This week–

THE evolutionary history of great

apes and humans may need some

rewriting, thanks to the discovery

of the fossilised teeth of a new

gorilla-like species. The teeth help

to plug a gaping hole in the fossil

record and could mean the orang-

utan and gorilla lineages diverged

from our own millions of years

earlier than previously thought.

Until now, most

palaeoanthropologists had

thought the gorilla lineage

diverged from that of humans

and chimpanzees sometime

between 6 and 8 million years

ago, based on comparisons

between the genomes of modern

species. However, firm proof has

been lacking, because very few

fossils exist from that time or the

preceding few million years.

The new fossils, which are

between 10 and 10.5 million years

old, fall squarely into this blank.

A team led by Gen Suwa of the

Tokyo University Museum in Japan

unearthed the teeth from the

Chorora formation in Ethiopia’s

Afar rift, in a region that was

probably forested and close to

water 10 million years ago. The

one canine and eight partial

molars are from at least three, but

perhaps six or more, individuals,

which the team have named

Chororapithecus abyssinicus ( Nature, vol 448, p 921 ).

The evidence suggests that

Chororapithecus may have been

a primitive gorilla, the researchers

say. For one thing, its teeth

are of about the same size and

proportions as modern gorilla

teeth. The molars also have

smaller versions of the long

crests that are characteristic of

the molars of modern gorillas

but no other apes. These crests

help with cutting tough fibrous

material, such as leaves and stems.

“The newly discovered teeth

are starting to show this

crestiness,” says Suwa, “so we

think this is an incipient form

of a gorilla.” Alternatively, the

crests might not be a sign that

Chororapithecus is related to

gorillas, but merely that its teeth

were beginning to adapt to a diet

richer in fibrous material, he says.

“Only more fossils will resolve

that question.”

Michel Brunet of the University

of Poitiers, France, who has seen

casts of the teeth, agrees that Suwa

is right to be cautious, though

he thinks the basic premise is

correct. “It’s completely clear that

these teeth must be related to a

gorilla-like group,” he says.

If Chororapithecus is indeed an

early gorilla, that would push back

the origins of the gorilla lineage to

at least 10 million years ago and

perhaps further, says Suwa.

That in turn could force

researchers to recalibrate their

estimates of rates of genetic

change, which could change the

timing of many events on the ape

family tree. For example, the

orang-utan lineage may have split

off around 20 million years ago,

rather than 13 million years ago as

previously thought, says Suwa.

The earlier date for the start of

the gorilla lineage would also fit

with the age of the earliest known

remains from the lineage leading

to humans , found in Chad and

dated at about 7 million years old,

Brunet says. Emma Young ●

SOUNDBITES

‹ The death was not sudden.›

Japanese nursing home official

Toshiro Tachibana, on the passing

of the world’s oldest person, Yone

Minagawa, at 114 years and 7 months

(Associated Press, 15 August)

‹ The comparison is night and day… This is a good example of how the shuttle programme has changed.›

John Logsdon, director of George

Washington University’s Space Policy

Institute, on NASA’s handling of

damage to the Endeavour space shuttle,

compared with its earlier handling

of similar damage to Columbia

(The New York Times, 20 August)

‹ I constantly get asked at cocktail parties what someone can do to protect their mental functioning. I tell them, ‘Put down that glass and go for a run.’›

Neurologist Scott Small of Columbia

University, New York, the lead scientist

on a study showing that age-related

shrinking of the hippocampus can be

slowed down with exercise (The New

York Times, 19 August)

‹ We can increase rainfall by 10 per cent. But Mother Nature has to cooperate. Ten per cent of zero is zero.›

Steve Johnson, director of the

cloud-seeding company Atmospherics

in Fresno, California. The firm is

finding few clouds to seed this year

(The Washington Post, 20 August)

‹ Those conditions are so horrendous that the only moral and ethical thing to do is to leave.›

Psychologist Laurie Wagner on the

decision by the American Psychological

Association not to ban its members from

aiding interrogators at Guantanamo

Bay. Instead, the group approved a

resolution reaffirming its opposition to

torture (Associated Press, 20 August)

12 | NewScientist | 25 August 2007 www.newscientist.com

New gorilla species rewrites ape evolution

MODERN HUMAN

Homo

Australopithecus

Sahelanthropus/Orrorin/Ardipithecus

CHIMPANZEEBONOBOGORILLAORANG-UTAN

ORANG

-UTAN

GORILLA

BONOBO

CHIMPANZEE

Chororapithecus

CHORORAPITHECUS

?

Proconsul

–Filling a gap in the fossil record–

GEN

SU

WA

AN

D R

EIKO

KO

NO

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