplest hypothesis (necessitating the fewest assumptions) is preferred.
[4] In phylogenetics, only synapomorphies (shared derived characters) are considered useful in determining the uniqueness of a (group of) organism.
Figure 1: cladogram of extant hominids
Pongo pygmaeus (orangutan)
Gorilla gorilla (gorilla)
Pan paniscus (bonobo)
Pan troglodytes (chimpanzee)
Homininae (see figure 2) - Homo sapiens (human)
Figure 2: cladogram of extant and extinct hominids
'Stem hominids' (see figure 1)
Unnamed fossil chimpanzee KNM-TH 45519-45521 (McBrearty et al, 2005)
Homininae - Sahelanthropus tchadensis
Orrorin tugenensis
Ardipithecus ramidus kadabba
Ardipithecus ramidus ramidus
Kenyanthropus platyops
Australopithecus anamensis
Australopithecus bahrelghazali
Australopithecus afarensis
Australopithecus africanus
Australopithecus garhi
Paranthropus aethiopicus
Paranthropus robustus
Paranthropus boisei
Homo rudolfensis
Homo habilis
Homo erectus (including Homo ergaster)
Homo floresiensis
Homo antecessor
Homo heidelbergensis
Homo neanderthalensis
Homo sapiens
References
Brown P et al (2004). A new small-bodied hominin from the late Pleistocene of Flores, Indonesia. Nature 431: 1055-1061
Burling R (2005). The talking ape: how language evolved. Oxford University Press, 296 pages.
Cantino PD and de Queiroz K (2006). International Code of Phylogenetic Nomenclature. Version 3a Part I: clade names. http://www.ohiou.edu/phylocode/
Carroll SB (2003). Genetics and the making of Homo sapiens. Nature 422:849-857
Cartmill M (1998). The gift of gab. Discover November 1998, 56-64
Finlayson C (2005). Neanderthals and modern humans: an ecological and evolutionary perspective. Cambridge University Press, 255 pages.
Leakey R et al (1992). Origins reconsidered: in search of what makes us human. Little, Brown and Company, 375 pages.
Linnaeus C (1758). Systemae Naturae per regna tria naturae, secundum classes, ordines, genera, species cum characteribus, differentiis, synonymis, locis.
McBrearty S et al (2005). First fossil chimpanzee. Nature 437:105-108
Morwood MJ et al (2005). Further evidence for small-bodied hominins from the late Pleistocene of Flores, Indonesia. Nature 437:1012-1017
Nishimura T (2003). Comparative morphology of the hyo-laryngeal complex in anthropoids: two steps in the evolution of the descent of the larynx. Primates 44:41-49.
Nishimura T et al (2003). Descent of the larynx in chimpanzee infants. Proceedings of the National Academy of Sciences, USA 100:6930-6933.
Nishimura T et al (2006). Descent of the hyoid in chimpanzees: evolution of face flattening and speech. Journal of Human Evolution 51:244-254
Nowak MA et al (2000). The evolution of syntactic communication. Nature 404:495-498
Petrides M et al (2005). Orofacial somatomotor responses in the macaque monkey homologue of Broca's area. Nature 435:1235-1238
de Waal FBM (1999). Cultural primatology comes of age. Nature 399:635-636
de Waal FBM (2005). A century of getting to know the chimpanzee. Nature 437:56-59
Whiten A et al (1999). Cultures in chimpanzees. Nature 399:682-685
Wood B et al (1999). The human genus. Science 284:65-71
Adapted © Leo W Sham, MMVII
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