"Long before it's in the papers"
January 28, 2015


Elephants recognize mirror image; elephant ancestor found

Oct. 30, 2006
Special to World Science  

Two new stud­ies rep­re­sent strides for­ward in el­e­phant bi­ol­o­gy, re­search­ers say: one found that el­e­phants can rec­og­nize them­selves in mir­rors, the oth­er turned up a “miss­ing link” fos­sil be­tween el­e­phants and their an­cient an­ces­tors.

An el­e­phant in front of a mir­ror. (Cour­te­sy Josh­ua Plot­nik, Frans de Waal & Di­an­a Reiss)

The first study shows that el­e­phants join hu­mans, apes, and dol­phins as the on­ly known an­i­mals with enough “self-awareness” for mir­ror self-rec­og­ni­tion, sci­en­tists said.

An an­i­mal dis­cov­er­ing it­self in a mir­ror typ­i­cal­ly car­ries out a sort of in­ves­ti­ga­tion in­volv­ing a se­ries of in­spec­tions, ac­cord­ing to the re­search­ers, Josh­u­a Plot­nik of Em­o­ry Uni­ver­si­ty in At­lan­ta, Ga., and col­leagues.

This ex­plo­ra­tion, they added, typ­i­cal­ly cul­mi­nates in a “l­it­mus test” of touch­ing a mark on its body which it can’t see oth­erwise. Sci­en­tists nor­mal­ly make a mark on the an­i­mal’s head, so if the an­i­mal starts touch­ing it be­fore the mir­ror, they con­clude that it rec­og­nizes it­self.

Mir­ror self-rec­og­ni­tion is cur­rent­ly known on­ly in an­i­mals that lead com­plex so­cial lives and dis­play em­pa­thy, Plot­nik and col­leagues not­ed. They ad­ded that el­e­phants, which have large brains, are al­so high­ly so­cial and show em­pa­thy.

Mir­ror self rec­og­ni­tion may in­di­cate that a spe­cies has “an in­creased self-oth­er dis­tinc­tion” com­pared to oth­er an­i­mals, Plot­nik’s team wrote in this week’s ear­ly on­line edi­tion of the re­search jour­nal Pro­ceed­ings of the Na­tio­n­al Aca­de­my of Sci­en­ces. That dis­tinc­tion, they added, may al­so un­der­lie “so­cial com­plexity and al­tru­is­tic ten­den­cies.”

The test in­volved three adult fe­male Asian el­e­phants. All three pro­gressed through var­i­ous mir­ror-testing stages, such as in­spect­ing be­hind the mir­ror and bring­ing food up to it, the re­search­ers said. Even­tu­al­ly, one be­gan re­peat­ed­ly touch­ing an X on her head with her trunk. Al­though just one pachyderm “pas­sed” the test, the sci­en­tists point­ed out that less than half of chim­panzees typ­i­cal­ly pass it as well.

A missing link

The “miss­ing link” fos­sil, de­scribed in the same edi­tion of the jour­nal, was found in Eri­t­rea and is 27 mil­lion years old, ac­cord­ing to re­search­ers.

Eritreum melakeg­he­b­re­k­ris­to­si, as drawn by bi­o­lo­gist-art­ist Ga­ry H. Mar­chant.

Ele­phants are the sole liv­ing mem­bers of an or­der of mam­mals known as Pro­bos­cid­ea, which in­cludes el­e­phants and mam­moths. This group un­der­went an ev­o­lu­tion­ary split some 24 mil­lion years ago, bio­lo­gists said, form­ing two groups: Ele­phan­ti­da—com­pris­ing el­e­phants, mam­moths, and pre­de­ces­sors—an Mam­mu­tida, or mastodons. 

Je­heskel Sho­sha­ni of the Uni­ver­si­ty of As­ma­ra, Er­i­tre­a, and col­leagues wrote that the fos­sil jaw shows a tooth struc­ture in­ter­me­di­ate be­tween that of mo­d­ern and an­cient el­e­phants. 

The re­search­ers es­ti­mat­ed the size of the an­i­mal, termed Er­i­t­reum me­la­ke­ghe­bre­kri­s­to­si, as 130 cm (4’3”) tall at the shoul­der and 484 kg (1,067 lb). That’s far smaller than mod­ern el­e­phants, though this spec­i­men is be­lieved to be youth­ful. The find, Shoshani and col­leagues ar­g­ued, adds to ev­i­dence that east Af­ri­ca was a ma­jor cen­ter for ear­ly el­e­phant ev­o­lu­tion.

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Two new studies represent strides forward in elephant biology, researchers say: one found that elephants can recognize themselves in mirrors, the other turned up a “missing link” fossil between elephants and their ancient ancestors. The first study shows that elephants join humans, apes, and dolphins as the only known animals with enough “self-awareness” for mirror self-recognition, scientists said. An animal discovering itself in a mirror typically carries out a sort of investigation involving a series of inspections, according to the researchers, Joshua Plotnik of Emory University in Atlanta, Ga., and colleagues. This exploration, they added, typically culminates in a “litmus test” of touching a mark on its body which it can’t see otherwise. Scientists normally make a mark on the animal’s head, so if the animal starts touching it before the mirror, they conclude that it recognizes itself. Mirror self-recognition is currently known only in animals that lead complex social lives and display empathy, Plotnik and colleagues noted, adding that elephants, which have large brains, are also highly social and show empathy. Mirror self recognition may indicate that a species has “an increased self-other distinction” compared to other animals, Plotnik’s team wrote in this week’s early online edition of the research journal pnas. That distinction, they added, may also underlie “social complexity and altruistic tendencies shared among these large-brained animals.” The test involved three adult female Asian elephants. All three progressed through various mirror-testing stages, such as inspecting behind the mirror and bringing food up to it, the researchers said. Eventually, one began repeatedly touching an X on her head with her trunk. Although just one elephant “passed” the test, the scientists pointed out that less than half of chimpanzees typically pass it as well. Missing link The “missing link” fossil, described in the same edition of the journal, is 27 million years old, according to researchers. Elephants are the sole living members of an order of mammals known as Proboscidea, which includes elephants and mammoths. This group underwent an evolutionary split around 24 million years ago, researchers said, forming two groups: Elephantida—including elephants, mammoths, and predecessors—and Mammutida, or mastodons. Jeheskel Shoshani of the University of Asmara, Eritrea, and colleagues wrote that the fossil jaw shows a tooth structure intermediate between that of modern and ancient elephants. The researchers estimated the size of the animal, termed Eritreum melakeghebrekristosi, as 130 cm (4’3”) tall at the shoulder and 484 kg (1,067 lb). That’s far smaller than modern elephants, though this specimen is believed to be youthful. The find, according to Shoshani and colleagues, adds to evidence that east Africa was a major center for early elephant evolution.