Theos-Talk Archives (July 2001 Message tt00242)

So are pigmies 4 feet or less tall == some live in the Jungles of
central Africa, and some in the Kalahari desert.

Has any one determined how those fossil bones happened to come to
the surface of the desert region in Abyssinia ? Why there and
not elsewhere? What about So. America in the Nasca plateau --
where those strange lines and pictures on the desert surface are
to be seen? What about Australia, where some interesting
petroglyphs are found in the North and West ( deserts)

Any comparable finds?

Dal

======================================


-----Original Message-----
From: R----- C---------,
Sent: Sunday, July 22, 2001 9:35 AM
To:
Subject: PROOFS NEEDED> traditional evolutionary theory

Below is the cover story from the current issue of Time Magazine.

Of course Theosophy asserts quite differently from this standard
view. We
can go into that more.

But I thought you might want to read this. Note that the
"missing link" of
this article is 4 feet tall. Quite at variance with what we have
been
discussing on this list! Also you should note the role of
bipedalism
(walking on two feet) in this article.

Reed

____________

One Giant Step for Mankind
Meet your newfound ancestor, a chimplike forest creature that
stood up and
walked 5.8 million years ago


By MICHAEL D. LEMONICK and ANDREA DORFMAN

The region of Ethiopia called the Middle Awash, some 140 miles
northeast of
the capital of Addis Ababa, is a hot, harsh and inhospitable
place-a rocky
desert punctuated by tree-lined rivers, the occasional lake and
patches of
lava that are slowly being buried by sediments flushed out of the
hills by
the torrential rains that come along twice a year.
But between 5 million and 6 million years ago, the landscape here
was very
different. The same tectonic forces that racked the region with
earthquakes
and volcanic eruptions had also thrust the land up as much as a
mile higher
than it is today. As a result, the area was cooler and wetter and
overgrown
with trees, bushes and patches of grass. These fertile woodlands
were rich
in wildlife. Primitive elephants, giant bears, horses, rhinos,
pigs, rats
and monkeys lived here, along with dozens of other mammal species
long since
extinct.
And it was here too that nature indulged in what was perhaps her
greatest
evolutionary experiment. For it was in eastern Africa at about
this time
that a new type of primate arose-an animal not so different from
its apelike
ancestors except in one crucial respect: this creature stood on
two legs
instead of scurrying along chimplike on all fours. Its
knuckle-walking
cousins would stay low to the ground and never get much smarter.
But while
it wouldn't happen until millions of years in the future, this
new primate's
evolutionary descendants would eventually develop a large,
complex brain.
And from that would spring all of civilization, from Mesopotamia
to Mozart
to Who Wants to Be a Millionaire.
That's the broad outline, anyway. While this view of human
evolution has
generally been accepted by scientists for decades, no one has yet
been able
to say precisely when that first evolutionary step on the road to
humanity
happened, nor what might have triggered it.
But a discovery reported last week in the journal Nature has
brought
paleontologists tantalizingly close to answering both these
questions.
Working as part of an international team led by U.S. and
Ethiopian
scientists, a graduate student named Yohannes Haile-Selassie (no
relation to
the Emperor), enrolled at the University of California, Berkeley,
has found
the remains of what appears to be the most ancient human ancestor
ever
discovered. It's a chimp-size creature that lived in the
Ethiopian forests
between 5.8 million and 5.2 million years ago-nearly a million
and a half
years earlier than the previous record holder and very close to
the time
when humans and chimps first went their separate evolutionary
ways.
"Having a fossil in this region of time, very near the divergence
point, is
really exciting," says anthropologist C. Owen Lovejoy of Ohio's
Kent State
University. "Going all the way back to Darwin, people have
speculated how,
when and why humans stood up on two legs. For paleontologists,
this find is
a dream come true."
As is often the case with discoveries like this, Haile-Selassie
was not
specifically looking for the things he found. He had set out to
better
understand how the ancient ecosystems worked and evolved. "I
didn't even
think about finding hominids," he says. "All I wanted to do was
collect
enough vertebrate bones so that I could write my dissertation."
In December
1997, though, at a place called Alayla, he spotted a piece of
jawbone lying
on the rock-strewn ground. "I picked up the mandible less than
five minutes
after we got there," he recalls, "but didn't realize I had
something really
special until a year later, when we found some more bones and I
started the
serious analysis."
In all, the team eventually found 11 specimens-from at least five
different
individuals-in a cluster of sites, including Haile-Selassie's
partial lower
jaw with associated teeth, several hand and foot bones, and
pieces of three
arm bones and a collarbone. Luckily, the fossils were trapped in
sediments
that were sandwiched between layers of volcanic ash, whose age
can be
accurately gauged by a technique known as argon-argon dating.
(This layering
is still visible in places that have not been so heavily eroded,
enabling
the scientists to trace the area's geologic history.) The
verdict, confirmed
by a second dating method and by the other primitive animals
found with the
hominid remains: most of the fossils are between 5.6 million and
5.8 million
years old, although one toe bone is a few hundred thousand years
younger.
It was the detailed anatomy of these fragmentary fossils,
especially the
teeth, that convinced Haile-Selassie that he had discovered a new
human
ancestor. Although apelike, the lower canines and upper
premolars, in
particular, display certain traits found only in the teeth of
later
hominids-the term scientists use to describe ourselves and our
non-ape
ancestors. They also differ in shape from the teeth of all known
fossil and
modern apes. Even the way in which the teeth had been worn down
was telling.
Explains Haile-Selassie's thesis adviser, Berkeley paleontologist
Tim White:
"Apes all sharpen their upper canines as they chew. Hominids
don't." The new
creature's back teeth are larger than a chimp's too, while the
front teeth
are narrower, suggesting that its diet included a variety of
fibrous foods,
rather than the fruits and soft leaves that chimps prefer.
When Haile-Selassie compared the newly discovered bones and teeth
with those
of Ardipithecus ramidus, a 4.4 million-year-old hominid found in
the Middle
Awash in the early 1990s that was the previous record holder, he
realized
that the two creatures were very similar. But the older one's
teeth, while
different from an ape's, do have a number of characteristics that
are
decidedly more apelike than those of the younger hominid.
On the basis of these minor but distinctive differences,
Haile-Selassie
decided to classify the new human ancestor as a subspecies, or
variant, of
ramidus and has given it the name Ardipithecus ramidus kadabba.
(The name is
derived from the local Afar language. Ardi means ground or floor;
ramid
means root; and kadabba means basal family ancestor. In
accordance with the
sometimes bizarre nomenclature of science, the younger creature
now gets
renamed Ardipithecus ramidus .)
Haile-Selassie and his colleagues haven't collected enough bones
yet to
reconstruct with great precision what kadabba looked like. But
they do know
it was about the size of modern common chimpanzees, which when
standing
average about 4 ft. tall. That makes it roughly the same size as
its close
relative A. ramidus ramidus and about 20% taller than Lucy, the
famous 3.2
million-year-old human ancestor discovered about 50 miles away in
1974 that
is even further along the evolutionary track. The size of
kadabba's brain
and the relative proportions of its arms and legs were probably
chimplike as
well.
But unlike a chimp or any of the other modern apes that amble
along on four
limbs, kadabba almost certainly walked upright much of the time.
The
inch-long toe bone makes that clear. Two-legged primates (modern
humans
included) propel themselves forward by leaving the front part of
their foot
on the ground and lifting the heel. This movement, referred to as
toeing
off, causes the bones in the middle of the foot to take on a
distinctive
shape-a shape that is readily apparent in the ancient toe bone.
"If you
compare a chimp's foot bones with its hand bones, they look the
same because
they're used for the same thing"-that is, for
grasping-Haile-Selassie
explains. "Hominid fingers and toes don't look alike at all."
Exactly how this hominid walked is still something of a mystery,
though with
a different skeletal structure, its gait would have been unlike
ours.
Details of kadabba's lifestyle remain speculative too, but many
of its
behaviors undoubtedly resembled those of chimpanzees today. It
probably
still spent some time in trees. It probably lived in large social
groups
that would include both sexes. And rather than competing with one
another
for mates, the males may well have banded together to defend the
troop
against predators, forage for food and even hunt for game.
But that kadabba walked upright at all is hugely significant.
Paleontologists have suspected for nearly 200 years that
bipedalism was
probably the key evolutionary transition that split the human
line off from
the apes, and fossil discoveries as far back as Java Man in the
1890s
supported that notion. The astonishingly complete skeleton of
Lucy, with its
clearly apelike skull but upright posture, cemented the idea a
quarter-century ago.
What's been much tougher to pin down is just why two-leggedness
arose. The
conventional wisdom has long focused on the fact that eastern
Africa became
significantly dryer about the time that humans first evolved. The
change
would have tended to favor grasslands over forests, and, so went
the theory,
our ancestors changed to take advantage of the new conditions. We
learned to
walk upright so that we could see over the tall grasses to spot
predators
coming; an upright posture, moreover, would offer a much smaller
target for
the oppressive heat of the grassland sun, and a larger target for
cooling
breezes.
The only trouble with this theory is that it's wrong. The
earliest humans,
it turns out, didn't live in grasslands. Dry climate or not, a
companion
paper published last week in Nature shows on the basis of the
other
fossilized flora and fauna, as well as the chemistry of the
ancient soil,
that Ardipithecus ramidus kadabba lived in a well-forested
environment.
That's also the case with other extremely ancient hominids found
during the
past several years, including Ardipithecus ramidus and a species
called
Orrorin tugenensis , announced last December by French and Kenyan
researchers. And while the ability to walk on two legs probably
started out
as an increasingly frequent behavior, evolution demands an
explanation for
why it persisted. On first blush, bipedalism just doesn't make
much sense.
For our earliest ancestors, it would have been slower than
walking on all
fours, while requiring the same amount of energy. Says Lovejoy
bluntly:
"It's unnatural. It's bizarre."

Yet the advantages of walking upright were somehow so great that
the
behavior endured through thousands of generations. Indeed, the
anatomy of
our ancestors underwent all sorts of basic changes to accommodate
this new
way of moving. Many of the changes help the body stay balanced by
stabilizing the weight-bearing leg and keeping the upper torso
centered over
the feet. Lovejoy, who studies the anatomy and biomechanics of
locomotion,
thinks the changes may have improved coordination as well. "To
walk upright
in a habitual way, you have to do so in synchrony," he says. "If
the
ligaments and muscles are out of synch, that leads to injuries.
And then
you'd be cheetah meat."
By far the most crucial changes, according to Lovejoy, were those
in the
spine. The distance between chest and pelvis is longer in humans
than in
apes, allowing the lower spine to curve, which locates the upper
body over
the pelvis for balance. The pelvis grew broader, meanwhile, and
humans
developed a hip joint and associated muscles that stabilize the
pelvis.
Explains Lovejoy: "That's why a chimp sways from side to side as
it walks
upright and humans don't."
Changes also had to take place in the femur, or thighbone. For
example, the
femoral neck-the bent portion at the top of the bone-is broader
in humans
than it is in apes, which improves balance. The human knee is
specialized
for walking upright too: to compensate for the thighbone's being
at an
angle, there's a lump, or groove, at the end of the femur that
prevents the
patella from sliding off the joint. "A chimp doesn't have this
groove
because there is no angulation between the hip and the knee,"
Lovejoy says.
"This change says you're a biped."
Finally, there's the foot. "What's important here is the arch,"
Lovejoy
says. "It's a really important shock absorber. It's like wearing
a good pair
of running shoes." In order to create that arch, the chimp's
opposable great
toe became aligned with the others, and the toe's muscles and
ligaments,
which had been used for grasping and climbing, were repositioned
under the
foot. "The shape of the big toe is indicative of this. You can
see it in
Lucy's species," Lovejoy says, but not in the bone Haile-Selassie
found,
because it's from a different toe. "What we can see [in the new
discovery's
foot] is that the base of the bone adjacent to the knuckle has a
distinct
angle, showing that the creature walked step after step after
step with its
heel off the ground, using the front of its foot as a platform."
That's how it walked. Why it walked is tougher to understand,
since
motivation leaves behind no physical remains. But armed with
knowledge about
our ancestors' physical attributes and the environment that
surrounded them,
scientists have come up with several theories. Anthropologist
Henry McHenry,
of the University of California, Davis, for example, champions
the idea that
climate variation was part of the picture after all. When Africa
dried out,
say McHenry and his colleague Peter Rodman, the change left
patches of
forest widely spaced between open savannah. The first hominids
lived mostly
in these forest refuges but couldn't find enough food in any one
place.
Learning to walk on two legs helped them travel long distances
over ground
to the next woodsy patch, and thus to more food.
Meave Leakey, head of paleontology at the National Museums of
Kenya and a
member of the world's most famous fossil-hunting family, suspects
the change
in climate rewarded bipedalism for a different reason. Yes, the
dryer
climate made for more grassland, but our early ancestors, she
argues, spent
much of their time not in dense forest or on the savannah but in
an
environment with some trees, dense shrubbery and a bit of grass.
"And if
you're moving into more open country with grasslands and bushes
and things
like this, and eating a lot of fruits and berries coming off low
bushes,
there is a hell of an advantage to be able to reach higher.
That's why the
gerenuk [a type of antelope] evolved its long neck and stands on
its hind
legs, and why the giraffe evolved its long neck. There's strong
pressure to
be able to reach a wider range of levels."
But for Kent State's Lovejoy, the real answer is sex. Males who
were best at
walking upright would get more of it, leading to more offspring
who were
good on two legs, who in turn got more sex. His reasoning, first
proposed
nearly two decades ago, goes like this: like many modern
Americans, monkeys
and apes of both genders work outside the home-in the latter
case, searching
for food. Early humans, though, discovered the Leave It to Beaver
strategy:
if males handled the breadwinning, females could stay closer to
home and
devote more time to rearing the children, thus giving them a
better shot at
growing up strong and healthy.
And if you're going to bring home the bacon, or the Miocene
equivalent, it
helps to have your hands free to carry it. Over time, female apes
would
choose to mate only with those males who brought them
food-presumably the
ones who were best adapted for upright walking. Is that the way
it actually
happened? Maybe, but we may never know for sure. Leakey, for one,
is
unconvinced. "There are all sorts of hypotheses," she says, "and
they are
all fairy tales really because you can't prove anything."
If paleontologists argue about why bipedalism evolved, they're
even more
contentious over the organization of the human family tree.
According to
Haile-Selassie and his colleagues, the picture looks pretty
straightforward
from about 5.8 million years ago to the present. First comes
Ardipithecus
ramidus kadabba, the newest find. Then, more than a million years
later, its
descendant, the newly renamed Ardipithecus ramidus , appears.
After that
comes a new genus, called Australopithecus (where Lucy belongs),
and
finally, about 2 million years ago, the first members of the
human genus
Homo.
But not everyone buys the story. Indeed, the French and Kenyan
team that
presented a 6 million-year-old fossil last December insists that
theirs,
known as Orrorin tugenensis (or, more familiarly, Millennium Man
because it
was announced in 2000), is the true human ancestor and that
Ardipithecus is
nothing more than a monkey's uncle-or a chimp's
great-great-grandfather,
anyway. They even dismiss Lucy and her close kin, about as firmly
entrenched
in the human lineage as you can get, as evolutionary dead ends
that left no
living descendants.
No one disputes that this competing ancestor is 6 million years
old and thus
more ancient than Ardipithecus. What's still to be proved is that
it's a
hominid. Says Leakey: "If you read their paper, almost everything
they say
about the teeth suggests it's more apelike." And when they get to
the femur,
she says, they present no evidence disproving that it walked on
all fours.
Haile-Selassie makes precisely the same point. But Brigitte Senut
of the
National Museum of Natural History in Paris and Martin Pickford,
chairman of
paleoanthropology and prehistory at the College de France,
co-leaders of the
team that found Orrorin, dismiss the criticisms. Additional
fossils found
just last March, they say, along with the more detailed analysis
they now
have in hand of the earlier bones, will prove their case. "We are
absolutely
delighted about it," says Senut. "We had the possibility to show
the
evidence to some colleagues in South Africa recently, and just
looking at
the cast they said, OEFantastic, it's a biped! And a better biped
than
Lucy.'"
Even if they're right, though, establishing the precise path of
human
descent might be very hard. For most of the past 6 million years,
multiple
hominid species roamed the earth at the same time-including a
mere 30,000
years ago, when modern humans and Neanderthals still coexisted.
We still
can't figure out exactly how Neanderthals relate to the human
family; it's
all the more difficult to know where these newly discovered
species, with
far fewer fossil remains to study, belong.
In the case of Ardipithecus, says Donald Johanson, professor of
anthropology
and director of the Institute of Human Origins at Arizona State
University
(and the man who discovered Lucy back in 1974), "when you put 5.5
million-year-old fossils together with 4.4 million-year-old ones
as members
of the same species, you're not taking into consideration that
these could
be twigs on a tree. Everything's been forced into a straight
line." Beyond
that, he's dubious about categorizing the 5.2 million-year-old
toe bone with
the rest of the fossils: not only is it separated in time by
several hundred
thousand years, but it was also found some 10 miles away from the
rest.
If Orrorin turns out to be a hominid, the same skepticism will
apply to any
claims about its pivotal position on the family tree. According
to
University of Tokyo paleontologist Gen Suwa, a co-discoverer of
the 4.4.
million-year-old Ardipithecus ramidus , Orrorin could well be
ancestral to
the new Ardipithecus remains, rather than the other way
around."There is
nothing in the fossils," he says, "that would preclude such a
position. But
which side of the chimp-hominid split Orrorin occupies can be
determined
only by further analyses and new finds." Indeed, suggests
Haile-Selassie,
while Orrorin may be one of the earliest chimps or an ape that
became
extinct, it could also turn out to be the last common ancestor of
humans and
chimps-a creature paleontologists have been dreaming of finding
for decades.
One of the most intriguing questions the new discoveries raise,
says Bernard
Wood, a professor of human origins at George Washington
University, is
whether bipedalism should still be considered the defining
characteristic of
being human. After all, all birds have wings, but not all
creatures with
wings are birds. It's already clear that eastern Africa was
bubbling with
evolutionary experiments 6 million years ago. Maybe two-legged
walking
evolved independently in several branches of the primate family.
Says Wood:
"This might be the first example of a creature it's not possible
to label as
hominid ancestor or chimp ancestor. But that doesn't make it the
last common
ancestor of both. I think it's going to be very hard to pin the
tail on that
donkey."
In the end, that may be the most exciting thing about these
latest
discoveries from the human race's birthing ground. Not that long
ago,
paleontologists were pretty certain we started on the road to
becoming human
by standing upright on the grassy savannah. Now that science is
actually
bringing in hard evidence, the story is getting more
complicated-and more
interesting. Clearly, there are still plenty of questions to ask,
and plenty
of surprises left to uncover, in the ancient sediments of eastern
Africa.
-With reporting by Simon Robinson/Nairobi



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