April 2020 BBC Wildlife 23
Suz
Eszterhas/naturep.comW
e mayshare 96 percentofour
geneticinformationwithchimps,
butthat4 percentallowsforsomestriking
differences.Taketheirsystemofraising
young:“Chimpanzeesandbonobos,our
closestrelatives,don’texhibitpaternalcare,”
saysAaronSandeloftheUniversityof
Texas.“Soit seemsthatactivepaternalcare
asweseeinhumansevolvedsometimeon
thehumanlineage,likelywhenhumans
formedpairbonds.”
AndyetSandelandhiscolleagues,
workinginUganda’sKibaleNationalPark,
havefoundevidencethatchimpfathers
andsons,atleast,dosharea specialbond.
“Alladolescentandyoungadultmales
seemtogrooma ‘father-figure’,”says
Sandel.“Theseoldermalesmaymake
idealpartnersbecausetheyarestillwell
connectedinthesocialnetwork,butnot
competingforstatusortryingtorisein
thehierarchy.”
ButSandelfoundthatthesespecial
relationshipsaremorelikelytooccur
betweenbiologicalfathersandsonsthan
wouldbeexpectedthroughchancealone.
Thisis ratherpuzzling,becausethe
matingsystemofchimps– inwhich
femalesmatewithmultiplemalesduring
a singleoestrus– makesit difficultto
identifywhofatheredwhom.Inthisrespect,
thebiologists,whocanestablishfamily
relationshipsviaDNAsamples,areatan
advantageovertheapes.
Sohowdofathersandsonsrecognise
eachother?Onepossibilityis thatthey
don’t.“Itmaybethattheydon’tknowit’s
theiractualfather,”hesays.“Aninfant
chimpanzeemaygrowupbeingmore
familiarwitha malewhohasa higher
chanceofbeingitsbiologicalfather.”
Alternatively,thechimpsareableto
spotphysicalsimilaritieswithrelatives.“I
definitelynoticesomefather-sonpairsthat
lookalike,aswellasmaternalhalf-brothers,
paternalhalf-brothers,andevencousinsand
uncles,”saysSandel.“Butoneproblemis
thatchimpanzeesdon’tnecessarilyknow
whattheythemselveslooklike.Thereare
nomirrorsintheforest.
“Maybetheyareusingothercues,like
scent.Chimpanzeeshavesmellyarmpits
justlikehumans.Don’taskmeif I think
I cantellchimpsapartbasedonhow
theysmell.”StuartBlackmanFIND OUT MORE American Journal of
Primatology: bit.ly/37y1pVsWILD NEWS