We’re All Out Of Africa

An impor­tant sci­en­tif­ic find­ing was report­ed a cou­ple of weeks back, that has very impor­tant impli­ca­tions.

Palaeon­tol­o­gists and mol­e­c­u­lar biol­o­gists have dis­agreed with each oth­er regard­ing the ori­gins of mod­ern Homo sapi­ens. Since 1987, mol­e­c­u­lar biol­o­gists have believed, using DNA evi­dence, that Homo sapi­ens evolved in Africa and then spread out to oth­er parts of the world. Pale­on­tol­o­gists, on the oth­er hand, said that mod­ern humans evolved sep­a­rate­ly in dif­fer­ent regions of the world, from the ear­li­er Homo erec­tus.070718-african-origin_170

Until now.

In a recent study in Nature, Andrea Man­i­ca of the Uni­ver­si­ty of Cam­bridge and his col­leagues show that the skull data and the genet­ic data actu­al­ly agree with each oth­er. They stud­ied 4,666 male skulls and 1,579 female ones, drawn from 105 groups of peo­ple from all six inhab­it­ed con­ti­nents, and showed that they var­ied in the same way as human genet­ic data do.

The Econ­o­mist reports:

One of the main lines of evi­dence for the “Out of Africa” hypoth­e­sis, as it is usu­al­ly known, is that the most genet­i­cal­ly var­ied human pop­u­la­tions are in that continent—particularly in the south and east of it. The far­ther you go from Africa, the less genet­ic vari­ety there is, because in a rapid­ly dis­pers­ing pop­u­la­tion genet­ic vari­ety is lost faster by ran­dom fail­ures to breed than it is replen­ished by evo­lu­tion.

If the “Out of Africa” hypoth­e­sis is right, that decreas­ing vari­abil­i­ty should be reflect­ed in skull shape—since this is ulti­mate­ly under genet­ic con­trol. As far as skulls are con­cerned, there is one con­found­ing vari­able: cli­mate. Things such as nos­tril size vary with tem­per­a­ture and humid­i­ty in ways that sug­gest evo­lu­tion is at work. Since Dr Man­i­ca was look­ing for effects oth­er than those pro­duced by nat­ur­al selec­tion, those things had to be elim­i­nat­ed. Which he did.

Using what was left, he esti­mat­ed the amount of diver­si­ty in groups of skulls from dif­fer­ent parts of the world using a sta­tis­ti­cal tech­nique called mul­ti­ple-regres­sion analy­sis, and com­pared the result­ing map with a sim­i­lar map of genet­ic diver­si­ty. The two matched per­fect­ly. There was no room for the influ­ence of local pop­u­la­tions of Homo erec­tus.

Also see Nation­al Geographic’s report here. Even if there is one notable skep­tic of the study, I find this reas­sur­ing for two rea­sons:

First, this is the beau­ty of sci­ence at work. We have two sci­en­tif­ic dis­ci­plines con­tra­dict­ing each oth­er. And when suf­fi­cient data from both streams is ana­lyzed and known influ­enc­ing fac­tors account­ed for, the data from the two inde­pen­dent streams match­es almost mirac­u­lous­ly. This is the true sci­en­tif­ic method at work.

Sec­ond, and more impor­tant, this find­ing effec­tive­ly kills the con­cept of “race”. We have all come from the same place, evolved from the same species. There are no sep­a­rate ori­gins, and hence no dif­fer­ent races of peo­ple. Race is a prod­uct of the imag­i­na­tion of Homo sapi­ens, not a nat­ur­al occur­rence.

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  • When I don’t find a com­ment I entered on a post of yours in this blog, I click ‘sub­mit’ again, but invari­ably get a mes­sage that says ‘don’t foc­k­een repeat your­self’. Now you sub­mit TWO posts with the same head­er and con­tents (I think) and you get away with it.…. how?

  • Reminds me of a sci­en­tist that told the jour­nal­ist, “This skull here is three mil­lion and four years and six months old.” “How can you spec­i­fy the date so accu­rate­ly?” asked the journo.
    Sci­en­tist: “When I first dis­cov­ered this skull four and a half years back, it was three mil­lion years old!”

  • The notable skep­tic is Fox News? The guys who can take this sen­tence “George Bush lied to the Amer­i­can Pub­lic about the Iraq War” and report it as “The Pres­i­dent kept Amer­i­ca safe by judi­cious­ly with­hold­ing infor­ma­tion relat­ed to Iraq”

  • So I am an African now?
    Killing the con­cept of race is a good thing, but I am sure it will start a cri­sis of Iden­ti­ty among many. I am already in 😉

  • Race is a prod­uct of the imag­i­na­tion of Homo sapi­ens, not a nat­ur­al occur­rence.”
    Eh? How did you arrive at that con­clu­sion?

    Race is nat­ur­al! African ele­phants are dif­fer­ent from Indi­an. African humans are dif­fer­ent from Indi­an. I do not under­stand why we are gen­er­al­ly try­ing to deny the exis­tence of race (or caste for that mat­ter).

    Acknowl­edg­ing races is not wrong. Racism is.
    kay mhan­tos?

  • Ram­bodoc: it was a glitch of using Win­dows Live Writer to edit and repost over an unsta­ble con­nec­tion. Thanks for point­ing it out.

    All: thanks for the com­ments. Past few days have been hec­tic, and am trav­el­ing to Mum­bai today. Will respond to your gra­cious com­ments lat­er. Also, haven’t vis­it­ed any of your inter­est­ing blogs…

  • Well I think recog­ni­tion or exis­tence of race depends on the time­line that we are look­ing at. If you say that all humans came out of Africa, I can say what about the humans before that. What­ev­er the­o­ry you give me I can say “…and before that??”. So it comes down to the The­o­ry of Begin­ning that you believe:

    [1] Big Bang The­o­ry — Every­thing start­ed from a point, so no ques­tion of dif­fer­ent races
    [2] Adam & Eve — Every­thing start­ed with this cou­ple, so no ques­tion of dif­fer­ent races (assum­ing both came from the same race)
    [3] Darwin’s The­o­ry — Ya here the sci­en­tists will have to find out first if Apes have races, then we can pro­ceed fur­ther.

  • Hmmm, inter­est­ing. Thank you. I didn’t know there had still been a debate. I thought it was set­tled years ago that human life began in Africa and moved around the rest of the world.

  • Priyank: The con­cept of ‘race’ is so con­tro­ver­sial and has many dif­fer­ent inter­pre­ta­tions, that most sci­en­tists today term it as a fuzzy con­cept that has no use. Regard­ing ele­phants, African and Indi­an ele­phants belong to two dif­fer­ent species alto­geth­er, not ‘races’.

    Among the many dif­fer­ent inter­pre­ta­tions of race and racism, I was refer­ring to the one that uses mul­ti-region­al ori­gin as a basis for declar­ing race supe­ri­or­i­ty. Whites descend­ed from Euro­pean ances­tors were deemed supe­ri­or to blacks descend­ed (sep­a­rate­ly) from Africans, and this jus­ti­fi­ca­tion was used to engage in slav­ery. I’m refer­ring to Brit­tan­i­ca Encyclopedia’s def­i­n­i­tion and using this sci­en­tif­ic dis­cov­ery to debunk sci­en­tif­ic racism in gen­er­al.

    Oemar: Since we and most peo­ple are con­cerned about Homo sapi­ens, the the­o­ries relat­ed to ‘what before humans’ are sort of out­side the cir­cle of con­cern here. As I’ve described above, the mul­ti-region­al the­o­ry of the ori­gins of Homo sapi­ens have been used in many ways through­out his­to­ry to pro­mote racism. This dis­cov­ery resolves that debate (and no, it doesn’t resolve debates about the the­o­ries of the begin­ning :-).

    Sib­bia: Thanks and wel­come to my blog!