The Genomic Prehistory Of People Speaking Khoisan Languages - Brigitte Pakendorf and Mark Stoneking

2021·0.52 MB·English

by  Pakendorf, Brigitte

HumanMolecularGenetics,2021,Vol.30,No.2 R49–R55
doi:10.1093/hmg/ddaa221
AdvanceAccessPublicationDate:19October2020
InvitedReview Article
INVITED REVIEW ARTICLE
The genomic prehistory of peoples speaking Khoisan
languages D
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Brigitte Pakendorf1,* and Mark Stoneking2,* ad
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1DynamiqueduLangage,UMR5596,CNRS&UniversitédeLyon,14avenueBerthelot,69007Lyon,Franceand from
2DepartmentofEvolutionaryGenetics,MPIforEvolutionaryAnthropology,DeutscherPlatz6,04103Leipzig, http
Germany s://a
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*Towhomcorrespondenceshouldbeaddressed.BrigittePakendorf,Tel:[phone];Email:[email protected];MarkStoneking, ad
Tel:[phone];Email:[email protected] em
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Abstract o
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Peoplesspeakingso-calledKhoisanlanguages—thatis,indigenouslanguagesofsouthernAfricathatdonotbelongtothe m
g
Bantufamily—areculturallyandlinguisticallydiverse.Theycompriseherders,hunter-gatherersaswellasgroupsofmixed /a
modesofsubsistence,andtheirlanguagesareclassifiedintothreedistinctlanguagefamilies.Thisculturalandlinguistic rtic
variationismirroredbyextensivegeneticdiversity.Weherereviewtherecentgenomicsliteratureanddiscussthegenetic le/3
evidenceforaformerlywidergeographicspreadofpeopleswithKhoisan-relatedancestry,forthedeepdivergenceamong 0/R
populationsspeakingKhoisanlanguagesoverlaidbymorerecentgeneflowamongthesegroupsandfortheimpactof 1
/R
admixturewithimmigrantfood-producersintheirprehistory. 4
9
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9
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b
Introduction Nowadays,peoplesspeakingKhoisanlanguageslivemainly y g
in Namibia, Botswana and Angola, with smaller numbers in ue
Inthispaper,weusetheterm‘Khoisan’asaloosecoverterm s
tnootrebfeerlotnogthtoeitnhdeigBeannotuusflaamngiulya—geasnodftshoautthaerrenmAofrsitcasathliaetntdloy Z(hFaaigvm.eb1g)i.aiIv,neZnSiomuupbthatbhAwefireri,coaSr,oimguiotnhsatlhAlaifsrntigcouari,acgaLelelsysoaktnnhdoowhananvKdehmoEiseswargnaetgdinrowiui(pt2hs) t on 09
characterized by their heavy use of click consonants—as well so-called Coloured populations (3).Two groups often included Ju
n
apseobpyleesxwtehnosisopneatok tthheesegelnanetgiucaagnecs.esTthrye atesrsmociwataesdcwoiinthedthbye isnhereepcsehnetargeernseotficthsetKuadrieosowarheoathreepKroabrraebtljyiepapretloypdlee,scietinndearanntst e 202
thebiologicalanthropologistSchulzein1928bycombiningthe of|Xamhunter-gatherers(4),andthe‡Khomani.Thislatterisa 1
Khoekhoeherders’termforthemselveswiththeirtermforfor-
groupofpeoplewithdiverseKhoisan-relatedancestriestracing
agers(1);variationsencounteredintheliteratureareKhoe-San
backtothesouthernKalahari,whojoinedtogetherinthe1990s
andKhoeSan.GiventhefactthatthepeoplesspeakingKhoisan
inordertofilealandrightsclaim(5).
languagesareculturallyandlinguisticallydistinctandeachhas
Although an initial broad classification of the languages
theirownparticularhistory,allumbrellatermsareflawed;itis
ofAfricaidentifiedasingleKhoisanphylumcomprisingthree
thusofcrucialimportancetokeepinmindthatuseofasingle
branchesinsouthernAfricaplustwolanguages—Sandaweand
termdoesnotsignifyaunifiedentity.
Hadza—spokeninEastAfrica(6),nowadaysspecialistsofthese
Received:August25,2020. Revised:September28,2020. Accepted:October8,2020
©TheAuthor(s)2020.PublishedbyOxfordUniversityPress.
ThisisanOpenAccessarticledistributedunderthetermsoftheCreativeCommonsAttributionLicense(http://creativecommons.org/licenses/by/4.0/),
whichpermitsunrestrictedreuse,distribution,andreproductioninanymedium,providedtheoriginalworkisproperlycited.
R49
R50 HumanMolecularGenetics,2021,Vol.30,No.2
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Figure1. MapshowingtheapproximatelocationofKhoisan-speakinggroups,basedonethnolinguisticdatafromGüldemann(1)andHitchcock(2),andinformation s
ontheKarretjiefromSchlebuschetal.(52).Coloursindicatethelanguagefamilyaffiliation:blue,Kx’a;red,Tuu;green,Khoe–Kwadi.Languagesthatareextinctare ://a
indicatedbycrosses.Someofthe‡KhomanistillrememberN|uu.‡’Amkoeistheactualnameofthelanguagespokenbythe‡Hoan,butastheinitialpublication ca
d
presentinggeneticdatafromthisgroupreferredtothembytheoldlanguagename,thishasbeenmaintainedingeneticpublications. e
m
ic
.o
u
languagesagreethattherearethreedistinctlanguagefamilies wellasbetweenthemandotherAfricangroups,andtheimpact p
.c
in southern Africa, namely Kx’a, Tuu and Khoe–Kwadi (1). Of of successive waves of migration of food-producing peoples o
m
these, Kx’a and Tuu might ultimately descend from a shared from East and West–Central Africa as well as in historical /h
ancestor,butthathasnotyetbeenconclusivelydemonstrated times of European colonizers [see (13) for a recent review]. m
g
(7).TheKhoe–KwadilanguagesarenotrelatedtoeithertheKx’a We here survey the recent literature and discuss the genetic /a
or the Tuu languages (1,8). As for the East African languages, evidence for an erstwhile wider geographic spread of peoples rtic
le
althoughthereisnodemonstrablerelationshipbetweenHadza withKhoisan-relatedancestry,forthedeepdivergenceamong /3
and any of the southern African Khoisan languages, there is populations speaking Khoisan languages overlaid by more 0/R
some indication that Sandawe might be related to the Khoe– recent gene flow among these groups and for the impact of 1
/R
Kwadi family; however, this, too, needs further corroboration admixture with immigrant food-producers in their prehistory. 4
9
(7). For convenience, we will refer to peoples speaking a Khoisan /5
9
Culturally,too,thereisconsiderableheterogeneityamongthe languageasaKhoisan-speakinggroupandtopeoplesspeaking 3
0
Khoisan-speakingpeoplesofsouthernAfrica(9):herdinggroups aBantulanguageasaBantu-speakinggroup(althoughofcourse 65
0
areknownhistoricallyfromcoastalandinteriorregionsofthe eachgroupspeaksaparticularlanguagebelongingtotheKx’a, b
Cape,thedescendantsofwhomaretheNama(nowadayssettled Tuu or Khoe–Kwadi families for Khoisan-speaking groups, or y g
mainlyinsouthernNamibia)aswellasseveralColouredgroups to the Bantu family). Throughout the paper, we follow the ue
s
inSouthAfrica(9,10).Furthermore,theKwepe,small-stockpas- nomenclatureofGüldemann(1),irrespectiveofthespellingof t o
toralistsfromsouthwesternAngola,areknowntohavespoken groupnamesfoundinindividualarticles. n
0
Kwadi,a language of the Khoe–Kwadi family,although this is 9
J
nowadayspracticallyextinct(9,11).Hunter-gatherersroamedthe u
n
CapeinteriorofSouthAfricainhistorictimesandarestillfound AWiderGeographicSpreadinPrehistoric e 2
intheKalahariregionspanningNamibia,Botswanaandpartsof 0
Times 2
SouthAfrica.Buttherearealsogroupsthatdonotneatlyfitinto 1
the herder–forager dichotomy. Foremost among these are the Recent genome-wide analyses of DNA from ancient human
Damara,aperipateticgroup(12)whotraditionallypracticedfor- remainsinEastAfricahavedemonstratedthepresenceinthe
aging,small-scaleherdingofgoatsandblacksmithinginaclient past of Khoisan-related ancestry in regions as distant from
relationship to the Nama and the Bantu-speaking pastoralist the Kalahari as Tanzania and Kenya (throughout this review,
Herero.AlongtheKavangoRiver,theKhwerelyonfishingaswell for convenience,we use present-day countries to refer to the
ashuntingandgathering,whereasintheeasternKalahari,the location of ancient remains that predate country formation).
ShuaandTshwaaretransitioningtofoodproductionandareina Thus, ∼60% of the ancestry of ancient remains from Malawi
clientrelationshiptotheirBantuneighboursinadditiontotheir datedtobetween2500and8100BPand∼30%oftheancestryof
foragingsubsistence. a1400-year-oldindividualfromTanzaniaisrelatedtoancestry
Giventhislinguisticandculturaldiversity,itisclearthatthe detectablebothin2000-year-oldhunter-gathererremainsfrom
prehistory of the peoples speaking Khoisan languages must South Africa and modern Ju|’hoan (14). Similarly, an ancient
have been highly complex. Numerous studies over the past individual from Kenya dated to 3500 BP shows evidence of
decade have highlighted the considerable genetic diversity low levels of Khoisan-related ancestry (15). In addition, there
found in these groups, the deep divergence among them as is evidence from whole genome sequences from modern
HumanMolecularGenetics,2021,Vol.30,No.2 R51
Table1. SalientfeaturesofrecentstudiesofwholegenomesequencesthatincludedKhoisan-speakinggroups
Study Samplesizesandgroups Deepestdivergencetimebetween Divergencetimeamong
Khoisan-speakingandothergroups Khoisan-speakinggroups
Fanetal.(19) FourJu|’hoana ∼200kya ∼30kya
Two‡Khomania
Lorente-Galdosetal.(20) TwoJu|’hoanb ∼190kya n/a
OneTaac
One‡Khomani
Bergströmetal.(21) SixJu|’hoand ∼162kya n/a
Schlebuschetal.(16) FiveJu|’hoan ∼200–300kya ∼160–190kya
Five‡Khomani
FiveNama
FiveKarretjie
FiveG|ui/G(cid:3)anae
D
o
aSequencesfromMallicketal.(53);Ju|’hoansamplesfromtheHumanGenomeDiversityPanel(HGDP). wn
bOnesequencefromMallicketal.(53)andonesequencefromMeyeretal.(54);samplesfromHGDP. lo
cSequencefromSchusteretal.(55),wherethisindividual(KB1)islabelledaTuuspeaker. ad
dAllsamplesfromHGDPandincludethefourJu|’hoanfromMallicketal.(53). ed
eMixedgroupofG|uiandG(cid:3)anaindividuals,seeSchlebuschetal.(30)fordetails. fro
m
h
ttp
pKohpouislaanti-osnpseafkoirngpogtreonutpiasl,el.ogn.gin-ditshteanschearminiggroaftipornisvaitnevaolllveilnegs wgrhooulpes.genome sequence studies of further Khoisan-speaking s://ac
between the Ju|’hoan and Mbuti central African rain forest Khoisan-speaking groups are also the first to branch off ad
e
foragers(16). in genomic studies of African or world-wide populations m
ic
Interestingly,theKhoisan-relatedancestryineasternAfrica (16,19,20,23), with their divergence from other populations .o
is related in equal degrees to the deeply diverging lineages dated to 160–300 kya (Table1). The fact that Khoisan-related up
identified in modern-day Khoisan-speaking populations see lineagesarethefirsttodivergehassometimesbeenerroneously .co
m
“HighLevelsofGeneticDiversityinKhoisan-SpeakingPeoples”, interpretedasstrongevidenceforanoriginofmodernhumans /h
implying that the Khoisan-related groups settled in eastern in southern Africa [(24), which is based solely on mtDNA m
g
Africa were genetically distinct from those living in southern lineages; see (25,26) for substantial critiques of this paper]. /a
Africa (14). These results mirror the results of mitochondrial However,asnotedabove,Khoisan-relatedgroupswereformerly rtic
DNA(mtDNA)analysesthatfoundacomplementarydistribution more widespread, and moreover, the divergence between le/3
of one of the Khoisan-specific haplogroups, L0k. Of three Khoisan-speaking groups and other African groups could, in 0/R
deeplydivergentbranches(L0k1a,L0k1bandL0k2),onlyL0k1a principle,haveoccurredanywhereinAfrica. 1
/R
is found among extant Khoisan-speaking groups of Namibia Khoisan-speaking peoples also show evidence of a larger 4
9
and Botswana, whereas L0k1b and L0k2 are found practically effective population size over time than other African pop- /5
9
exclusively in Bantu-speaking populations settled in Zambia. ulations (16,19,20,27). All human populations show a signal 3
0
Thisimpliesthatpeoplegeneticallyrelatedtocurrentlyknown of decreasing effective population size beginning around the 6
5
Khoisan-speaking groups, yet carrying distinct lineages, were timeofthedivergenceofAfricanfromnon-Africanpopulations, 0 b
residentinregionsbeyondthosepreviouslyattested(17).There ∼50–100kya;however,Khoisan-speakinggroupsshowlessofa y g
are no historically known Khoisan-speaking groups in either reductionineffectivepopulationsizethandootherpopulations u
e
ZambiaorMalawiorfurthernortheast,andmodern-daypopula- (16,19,20). Some of this diversity might be due to archaic st o
tionsofMalawishownotracesofKhoisan-relatedancestry.Itis admixture from an as yet undiscovered population (28). For n
thusclearthattheincomingBantu-speakingpopulationsmust example,wholegenomesequencing(20)suggests∼4%ancestry 09
J
havereplacedtheKhoisan-relatedautochthonouspopulations fromanarchaic‘ghost’populationinthefourKhoisan-speaking u
n
withhardlyanyadmixture.Linguisticanalyses,too,showthat individualsanalyzed. e
2
some Bantu languages of the Kavango–Zambezi transfrontier In addition to carrying considerable amounts of genetic 0
2
area borrowed words with click consonants from Khoisan diversity,Khoisan-speakingpopulationsarealsoquitediverged 1
languagesthatarenowadaysextinct,inadditiontoborrowing fromoneanother,asshownbyadeepsplitbetweenpopulations
wordsfromKhweandJulanguages(18). residing in the northwestern Kalahari and those from the
southeastern Kalahari or South Africa (29,30), respectively.
Recentreanalysesofthesedatatogetherwithsomenewdata
HighLevelsofGeneticDiversityin
(31)—providing the most complete geographical coverage of
Khoisan-SpeakingPeoples
extantKhoisan-speakinggroups—thatfocussolelyongenomic
Khoisan-speaking groups are consistently found to harbour segments of Khoisan-related ancestry have demonstrated a
highlevelsofgeneticdiversity.Severalrecentstudiesofwhole tripartite split into northern, central and southern Khoisan-
genomesequencesfoundhighestlevelsofgeneticdiversityin speaking groups [roughly corresponding to Pickrell et al.’s
Khoisan-speakingindividuals(16,19–21),andtheseindividuals (29) northwestern and southwestern and Schlebusch et al.’s
also have the highest frequencies, on average, of population- (30) southern groups, respectively, and also corresponding to
specificcopynumbervariantsworldwide(22).However,sample groups defined by ecogeographic boundaries in (32); Fig.2]. It
sizes and ethnolinguistic diversity of the groups analyzed should be noted that these northern, central and southern
remainquitelimited(Table1);thereisaclearneedforadditional genetic groupings do not correspond to a previous linguistic
R52 HumanMolecularGenetics,2021,Vol.30,No.2
thattheymusthavebeenisolatedfromeachotherforaconsid-
erableperiodoftime,thereisalsoevidenceforgeneflowamong
Khoisan-speaking groups taking place at a more recent time-
scale.Thisisshownbyanalysesfocussingongenomesegments
of Khoisan-specific ancestry that show a high correlation of
geneticwithgeographicdistances,andaclearsignalofisolation
bydistance(31,33).Itisthereforepossiblethatthedeepdiver-
gencetimesarisepurelyasaconsequenceoflong-distancesepa-
rationinwhatisactuallyagradientofrelatedness.However,itis
alsopossiblethatthesignalsofisolationbydistancereflectmore
recentprocessesafterinitialolderdivergenceevents.Inpartic-
ular,ithasbeensuggestedthatKhoisan-speakinggroupswere
initiallysplitbytheprehistoriclakeMakgadigadi,withgeneflow
beingreinitiatedwhenthelakedrieduparound10kya(34).One
groupinparticularthatshowsevidenceforadmixturearethe D
o
Naro,whoarebothgeographically(Fig.1)andgenetically(Fig.2) w
n
intermediate between the northwestern/northern and south- lo
a
eastern/centralgroupings (29,31) and who also show evidence d
forgeneflowfromtheG|uiandanethnolinguisticallyundefined ed
groupfromXadeintheCentralKalahariGameReserve(33).In fro
m
addition,the‡Hoan,whospeakadivergentlanguageoftheKx’a h
familynowadayscalled‡’Amkoe,showonly5%sharedancestry ttp
with their linguistic relatives the !Xuun and the Ju|’hoan (33), s://a
whereastheyaregeneticallyclosetotheneighbouringTaa(who c
a
speak a Tuu language) and the G|ui, whose language belongs d
e
totheKhoefamily(31)(cf.34,35).Distinguishingbetweenlong- m
ic
Figure2.Plotofthefirsttwodimensionsofamultidimensionalscalinganalysis termisolationbydistance,versusdeepdivergencefollowedby .o
u
of Khoisan-speaking groups,illustrating the northern,central and southern morerecentcontact,maybepossiblewhenmorewholegenome p
geneticgroupingsofKhoisan-speakinggroups.Theplotisbasedongenome- sequencedatabecomeavailable. .co
wideSNParraydatawithnon-Khoisan-relatedancestrymasked.Thevertical m
axisisthefirstdimensionandthehorizontalaxisistheseconddimension.The /hm
contoursdepict90%utilizationdistributiondensities,i.e.thesmallestareaofthe g
pgrlootuipn,wanhdicahrethceorleoiusrac9o0d%edpraocbcaobrdiliintygotfololacnatgiunaggtehefaimndiliyv:idbuluaels,fKrxo’ma;trheed,saTumue; AdmixturewithImmigratingFood-Producing /artic
Populations le
green,Khoe.ModifiedfromMontinaroetal.(31),whichshouldbeconsultedfor /3
furtherdetails. InadditiontogeneflowamongKhoisan-speakinggroups,these 0/R
havealsoundergonevariableamountsofadmixturefromimmi- 1/R
gratingfood-producers(23,36)(Fig.3).Sheepandgoatpastoral- 4
9
ists are thought to have immigrated to southern Africa from /5
9
classification of southern African Khoisan languages into EastAfricaafewcenturiesbeforetheimmigrationofIronAge 3
0
Northern (Khoisan), Central (Khoisan), Southern (Khoisan) agropastoralists commonly associated with the expansion of 65
0
branches(6):thenorthwestern/northerngroupingincludesnot Bantu-speakingpeoplesintolargepartsofsub-SaharanAfrica b
onlythe!XuunandJu|’hoan,whoselanguagesbelongtotheKx’a (37).ThepresenceamongsouthernAfricanpopulationsofthe y g
family,butalsotheHai(cid:3)om,whoselanguagebelongstotheKhoe LactasePersistencevariantC-14010(30,38,39),whichisofprob- ue
s
family;thesoutheastern/centralgroupingincludespopulations ableEastAfricanorigin(40),pointstowardsademicdiffusionof t o
speaking languages belonging to all three families, and the pastoralismintosouthernAfrica.Significantlyhigherfrequen- n 0
southerngroupingincludesboththe pastoralistNama,whose ciesofthisvariantinpastoralistpopulationsthaninforagers, 9
J
language belongs to the Khoe family,and the descendants of and in groups speaking languages of the Khoe family than in u
n
foragers,theKarretjieand‡Khomani,whoseheritagelanguages Tuu-orKx’a-speakingpopulations(39),supportthehypothesis e 2
belongedtotheTuufamily. thattheKhoe–KwadilanguageswerebroughttosouthernAfrica 02
1
However, there is uncertainty as to when this deep split by a migration of pastoralists from East Africa (8). Unexpect-
occurred.Initialstudiesbasedongenome-widesingle-nucleotide edly, however, the formerly Khoe–Kwadi-speaking pastoralist
polymorphism (SNP) array data dated the divergence to ∼25– KwepefromsouthwesternAngolahaveonlylowfrequenciesof
35 kya (29–31). The inclusion of genome sequence data from this allele (41),in accordance with their low frequency of the
a 2000-year-old hunter-gatherer individual from South Africa EastAfricanY-chromosomehaplogroupE-M293.Thespreadof
pushed back the date of divergence between ‘northern’ and pastoralism and the Khoe–Kwadi languages is therefore likely
‘southern’ Khoisan to 156–185 kya (23), which might suggest to been a complex process, which might also have involved
that the SNP array data underestimate divergence times due shift of Bantu-speaking groups to Khoe–Kwadi languages (42).
to ascertainment bias. Nevertheless, subsequent estimates Interestingly,twomodern-dayforagergroups,theG|uiandthe
based on whole genome sequences range from ∼30 to ∼160 Tshwa, show evidence for ongoing positive selection for the
kya (Table1); different mutation rates can account for some C-14010 allele, indicating a possibly recent reversion from a
differencesintheseestimates,butnotall,leavingthisanopen herdingwayoflifetoforaging(39).AncientDNAanalyseshave
question. providedfurtherdirectevidenceforadmixturewithEastAfrican
Inanyevent,whilethisdeepdivergencebetweennorthern, pastoralists:a1200-year-oldspecimenfoundinaherdercontext
central and southern Khoisan-speaking populations suggests inthewesternCapewasshowntohave∼40%ancestryrelated
HumanMolecularGenetics,2021,Vol.30,No.2 R53
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Figure3. VariableamountsofKhoisan-related,Bantu-relatedandEastAfrican-relatedancestriesinKhoisan-speakinggroups,basedonPickrelletal.(36). ://a
c
a
d
e
m
toanearlypastoralistfromTanzaniaand∼60%ancestryrelated in research on indigenous peoples can fail to appreciate how ic
to2000-year-oldSouthAfricanforagers(14).TwoEarlyIronAge their scientific statements about their results may be viewed .ou
p
individualsfromBotswana—whoarelikelytohavespokenBantu andinterpretedbytheindividualsandcommunitiesstudied— .c
o
languages—confirm the earlier presence of East African pas- a prominent example involved a study that sequenced the m
toraliststhanIronAgeagropastoralistsintheregion,sincethey genomes of four Khoisan-speaking individuals (cf. 48). One /hm
carryancestryrelatedtothe1200-year-oldadmixedherderfrom outcomeofsuchmisunderstandingswastheestablishmentof g
/a
thewesternCape(15). theSanCodeofResearchEthicsin2017(https://www.globalco rtic
The admixture with food-producing populations did not deofconduct.org/affiliated-codes/),thefirstsuchethicscodeby le
take place at the same time or to the same extent across anindigenousAfricangroup,andamodelforresearchinvolving /30
southern Africa (29,36). Analyses of uniparental data show a Khoisan-speaking groups. Nonetheless, ethical difficulties /R
1
stronglysex-biasedsignalofgeneflowinsouthernAfrica,with continuetoarise(49). /R
4
Khoisan-speakingpopulationsreceivingpaternallineagesfrom 9
/5
food-producers, whereas Bantu-speaking groups incorporated 9
Conclusion 3
mainlyKhoisan-relatedmaternallineages.Theintensityofthis 0
6
sex bias increases from North to South, possibly indicating ThestereotypicalimageofKhoisan-speakingpeoplesasStone 50
changes in social interactions between immigrating groups b
Agehunter-gathererswhohavelivedinsplendidisolationsince y
and autochthonous peoples over time (35). Such changes in g
thedawnofhumankindcan,withoutanydoubt,belaidtorest. u
irneltaetreadctioannsceasrteryalsdoetiemctpalbieledbiynthmeovdaerryni-ndgaylevBealsntouf-Kspheoaiskainng- Thesegroupsexhibitextensivecultural,linguisticandbiologi- est o
cal diversity.They harbour more genetic diversity,the earliest n
populations of southern Africa: populations from Malawi do divergences and larger effective population sizes than other 09
not show any evidence for Khoisan-related ancestry (14),and humanpopulations.Theyusedtobemorewidespreadinformer Ju
populations from southern Mozambique show only low levels n
times, are likely to have engaged in long-distance migrations e
of such ancestry [4–5% maximum (43)]. This is in contrast to 2
andtheyhavebothinfluencedandbeeninfluencedbyatleast 0
populationssuchastheKgalagadiandTswanafromBotswana twomigrations,anearliermigrationofpastoralistsfromeast- 21
with33–39%and22–24%Khoisan-relatedancestry,respectively
ernAfricaandalatermigrationofagropastoralistsassociated
(29,36), or the Sotho, Xhosa and Zulu from South Africa
withthespreadofBantulanguages.Understandingthecomplex
with between ∼10–24% Khoisan-related ancestry (43,44). Such
genomichistoryandstructureofKhoisan-speakingpopulations
changes in social interactions between immigrating Iron Age
hasimportantimplicationsnotonlyfortheirindividualhistories
agropastoralists and resident Khoisan-speaking populations
and the history of humans in general, but also for potential
mightalsoexplainvariablepatternsofclickborrowinginBantu
variationindiseasesusceptibility(cf.50,51).Thereisaclearneed
languages(18,45).
forfurtherwholegenomesequencestudiesofKhoisan-speaking
groups,inordertoachievethesegoals.
EthicalConsiderations
Acknowledgements
Indigenouscommunitiesareplayinganincreasinglyprominent
role in genomics research, going beyond merely providing M.S. acknowledges support from the Max Planck Society. The
samplestobeingfullyinformedabouttheresultsandhowthey authors thank Linda Schymanski for help with the figures.
are presented (46,47). Even well-meaning scientists engaged B.P. is grateful to the LABEX ASLAN (ANR-10-LABX-0081)
R54 HumanMolecularGenetics,2021,Vol.30,No.2
of Université de Lyon for its financial supportwithin the Peltzer, A. et al. (2017) Reconstructing prehistoric African
programme ‘Investissements d’Avenir’ (ANR-11-IDEX-0007) of populationstructure.Cell,171,59–71.e21.
the French government operated by the National Research 15. Wang,K.,Goldstein,S.,Bleasdale,M.,Clist,B.,Bostoen,K.,
Agency(ANR). Bakwa-Lufu,P.,Buck,L.T.,Crowther,A.,Dème,A.,McIntosh,
R.J.etal.(2020)Ancientgenomesrevealcomplexpatternsof
populationmovement,interaction,andreplacementinsub-
ConflictofIntereststatement.Nonedeclared. SaharanAfrica.Sci.Adv.,6,eaaz0183.
16. Schlebusch,C.M.,Sjödin,P.,Breton,G.,Günther,T.,Naidoo,T.,
Hollfelder,N.,Sjöstrand,A.E.,Xu,J.,Gattepaille,L.M.,Vicente,
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