g fl» B t T W e’re All O ut Of Africa B y J ane E llen B lair C ontributing S cience W riter February is Black H istory M onth and an excellent tim e to reexam ine the scientific evidence regarding the am o u n t o f g en etic d iversity am ong hum ans and the antiquity o f that diversity. ay'& m o d em society, evolution, mi- je d in g w hich hgly m ore di- i. d em onstrate ’ an d variable we J id e r the fact ghiyanability in a “ 7 o f D rain, Or- he entire planet. ____Be possib le scien- Jftons for the tim ing and l 8 f em erg en ce o f m odem sa p ien s {H. sa p ie n s) (from T h ese tire th e O u t o f A r i c a the Mu •R egional Mddrs, H om o erectus, our predec lea and then m igrated evolved in g io n approxim ately outside o f th its ago. T here m ust 1.8 m illion least one later tim e have been fvolved pop u latio n o f w hen a mo the A frican co n ti­ H. sa p ien s n e n c e is not conclu- nent. The sive regari [g the degree to w hich these anat fically m o d e m //, sapi- w ith p opulations o f ens inter apiens, how quickly archaic if archaic hum ans were population anatom ically m od em replaced w hat the pattern s o f hum ans, 'ere into o th er areas. m igratio :al with scientific theo- As is t little com m on ground ries, the betw een le supporters o f these Ies. three th e several dating tech- T here to determ ine w hen an- niques u lulations o f H om o sapi- cestral ly left the A frican conti- ens ac [ecular tim e clocks are nent ites o f m utation and can based o assess the age o f hu- potenti Isil specim ens, or the rocks mans, they using cable 500, longevity o f the a n d the interbreeding w ith va archaic populations. T h e M u lti-R e g io n a l M odel R egional C on tin u ity M odel implies that the variability b etw een popu- lem hum ans devel- can co n tinent and ie betw een440,000 ag o (o re v e n c o n ­ fer ago by som e sci- o n tain ed in, can be dated ety o f techniques appli- le tim escale from 50,000 to ears ago. M ethods for fos- [g include uranium series, lum incsence and electro n o nance techniques. Each techniques has different Ions and ranges o f accuracy the results to be som ew hat ious . A dding to the am bigu- fossil specim ens them selves sp arse to be con clu siv e 'w hat happened during these tim e periods. p u g h the results are incon- there is som e genetic evi- ln the Y chrom osom e and on romosome 21 w hich show s that there is m ore div ersity am ong A iri­ can p o p u latio n s than w ith in non- A frican p o p u latio n s. T his w ould be ex pected u n d er th e C o m p lete R eplacem ent M odel due to the cycle o f breeding and lo n g ev ity w ithin A frica, w ith o nly su b sets o f these peo p le p o p u latin g o th e r areas. T h e C o m p le te R e p la c e m e n t M odel also relies h eav ily upon g e­ netic sequencing d ata from m ito ­ chondrial D NA (m tD N A ), w hich is passed intact form m other to d au g h ­ ter. T he so c a lled “ M ito c h o n d ria l E v e” theory sh o w s all m o d em h u ­ m ans stem m ing from a single A fri­ can woman. H ow ever, it is no longer co n sid ered a v iab le ex p lan atio n by m ost scientists. In co rrect estim ated rates o f m u tatio n s, d ifferen t p o p u ­ lation sizes, m ultiple m igrations and q u estio n ab le sta tistica l techniques for identifying p o p u latio n relatio n ­ ships and d raw ing fam ily trees may all co ntribute to m tD N A b ein g d is­ credited. In ad d itio n , o th e r eq u ally v alid results and fam ily trees can be g enerated using th e sam e set o f data. T here are sig n ific an t im p lica­ tions regarding m o d em hum an vari­ ab ility in all o f th ese th eo ries. The p hrase hum an v ariab ility refers to how m any po ssib ilities there are for people to express d ifferen t form s o f various traits. S in ce scien tists truly d o n ’t know how q u ick ly the tra n si­ tion from archaic to an ato m ically m od em species occurred, it is d iffi­ cu lt to determ in e the am o u n t o f variability introduced into the popu­ lation during th at transition. H o w ­ ev er, it is clear from m o d em re­ search that there is m ore v ariab ility w ithin a single h um an pop u latio n th an there is b etw een populations. S ta tis tic a l/m a th e m a tic a l stu d ies h a v e b ee n d o n e w h ic h sh o w th e re is n o se t o f tra its w h ich ca n co n ­ c lu s iv e ly s e p a ra te m o d e rn h u ­ m a n s in to d iffe re n t rac es. In fact, a ll d iv id in g lin es w e c u rre n tly see a re b a se d o n so c ia l an d c u ltu ral d iffe re n c e s w ith no rea l b a s is in s c ie n tific fact. I t is im p o rta n t to u n d ersta n d th a t h u m a n v a ria b ility does not ju s tr e f e r to o u tw a rd a p p earan ces. O u tw a rd a p p e a r a n c e s are f r e ­ q u e n tly th e e x p re ssio n o f in te r­ n a l tra its. T h e re can be m any ty p e s o f g e n e tic v a ria b ility b ased in th e h u m an g en o m e th at are n ot e x te rn a lly e x p re sse d . W h en c o m ­ p a rin g h u m an s to c h im p an z ee s, th e re is a c tu a lly o n ly a 1 '/i% d iffe re n c e in th e ir g e n e tic code. A d d itio n a lly , th e D N A in h um an m ito c h o n d ria is o n ly aro u n d 2 14% as v a ria b le as th a t in ch im ­ p a n z e e m ito c h o n d ria . A lth o u g h w e d o n ’t k now the d e ta ils o f e x a c tly w h en an d how o u r a n c e s t o r s p o p u l a t e d th e w o rld , w h at w e d o know is th a t w e are all o f on e sp e cie s and th e re is no su c h th in g as d iffe ren t hum an races. T h ere are m any d an g ero u s so c ia l co n se q u e n c e s to an y so rt o f ra c ia l d iv isio n an d th ere is no sci­ e n tific ev id en c e to su p p o rt o r en ­ co u ra g e th is v ie w p o in t. It is c riti­ c a lly im p o rta n t th a t a ll p eo p le u n ­ d e rsta n d the la c k o f sc ien tific ju s ­ tific a tio n fo r a n y rac ial categ o ries o r d e sig n a tio n s b ased upon a n y ­ th in g o th e r th a n cu ltu re and ac­ c e ss to re so u rc e s. In to d a y ’s cu l­ tu ra lly d iv e rse so c iety , th o se c u l­ tu ra l d iffe re n c e s th a t do ex ist b e­ tw een g roups sh o u ld be em braced. CcicÒRArc BtAck hisroRy CDonch œ Çet Steady fee ‘Vatentine’i flay. H O ur G enetic Link As Africans B y P rofessor K kbkca C ann In the past, anthropologists explored the history o f our species by using either bones preserved as fossils or tools and other artifacts, sue has pots, cloth, metals, or wooden implements tound m archaeo­ logical deposits. In the 1960’s, this focus began to change, with the recognition by biologists that we all cany the evidence o f evolution in our genetic material, and that modem people can be a key to unlocking that past The changes in our genetic material, mutations, that have accumulated in our DNA over time, can reveal w here we came from, how we spread as a species, and when we began that spread By 1980, the idea emerged that all humans alive today can trace at least some o f their genes to a woman who probably lived in Africa about 100,000- 200,000 years ago. She wasn’t the only woman alive at the time, but she repre­ sents the only woman who had an unbro­ ken line o f female descendants, all the way to the present Her daughters passed on a unique set o f genes, mitochondrial genes, that control the rate at which energy is produced in all the cells o f our bodies. Men and w omen have these genes but only women transmit them. Scientists estimate that humans have about 60,000 different genes, and 37 o f them fit this pattern. Because they arc inherited only through the female line, they are easy to trace and help reveal how humans dispersed around the wodd By comparing the patterns o f muta­ tions in these genes, and using a com­ puter to help reconstruct family trees, scientists in 1987 published the data for 142 human female lineages from donors around the world The tree had 2 major branches, one that contained only Africans, and the second that contained Africans and ev- eryoneelse. The simplest explanation for tins pattern is that the ancestor of these people was an African, some people stayed in Africa and gave rise to modem African populations, but others migrated out o f Africa and gave rise to other continental populations, including a group that went back into Africa. Researchers in both fields o f anthro­ pology and human genetics w ere aston­ ished. Many people assumed tliat earlier groups o f archaic people would be di­ rectly ancestral to the modem popula­ tions found in those same places today. This idea said it wasn’t true, all modem people shared a recent common origin, and therefore, the implication was tliat modem human races were a new phe­ nomenon, and the biological basis o f racial differentiation had to be trivial, ui- volvingonlyafew genes. These ideas are still stimulatingmajorresearchprograms Y In 1980, Professor Rebecca Cann o f The University o f Hawai'i at Manoa found genetic evidence o f our African origins. Her work was based on 182 current mitochondrial DNA types which pointed to the existence o f a common female ancestor who lived 200,00 0years ago in Africa. on a variety o f levels, including a search for the dispersal out o f Africa in the archaeological record, the comparison of modem human groups for genetic mark­ ers that correlate with racial differences, and the exploration o f cultural and lin­ guistic differences that correspond to racial boundaries, however close or changing those boundaries may be. Kofi Agorsah from Portland State University is screening dirt with a sieve to look for minute artifacts at an archaeological site. Dedicated to reducing traffic congestion and providing mobility choices for all 15% O ff Purchase TJnique Clothes, Shoes, H a ts & /Accessories & o r «Women & 275« qjnxdw aY,