Clues to language origins seen in ape gestures

Sci­en­tists have found what they call new ev­i­dence for a the­ory that
lan­guage be­gan with ges­tures. Chim­p­an­zees and their close rel­a­tives
use ges­tures more flex­i­bly than fa­cial ex­pres­sions and sounds to
com­mu­ni­cate, the re­search­ers say.

Amy Pol­lick and Frans de Waal at the Yer­kes Na­tion­al Pri­mate Re­search
Cen­ter of Em­o­ry Uni­ver­si­ty in At­lan­ta, worked with two groups each
of two close hu­man rel­a­tives, chimps and bono­bos, 47 an­i­mals in all.



The bonobo, Pan panis­cus, un­til re­cent­ly called pyg­my
chim­pan­zee. They are close rel­a­tives of chimps, be­lieved to have
branched off the chimp line­age af­ter that line­age split off from hu­man
an­ces­tors. (Im­age cour­te­sy Wa­rimo)


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The pair dis­tin­guished 31 man­u­al ges­tures and 18 fa­cial or vo­cal
sig­nals. They al­so found si­m­i­lar use of fa­cial and vo­cal sig­nals,
but not of the ges­tures, be­t­ween the spe­cies.

Man­u­al ges­tures were less close­ly tied to par­tic­u­lar emo­tions and,
there­by, were more adapt­a­ble, the in­ves­ti­ga­tors said. A ges­ture may
com­mu­ni­cate a to­tal­ly dif­fer­ent mes­sage de­pend­ing up­on the
con­text, they added.

"A chim­pan­zee may stretch out an open hand to an­oth­er as a sig­nal for
sup­port, where­as the same ges­ture to­ward a pos­ses­sor of food sig­nals
a de­sire to share," said Pol­lick.

"A scream, how­ev­er, is a typ­i­cal re­s­ponse for vic­tims of
in­tim­i­da­tion, threat or at­tack. This is so for both bo­no­bos and
chim­pan­zees, and sug­gests the vo­ca­l­i­z­a­tion is rel­a­tively
in­va­ri­ant."

By stu­dy­ing si­m­i­lar types of com­mu­ni­ca­tion in close­ly re­lat­ed
spe­cies, re­search­ers can make de­duc­tions about shared an­ces­try. We
know ges­tures are a more re­cent ev­o­lu­tion­ary de­vel­op­ment than
fa­cial ex­pres­sions and vo­calizations, Pol­lick and de Waal said,
be­cause apes and hu­mans ges­tic­u­late-but not mon­keys, a more an­cient
line­age.

"A ges­ture that oc­curs in bono­bos and chim­pan­zees as well as hu­mans
like­ly was pre­s­ent in the last com­mon an­ces­tor" of all three, said
Pol­lick. "A good ex­am­ple of a shared ges­ture is the open-hand beg­ging
ges­ture, used by both apes and hu­mans. This ges­ture can be used for food,
if there is food around, but it al­so can be used to beg for help, for
sup­port, for mon­ey and so on. Its mean­ing is con­text-dependent," added
de Waal.

The re­search­ers al­so found bono­bos use ges­tures more flex­i­bly than do
chim­pan­zees. "D­if­fer­ent groups of bono­bos used ges­tures in spe­cif­ic
con­texts less con­sist­ent­ly than did dif­fer­ent groups of
chim­pan­zees," said Pol­lick. The re­searchers' find­ings al­so sug­gest
bo­no­bos and chim­pan­zees en­gage in multi-modal com­mu­ni­ca­tion,
com­bin­ing their ges­tures with fa­cial ex­pres­sions and vo­calizations to
com­mu­ni­cate a mes­sage, they added. "While chim­pan­zees pro­duce more of
these com­bi­na­tions, bono­bos re­spond to them more of­ten. This find­ing
sug­gests the bonobo is a bet­ter mod­el of sym­bol­ic com­mu­ni­ca­tion in
our ear­ly an­ces­tors," con­clud­ed Pol­lick.

The idea that lan­guage arose from ges­tures dates back to the 18th
cen­tu­ry and draws sup­port from sev­er­al mod­ern lines of ev­i­dence,
sci­ent­ists say. These include the neu­rol­o­gy of lan­guage; the
com­p­lex­ity and cross-cultural na­ture of sign lan­guages; and apes'
abi­li­ties to learn sign language.