sarv to maintain human populations as PRESENT AFRICAN EUROPEAN EAST ASIAN AUSTRALIAN one biological species. The multiregion al evolution model also predicts that at least some genes in the modern east Asian population would be linked more closely to those of their archaic Asian 100,000| NEANDERTHAL redecessors than to those of modern DALI Africans. We would expect to find deep eages in Eurasia, especially in the far East. Yet survey s in our laboratories and in others, involving more than 1,000 2 300.000 SALDANHA PETRALONA BEIING") SAMBUNGMACHAN people from Eurasia and its mitochon- s drial DNA satellites(Australia, Oceania and the Americas), have given no hint of that result It therefore seems very unlikely that 700.000 OLDUVA EUROPEAN LANTIAN JAVA any truly ancient lineages survive un- detected in Eurasia. We simply do not see the result predicted by the regional odel. Moreover. geneticists such as OMO ERECTUS Masatoshi Nei of Pennsylvania State Uni- HUMAN GROUPS WERE REPLACED throughout the old world by modern hu versity, Kenneth K. Kidd of Yale Univer- from Africa. Archaic females do not seem to have contributed mitochondrial genes sity, James wainscot of the University to the modem people of Europe, east Asia and Australia of oxford and luigi l cavalli-Sforza of Stanford University have found support for an African origin model in their in Israel suggest Neanderthals and mod- duct a detailed genealogical analysis studies of nuclear genes em humans lived side by side for Still more progress can be expected 40,000 years, yet they left little evidence in the immediate future as molecular P Its of the multiregional biologists learn to apply their tech- evolution model emphasize the How one human population might niques to materials uncovered by our have documented a continuity of have replaced archaic humans without friendly rivals, the paleontologists. Pre- anatomic morphologies between the ar. any detectable genetic mixing is still liminary molecular studies have al chaic and modem residents of different a mystery. One of us( Cann)suspects ready been conducted on DNA from regions; they insist these morphologies infectious diseases could have con. mummified tissues found in a Florida would be unlikely to evolve indepen- tributed to the process by helping to bog and dated to 7,500 years ago. Im- dently in any invading people. For that eliminate one group. Cavalli-Sforza has I proved methods of extracting DNA argument to hold true, it must also be speculated the ancestors of modern from still older fossilized bone now ap shown that the cranial features in ques- humans may have developed some pear close at hand. With them, we may tion are truly independent of one an- modern trait, such as advanced lan- begin building the family tree from a other-that is, that natural selection guage skills, that effectively cut them i root that was alive when the human would not tend to favor certain constel- off from breeding with other hominids. family was young ations of functionally related features. This and related questions may yield Yet we know powerful jaw muscles may as molecular biologists learn how to impose changes on the mandible, the link specific genetic sequences to the brow-ridge and other points on the physical and behavioral traits those se- FURTHER READING skull; circumstances that promoted the quences influence MITocHONDRIAL DNA AND HUMAN EVO evolution of these features in one pop- Even before then, further studies of LUTION. Rebecca L Cann, Mark stor ulation might do so again in a related both nuclear and mitochondrial dNa d Allan C. wilson in Nature, Vol ulation will render more informative genetic lo. 6099, pages 31-36, January the evidence for continuity. They argue quences on the Y chromosome that de-A. c. Wilson in the colonization of the modern populations are not linked to termine maleness and that are there- Paciic: A Genetic Trail. Edited by Adri- past ones by morphological character- fore inherited from the father alone. an V.S. Hill and Susan W Serjeantson. istics that evolved uniquely in the fossil Gerad Lucotte's laboratory at College Oxford University Press, 1989 record. Instead fossils and modem pop- de France has indirectly compared MTOCHONDRIAL DNA SEQUENCES DN SIN ulations are united by their shared re- such sequences in an effort to trace pa- GLE H AIRS FROMA SOUTHERN AFRT. teristic. The continuity seen by believ."Adam, if you will. Those prelimimary kocher Hn A ln e wisTh pased llusion The idea that modem humans could wo nal lineages may be ab cohabit a region with archaic ones and to provide an invaluable check on our SEQUENCE EVOLUTION OF replace them completely without any results for maternal lineages. Unfortu- AL DNA D HUMANS AND NZEES mixture may sound unlikely. Never Evolu less, some fossil finds do sup on useful regions of the y chromosome. tion of tife Idea. Discoveries in the caves at Qafzeh making it technically difficult to con- SCIENTIFIC AMERICAN April 1992 73sarv to maintain human Dooulations as 1 one biological species. T<e hultiregion￾al evolution model also predicts that at least some genes in the modern east Asian population would be linked more closely to those of their archaic Asian predecessors than to those of modern Africans. Il’e would expect to find deep lineages in Eurasia, especially in the Far East. Yet sume)a in our laboratories and in others, invohing more than 1,000 people from Eurasia and its mitochon￾drial DNA satellites (Australia, Oceania and the Americas), have given no hint of that result. PRESENT AFRICAN EUROPEAN EAST ASIAN AUSTRALIAN It therefore seems very unlikely that an). trul), ancient lineages survive un￾detected in Eurasia. We simply do not see the result predicted by the regional model. Moreover, geneticists such as hlasatoshi Nei of Pennsylvania State Uni￾versity, Kenneth K. Kidd of Yale Univer￾siv, James Wainscoat of the University of Oxford and Luigi L. Cavalli-Sforza of Stanford University have found support for an African origin model in their studies of nuclear genes. P roponents of the multiregional evolution model emphasize they have documented a continuity of anatomic morphologies between the ar￾chaic and modem residents of different regions; they insist these morphologies would be unlikely to evolve indepen￾dently in any invading people. For that argument to hold true, it must also be sho\%n that the cranial features in ques￾tion are truly independent of one an￾other-that is, that natural selection would not tend to favor certain constel￾lations of functionally related features. Yet we know powerful jaw muscles may impose changes on the mandible, the brow-ridge and other points on the skull; circumstances that promoted the evolution of these features in one pop￾ulation might do so again in a related population. Other paleontologists also dispute the evidence for continuity. They argue modern populations are not linked to past ones by morphological character￾istics that evol\.ed uniquely in the fossil record. instead fossils and modem pop￾ulations are united by their shared re￾tention of still older ancestral charac￾teristics. The continuity seen by believ￾ers in multiregional evolution may be an illusion. The idea that modem humans could cohabit a region with archaic ones and replace them completely without any mixture may sound unlikely. Neverthe￾less, some fossil finds do support the idea. Discoveries in the caves at Qafzeh 100,000~ v(1] NGAN;IONG 700,000 1 OLDUVAI 1 1 EUROPEAN 1 1 LANTIAN 1 1 JAVA I I I I I I I I I Hot40 &TUS HUMAN GROUPS WERE REPLACED throughout the Old World by modern humans from Africa. Archaic females do not seem to have contributed mitochontial genes to the modem people of Europe, east Asia and Australia. in Israel suggest Neanderthals and mod- ’ duct a detailed genealogical analysis. em humans lived side by side for Still more progress can be expected 40,000 years, yet they left little evidence in the immediate future, as molecular of interbreeding. biologists learn to apply their tech￾How one human population might niques to materials uncovered by our have replaced archaic humans without friendly rivals, the paleontologists. Pre￾any detectable genetic mixing is still liminary molecular studies have al￾a mystery. One of us (Cann) suspects ’ ready been conducted on DNA from. infectious diseases could have con- mummified tissues found in a Florida tributed to the process by helping to bog and dated to 7,500 years ago. Im￾eliminate one group. Cavalli-Sforza has proved methods of extracting DNA speculated the ancestors of modern from still older fossilized bone now ap￾humans may have developed some pear close at hand. With them, we may modern trait, such as advanced lan- begin building the family tree from a guage skills, that effectively cut them j root that was alive when the human off from breeding with other hominids. ,I family was young. This and related questions may yield as molecular biologists learn how to link specific genetic sequences to the physical and behavioral traits those se￾quences influence. FURTHER READING Even before then, further studies of both nuclear and mitochondrial DNA will render more informative genetic trees. Particularly enticing are the se￾quences on the Y chromosome that de￾termine maleness and that are there￾fore inherited from the father alone. Gerad Lucotte’s laboratory at College de France has indirectly compared such sequences in an effort to trace pa￾ternal lineages to a single progenitor- “Adam,” if you will. Those preliminary results also point to an African home￾land, and with further refinements this work on paternal lineages may be able to provide an invaluable check on our results for maternal lineages. Unfortu￾nately, base changes accumulate slowly on useful regions of the Y chromosome, making it technically difficult to con- ~IITOCHONDRIALDNAANDHUMAN Evo￾LUTION. Rebecca L Cann, Mark Stone￾king and Allan C. Wilson in Nature, Vol. 325, No. 6099, pages 31-36; January l-7,1987. ~IITOCHOMXULDNA. M. Stonekingand A. C. Wilson in The Colonization of the Pacific: A Genetic Trail. Edited by Adri￾an V. S. Hill and Susan W. Serjeantson. Oxford University Press, 1989. hlrrOCHO~~DNASEQLTENCESNSIN￾GLEkiAIRS FROMASOUTHERN AFRICAN POPIJUTION. Linda Vigilant, Renee Pen￾nington, Henry Harpending, Thomas D. Kocher and Allan C. Wilson in Proceed￾ings of the National Academy of Sci￾ences, Vol. 86, No. 23, pages 9350-9354; December 1989. SEQUENCEEVOLUIIONOFMTOCHONDRI￾ALDNANHuMANsANDCHI?~PANZEES. T. D. Kocher and A. C. Wilson in Evolu￾tion of Life. Edited by S. Osawa and T. Honjo. Springer-Verlag, Tokyo, 1991. SCIENTIFIC AMERICAN April 1992 73