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David Fren

Sun, Aug-11-02, 20:57

All,

Apologies in advance, but I'm going to ask a really stupid
question which any 16 year old Anthropology student would
probably know the answer too. My excuse is that I was a
geologist, and now I work for a software company, so I'm not
supposed to know better. Here goes.

Given that we evolved from animals with tails, and we are
bipedal, why did we lose the tail? Isn't a tail useful for
a biped - in fact more so than for a quadruped? And what
is the evolutionary benefit in *not* having a tail - how
would evolution have selected for an animal which was
losing its tail?

I'm curious to know why the tail wasn't just left intact.

TIA, David.

Richard Wa

Sun, Aug-11-02, 20:57

David French wrote:

> All,
>
> Apologies in advance, but I'm going to ask a really stupid
> question which any 16 year old Anthropology student would
> probably know the answer too. My excuse is that I was a
> geologist, and now I work for a software company, so I'm not
> supposed to know better. Here goes.
>
> Given that we evolved from animals with tails, and we are
> bipedal, why did we lose the tail? Isn't a tail useful for
> a biped - in fact more so than for a quadruped? And what
> is the evolutionary benefit in *not* having a tail - how
> would evolution have selected for an animal which was
> losing its tail?
>
> I'm curious to know why the tail wasn't just left intact.
>
> TIA, David.

This is one of those little mysteries. One idea is that as
cautious climbers, as opposed to reckless scamperers and
leapers, hominoid apes lost the need for a tail as a balancing
tool. Even gibbons, who don't look to be particularly
cautious, have developed a particular form of locomotion which
does not involve leaping from branch to branch where the
stabilizing support of a tail would be an advantage but rather
swing from secure handhold to secure handhold - even if it is
under the branch in the tops of very tall trees. Why would the
tail disappear utterly I hear you ask. Impossible to say but
one notion has apes constantly assuming an upright sitting
posture and having a tail might interfere somewhat with this.

But there is really no way of resolving this.

Rick Wagler

James Mich

Sun, Aug-11-02, 20:57

I will attempt to answer your question. It is my hypothesis
that humans evolved because of increases in the gonadal
hormone, testosterone. It is also my hypothesis that all
tissue growth is optimized by the adrenal hormone,
dehydroepiandrosterone (DHEA). Furthermore, I suggest
testosterone directs use of DHEA for growth and development of
all tissues. It follows from these hypotheses that if
testosterone is higher, then DHEA should be lower; the
testosterone is directing more DHEA for use by tissues. This
is proven; testosterone is higher in male and female humans
compared to chimpanzees, but DHEA is much higher in chimps
than in humans.

It is my hypothesis that the brain is a primary site of the
effects of testosterone. That is, the brain is more affected
by testosterone to use more DHEA. This translates into the
brain using DHEA at the expense of other tissues. For example,
I think our teeth are smaller than chimpanzee teeth because of
increased brain size using available DHEA at the expense of
teeth. Now, to your question; I suggest the loss of the tail
is directly the result of this same mechanism. As the brain
increases in size, the tail simply looses in the competition
for growth and development due to DHEA. As the body and brain
sizes of gorillas, chimpanzees, and humans increased, the tail
simply does not get enough DHEA for growth.

(I invite you to read my explanation of mammalian evolution
which explains the selection for DHEA and the formation of
mammals which was published last year: "Hormones in Mammalian
Evolution," Rivista di Biologia / Biology Forum 2001;
94: 177-184. Also, please read "Androgens in Human Evolution.
A New Explanation of Human Evolution," Rivista di Biologia
/ Biology Forum 2001; 94: 345-362. The next issue of
Rivista… (95: number 2) will carry my explanation of the
effects of testosterone on the formation of primates,
"Mitochondrial Eve," and "Y Chromosome Adam.")

James Michael Howard Fayetteville, Arkansas, U.S.A.

On Sun, 11 Aug 2002 22:34:10 +0100, "David French"
<takethisbitout.david.french@virgin.net> wrote:

>All,
>
>Apologies in advance, but I'm going to ask a really stupid
>question which any 16 year old Anthropology student would
>probably know the answer too. My excuse is that I was a
>geologist, and now I work for a software company, so I'm not
>supposed to know better. Here goes.
>
>Given that we evolved from animals with tails, and we are
>bipedal, why did we lose the tail? Isn't a tail useful for
>a biped - in fact more so than for a quadruped? And what
>is the evolutionary benefit in *not* having a tail - how
>would evolution have selected for an animal which was
>losing its tail?
>
>I'm curious to know why the tail wasn't just left intact.
>
>TIA, David.

James Mich

Sun, Aug-11-02, 20:57

Richard Wa

Sun, Aug-11-02, 20:57

Richard Wagler wrote:

> David French wrote:
>
> > All,
> >
> > Apologies in advance, but I'm going to ask a really stupid
> > question which any 16 year old Anthropology student would
> > probably know the answer too. My excuse is that I was a
> > geologist, and now I work for a software company, so I'm
> > not supposed to know better. Here goes.
> >
> > Given that we evolved from animals with tails, and we are
> > bipedal, why did we lose the tail? Isn't a tail useful for
> > a biped - in fact more so than for a quadruped? And what
> > is the evolutionary benefit in *not* having a tail - how
> > would evolution have selected for an animal which was
> > losing its tail?
> >
> > I'm curious to know why the tail wasn't just left intact.
> >
> > TIA, David.
>
> This is one of those little mysteries. One idea is that as
> cautious climbers, as opposed to reckless scamperers and
> leapers, hominoid apes lost the need for a tail as a
> balancing tool. Even gibbons, who don't look to be
> particularly cautious, have developed a particular form of
> locomotion which does not involve leaping from branch to
> branch where the stabilizing support of a tail would be an
> advantage but rather swing from secure handhold to secure
> handhold - even if it is under the branch in the tops of
> very tall trees. Why would the tail disappear utterly I hear
> you ask. Impossible to say but one notion has apes
> constantly assuming an upright sitting posture and having a
> tail might interfere somewhat with this.
>
> But there is really no way of resolving this.
>
> Rick Wagler

To add to the above.....tail loss only has to happen once in
the creature that gave rise to the Hominoid apes and once gone
the trait need never re-emerge without a strong selective
force mandating the re-emergence of a tail. So we don't have
to figure out why chimps don't have tails and why orangs don't
have tails and why we don't have tails and so on. Something
inherited from the stem Hominoid can be fixed in the lineage
and requires no subsequent explanation.

Rick Wagler

Philip Dei

Sun, Aug-11-02, 23:56

On Sun, 11 Aug 2002 22:34:10 +0100, "David French"
<takethisbitout.david.french@virgin.net> wrote:

>All,
>
>Apologies in advance, but I'm going to ask a really stupid
>question which any 16 year old Anthropology student would
>probably know the answer too. My excuse is that I was a
>geologist, and now I work for a software company, so I'm not
>supposed to know better. Here goes.
>
>Given that we evolved from animals with tails, and we are
>bipedal, why did we lose the tail? Isn't a tail useful for
>a biped - in fact more so than for a quadruped? And what
>is the evolutionary benefit in *not* having a tail - how
>would evolution have selected for an animal which was
>losing its tail?
>
>I'm curious to know why the tail wasn't just left intact.

Apes lost tail several million years before bipedality
evolved, whether or not its selective in hominids, it may have
never appearred to be tested.

Email account is blocked on return mail only persons who
register with DNApaleoAnth @ att dot net will be given access.
DNApaleoAnth is for registration only.

Deowll

Sun, Aug-11-02, 23:56

"David French" <takethisbitout.david.french@virgin.net> wrote
in message
news:oLA59.2313$td2.25894@newsfep3-gui.server.ntli.net...
> All,
>
> Apologies in advance, but I'm going to ask a really stupid
> question which any 16 year old Anthropology student would
> probably know the answer too.
My
> excuse is that I was a geologist, and now I work for a
> software company,
so
> I'm not supposed to know better. Here goes.
>
> Given that we evolved from animals with tails, and we are
> bipedal, why did we lose the tail? Isn't a tail useful for a
> biped - in fact more so than for a quadruped? And what is
> the evolutionary benefit in *not* having a tail - how would
> evolution have selected for an animal which was losing
its
> tail?

Take a look at a skeleton. You have a tail. It may not stick
out of your body but you have one. One person in about 10,000
births now has an external tail removed before they go home
from the hospital.

Apes lost their tails a long time before humans came along.

Body parts that no longer serve a useful purpose tend to
get smaller through the generations. Tails in monkeys seem
to be used mainly for balancing except in some new world
species where they have been adapted for grasping. There
are other ways of balancing. Not having been on the
committee involved in making these design alterations that
is as for as I want to go.

>
> I'm curious to know why the tail wasn't just left intact.
>
> TIA, David.

Harry Erwi

Mon, Aug-12-02, 14:00

David French <takethisbitout.david.french@virgin.net> wrote:

> All,
>
> Apologies in advance, but I'm going to ask a really stupid
> question which any 16 year old Anthropology student would
> probably know the answer too. My excuse is that I was a
> geologist, and now I work for a software company, so I'm not
> supposed to know better. Here goes.
>
> Given that we evolved from animals with tails, and we are
> bipedal, why did we lose the tail? Isn't a tail useful for
> a biped - in fact more so than for a quadruped? And what
> is the evolutionary benefit in *not* having a tail - how
> would evolution have selected for an animal which was
> losing its tail?

The tail is a balance organ. It's useful in above-branch
movements and in vertical clinging and leaping. It's not much
good for a relatively slow orthograde below-branch feeder.

>
> I'm curious to know why the tail wasn't just left intact.
>
> TIA, David.

--
Harry Erwin <http://www.theworld.com/~herwin/

John Roth

Mon, Aug-12-02, 14:00

"David French" <takethisbitout.david.french@virgin.net> wrote
in message
news:oLA59.2313$td2.25894@newsfep3-gui.server.ntli.net...
> All,
>
> Apologies in advance, but I'm going to ask a really stupid
> question
which
> any 16 year old Anthropology student would probably know
> the answer
too. My
> excuse is that I was a geologist, and now I work for a
> software
company, so
> I'm not supposed to know better. Here goes.
>
> Given that we evolved from animals with tails, and we are
> bipedal, why
did
> we lose the tail? Isn't a tail useful for a biped - in
> fact more so
than
> for a quadruped? And what is the evolutionary benefit in
> *not* having
a
> tail - how would evolution have selected for an animal
> which was
losing its
> tail?
>
> I'm curious to know why the tail wasn't just left intact.

As Richard Wagner and Philip Decker have already commented, it
happened long before the chimpanzee / pre-human split. The
only thing I'd add is that losing a feature doesn't really
need a selective "pressure." It only needs a mutation that
eliminates the feature, and then the "lack" of a selective
pressure causing the mutant to be less fit.

Notice that a tail is a somewhat expensive feature. It has to
grow, it has to be maintained by a certain amount of food
intake. If the tail contributed less than that to the animal,
it would tend to vanish.

I suspect a lot of what happens in evolution is pure,
unadulterated happenstance, followed by unabashed opportunism
in taking advantage of the change.

John Roth

>
> TIA, David.

Otter Nunc

Mon, Aug-12-02, 14:00

--WebTV-Mail-7089-11410 Content-Type: Text/Plain;
Charset=US-ASCII Content-Transfer-Encoding: 7Bit

There is no such thing as a dumb question. Dumb answers
will always continue to be free. When proto ape started
living more so on the ground the tail would be a
disadvantage fleeing big cats. As a house cat will catch a
mouse and play with it by putting a paw on its tail that is
my best guestimate.The last one standing in the living game
of musical tails gets to go home and get some. LOL

--WebTV-Mail-7089-11410 Content-Description: signature
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Paul Crowl

Mon, Aug-12-02, 14:00

"David French" <takethisbitout.david.french@virgin.net> wrote
in message
news:oLA59.2313$td2.25894@newsfep3-gui.server.ntli.net...
>
> Given that we evolved from animals with tails, and we are
> bipedal, why did we lose the tail? Isn't a tail useful for
> a biped - in fact more so than for a quadruped? And what
> is the evolutionary benefit in *not* having a tail - how
> would evolution have selected for an animal which was
> losing its tail?

The answer seems obvious enough to me. At one stage (?~15 mya)
our ancestors were gibbons (or 'gibbons'). A tail would be no
use to a gibbon. It brachiates at a very fast rate through the
high canopy with its long arms, curling its legs up on to its
body. (Females use their legs to cradle their infant.)

> I'm curious to know why the tail wasn't just left intact.

Any tail (or even stump) would stick out and be constantly
bumping into things or getting caught. This was the point were
anthropoids lost all external trace.

From being a gibbon, our ancestors then grew larger and
became something like an orang- utan, then descended to the
ground and became something like a gorilla, and then
something like a chimp.

Well, that's my own version of our evolution -- the most
conservative scheme imaginable! The major ancestors are
extant. And why wouldn't they be? They had no reason to
go extinct.

Hopefully, it will soon be possible to date (or at least
sequence) chunks of DNA. If so, all the books on human
evolution will be due for a drastic re-write.

Paul.

Algis Kuli

Tue, Aug-13-02, 05:55

"David French" <takethisbitout.david.french@virgin.net> wrote
in message
news:<oLA59.2313$td2.25894@newsfep3-gui.server.ntli.net>...

> Apologies in advance, but I'm going to ask a really stupid
> question which any 16 year old Anthropology student would
> probably know the answer too.

I think it's an excellent question in fact.

> Given that we evolved from animals with tails, and we are
> bipedal, why did we lose the tail?

Considering that most arboreal primates and many terrestrial
mammals have tails most the explanations given so far are
possible but, I'd argue, rather weak.

It also should be considered if early hominoids were wading
animals. As far as I know no aquatic/semi-aquatic animals have
the need for balancing tails - as opposed to powerful
propulsive ones. I would therefore expect this would
significantly contribute to the 'pressure' to drop the tail.

Algis Kuliukas

John Cartm

Tue, Aug-13-02, 14:01

In article <442d7042.0208122200.459b9eb9@posting.google.com>,
Algis Kuliukas <algis@riverapes.com> wrote:
> It also should be considered if early hominoids were wading
> animals. As far as I know no aquatic/semi-aquatic animals
> have the need for balancing tails - as opposed to powerful
> propulsive ones. I would therefore expect this would
> significantly contribute to the 'pressure' to drop the tail.

Are we putting an aquatic phase before the tail is lost in
apes? Doesn't that put rather an early date on it? That seems
to compound rather than simplify the problem.

--
John Cartmell john@cartmell.demon.co.uk

Fleur Designs (boardgames) http://www.cartmell.demon.co.uk
Acorn Publisher magazine http://www.acornpublisher.com

Harry Erwi

Tue, Aug-13-02, 14:01

John Cartmell <john@cartmell.demon.co.uk> wrote:

> In article
> <442d7042.0208122200.459b9eb9@posting.google.com>, Algis
> Kuliukas <algis@riverapes.com> wrote:
> > It also should be considered if early hominoids were
> > wading animals. As far as I know no aquatic/semi-aquatic
> > animals have the need for balancing tails - as opposed to
> > powerful propulsive ones. I would therefore expect this
> > would significantly contribute to the 'pressure' to drop
> > the tail.
>
> Are we putting an aquatic phase before the tail is lost in
> apes? Doesn't that put rather an early date on it? That
> seems to compound rather than simplify the problem.

It simplifies it greatly. According to my notes, Proconsul ca
20 MYr BP had lost the tail. (Which, BTW, makes my earlier
comment about the loss of tail being associated with a
below-branch orthograde posture invalid. Proconsul was an
arboreal quadruped with an above-branch pronograde posture.)
So if the aquatic phase predates Proconsul, that places it
long before the development of the savannah in the terminal
Miocene/Pliocene. Both sides more or less can claim to have
won. Perhaps the AA was as early as Eocene, given the evidence
from Messel (Germany) and South America for early species
exchanges across the Atlantic.

I love it when we finally reach closure 8).
--
Harry Erwin <http://www.theworld.com/~herwin/

Ejudy

Tue, Aug-13-02, 23:56

herwin@theworld.com (Harry Erwin) wrote:
> John Cartmell wrote:
>
> >
> > Algis Kuliukas <algis@riverapes.com> wrote:
> > > It also should be considered if early hominoids were
> > > wading animals. As far as I know no aquatic/semi-aquatic
> > > animals have the need for balancing tails - as opposed
> > > to powerful propulsive ones. I would therefore expect
> > > this would significantly contribute to the 'pressure' to
> > > drop the tail.
> >
> > Are we putting an aquatic phase before the tail is lost in
> > apes? Doesn't that put rather an early date on it? That
> > seems to compound rather than simplify the problem.
>
> It simplifies it greatly. According to my notes, Proconsul
> ca 20 MYr BP had lost the tail. (Which, BTW, makes my
> earlier comment about the loss of tail being associated with
> a below-branch orthograde posture invalid. Proconsul was an
> arboreal quadruped with an above-branch pronograde posture.)
> So if the aquatic phase predates Proconsul, that places it
> long before the development of the savannah in the terminal
> Miocene/Pliocene. Both sides more or less can claim to have
> won. Perhaps the AA was as early as Eocene, given the
> evidence from Messel (Germany) and South America for early
> species exchanges across the Atlantic.
>
> I love it when we finally reach closure 8).

AHA! Humorous marbles roll around in there with those chess
pieces ;-)))

ej;-)

"It occurred to me the other day that I am rather accurately
modeled by a thunk -- I frequently need to be forced to
completion." -- paraphrased from a {plan file}.

Marc Verha

Thu, Aug-15-02, 06:57

"David French" <takethisbitout.david.french@virgin.net>
schreef in bericht
news:oLA59.2313$td2.25894@newsfep3-gui.server.ntli.net...

> Given that we evolved from animals with tails, and we are
> bipedal, why did we lose the tail? Isn't a tail useful for a
> biped - in fact more so than for a quadruped? And what is
> the evolutionary benefit in *not* having a tail - how would
> evolution have selected for an animal which was losing its
> tail? I'm curious to know why the tail wasn't just left
> intact. TIA,
David

Excellent question IMO. In hominoids, it's not only tail
reduction, but +-complete disappearance, IOW, the reason(s)
must have been important. Tails are generally longer in small
than in large animals, and in arboreal/jumping/gliding than
in ground-dwelling animals. This suggests its function is
often equilibrium. Other possible functions are propulsion in
water (beavers, otters...) and branch-holding in trees
(spider monkeys, possums...). Our large size could explain
tail loss, but then why have gibbons lost their tails? or
were they a lot larger in the past? Another (additional?)
possible explanation is that hominoid ancestors at one time
didn't need a tail for fast locomotion: slow? eg,
branch-hanging? Loss of arboreality (eg, in combination with
bigger size) is not the explanation: in that case, the
non-Homo hominoids would probably have kept their tails. Slow
branch-hanging is not unlikely (eg, sloths & koalas), but
then gibbons must have had very slow ancestors once (New
World brachiators OTOH have extremely well-developed tails).

Integration of other evidence (mostly comparative) suggests
the early hominoids lived in flooded forests: this explains,
eg, the later development of bipedality in Homo, the
knuckle-walking in Pan & Gorilla, the brachiation in gibbons,
and the slow branch-hanging in Pongo. And also the loss of the
tail: "Quite possibly, the features that typically distinguish
apes from monkeys (i.e. large size, tail-loss and arm-hanging)
were adaptations for what we call an 'aquarboreal' locomotion
in an environment that included both trees and water. A
vertical posture and an ability to climb with the arms raised
above the head could have helped a wading primate to enter or
leave the water by grasping overhanging branches or waterside
vegetation, and to grasp fruits above the water. Body
enlargement and tail reduction would hinder agile arborealism,
whereas a larger body is more easily supported in water and
helps reduce heat loss (explaining why aquatic mammals are
larger than related terrestrial forms). Tails would be of
little use for a wading and/or swimming primate and cause both
drag and heat loss."
M.Verhaegen, P.-F.Puech & S.Munro 2002 "Aquarboreal
ancestors?" Trends in Ecology & Evolution 17:212-217 http:/-
/reviews.bmn.com/journals/atoz/latest?pii=S0169534702024904-
&node=TOC%4 %40TREE%40017%4005%40017_05

Marc Verhaegen http://www.onelist.com/community/AAT
http://allserv.rug.ac.be/~mvaneech/Verhaegen.html

Algis Kuli

Thu, Aug-15-02, 13:59

"Marc Verhaegen" <marc.verhaegen@village.uunet.be> wrote in
message news:<3d5b743d$0$263$ba620e4c@news.skynet.be>...

> Excellent question IMO. In hominoids, it's not only tail
> reduction, but +-complete disappearance, IOW, the reason(s)
> must have been important. Tails are generally longer in
> small than in large animals, and in arboreal/jumping/gliding
> than in ground-dwelling animals. This suggests its function
> is often equilibrium. Other possible functions are
> propulsion in water (beavers, otters...) and branch-holding
> in trees (spider monkeys, possums...). Our large size could
> explain tail loss, but then why have gibbons lost their
> tails? or were they a lot larger in the past? Another
> (additional?) possible explanation is that hominoid
> ancestors at one time didn't need a tail for fast
> locomotion: slow? eg, branch-hanging? Loss of arboreality
> (eg, in combination with bigger size) is not the
> explanation: in that case, the non-Homo hominoids would
> probably have kept their tails. Slow branch-hanging is not
> unlikely (eg, sloths & koalas), but then gibbons must have
> had very slow ancestors once (New World brachiators OTOH
> have extremely well-developed tails).
>
> Integration of other evidence (mostly comparative) suggests
> the early hominoids lived in flooded forests: this
> explains, eg, the later development of bipedality in Homo,
> the knuckle-walking in Pan & Gorilla, the brachiation in
> gibbons, and the slow branch-hanging in Pongo. And also the
> loss of the tail: "Quite possibly, the features that
> typically distinguish apes from monkeys (i.e. large size,
> tail-loss and arm-hanging) were adaptations for what we
> call an 'aquarboreal' locomotion in an environment that
> included both trees and water. A vertical posture and an
> ability to climb with the arms raised above the head could
> have helped a wading primate to enter or leave the water by
> grasping overhanging branches or waterside vegetation, and
> to grasp fruits above the water. Body enlargement and tail
> reduction would hinder agile arborealism, whereas a larger
> body is more easily supported in water and helps reduce
> heat loss (explaining why aquatic mammals are larger than
> related terrestrial forms). Tails would be of little use
> for a wading and/or swimming primate and cause both drag
> and heat loss."
> M.Verhaegen, P.-F.Puech & S.Munro 2002 "Aquarboreal
> ancestors?" Trends in Ecology & Evolution 17:212-217 http-
> ://reviews.bmn.com/journals/atoz/latest?pii=S016953470202-
> 4904&node=TOC%4 %40TREE%40017%4005%40017_05

Thanks, Marc. Excellent question, excellent answer IMO. I was
hoping you'd chip in with this one.

I'm interested in the statement "Tails would be of little use
for a wading and/or swimming primate and cause both drag and
heat loss." Could it also be true that they'd be a liability
in escaping predators?

And what about proconsul?

Algis Kuliukas

Grelbr

Thu, Aug-15-02, 13:59

jmhoward@arkansas.net (James Michael Howard) wrote in message
news:<3d56e05b.2910437@news.arkansas.net>... [Some stuff about
hormones that I don't get.]

Urm. Does all this really apply to human ancesters losing
tails? After all, the lineage lost tails some significant time
before the brain growth really got going. The fossil Lucy, for
example, had no tail. grelbr

Marc Verha

Fri, Aug-16-02, 06:56

"Algis Kuliukas" <algis@riverapes.com> schreef in bericht
news:442d7042.0208150904.49867726@posting.google.com...

> > Excellent question IMO. In hominoids, it's not only tail
> > reduction, but
+-complete disappearance, IOW, the reason(s) must have been
important. Tails are generally longer in small than in large
animals, and in arboreal/jumping/gliding than in
ground-dwelling animals. This suggests its function is often
equilibrium. Other possible functions are propulsion in water
(beavers, otters...) and branch-holding in trees (spider
monkeys, possums...). Our large size could explain tail loss,
but then why have gibbons lost their tails? or were they a lot
larger in the past? Another (additional?) possible explanation
is that hominoid ancestors at one time didn't need a tail for
fast locomotion: slow? eg, branch-hanging? Loss of arboreality
(eg, in combination with bigger size) is not the explanation:
in that case, the non-Homo hominoids would probably have kept
their tails. Slow branch-hanging is not unlikely (eg, sloths &
koalas), but then gibbons must have had very slow ancestors
once (New World brachiators OTOH have extremely well-developed
tails). Integration of other evidence (mostly comparative)
suggests the early hominoids lived in flooded forests: this
explains, eg, the later development of bipedality in Homo, the
knuckle-walking in Pan & Gorilla, the brachiation in gibbons,
and the slow branch-hanging in Pongo. And also the loss of the
tail: "Quite possibly, the features that typically distinguish
apes from monkeys (i.e. large size, tail-loss and arm-hanging)
were adaptations for what we call an 'aquarboreal' locomotion
in an environment that included both trees and water. A
vertical posture and an ability to climb with the arms raised
above the head could have helped a wading primate to enter or
leave the water by grasping overhanging branches or waterside
vegetation, and to grasp fruits above the water. Body
enlargement and tail reduction would hinder agile arborealism,
whereas a larger body is more easily supported in water and
helps reduce heat loss (explaining why aquatic mammals are
larger than related terrestrial forms). Tails would be of
little use for a wading and/or swimming primate and cause both
drag and heat loss." M.Verhaegen, P.-F.Puech & S.Munro 2002
"Aquarboreal ancestors?" Trends in Ecology & Evolution
17:212-217 http://reviews.bmn.com/journals/atoz/latest?pii=S0-
169534702024904&node=TOC%4 %40TREE%40017%4005%40017_05

> Thanks, Marc. Excellent question, excellent answer IMO. I
> was hoping you'd
chip in with this one. I'm interested in the statement "Tails
would be of little use for a wading and/or swimming primate
and cause both drag and heat loss."

- Of little use for progression in water? For a large primate,
this is obvious I'd think. Even for medium-sized primates,
it's difficult to see how a monkey-like mammal could start
using its tail for swimming, but what about primates of rat
or weasel size (ancestors of beavers & otters?), eg, to swim
to other trees in the flooded forests? perhaps the use of a
tail in an aboreal context (feathery or grasping) & in an
aquatic context (paddle or rudder) are not very compatible?
Why exactly do koalas & sloths have shortened tails (though
not absent AFAIK)?
- Cause drag & heat loss: if a tail was not used for
locomotion (progression or equilibirum), it had no function
in the water, and would only have been disadvantageous. This
is IMO why it was completely lost in the early hominoids. A
rather unique situation I believe. Even pigs & bears retain
short tails. It suggests IMO they must have spent a lot of
time in water.

> Could it also be true that they'd be a liability in escaping
> predators?

Yes, I hadn't thought of that. I think it's unlikely that
this would explain the +-complete disappearance of a tail
in hominoids. But shortening? Not impossible, but difficult
to know IMO: comparative data? Do herbivores have shorter
tails than equally large carnivores? in or outside the
water you mean?

> And what about proconsul? Algis Kuliukas

I don't know. Isn't Proconsul usu. described as having
above-branch locomotion? If it lacked a tail (is this
certain?), it might have been aquarboreal.

Marc

Algis Kuli

Fri, Aug-16-02, 23:56

"Marc Verhaegen" <marc.verhaegen@village.uunet.be> wrote in
message news:<3d5cac6a$0$207$ba620e4c@news.skynet.be>...
> "Algis Kuliukas" <algis@riverapes.com> schreef in bericht
> news:442d7042.0208150904.49867726@posting.google.com...

> I'm interested in the statement "Tails would be of little
> use for a wading and/or swimming primate and cause both drag
> and heat loss."
>
> - Of little use for progression in water? For a large
> primate, this is obvious I'd think. Even for medium-sized
> primates, it's difficult to see how a monkey-like mammal
> could start using its tail for swimming, but what about
> primates of rat or weasel size (ancestors of beavers &
> otters?), eg, to swim to other trees in the flooded
> forests? perhaps the use of a tail in an aboreal context
> (feathery or grasping) & in an aquatic context (paddle or
> rudder) are not very compatible? Why exactly do koalas &
> sloths have shortened tails (though not absent AFAIK)?

It's an intersting area, that's for sure.

> - Cause drag & heat loss: if a tail was not used for
> locomotion (progression or equilibirum), it had no
> function in the water, and would only have been
> disadvantageous. This is IMO why it was completely lost in
> the early hominoids. A rather unique situation I believe.
> Even pigs & bears retain short tails. It suggests IMO they
> must have spent a lot of time in water.

Logical.

> > Could it also be true that they'd be a liability in
> > escaping predators?
>
> Yes, I hadn't thought of that. I think it's unlikely that
> this would explain the +-complete disappearance of a tail
> in hominoids. But shortening? Not impossible, but difficult
> to know IMO: comparative data? Do herbivores have shorter
> tails than equally large carnivores? in or outside the
> water you mean?

That would be a good indicator. Perhaps it might explain pigs'
shorter tails. Just thinking aloud really.

> > And what about proconsul?
>
> I don't know. Isn't Proconsul usu. described as having
> above-branch locomotion? If it lacked a tail (is this
> certain?), it might have been aquarboreal.

That was my understanding. Proconsul heseloni (KNM-RU-2036) is
described (and shown) in Klien (1999) p 123 as having no tail.
I don't know how strong a case there would be for it being
aquarboreal.

Algis Kuliukas Algis Kuliukas

Marc Verha

Sat, Aug-17-02, 13:57

"Algis Kuliukas" <algis@riverapes.com> schreef in bericht
news:442d7042.0208161825.35bf7785@posting.google.com...

> > > Could it also be true that they'd be a liability in
> > > escaping
predators?
> >
> > Yes, I hadn't thought of that. I think it's unlikely that
> > this would
explain
> > the +-complete disappearance of a tail in hominoids. But
> > shortening? Not impossible, but difficult to know IMO:
> > comparative data? Do herbivores
have
> > shorter tails than equally large carnivores? in or outside
> > the water you mean?
>
> That would be a good indicator. Perhaps it might explain
> pigs' shorter tails. Just thinking aloud really.

Yes, why do they retain short tails? I wouldn't know. Their
tails obviously have no function in locomotion. To chase away
insects? To protect their behind? Do they wag their tails in
social contexts?

> > > And what about Proconsul?
> >
> > I don't know. Isn't Proconsul usu. described as having
> > above-branch locomotion? If it lacked a tail (is this
> > certain?), it might have been aquarboreal.
>
> That was my understanding. Proconsul heseloni (KNM-RU-2036)
> is described (and shown) in Klien (1999) p 123 as having no
> tail. I don't know how strong a case there would be for it
> being aquarboreal. Algis Kuliukas

Not impossible. It probably had very large relatives
(Proc.maior). Large size is unexpected in arboreal animals,
but might be an indication for aquarboreality?

Marc

Whitedog

Sat, Aug-17-02, 13:57

On Sat, 17 Aug 2002 15:41:00 +0200, "Marc Verhaegen"
<marc.verhaegen@village.uunet.be> wrote:

>
>"Algis Kuliukas" <algis@riverapes.com> schreef in bericht
>news:442d7042.0208161825.35bf7785@posting.google.com...
>
>> > > Could it also be true that they'd be a liability in
>> > > escaping
>predators?
>> >
>> > Yes, I hadn't thought of that. I think it's unlikely that
>> > this would
>explain
>> > the +-complete disappearance of a tail in hominoids. But
>> > shortening? Not impossible, but difficult to know IMO:
>> > comparative data? Do herbivores
>have
>> > shorter tails than equally large carnivores? in or
>> > outside the water you mean?
>>
>> That would be a good indicator. Perhaps it might explain
>> pigs' shorter tails. Just thinking aloud really.
>
>Yes, why do they retain short tails? I wouldn't know. Their
>tails obviously have no function in locomotion. To chase away
>insects? To protect their behind? Do they wag their tails in
>social contexts?

Praise the lard, a pigs question! Pig generally have a hairy
tuft at the end of the tail.When lying in wallows they flick
the wet tail end often. This may be a supplementary cooling
device, though it's not very effective, probably more useful
to deter insects from the vulva and anus. Tail wagging and
specific positioning of the tail does occur in social contexts
though for an animal that engages in a lot of face to face
contact it doesn't appear to be too useful either.Tail wagging
is also observed when expressing an interest in something,
this might be a more useful clue, signalling a new food source
for instance. Perhaps the tail (which can be long enough to
reach the hocks, though in domestic pigs is often docked to
prevent tail biting vices) is retained for a combination of
these uses.

I had the misfortune of assisting an animal behaviourist in
data recording for her thesis once. This has made me deeply
suspicious of reading too much into behavioural literature
since. If I know about anything from years of observation,
it's pigs; this person's approach to the questions was mind
boggling and she didn't once ask me what I thought was
happening as she merrily scribbled her dubious observations
down. By the way, it wasn't about tails! In case you were
dying to ask, yes I do speak swine....

...... Whitedog: [whitedog_o_hound@hotREMOVEBLINKERSmail.com

Harry Erwi

Sun, Aug-18-02, 06:56

Whitedog <seemysig@notmail.com> wrote:

>
> I had the misfortune of assisting an animal behaviourist in
> data recording for her thesis once. This has made me deeply
> suspicious of reading too much into behavioural literature
> since. If I know about anything from years of observation,
> it's pigs; this person's approach to the questions was mind
> boggling and she didn't once ask me what I thought was
> happening as she merrily scribbled her dubious observations
> down. By the way, it wasn't about tails! In case you were
> dying to ask, yes I do speak swine....
>

Reminds me of when I was helping a post-doc do a behavioral
study of bats. He was training one to search for mealworms on
a tether. The bat was circling him as he did the set up,
obviously observing everything and waiting for him to stop
fiddling with the apparatus and get out of the way. No search
at all involved. Thereafter my job was to hold the bat and
obscure her observation of the setup.
--
Harry Erwin <http://www.theworld.com/~herwin/

Marc Verha

Sun, Aug-18-02, 06:56

"Whitedog" <seemysig@notmail.com> schreef in bericht
news:3d5e73aa.23633593@News.CIS.DFN.DE...

> >> > > Could it also be true that they'd be a liability in
> >> > > escaping
> >predators?
> >> >
> >> > Yes, I hadn't thought of that. I think it's unlikely
> >> > that this would
> >explain
> >> > the +-complete disappearance of a tail in hominoids.
> >> > But shortening?
Not
> >> > impossible, but difficult to know IMO: comparative
> >> > data? Do
herbivores
> >have
> >> > shorter tails than equally large carnivores? in or
> >> > outside the water
you
> >> > mean?
> >>
> >> That would be a good indicator. Perhaps it might explain
> >> pigs' shorter tails. Just thinking aloud really.
> >
> >Yes, why do they retain short tails? I wouldn't know.
> >Their tails
obviously
> >have no function in locomotion. To chase away insects? To
> >protect their behind? Do they wag their tails in social
> >contexts?
>
> Praise the lard, a pigs question!

:-) Very interesting creatures, pigs.

> Pig generally have a hairy tuft at the end of the tail.When
> lying in wallows they flick the wet tail end often. This
> may be a supplementary cooling device, though it's not very
> effective, probably more useful to deter insects from the
> vulva and anus. Tail wagging and specific positioning of
> the tail does occur in social contexts though for an animal
> that engages in a lot of face to face contact it doesn't
> appear to be too useful either. Tail wagging is also
> observed when expressing an interest in something, this
> might be a more useful clue, signalling a new food source
> for instance. Perhaps the tail (which can be long enough to
> reach the hocks, though in domestic pigs is often docked to
> prevent tail biting vices) is retained for a combination of
> these uses.

I'm always aware of combinations of explanations: some
functions are probably more important than others. Hippos use
their tails in spreading their feces IIRC, a territorial
behaviour to disperse feromones. Do suids do that?

Marc

Whitedog

Mon, Aug-19-02, 13:59

On Sun, 18 Aug 2002 11:57:41 +0200, "Marc Verhaegen"
<marc.verhaegen@village.uunet.be> wrote:

>:-) Very interesting creatures, pigs.
>
>I'm always aware of combinations of explanations: some
>functions are probably more important than others. Hippos use
>their tails in spreading their feces IIRC, a territorial
>behaviour to disperse feromones. Do suids do that?

Not as far as I know. Boars sniff at close quarters and taste
urine for hormonal clues. Sows and boars respond to pheromones
in boar saliva and urine but again at fairly close range.
Faeces are dropped randomly and little interest is shown in
them by others (apart from me, who has to clear them up!)
though piglets may derive some elements from eating them.So it
looks like there's a very dull paper for some poor student in
determining tail retention.

...... Whitedog: [whitedog_o_hound@hotREMOVEBLINKERSmail.com

Whitedog

Mon, Aug-19-02, 13:59

On Sun, 18 Aug 2002 06:57:09 +0100, herwin@theworld.com (Harry
Erwin) wrote:

>Whitedog <seemysig@notmail.com> wrote:
>
>> I had the misfortune of assisting an animal behaviourist in
>> data recording for her thesis once. This has made me deeply
>> suspicious of reading too much into behavioural literature
>> since. If I know about anything from years of observation,
>> it's pigs; this person's approach to the questions was mind
>> boggling and she didn't once ask me what I thought was
>> happening as she merrily scribbled her dubious observations
>> down. By the way, it wasn't about tails! In case you were
>> dying to ask, yes I do speak swine....
>>
>
>Reminds me of when I was helping a post-doc do a behavioral
>study of bats. He was training one to search for mealworms on
>a tether. The bat was circling him as he did the set up,
>obviously observing everything and waiting for him to stop
>fiddling with the apparatus and get out of the way. No search
>at all involved. Thereafter my job was to hold the bat and
>obscure her observation of the setup.

Lol, I suppose that's the problem with focussing on
echolocation and forgetting eyes!

...... Whitedog: [whitedog_o_hound@hotREMOVEBLINKERSmail.com

Marc Verha

Mon, Aug-19-02, 20:58

"Whitedog" <seemysig@notmail.com> schreef in bericht
news:3d60e33f.7498457@News.CIS.DFN.DE...

> >:-) Very interesting creatures, pigs.
> >
> >I'm always aware of combinations of explanations: some
> >functions are probably more important than others. Hippos
> >use their tails in spreading their feces IIRC, a
> >territorial behaviour to disperse feromones. Do suids
do
> >that?
>
> Not as far as I know. Boars sniff at close quarters and
> taste urine for hormonal clues. Sows and boars respond to
> pheromones in boar saliva and urine but again at fairly
> close range. Faeces are dropped randomly and little interest
> is shown in them by others (apart from me, who has to clear
> them up!) though piglets may derive some elements from
> eating them.So it looks like there's a very dull paper for
> some poor student in determining tail retention.

:-D Thanks, Whitedog!

Marc

John David

Wed, Aug-21-02, 13:59

"Marc Verhaegen" <marc.verhaegen@village.uunet.be> wrote in
message news:3d5cac6a$0$207$ba620e4c@news.skynet.be...
>
> "Algis Kuliukas" <algis@riverapes.com> schreef in bericht
> news:442d7042.0208150904.49867726@posting.google.com...
>
> > > Excellent question IMO. In hominoids, it's not only tail
> > > reduction,
but
> +-complete disappearance, IOW, the reason(s) must have been
> important.
Tails
> are generally longer in small than in large animals, and in
> arboreal/jumping/gliding than in ground-dwelling animals.
> This suggests
its
> function is often equilibrium. Other possible functions are
> propulsion in water (beavers, otters...) and branch-holding
> in trees (spider monkeys, possums...). Our large size could
> explain tail loss, but then why have gibbons lost their
> tails? or were they a lot larger in the past? Another
> (additional?) possible explanation is that hominoid
> ancestors at one time didn't need a tail for fast
> locomotion: slow? eg, branch-hanging? Loss of arboreality
> (eg, in combination with bigger size) is not the
> explanation:
in
> that case, the non-Homo hominoids would probably have kept
> their tails.
Slow
> branch-hanging is not unlikely (eg, sloths & koalas),

Koalas are certainly not branch-hangers. They are rather slow
in the tree, but quite fast on the ground (unlike sloths).

In any case, the koala almost certainly lost its tail (or most
of it) before it took to the trees. Koalas are closely related
to wombats, which are ground-dwellers, and always were,
judging from their fossil ancestors (some of which were much
larger than modern wombats and koalas). Modern wombats are
specialised burrowers, but this was apparently not true for
many of their recent ancestors.

Both koalas and wombats (and their slightly more distant
relations, the diprotodons) have very small tails. What
evidence there is suggests that their tail reduction (compared
with other marsupials) occurred before they split up.
Arguably, the proto-koala/wombat was a rhinocerous analog,
with a lifestyle similar to the diprotodons and giant wombats
of more recent times.

John.

Marc Verha

Wed, Aug-21-02, 20:59

"John David Atkinson" <johnacko@bigpond.com> schreef in
bericht news:_1K89.11369$g9.36755@newsfeeds.bigpond.com...
> "Marc Verhaegen" <marc.verhaegen@village.uunet.be> wrote in
> message news:3d5cac6a$0$207$ba620e4c@news.skynet.be...
> > "Algis Kuliukas" <algis@riverapes.com> schreef in bericht
> > news:442d7042.0208150904.49867726@posting.google.com...

> > > > Excellent question IMO. In hominoids, it's not only
> > > > tail reduction,
but +-complete disappearance, IOW, the reason(s) must have
been important. Tails are generally longer in small than in
large animals, and in arboreal/jumping/gliding than in
ground-dwelling animals. This suggests its function is often
equilibrium. Other possible functions are propulsion in water
(beavers, otters...) and branch-holding in trees (spider
monkeys, possums...). Our large size could explain tail loss,
but then why have gibbons lost their tails? or were they a
lot larger in the past? Another (additional?) possible
explanation is that hominoid ancestors at one time didn't
need a tail for fast locomotion: slow? eg, branch-hanging?
Loss of arboreality (eg, in combination with bigger size) is
not the explanation: in that case, the non-Homo hominoids
would probably have kept their tails. Slow branch-hanging is
not unlikely (eg, sloths & koalas),

> Koalas are certainly not branch-hangers. They are rather
> slow in the tree,
but quite fast on the ground (unlike sloths).

OK, thanks. I should have said "slow arboreals" or so.

> In any case, the koala almost certainly lost its tail (or
> most of it)
before it took to the trees. Koalas are closely related to
wombats, which are ground-dwellers, and always were, judging
from their fossil ancestors (some of which were much larger
than modern wombats and koalas). Modern wombats are
specialised burrowers, but this was apparently not true for
many of their recent ancestors. Both koalas and wombats (and
their slightly more distant relations, the diprotodons) have
very small tails. What evidence there is suggests that their
tail reduction (compared with other marsupials) occurred
before they split up. Arguably, the proto-koala/wombat was a
rhinocerous analog, with a lifestyle similar to the
diprotodons and giant wombats of more recent times. John

Interesting, thanks. Koalas are phalangeroids, with
syndactylous pedal 2d-3d digits. This is likely an arboreal
(branch-grasping) adaptation. In that case, wombats must have
had arboreal ancestors (aquarboreal? cf. large size). The
rhino-like species could have been semi-aquatic like the
pachyderms. All this could be compatible with tail loss in
aquarboreal acestors, just as in early hominoids. The sequence
in wombat ancestors would then be:
arboreal>aquarboreal>semi-aquatic>burrowing.

Marc Verhaegen http://www.onelist.com/community/AAT
http://allserv.rug.ac.be/~mvaneech/Verhaegen.html