Australopiths - Shorter Legs For Fighting

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Rich Travsky

Posted: Tue Mar 13, 2007 11:31 pm

Guest

http://caribjournal.com/2007/03/12/short-leg-human-ancestors-better-fighters/

In a recent study conducted by the University of Utah, which analyzed leg lengths
and indicators of aggression in nine primate species, including human aborigines.
Published in the March issue of the journal Evolution, the study showed that
Ape-like human ancestors known as australopiths maintained short legs for 2 million
years because a squat physique and stance helped the males fight over access to
females.

“The old argument was that they retained short legs to help them climb trees that
still were an important part of their habitat,” says David Carrier, a professor of
biology. “My argument is that they retained short legs because short legs helped
them fight.”
....
“For that entire period, they had relatively short legs – longer than chimps’ legs
but shorter than the legs of humans that came later,” Carrier says. “So the question
is, why did australopiths retain short legs for 2 million years? Among experts on
primates, the climbing hypothesis is the explanation. Mechanically, it makes sense.
If you are walking on a branch high above the ground, stability is important because
if you fall and you’re big, you are going to die. Short legs would lower your center
of mass and make you more stable.” Carrier added.

Yet Carrier says his research suggests short legs helped australopiths fight because
“with short legs, your center of mass is closer to the ground. It’s going to make
you more stable so that you can’t be knocked off your feet as easily. And with short
legs, you have greater leverage as you grapple with your opponent.”

While Carrier says his aggression hypothesis does not rule out the possibility that
short legs aided climbing, but “evidence is poor because the apes that have the
shortest legs for their body size spend the least time in trees – male gorillas and
orangutans.”
....
Carrier set out to find how aggression related to leg length. He compared Australian
aborigines with eight primate species: gorillas, chimpanzees, bonobos, orangutans,
black gibbons, siamang gibbons, olive baboons and dwarf guenon monkeys. Carrier used
data on aborigines because they are a relatively natural population.

For the aborigines and each primate species, Carrier used the scientific literature
to obtain typical hindlimb lengths and data on two physical features that previously
have been shown to correlate with male-male competition and aggressiveness in
primates:

* The weight difference between males and females in a species. Earlier studies found
males fight more in species with larger male-female body size ratios.

* The male-female difference in the length of canine teeth, which are next to the
incisors and are used for biting during fights.
....
The study found that hindlimb length correlated inversely with both indicators of
aggressiveness: Primate species with greater male-female differences in body weight
and length of the canine teeth had shorter legs, and thus display more male-male
combat.

There was no correlation between arm length and the indicators of aggression. Carrier
says arms are used for fighting, but “for other things as well: climbing, handling
food, grooming. Thus, arm length is not related to aggression in any simple way.”
....
The study also found that females in each primate species except humans have
relatively
longer legs than males. “If it is mainly the males that need to be adapted for
fighting,
then you’d expect them to have shorter legs for their body size,” Carrier says.

He notes there are exceptions to that rule. Bonobos have shorter legs than chimps,
yet
they are less aggressive. Carrier says the correlation between short legs and
aggression
may be imperfect because legs are used for many other purposes than fighting.

Humans “are a special case” and are not less aggressive because they have longer
legs,
Carrier says. There is a physical tradeoff between aggression and economical walking
and
running. Short, squat australopiths were strong and able to stand their ground when
shoved, but their short legs made them ill-suited for distance running. Slender,
long-legged humans excel at running. Yet, they also excel at fighting. In a 2004
study,
Carrier made a case that australopiths evolved into lithe, long-legged early humans
only
when they learned to make weapons and fight with them.

Now he argues that even though australopiths walked upright on the ground, the reason
they retained short legs for 2 million years was not so much that they spent time in
trees, but “the same thing that selected for short legs in the other great apes:
male-male aggression and competition over access to reproductively active females.”
....

Eh. Wrestlers and those in martial arts would agree about the lower center of mass
advantage, but...

circean0circle@gmail.com

Posted: Tue Mar 13, 2007 11:31 pm

Guest

I think Carrier would have made a stronger case if the earliest
remains of H. ergaster & erectus showed human-inflicted trauma. To my
knowledge, they don't. I haven't read anything in the literature
saying that they show evidence of blunt force trauma (we can safely
rule out projectile trauma since projectile weaponry wasn't invented
until at least the Middle Stone Age). It also sounds like he's trying
to fit too many behaviors under one hypothetical umbrella.

Paul Crowley

Posted: Wed Mar 14, 2007 3:47 am

Guest

"Rich Travsky" <traRvEsky@hotmMOVEail.com> wrote in message
news:45F77AB1.B6FD58C4@hotmMOVEail.com...

Quote:

The question is a good one -- and climbing
trees was never much of an answer.

Quote:

Carrier made a case that australopiths evolved into lithe, long-legged
early humans only when they learned to make weapons and fight
with them.

This is very silly, since australopiths would
have used weapons from the start. It was a
(if not 'the') major reason for bipedalism.

But a low centre of gravity and stability are
just as important there as in normal fighting.

Quote:

Now he argues that even though australopiths walked upright on the
ground, the reason they retained short legs for 2 million years was not
so much that they spent time in trees, but "the same thing that selected
for short legs in the other great apes: male-male aggression and
competition over access to reproductively active females."

Prionesse

Posted: Wed Mar 14, 2007 10:54 am

Guest

Quote:

This is very silly, since australopiths would
have used weapons from the start. It was a
(if not 'the') major reason for bipedalism.

What makes you say that?

Quote:

The silliness here is in forgetting that
australopiths (and all other hominids) would
have been intensely social and lived in large
groups. Most of the fighting would have been
more akin to war,

Most other large group-living primates (chimps, baboons, and the like)
resort to inter-group violence only very rarely. Being intensely
social they live in complex dominance hierarchies and depend on
dominance relationships to sort out the outcome of confrontations.
Also, most of the intra-group fighting in these groups is non-fatal.
Animals avoid physical fights whenever possible.

-Prionesse.

Paul Crowley

Posted: Wed Mar 14, 2007 4:28 pm

Guest

"Prionesse" <circean0circle@gmail.com> wrote in message
news:1173887665.209272.170070@l77g2000hsb.googlegroups.com...

Quote:

This is very silly, since australopiths would
have used weapons from the start. It was a
(if not 'the') major reason for bipedalism.

What makes you say that?

The last time anyone thought seriously
about bipedalism (i.e. Darwin) it was realised
that the posture was adopted to carry and
wield things in the hands. At the same
time (something he did not know) the
taxon lost the distinctive weapons of the
whole Primate order -- its large canines.

Quote:

The silliness here is in forgetting that
australopiths (and all other hominids) would
have been intensely social and lived in large
groups. Most of the fighting would have been
more akin to war,

Most other large group-living primates (chimps, baboons, and the like)
resort to inter-group violence only very rarely.

Quote:

Being intensely
social they live in complex dominance hierarchies and depend on
dominance relationships to sort out the outcome of confrontations.

Read some field reports on chimps sometime
-- such as by Goodall.

Quote:

Also, most of the intra-group fighting in these groups is non-fatal.

So what? One fatality per individual
in a lifetime is good enough for most
of us,

Quote:

Animals avoid physical fights whenever possible.

For social and territorial animals with
dangerous weaponry, the possibility
cannot always be avoided. A very
high proportion of many species end
their lives as the result of actions of
their own species -- often an exclusion
from the social group is sufficient: it's
a death sentence.

Paul.

Prionesse

Posted: Wed Mar 14, 2007 6:18 pm

Guest

Quote:

Paleoanthropologists have been theorizing about bipedalism ever since
Darwin. If the Origin of Species or the Descent of Man are the only
two books you've ever read on the subject, I suggest you open any
human evolution textbook (I recommend Foley 2004 or Klein 1999) and
read up on the slew of theories that try to account for facultative
bipedalism in the earliest hominins. And although the canines are
reduced in Ar. ramidus and A. anamensis, you still find a honing
facet, which means the canines were still relatively sharp. It's more
likely that the reduction in canine size in Australopithecus was
primarily due to a dietary shift from fruits to roots/tubers that
require grinding action. This accounts for the reduction in anterior
teeth and corresponding increase in the size of the premolars and
molars.

Quote:

Though as long as they survive past reproductive age, or an age where
they've already produced a few offspring, then fatal physical
encounters shouldn't have that much influence on reproductive
success.

Quote:

So what? One fatality per individual
in a lifetime is good enough for most
of us,

For social and territorial animals with
dangerous weaponry, the possibility
cannot always be avoided. A very
high proportion of many species end
their lives as the result of actions of
their own species -- often an exclusion
from the social group is sufficient: it's
a death sentence.

Point well taken about banishment/ostracism being a death sentence.
Even the very lowest ranking individuals in a social group have
significantly lower reproductive success over a lifetime. Over many
generations, this produces evolutionarily significant results, as the
genotypes of higher ranking individuals come to represent a
disproportionately large percentage of the gene pool. As you've
hinted, violence isn't necessary to suppress the reproductive
potential of an individual in your group. Making sure that they occupy
the bottom rungs of the social ladder does the job sufficiently well.

richard01

Posted: Thu Mar 15, 2007 3:45 am

Guest

On Mar 14, 4:47 pm, "Paul Crowley"
<slkwuoiutiuytciu...@slkjlskjoioue.com> wrote:

Quote:

"Rich Travsky" <traRvE...@hotmMOVEail.com> wrote in message

news:45F77AB1.B6FD58C4@hotmMOVEail.com...

http://caribjournal.com/2007/03/12/short-leg-human-ancestors-better-f...

In a recent study conducted by the University of Utah, which analyzed leg lengths
and indicators of aggression in nine primate species, including human aborigines.
Published in the March issue of the journal Evolution, the study showed that
Ape-like human ancestors known as australopiths maintained short legs for 2 million
years because a squat physique and stance helped the males fight over access to
females.

"The old argument was that they retained short legs to help them climb trees that
still were an important part of their habitat," says David Carrier, a professor of
biology. "My argument is that they retained short legs because short legs helped
them fight."

The question is a good one -- and climbing
trees was never much of an answer.

Carrier made a case that australopiths evolved into lithe, long-legged
early humans only when they learned to make weapons and fight
with them.

This is very silly, since australopiths would
have used weapons from the start. It was a
(if not 'the') major reason for bipedalism.

But a low centre of gravity and stability are
just as important there as in normal fighting.

Now he argues that even though australopiths walked upright on the
ground, the reason they retained short legs for 2 million years was not
so much that they spent time in trees, but "the same thing that selected
for short legs in the other great apes: male-male aggression and
competition over access to reproductively active females."

The silliness here is in forgetting that
australopiths (and all other hominids) would
have been intensely social and lived in large
groups. Most of the fighting would have been
more akin to war,

Paul.

You're all on the wrong track.

Take time off and read some authoritative articles, like:

"Short, Stubby Legs and Rotational Geometry"
Rumsfeld et al
Anthropometry and Popular Mechanics - Vol 368 No 2 - April 1 2007

Where you'll find that Australopithecines were trying to evolve
wheels, and failed.

regards

Richard

Paul Crowley

Posted: Thu Mar 15, 2007 6:45 am

Guest

"Prionesse" <circean0circle@gmail.com> wrote in message
news:1173914322.957388.120090@n76g2000hsh.googlegroups.com...

Quote:

I am all too well aware of that.

Quote:

If the Origin of Species or the Descent of Man are the only
two books you've ever read on the subject, I suggest you open any
human evolution textbook (I recommend Foley 2004 or Klein 1999) and
read up on the slew of theories that try to account for facultative
bipedalism in the earliest hominins.

Much better advice would be to read
absolutely nothing after Darwin. The
'science' has forgotten almost all he
knew, and degenerated into a set of
(mostly politically-correct) superstitions
that would shame a Lysenko.

Quote:

And although the canines are
reduced in Ar. ramidus and A. anamensis, you still find a honing
facet, which means the canines were still relatively sharp. It's more
likely that the reduction in canine size in Australopithecus was
primarily due to a dietary shift from fruits to roots/tubers that
require grinding action. This accounts for the reduction in anterior
teeth and corresponding increase in the size of the premolars and
molars.

This is as good an illustration of my
point as could be found -- although
there are about a thousand others.
Darwin would have been aware of the
huge variation in diet throughout the
primate order -- and among the numerous
other mammals which also have large
canines. At no point in the evolution of
any other taxon has a change in diet
been postulated for any loss of them --
one reason being that they are so
valuable that they are very rarely lost.

The 'grinding action' you propose, as
the reason for their reduction in size,
is nonsensical. It does not become
possible until after they are fully
reduced in size.

It is quite strange how such childish
mistakes have not merely become
common in the 'discipline' -- they make
up almost the whole of its fabric. It is
as though there were some ruling Stalin-
like figure, suppressing all internal
dissent, and forbidding any kind of
debate or questioning. Obviously
there is no such figure -- but that
makes the ubiquity (and intensity)
of the nonsense very hard to explain.

Quote:

The 'only rarely' is sufficient to ensure that
most (i.e. almost all) male chimps die as a
result of such encounters -- often at a fairly
young age. Many female chimps die from
the same (or similar) causes.

Read some field reports on chimps sometime
-- such as by Goodall.

Though as long as they survive past reproductive age, or an age where
they've already produced a few offspring, then fatal physical
encounters shouldn't have that much influence on reproductive
success.

The proportion of male chimps that
do successfully reproduce is small.
Those which fight best lead long lives
and reproduce far more than the rest.

Paul.

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