Found, cra­dle of hu­man­ity

Bar­ren salt flats in Botswana were once the Gar­den of Eden, say sci­en­tists

Scottish Daily Mail - - Life - By Colin Fer­nan­dez Sci­ence Cor­re­spon­dent

A VAST area of arid salt pans, it ap­pears to be an un­likely Gar­den of Eden.

But Lake Mak­gadik­gadi in north­ern Botswana is the spot where mod­ern hu­mans f i rst evolved 200,000 years ago, ac­cord­ing to re­searchers.

Back then, the area was a fer­tile wet­land, alive with fish, shell­fish and wa­ter­birds, as well as mam­mals such as gi­raffes, li­ons and ze­bras.

Our an­ces­tors set­tled there for 70,000 years, un­til the lo­cal cli­mate changed, the re­searchers sug­gest.

They be­gan to move on when fer­tile green cor­ri­dors opened up around them, paving the way for fu­ture mi­gra­tions out of Africa.

The as­ser­tion has trig­gered de­bate i n sci­en­tific cir­cles be­cause not all ex­perts believe the area is the cra­dle of hu­man­ity.

‘It has been clear for some time that anatom­i­cally mod­ern hu­mans ap­peared in Africa roughly 200,000 years ago,’ said Pro­fes­sor Vanessa Hayes who led the re­search. ‘ What has been long de­bated is the ex­act lo­ca­tion of this emer­gence and sub­se­quent dis­per­sal of our ear­li­est an­ces­tors.’

To lo­cate the cra­dle of hu­man­ity, the team took sam­ples of mi­to­chon­drial DNA f rom 1,217 Africans. Un­like nu­clear DNA, a 50-50 mix of our moth­ers’ and fa­thers’ genes, mi­to­chon­drial rial DNA is only passed down from our moth­ers.

Pro­fes­sor Hayes, a ge­neti­cist at the Gar­van In­sti­tute of Med­i­cal Re­search in Syd­ney, Aus­tralia, said: ‘Mi­to­chon­drial DNA acts like a time capsule of our an­ces­tral moth­ers, ac­cu­mu­lat­ing changes slowly over gen­er­a­tions.’ Com­par­ing each in­di­vid­ual’s dif­fer­ent DNA code ‘pro­vides in­for­ma­tion on how closely they are re­lated’ and en­ables re­searchers to map their likely move­ments.

The aca­demics then com­bined ge­net­ics with ge­ol­ogy and cli­matic physics, to paint a pic­ture of what the world looked like at around 200,000BC.

Cli­mate com­puter model sim­u­la­tions in­di­cate that ‘ the slow wob­ble of Earth’s axis’ brought ‘pe­ri­odic shifts in rain­fall’ across the re­gion, en­cour­ag­ing dry sur­round­ing ar­eas to bloom.

Pro­fes­sor Axel Tim­mer­mann, a cli­mate sci­en­tist at Pu­san Na­tional Uni­ver­sity in South Korea, said: ‘These shifts in cli­mate would have opened green, veg­e­tated cor­ri­dors, first 130,000 years ago to the north east, and then around 110,000 years ago to the south west, al­low­ing our ear­li­est an­ces­tors to mi­grate away from the home­land for the first time.’

Few fos­sils re­main in the harsh Lake Mak­gadik­gadi area, though stud­ies of pollen pro­vide ev­i­dence of for­est and grass­land around it.

The au­thors stressed they ‘ can­not rule out’ al­ter­na­tive ex­pla­na­tions, but said their find­ings show that the lake area was ‘an ideal geo­graph­i­cal lo­cal­ity’ for mankind’s sus­tained sur­vival for 70,000 years.

Lake Mak­gadik­gadi once cov­ered an area about the size of Aus­tria, but dried up sev­eral thou­sand years ago. Lit­tle now grows on the mas­sive salt pans left be­hind, which are part of a na­tional park, but there are ar­eas of grass­land.

While largely desert, a cou­ple of years of good rains can cre­ate a tem­po­rary wet­land, a mag­net for wildlife, par­tic­u­larly flamin­gos.

Pro­fes­sor Chris Stringer, of the Nat­u­ral His­tory Mu­seum voiced scep­ti­cism over whether mankind’s first ‘base’ has been found based on just one as­pect of the ge­netic code. He said: ‘ I’m cau­tious about us­ing mod­ern ge­netic dis­tri­bu­tions to i nfer ex­actly where an­ces­tral pop­u­la­tions were liv­ing 200,000 years ago, par­tic­u­larly in a con­ti­nent as large and com­plex as Africa.

‘And, like so many other stud­ies that con­cen­trate on one small bit of the genome, or one re­gion, or one stone tool in­dus­try, or one “crit­i­cal” fos­sil, it can­not cap­ture the full com­plex­ity of our ori­gins.’

He said that an­other way of look­ing at DNA – fo­cus­ing on the Y-chro­mo­some – points in a dif­fer­ent di­rec­tion. ‘When we look at the male-in­her­ited Y chro­mo­some, the most diver­gent lin­eages cur­rently known in ex­tant hu­mans are found in West Africa, not South Africa.’

He added that Swedish re­search by evo­lu­tion­ary sci­en­tist Ca­rina Sch­le­busch and col­leagues in 2017 pre­sented ‘a much more com­plex pic­ture’, adding: ‘These and many other data sug­gest we are an amal­gam of an­ces­try from dif­fer­ent re­gions of Africa.’

‘An amal­gam of an­ces­try’

Sparse: Scrub­land in the Lake Mak­gadik­gadi dis­trict

Fer­tile: Early mankind flour­ished in the Lake Mak­gadik­gadi area

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