Afroasiatic Urheimat

From Wikipedia, the free encyclopedia
Jump to: navigation, search
The Afroasiatic languages, as they are distributed today.

The term Afroasiatic Urheimat refers to the hypothetical place where Proto-Afroasiatic speakers lived in a single linguistic community, or complex of communities, before this original language dispersed geographically and divided into distinct languages. This speech area is known as the Urheimat ("original homeland" in German). Afroasiatic languages are today distributed in parts of Africa and Western Asia.

The contemporary Afroasiatic languages are spoken in the Near East, North Africa, the Horn of Africa, and parts of the Sahara/Sahel. The various hypotheses for the Afroasiatic Urheimat are distributed throughout this territory;[1][2][3][4] That is, it is generally assumed that Proto-Afroasiatic was spoken in some region where Afroasiatic languages are still spoken today. However, there is no consensus as to which part of the contemporary Afroasiatic speech area corresponds with the original homeland.

Date of Afroasiatic[edit]

The earliest written evidence of an Afroasiatic language is an Ancient Egyptian inscription dated c. 3400 BC (5,400 years ago).[5] Symbols on Gerzean pottery resembling Egyptian hieroglyphs date back to c. 4000 BC, suggesting a still earlier possible date. This gives us a minimum date for the age of Afroasiatic. However, Ancient Egyptian is highly divergent from Proto-Afroasiatic (Trombetti 1905: 1–2), and considerable time must have elapsed in between them. Estimates of the date at which the Proto-Afroasiatic language was spoken vary widely. They fall within a range between approximately 7,500 BC (9,500 years ago) and approximately 16,000 BC (18,000 years ago). According to Igor M. Diakonoff (1988: 33n), Proto-Afroasiatic was spoken c. 10,000 BC. According to Christopher Ehret (2002: 35–36), Proto-Afroasiatic was spoken c. 11,000 BC at the latest, and possibly as early as c. 16,000 BC. These dates are older than dates associated with most other proto-languages. Culturally this falls within the period of the Halfan culture which may have been Proto-Afroasiatic.

Urheimat hypotheses[edit]

Levant theory[edit]

Supporters of a non-North or Northeast African origin for Afroasiatic are particularly common among those with a background in Semitic or Egyptological studies,[1] or amongst archaeological proponents of the "farming/language dispersal hypothesis" according to which major language groups dispersed with early farming technology in the Neolithic.[6][7] The leading linguistic proponent of this idea in recent times is Alexander Militarev. Arguments for and against this position depend upon the contested proposal that farming-related words can be reconstructed in Proto-Afroasiatic, with farming technology being widely thought to have spread from the Levant into Africa.

Militarev, who linked proto-Afroasiatic to the Levantine Natufian culture, that preceded the spread of farming technology, believes the language family to be about 10,000 years old. He wrote (Militarev 2002, p. 135) that the "Proto-Afrasian language, on the verge of a split into daughter languages", meaning, in his scenario, into "Cushitic, Omotic, Egyptian, Semitic and Chadic-Berber", "should be roughly dated to the ninth millennium BC". But an Asiatic origin need not be associated exclusively with the migration of agricultural populations: according to linguists, words for dog (an Asian domesticate) reconstruct to Proto-Afroasiatic[8] as well as words for bow and arrow,[9] which according to archaeologists spread rapidly across North Africa once they were introduced from the Near East i.e. Ounan points.[10] A scenario that also fits the linguistic evidence is one in which Afroasiatic languages were introduced into Africa together with advanced hunting techniques before the subsequent introduction of agriculture.

Red Sea/Horn of Africa theory[edit]

The Horn of Africa, particularly the area of Ethiopia and Eritrea, has been proposed by some linguists as the origin of the language group because it includes the majority of the diversity of the Afroasiatic language family and has very diverse groups in close geographic proximity, sometimes considered a telltale sign for a linguistic geographic origin. Within this hypothesis there are several variants:

  • Christopher Ehret has proposed the western Red Sea coast from Eritrea to southeastern Egypt. While Ehret disputes Militarev's proposal that Proto-Afroasiatic shows signs of a common farming lexicon, he suggests that early Afroasiatic languages were involved in the even earlier development of intensive food collection in the areas of Ethiopia and Sudan. In other words, he proposes an even older age for Afroasiatic than Militarev, at least 15,000 years old and possibly older, and believes farming lexicon can only be reconstructed for branches of Afroasiatic.[11][12][13][14] But, the appearance of linguistic terms such as dog, bow, and arrow[15] in Proto-Afroasiatic makes a date earlier than 9,500 BC (coinciding with the end of the Younger Dryas) highly unlikely since dogs only appear at the earliest in the archaeological record after 12,000 BC in the Near East,[16] and arrowheads only appear after 9,500 BC in Africa[10] as a result of introduction from the Near East.[10]
In the next phase, unlike many other authors Ehret proposed an initial split between northern, southern and Omotic. The northern group includes Semitic, Egyptian and Berber (agreeing with others such as Diakonoff). He proposed that Chadic stems from Berber (some other authors group it with southern Afroasiatic languages such as Cushitic ones).
  • Roger Blench has proposed Southwestern Ethiopia, in or around the Omo Valley. Compared to Militarev and Ehret he proposed a relatively young time-depth of approximately 7,500 years. Like Ehret he accepts that Omotic is Afroasiatic and sees the split of northern languages from Omotic as an important early development, but he did not group Egyptian or Chadic with any of these.

North Africa theory[edit]

A more typical proposal is that Semitic is an offshoot of a northern family of Afroasiatic languages, including Berber, and possibly Egyptian. It then entered the Levant and was possibly spread by what Juris Zarins calls the Syro-Arabian nomadic pastoralism complex,[17] spreading south along the shores of the Red Sea and northeast around the edge of the "Fertile Crescent". It is thought that Semitic speakers then crossed from South Arabia back into Eritrea.[18]

In contrast, Bender proposed on linguistic grounds that Cushitic (found in the Horn of Africa) shares important innovations with Semitic and Berber, and that these three split off early from the others, while still near an original homeland of all Afroasiatic.[clarification needed]

Sahel/Sahara theory[edit]

Igor Diakonoff proposed the Eastern Sahara region, specifically the southern fringe of the Sahara.[3][19]

Lionel Bender proposed the area near Khartoum, Sudan, at the confluence of the Blue Nile and White Nile.[3][19] The details of his theory are widely cited but controversial, as it involves the proposal that Semitic originated in Ethiopia and crossed to Asia directly from there over the Red Sea. This could also potentially solidify Bender's argument, in that scholars today believe that there is a relationship between the Cushitic branch and the Chadic Branch; arguing that perhaps Chadic descends from Cushitic.

Prior to Colonialism the Hausa peoples of present day Niger, Nigeria, Burkina Faso, and Chad were not united as a single polity, but rather they existed as a sequence of seven city-states (situated between the Niger River and Lake Chad); each with their own Sovereign dynasty named after their shared common progenitor known as Bayajidda, who apparently came from the "East" to which a great deal of scholars attribute to being the "Middle East', though this is contested. Each City-State were their own entities but were intertwined through trade, language, religion, customs, and ethnic identity/relations; hence comprising a sizable cultural stock that had greater trade links with larger states and empires such as the Ghana Empire, Mali Empire, Kanem-Bornu Empires, etc.

In current day southwestern Chad and northeastern Cameroon in the Lake Chad Basin, there are several ethnic groups that also speak an Afroasiatic language similar to the Hausas. They are known as respectively: the Biu–Mandara, Tumak, Nancere, Kera, Dangaléat, Mukulu, Sokoro, etc. Together with the Hausa, they collectively comprise the Chadic branch of the Afro-Asiatic family. There are also remnants of a civilization on the Cameroon side of Lake Chad that date back to at least the sixth Century BCE; which is suspected of being the remains of the late Sao civilisation, which scholars suspect as being the result of waves of Nubian migrations into West Africa (further substantiating the claims that 'Bayajidda' hence Hausas, came from the "East").[citation needed] Sub-groups such as the Gamergu, Kanembu, Sokoro, and Musgum all claim relations to one another as well as descent from the Sao.[citation needed]

Martin Bernal's hypothesis[edit]

Martin Bernal in his Black Athena proposed the area around the KenyaEthiopia border, before moving his focus south to the Great Rift Valley.[19] More controversially, Bernal came to argue for this Urheimat further south based upon perceived connections between Afroasiatic and Khoisan languages, chiefly the presence of sex-based grammatical gender in contrast to other African languages. This proposal has not been extensively cited as a mainstream theory.[19]

Evidence from population genetics[edit]

For a basic introduction to population genetics, see Population genetics.
Frequency of haplogroup E1b1b in select Afro-Asiatic speakers [20][21]
Language (Region where historically spoken) Frequency
Cushitic 32–81%
Egyptian languages 36–60%
Berber languages 40–91%
Semitic languages 7–29%
Omotic languages >50%

The most commonly cited genetic marker in recent decades has been the Y chromosome, which is passed from father to son along paternal lines in un-mixed form, and therefore gives a relatively clear definition of one human line of descent from common ancestors.

Several branches of humanity's Y DNA family tree have been proposed as having an association with the spread of Afroasiatic languages.

1. Haplogroup E1b1b is thought to have originated in Horn of Africa. In general, Afroasiatic speaking populations have relatively high frequencies of this haplogroup, with the notable exception of Chadic speaking populations. Christopher Ehret and Shomarka Keita have suggested that the geography of the E1b1b lineage coincides with the distribution of Afroasiatic languages.[22]

2. Haplogroup J1c3 (Y-DNA), formally known as "J1e", is actually a more common paternal lineage than E1b1b in most Semitic speaking populations, but this is associated with Middle Eastern origins and has apparently been spread from there after the original dispersion of Afroasiatic.[23]

Frequency of Sub-Haplogroup R1b1a in select Afro-Asiatic speakers[24]
Chadic languages 28.6-95.5%
Berber languages 0-26.9%
Semitic languages 0-40%

3. Haplogroup R1b1a (R-V88), and specifically its sub-clade R-V69, has a very strong relationship with Chadic speaking populations, who unlike other Afroasiatic speakers have low frequencies of Haplogroup E1b1b.[25] The majority of R-V88 was found in northern and central Africa, in Chadic speaking populations. It is less common in neighbouring populations. The authors also found evidence of high concentration in Western Egypt and evidence that the closest related types of R1b are found in the Middle East, and to a lesser extent southern Europe. They proposed that an Eastern Saharan origin for Chadic R1b would agree with linguistic theories such as those of Christopher Ehret, that Chadic and Berber form a related group within Afroasiatic, which originated in the area of the Sahara.[25]

In contrast to the evidence from paternally inherited Y DNA, a recent study has shown that a branch of mitochondrial haplogroup L3 links the maternal ancestry of Chadic speakers from the Sahel with Cushitic speakers from Horn of Africa.[26]

Other mitochondrial lineages that are associated with Afroasiatic include mitochondrial haplogroups M1 and haplogroup U6. Gonzalez et al. 2007 suggest that Afroasiatic speakers may have dispersed from Horn of Africa carrying the subclades M1a and U6a1.[27]

According to an autosomal DNA study by Hodgson et al. (2014), the Afroasiatic languages were likely spread across Africa and the Near East by an ancestral population(s) carrying a newly identified non-African genetic component, which the researchers dub the "Ethio-Somali". This Ethio-Somali component is today most common among Afroasiatic-speaking populations in the Horn of Africa. It is most closely related to the Maghrebi non-African genetic component, and is believed to have diverged from all other non-African ancestries at least 23,000 years ago. On this basis, the researchers suggest that the original Ethio-Somali carrying population(s) probably arrived in the pre-agricultural period from the Near East, having crossed over into northeastern Africa via the Sinai peninsula. The population then likely split into two branches, with one group heading westward toward the Maghreb and the other moving south into the Horn.[28] A related hypothesis that associates the origin of the ancestors of Afroasiatic speakers as the result of a reflux population from Southwest Asia during the Late Palaeolithic was previously put forward by Daniel McCall.[29]

Nostratic hypothesis[edit]

The Nostratic language family is a proposed macrofamily grouping together a number of language families including Indo-European, Uralic, Altaic, and more controversially Afroasiatic. Following Pedersen, Illich-Svitych, and Dolgopolsky, most advocates of the theory have included Afroasiatic in Nostratic, though criticisms by Joseph Greenberg and others from the late 1980s onward suggested a reassessment of this position.

Ilya Yabonovich and other linguists, in examining the differences between the various members of the Afroasiatic family have realised that all of the old etymologies for this group were inherently semitocentric. The differences between Chadic, Omotic, Cushitic and Semitic, were wider than those seen between any members of the Indo-European family and as wide as some of the differences seen within and between separate language families, for example, Indo-European and Altaic. Certainly the exclusion of Afroasiatic from the controversial Nostratic family has simplified matters of phonemics, not having to include the complex patterns seen in Afroasiatic languages.

Allan Bomhard (1994) retains Afroasiatic within Nostratic, despite his admission that Proto–Afroasiatic is very different from the other members of the proposed linguistic Nostratic superfamily.[30] As a result he suggests it was probably the first language to have split from the Nostratic linguistic superfamily. Recently, however, a consensus has been emerging among proponents of the Nostratic hypothesis. Greenberg in fact basically agreed with the Nostratic concept, though he stressed a deep internal division between its northern 'tier' (his Eurasiatic) and a southern 'tier' (principally Afroasiatic and Dravidian). The American Nostraticist Bomhard considers Eurasiatic a branch of Nostratic alongside other branches: Afroasiatic, Elamo-Dravidian, and Kartvelian. Similarly, Georgiy Starostin (2002) arrives at a tripartite overall grouping: he considers Afroasiatic, Nostratic and Elamite to be roughly equidistant and more closely related to each other than to anything else.[31] Sergei Starostin's school has now re-included Afroasiatic in a broadly defined Nostratic, while reserving the term Eurasiatic to designate the narrower subgrouping which comprises the rest of the macrofamily. Recent proposals thus differ mainly on the precise placement of Dravidian and Kartvelian.

See also[edit]

References[edit]

  1. ^ a b Blench R (2006) Archaeology, Language, and the African Past, Rowman Altamira, ISBN 0-7591-0466-2, ISBN 978-0-7591-0466-2, http://books.google.be/books?id=esFy3Po57A8C
  2. ^ Ehret C, Keita SOY, Newman P (2004) The Origins of Afroasiatic a response to Diamond and Bellwood (2003) in the Letters of SCIENCE 306, no. 5702, p. 1680 doi:10.1126/science.306.5702.1680c
  3. ^ a b c Bender ML (1997), Upside Down Afrasian, Afrikanistische Arbeitspapiere 50, pp. 19-34
  4. ^ Militarev A (2005) Once more about glottochronology and comparative method: the Omotic-Afrasian case, Аспекты компаративистики - 1 (Aspects of comparative linguistics - 1). FS S. Starostin. Orientalia et Classica II (Moscow), p. 339-408. http://starling.rinet.ru/Texts/fleming.pdf
  5. ^ Earliest Egyptian Glyphs
  6. ^ Diamond J, Bellwood P (2003) Farmers and Their Languages: The First Expansions SCIENCE 300, doi:10.1126/science.1078208
  7. ^ Bellwood P, Renfrew C (2002 eds) Examining the farming/language dispersal hypothesis, McDonald Institute for Archaeological Research, Cambridge.
  8. ^ Blench, Roger. Archaeology, Language, and the African Past. Rowman: Altamira, 2006 ISBN 9780759104662
  9. ^ Diakonoff, Igor. The Earliest Semitic Society: Linguistic Data. Journal of Semitic Studies, Vol. 43 Iss. 2 (1998).
  10. ^ a b c Shirai, Noriyuki. The Archaeology of the First Farmer-Herders in Egypt: New Insights into the Fayum Epipalaeolithic and Neolithic. Leiden University Press, 2010. ISBN 9789087280796.
  11. ^ Ehret, Christopher (1982), "On the antiquity of agriculture in Ethiopia" Journal of African History (Univ. of Calif. Berkeley Press)
  12. ^ Ehret C (1995) Reconstructing Proto-Afroasiatic (Proto-Afrasian): Vowels, Tone, Consonants, and Vocabulary, University of California Press, ISBN 0-520-09799-8, ISBN 978-0-520-09799-5
  13. ^ Ehret C (2002a) The Civilizations of Africa: A History to 1800, James Currey Publishers, ISBN 0-85255-475-3, ISBN 978-0-85255-475-3 http://books.google.be/books?id=0K0p8wCNKTQC
  14. ^ Ehret C (2002b) Language Family Expansions: Broadening our Understandings of Cause from an African Perspective, in Bellwood and Renfrew (2002 eds).
  15. ^ CARTA: The Origins of Us-Relationships of Ancient African Languages. Presented by Christopher Ehret. A Public Symposium: May 10, 2013. University of California Television. http://www.youtube.com/watch?v=7btmAMpRLJE Time 27:42.
  16. ^ Clutton-Brock, Juliet (1995), "Origins of the dog: domestication and early history", in Serpell, James, The domestic dog: its evolution, behaviour and interactions with people, Cambridge: Cambridge University Press, ISBN 0-521-41529-2
  17. ^ Zarins, Juris (1990), "Early Pastoral Nomadism and the Settlement of Lower Mesopotamia", (Bulletin of the American Schools of Oriental Research)
  18. ^ Kitchen, Andrew, Christopher Ehret, et al. 2009. "Bayesian phylogenetic analysis of Semitic languages identifies an Early Bronze Age origin of Semitic in the Near East." Proceedings of the Royal Society B: Biological Sciences 276 no. 1665 (June 22)
  19. ^ a b c d Bernal M. (1987), Black Athena: the Afroasiatic roots of classical civilization, Rutgers University Press, ISBN 978-0-8135-3655-2.
  20. ^ Keita (2008). "Geography, selected Afro-Asiatic families, and Y chromosome lineage variation". In Hot Pursuit of Language. 
  21. ^ Lancaster, Andrew (2009). "Y Haplogroups, Archaeological Cultures and Language Families: a Review of the Multidisciplinary Comparisons using the case of E-M35". Journal of Genetic Genealogy 5 (1). 
  22. ^ Ehret, Christopher; Shomarka Keita (2004). "The Origins of Afroasiatic". Science 306 (5702): 1680; author reply 1680. doi:10.1126/science.306.5702.1680c. PMID 15576591. 
  23. ^ Chiaroni et al. (2010). "The emergence of Y-chromosome haplogroup J1e among Arabic-speaking populations". European Journal of Human Genetics 18 (3). doi:10.1038/ejhg.2009.166. PMC 2987219. PMID 19826455. 
  24. ^ http://www.nature.com/ejhg/journal/v18/n7/full/ejhg2009231a.html
  25. ^ a b Cruciani, F; Trombetta, B; Sellitto, D; Massaia, A; Destro-Bisol, G; Watson, E; Beraud Colomb, E; Dugoujon, JM; Moral, P; Scozzari, R (2010). "Human Y chromosome haplogroup R-V88: a paternal genetic record of early mid Holocene trans-Saharan connections and the spread of Chadic languages". European Journal of Human Genetics 18 (7): 800–7. doi:10.1038/ejhg.2009.231. PMC 2987365. PMID 20051990. 
  26. ^ Cerny, V; Fernandes, V; Costa, MD; Hájek, M; Mulligan, CJ; Pereira, L (2009). "Migration of Chadic speaking pastoralists within Africa based on population structure of Chad Basin and phylogeography of mitochondrial L3f haplogroup". BMC Evolutionary Biology 9: 63. doi:10.1186/1471-2148-9-63. PMC 2680838. PMID 19309521. 
  27. ^ Gonzalez et al, AM; Larruga, JM; Abu-Amero, KK; Shi, Y; Pestano, J; Cabrera, VM (2007). "Mitochondrial lineage M1 traces an early human backflow to Africa". BMC Genomics 8: 223. doi:10.1186/1471-2164-8-223. PMC 1945034. PMID 17620140. 
  28. ^ Hodgson, Jason A.; Mulligan, Connie J.; Al-Meeri, Ali; Raaum, Ryan L. (2014). "Early Back-to-Africa Migration into the Horn of Africa". PLoS Genetics. doi:10.1371/journal.pgen.1004393. 
  29. ^ McCall, Daniel P. The Afroasiatic Language Phylum: African in Origin, or Asian? Current Anthropology, Volume 39 Number 1, February 1998.
  30. ^ Bomhard, Alan and John Kerns (1994) "The Nostratic Macrofamily: A Study in Distant Linguistic Relationship" (Walter de Gruyter)
  31. ^ George Starostin, On the genetic affiliation of the Elamite language

Bibliography[edit]

  • Barnett, William and John Hoopes (editors). 1995. The Emergence of Pottery. Washington, DC: Smithsonian Institution Press. ISBN 1-56098-517-8
  • Bender, Lionel et al. 2003. Selected Comparative-Historical Afro-Asiatic Studies in Memory of Igor M. Diakonoff. LINCOM.
  • Bomhard, Alan R. 1996. Indo-European and the Nostratic Hypothesis. Signum.
  • Diakonoff, Igor M. (1996). "Some reflections on the Afrasian linguistic macrofamily". Journal of Near Eastern Studies 55: 293. doi:10.1086/373865. 
  • Diakonoff, Igor M. (1998). "The earliest Semitic society: Linguistic data". Journal of Semitic Studies 43: 209. doi:10.1093/jss/43.2.209. 
  • Dimmendaal, Gerrit, and Erhard Voeltz. 2007. "Africa". In Christopher Moseley, ed., Encyclopedia of the world's endangered languages.
  • Ehret, Christopher. 1997. Abstract of "The lessons of deep-time historical-comparative reconstruction in Afroasiatic: reflections on Reconstructing Proto-Afroasiatic: Vowels, Tone, Consonants, and Vocabulary (U.C. Press, 1995)", paper delivered at the Twenty-fifth Annual Meeting of the North American Conference on Afro-Asiatic Linguistics, held in Miami, Florida on March 21–23, 1997.
  • Finnegan, Ruth H. 1970. "Afro-Asiatic languages West Africa". Oral Literature in Africa, pg 558.
  • Fleming, Harold C. 2006. Ongota: A Decisive Language in African Prehistory. Wiesbaden: Otto Harrassowitz.
  • Greenberg, Joseph H. (1950). "Studies in African linguistic classification: IV. Hamito-Semitic". Southwestern Journal of Anthropology 6 (1): 47–63. JSTOR 3628690. 
  • Greenberg, Joseph H. 1955. Studies in African Linguistic Classification. New Haven: Compass Publishing Company. (Photo-offset reprint of the SJA articles with minor corrections.)
  • Greenberg, Joseph H. 1963. The Languages of Africa. Bloomington: Indiana University. (Heavily revised version of Greenberg 1955.)
  • Greenberg, Joseph H. 1966. The Languages of Africa (2nd ed. with additions and corrections). Bloomington: Indiana University.
  • Greenberg, Joseph H. 1981. "African linguistic classification." General History of Africa, Volume 1: Methodology and African Prehistory, edited by Joseph Ki-Zerbo, 292–308. Berkeley and Los Angeles: University of California Press.
  • Greenberg, Joseph H. 2000–2002. Indo-European and Its Closest Relatives: The Eurasiatic Language Family, Volume 1: Grammar, Volume 2: Lexicon. Stanford: Stanford University Press.
  • Hayward, R. J. 1995. "The challenge of Omotic: an inaugural lecture delivered on 17 February 1994". London: School of Oriental and African Studies, University of London.
  • Heine, Bernd and Derek Nurse. 2000. African Languages, Chapter 4. Cambridge University Press.
  • Hodge, Carleton T. (editor). 1971. Afroasiatic: A Survey. The Hague - Paris: Mouton.
  • Hodge, Carleton T. 1991. "Indo-European and Afro-Asiatic." In Sydney M. Lamb and E. Douglas Mitchell (editors), Sprung from Some Common Source: Investigations into the Prehistory of Languages, Stanford, California: Stanford University Press, 141–165.
  • Huehnergard, John. 2004. "Afro-Asiatic." In R.D. Woodard (editor), The Cambridge Encyclopedia of the World’s Ancient Languages, Cambridge - New York, 2004, 138–159.
  • Militarev, Alexander. "Towards the genetic affiliation of Ongota, a nearly-extinct language of Ethiopia," 60 pp. In Orientalia et Classica: Papers of the Institute of Oriental and Classical Studies, Issue 5. Мoscow. (Forthcoming.)
  • Newman, Paul. 1980. The Classification of Chadic within Afroasiatic. Leiden: Universitaire Pers Leiden.
  • Ruhlen, Merritt. 1991. A Guide to the World's Languages. Stanford, California: Stanford University Press.
  • Sands, Bonny (2009). "Africa's Linguistic Diversity". Language and Linguistics Compass 3 (2): 559–580. doi:10.1111/j.1749-818x.2008.00124.x. 
  • Theil, R. 2006. Is Omotic Afro-Asiatic? Proceedings from the David Dwyer retirement symposium, Michigan State University, East Lansing, 21 October 2006.

External links[edit]