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How old is man? Depends on how you're counting
 Q:
How old is man? (Sidney, Port Harcourt, Nigeria)
A reconstruction of an early man (Austrolopithecus
africanus) [Toni Wirts, National Park Service employee]
A: Old. Maybe as old as 7 million years. How old depends on
what we call "man."
The skull of a
hominid who
lived 7 million years ago looks partly like a chimpanzee’s skull and partly like
a human’s skull. Is that creature — a man?
No sharp line separates early apes from early men. Instead,
it’s a continuum whose nature we decipher from sparse fossil remains.
Earliest men looked much like we do now from the neck down.
They walked on two legs as we do — not four like a chimp or gorilla. By 3
million years ago, they were nearly as efficient walkers as we. Their pelvises
(round like a bowl for stable support) and feet (long and skinny with arches for
strength) looked more like ours than a chimpanzee’s.
Their heads were different from modern humans. Tiny brain
cases — about a third our size — big faces, big teeth with thick enamel, large
jaws, and powerful jaw muscles.
How to tell if an early hominid was an early man? Walking
upright is the hallmark. Men didn’t get smart and then learn to walk upright.
Apes first learned to walk on two feet and that allowed them to develop
intelligence.
"Bipedality, increasingly, is being used as the critical
criterion; the other thing is a reduced canine — smaller than in other
primates," says
Gail Kennedy, anthropology professor at the University of California at Los
Angeles.
If a creature meets these two conditions — walking upright and
small canines — we define him to be a man.
Let’s follow hominids forward and look at candidates for the
"earliest man."
7 to 6 million years ago. Sahelanthropus tchadensis.
This creature is a good candidate. But, we know too little yet about the
species to be certain.
We found seven pieces from two skulls in the Sahel region,
south of the Sahara, in Chad. A cranium, two jaw pieces, and some teeth. The
braincase is like a chimpanzee’s but the teeth are more like ours (small
canine). The face has brow ridges, a human feature not found on living great
apes. The way the neck muscles attach to the skull indicates upright walk.
Maybe. One scientist thinks it may be an early gorilla. It’s hard to say with so
few pieces.
6 million years ago. Orrorin tugenensis. Not too
good a candidate. Perhaps an early ape. We found pieces of arm and thighbones,
lower jaws, and teeth in western Kenya. About the size of a female chimpanzee.
Perhaps bipedal and a tree climber. If it turns out that the creature was
bipedal, then his rating goes up to ‘likely early man.’
5.5 to 4.5 million years ago. Ardipithecus
ramidus. Fair candidate as an early man. Relatively large canine teeth,
narrow molars, thin enamel. Just a few skull fragments found so far. Possibly
bipedal. May have been a forest dweller. Probably ate leaves and fruit.
4.2 to 3.0 million years ago. Australopithecines. This
group of hominids were definitely bipedal, had small canine teeth and,
therefore, were early men. The Smithsonian Institute refers to them as the first
humans.
We’ve found fossils from various species within this group —
the most famous, of course, is Lucy, a 3.5- to 4-foot (1.1 to 1.2 m) tall woman
who lived about 3.2 million years ago.
Early men of Lucy’s species (afarensis) had low
foreheads, bony ridges over the eyes, flat noses, and no chins. Protruding jaws,
large back teeth. Their skull was much like a chimps except for the teeth. The
canine teeth were smaller than apes and not so pointed. The legs and pelvis,
however, were definitely like modern men except better suited to walking than
running.
2.4 to 1.5 million years ago. Homo habilis.
Bipedal and similar to the australopithecines but with smaller back teeth.
Definitely an early man.
Possibly able to talk, judging from a bulge (Broca’s area) in
the cranium (visible in only one skull) that is essential for speech.
Habilis was about 4 feet (1.2 m)
tall.
So, to answer your question. Man is, maybe, as old as 7
million years and, surely, as old as 2.4 million years.
Further Reading:
TalkOrigins: Hominid species
Palomar
College: Early hominid evolution by Dennis O’Neil
Wikipedia: Australopithecine
News in science: New ape ancestor (13 million years ago)
Tech News World: Running may have been the key to evolution
Smithsonian Institute: Homo habilis
(Answered Dec. 10, 2004)
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