Marc Verha
Wed, Jun-20-07, 17:16
Algis at AAT (+ my comments --MV):
I don't think anyone has posted this before but if not, I
thought it might be of some interest to read what Jablonski
wrote about the AAH in her latest book "Skin" (I have included
relevent footnotes with the text where relevant): Jablonski,
Nina G 2006 "Skin - a natural history" University of
California "Explantions for the nearly hairless state of the
human body abound. Without direct fossil evidence that could
document the timing and content of hair loss in humans,
scientists have proposed likely evolutionary scenarios using
comparative anatomical, physiological, and behavioural
information, as well as varying amounts of imagination. The
resulting hypotheses range from the well founded to the wacky,
with hairlessness being attributed to everything from a
heritage of swimming to nit-picking. The best supported
theories involve the importance of sweat in human evolution
(MV: Just-so statement without evidence (perhaps elsewhere
in her book?), but not impossible: overheated sealions
on land sweat on their naked hindlimbs.)
- the topic of this chapter. It might be useful, however, to
take a look at some of the other ideas that have gained
notice over the years. The explanation that has had the
greatest popular appeal is the so-called aquatic ape
hypothesis [1 - Hardy 1960, Morgan 1982]. According to this
idea, the beginning of the human lineage around six to seven
million years ago was marked by an aquatic phase, during
which ancient hominids - a term that describes all the
members of our lineage since we last shared a common
ancestor with chimpanzees - lost most of their body hair,
gained a layer of body fat under the skin (subcutaneously),
and made the transition from being routinely on four legs to
standing and moving on two (that is, became bipedal.) [2 a
definition of the term `hominid']
(MV: Hardy thought the semi-aq.phase happened more than 10
Ma. Elaine has no clear opinion, but AFAICT she used
to believe it happened after the H/P split & before
the apiths. I don't think most people who know
something on AAT still believe that. Jablonski is
ill-informed: why not read the recent literature on
AAT before trying to discuss it?)
As evidence of the aquatic phase, this hypothesis notes that
fossil remains of our distant hominid relatives of our distant
hominid relatives are most often found in the vicinity of
ancient lakes.
(MVI: Not so: AAT evidence is based on *comparative* data.)
It also observes that several of the anatomical
characteristics of modern humans, such as hairless bodies and
subcutaneous fat, are shared by aquatic mammals like dolphins
and whales. In the peak years of its popularity (the
1970s), the aquatic ape theory - which sounded relatively
simple and described out ancestors swimming and carrying
babies in water - seemed an attractive alternative to
the other hypotheses then available for the emergence of
humans, many of which cast our beginnings in a context
of mindless violence and conflict. [3 Notes that in
the 60s and 70s lots of work promoted hunting and that
this inspired works such as Ardrey's `African Genesis'
suggesting that human ancestors were `killer apes'.
Jablonski concludes: "The enormous popularity of the
aquatic ape hypothesis was a reaction against Ardrey's
view of human nature" pp187] The aquatic ape hypothesis
is not, however, supported by the facts.
(MV: Jablonski doesn't address the SC fat & furlessness,
but simply states her belief on the matter.)
Let's look at the situation in which our distant ancestors
found themselves in tropical Africa.
(MVI: ?? "our distant relatives"(when??) in trop.Africa"??
Hasn't Jablonski heard of the retroviral data, which
suggest our ancestors were absent from Africa 4-3 Ma??
This alone makes what follows irrelevant.)
First, a hominid ancestor who spent much of its time in a lake
would have had to enter the water from the shoreline. For
millions of years the shores of African rivers, lakes and
waterholes have not been friendly places. Thick with
crocodiles constantly on the prowl for hapless prey,
shorelines are dangerous places where few animals linger. Our
hominid ancestors, only about one metre (a little over three
feet) tall and lacking claws, big teeth, or weapons, would
have been no match for such formidable predators.
(MVII: Apparently Jablonski still believes she descends
from Lucy??)
Even if they managed to get into the water, ancient hominids
would have faced other big problems. Human skin has few
defences against the waterborne parasites that live in African
lakes and rivers. In the African tropics, one of the greatest
health risks for people who spend time in and around water is
schistosomiasis, a parasitic infestation caused by a tiny worm
that can swiftly penetrate and migrate through the skin. Many
other parasitic diseases are transmitted to humans this way,
leading to untold numbers of deaths and a calamitous loss of
vigour and livelihood for many populations who depend on water
[4 "In addition to diseases that involve waterborne parasites
burrowing into the body, malaria - caused by a parasite that
infects a water-breeding mosquito - leads to even greater
morbidity and mortality throughout the tropics" pp187].
(MVIII: Ever heard of the untold deaths & calamities caused by
lack of water?? Moreover, there is no schistozomiasis
in seawater.)
If hominid ancestors had lived in an aquatic habitat during
their early evolution, the human immune system would reflect a
history of assault by such parasites. It doesn't. Only in the
last ten thousand years or so have we started spending much
time in the water, as we developed agriculture and fishing,
and our immune systems have not yet been sharpened by natural
selection to resist the attack of the nasty organisms that
inhabit these freshwater lakes and rivers.
(MIX: Just-so statements without evidence & relevance &
wrong AFAICS.)
The aquatic ape hypothesis also doesn't adequately explain why
hominids would have evolved hairless skin. Naked skin is
advantageous to fully aquatic mammals like whales and dolphins
because it reduces drag and buoyancy. This is especially
important when the animal is diving or speeding along in the
water, either in search of food or on long-distance migration.
(MX: Just-so statements without evidence. Human hairiness
is as in other tropical medium-sized semi-aquatic
mammals such as babirusas (+-naked, but patches of
hairs). No need to construct far-fetched
"explanations".)
But we have no evidence to suggest that hominids ever engaged
in such activities, although they have occasionally foraged
along shorelines and in shallow water for shellfish and
similar food.
MXI: There is obvious behavioural evidence: that humans as
opposed to chimps can dive for severql minutes & can
swallow food underwater proves our ancestors were
parttime divers once.
[5 - "The idea that hominids may have utilized shellfish and
other shallow-water food resources is currently being pursued
by Alan Shabel, a PhD student in the department of integrative
biology at UCLA" pp187] For animals who spend only part of
their time in water, a naked skin is in fact something of a
liability because it leaves them vulnerable to the problems of
thermoregulation when they are on land. Animals like otters,
fur seals, and sea lions, which weigh less than 1000 kilograms
(or less than a ton) and spend some time on land, are covered
with smooth, dense fur that insulates them against the cold
when they are out of the water. Only the giant semi-aquatic
mammals such as the walruses and hippos, whose large size and
barrel shape make it hard for them to lose heat from the
body's surface, have naked skin.
(MXII: The usual black-white thinking of anti-AAT people. AAT
says human ancestors were medium-sized tropical
semi-aquatics: these animals seem to be about as
haired as humans are.)
In addition, all mammals committed to a fully aquatic or semi
aquatic lifestyle have evolved a streamlined body shape with
small appendages such as fins or flippers to improve their
hydrodynamics and minimize the area of skin in contact with
the water [6 - Wheeler 1985]. If you spend much of your life
in the water surrounded by watchful and hungry predators, you
need to be able to move fast and maneuver deftly in water. The
ancient hominids, in contrast, were fairly short, bipedal
apes, with long gangly arms, who wouldn't have been able to
dog-paddle or defend themselves in the water for five minutes,
let alone spend their days diving and cavorting while swimming
after prey or one another.
(MXIII: If Jablonski had compared chimp to human
hydrodynamics, she hadn't said all that & she had
known that humans are extremely versatile in the
water. Hasn't she heard of the Moken, Ama etc.?)
In short, we didn't lose our body hair because we passed
through an aquatic phase. All the human features that this
hypothesis ascribes to a heritage of swimming and diving can
be explained far more convincingly and parsimoniously as our
adaptations to an active life in a hot and mostly open
environment.
(MXIV: Yes, in short, all antelopes & lions are naked & fat &
run on 2 legs...)
[7 "The advocates of the aquatic ape hypothesis have also
opined that habitual bipedal posture and locomotion originated
while humans were partially aquatic. Many other more
convincing hypotheses that are consistent with available facts
have been developed to account for this key innovation in
human history. George Chaplin and I have advocated a
hypothesis for the origin of bipedalism based on bipedal
social displays as efficacious methods of social control
(Jablonski and Chaplin 1993.)" p187]." Jablonski
(2006:39-41)
(MV: We're no interested in Jablonski's fantasies.
Facts please.)
Thanks a lot, Algis!
--Marc Verhaegen http://groups.yahoo.com/group/AAT
AAT = Homo littoral dispersal after the Homo/Pan split c.5 Ma.
³Aquatic Ape Theory², contrary to what many PAs still think,
is not about apes, nor about having been aquatic, nor about
australopiths. The physiological, anatomical, behavioural &
DNA differences between Homo & Pan show that our Homo
ancestors some time after the Homo/Pan split ~5 Ma lived at
the waterside (coast/lake/river). AAT says our ancestors after
the H/P split got at Java, Dmanisi, Flores... along the
waterside, not over dry & open plains. A lot PAs now agree
with a warm+wet rather than warm+dry past, eg, Wrangham's
delta hypothesis Ph.Tobias
http://allserv.rug.ac.be/~mvaneech/outthere.htm Chr.Stringer
http://www.gnxp.com/MT2/archives/003982.html
I don't think anyone has posted this before but if not, I
thought it might be of some interest to read what Jablonski
wrote about the AAH in her latest book "Skin" (I have included
relevent footnotes with the text where relevant): Jablonski,
Nina G 2006 "Skin - a natural history" University of
California "Explantions for the nearly hairless state of the
human body abound. Without direct fossil evidence that could
document the timing and content of hair loss in humans,
scientists have proposed likely evolutionary scenarios using
comparative anatomical, physiological, and behavioural
information, as well as varying amounts of imagination. The
resulting hypotheses range from the well founded to the wacky,
with hairlessness being attributed to everything from a
heritage of swimming to nit-picking. The best supported
theories involve the importance of sweat in human evolution
(MV: Just-so statement without evidence (perhaps elsewhere
in her book?), but not impossible: overheated sealions
on land sweat on their naked hindlimbs.)
- the topic of this chapter. It might be useful, however, to
take a look at some of the other ideas that have gained
notice over the years. The explanation that has had the
greatest popular appeal is the so-called aquatic ape
hypothesis [1 - Hardy 1960, Morgan 1982]. According to this
idea, the beginning of the human lineage around six to seven
million years ago was marked by an aquatic phase, during
which ancient hominids - a term that describes all the
members of our lineage since we last shared a common
ancestor with chimpanzees - lost most of their body hair,
gained a layer of body fat under the skin (subcutaneously),
and made the transition from being routinely on four legs to
standing and moving on two (that is, became bipedal.) [2 a
definition of the term `hominid']
(MV: Hardy thought the semi-aq.phase happened more than 10
Ma. Elaine has no clear opinion, but AFAICT she used
to believe it happened after the H/P split & before
the apiths. I don't think most people who know
something on AAT still believe that. Jablonski is
ill-informed: why not read the recent literature on
AAT before trying to discuss it?)
As evidence of the aquatic phase, this hypothesis notes that
fossil remains of our distant hominid relatives of our distant
hominid relatives are most often found in the vicinity of
ancient lakes.
(MVI: Not so: AAT evidence is based on *comparative* data.)
It also observes that several of the anatomical
characteristics of modern humans, such as hairless bodies and
subcutaneous fat, are shared by aquatic mammals like dolphins
and whales. In the peak years of its popularity (the
1970s), the aquatic ape theory - which sounded relatively
simple and described out ancestors swimming and carrying
babies in water - seemed an attractive alternative to
the other hypotheses then available for the emergence of
humans, many of which cast our beginnings in a context
of mindless violence and conflict. [3 Notes that in
the 60s and 70s lots of work promoted hunting and that
this inspired works such as Ardrey's `African Genesis'
suggesting that human ancestors were `killer apes'.
Jablonski concludes: "The enormous popularity of the
aquatic ape hypothesis was a reaction against Ardrey's
view of human nature" pp187] The aquatic ape hypothesis
is not, however, supported by the facts.
(MV: Jablonski doesn't address the SC fat & furlessness,
but simply states her belief on the matter.)
Let's look at the situation in which our distant ancestors
found themselves in tropical Africa.
(MVI: ?? "our distant relatives"(when??) in trop.Africa"??
Hasn't Jablonski heard of the retroviral data, which
suggest our ancestors were absent from Africa 4-3 Ma??
This alone makes what follows irrelevant.)
First, a hominid ancestor who spent much of its time in a lake
would have had to enter the water from the shoreline. For
millions of years the shores of African rivers, lakes and
waterholes have not been friendly places. Thick with
crocodiles constantly on the prowl for hapless prey,
shorelines are dangerous places where few animals linger. Our
hominid ancestors, only about one metre (a little over three
feet) tall and lacking claws, big teeth, or weapons, would
have been no match for such formidable predators.
(MVII: Apparently Jablonski still believes she descends
from Lucy??)
Even if they managed to get into the water, ancient hominids
would have faced other big problems. Human skin has few
defences against the waterborne parasites that live in African
lakes and rivers. In the African tropics, one of the greatest
health risks for people who spend time in and around water is
schistosomiasis, a parasitic infestation caused by a tiny worm
that can swiftly penetrate and migrate through the skin. Many
other parasitic diseases are transmitted to humans this way,
leading to untold numbers of deaths and a calamitous loss of
vigour and livelihood for many populations who depend on water
[4 "In addition to diseases that involve waterborne parasites
burrowing into the body, malaria - caused by a parasite that
infects a water-breeding mosquito - leads to even greater
morbidity and mortality throughout the tropics" pp187].
(MVIII: Ever heard of the untold deaths & calamities caused by
lack of water?? Moreover, there is no schistozomiasis
in seawater.)
If hominid ancestors had lived in an aquatic habitat during
their early evolution, the human immune system would reflect a
history of assault by such parasites. It doesn't. Only in the
last ten thousand years or so have we started spending much
time in the water, as we developed agriculture and fishing,
and our immune systems have not yet been sharpened by natural
selection to resist the attack of the nasty organisms that
inhabit these freshwater lakes and rivers.
(MIX: Just-so statements without evidence & relevance &
wrong AFAICS.)
The aquatic ape hypothesis also doesn't adequately explain why
hominids would have evolved hairless skin. Naked skin is
advantageous to fully aquatic mammals like whales and dolphins
because it reduces drag and buoyancy. This is especially
important when the animal is diving or speeding along in the
water, either in search of food or on long-distance migration.
(MX: Just-so statements without evidence. Human hairiness
is as in other tropical medium-sized semi-aquatic
mammals such as babirusas (+-naked, but patches of
hairs). No need to construct far-fetched
"explanations".)
But we have no evidence to suggest that hominids ever engaged
in such activities, although they have occasionally foraged
along shorelines and in shallow water for shellfish and
similar food.
MXI: There is obvious behavioural evidence: that humans as
opposed to chimps can dive for severql minutes & can
swallow food underwater proves our ancestors were
parttime divers once.
[5 - "The idea that hominids may have utilized shellfish and
other shallow-water food resources is currently being pursued
by Alan Shabel, a PhD student in the department of integrative
biology at UCLA" pp187] For animals who spend only part of
their time in water, a naked skin is in fact something of a
liability because it leaves them vulnerable to the problems of
thermoregulation when they are on land. Animals like otters,
fur seals, and sea lions, which weigh less than 1000 kilograms
(or less than a ton) and spend some time on land, are covered
with smooth, dense fur that insulates them against the cold
when they are out of the water. Only the giant semi-aquatic
mammals such as the walruses and hippos, whose large size and
barrel shape make it hard for them to lose heat from the
body's surface, have naked skin.
(MXII: The usual black-white thinking of anti-AAT people. AAT
says human ancestors were medium-sized tropical
semi-aquatics: these animals seem to be about as
haired as humans are.)
In addition, all mammals committed to a fully aquatic or semi
aquatic lifestyle have evolved a streamlined body shape with
small appendages such as fins or flippers to improve their
hydrodynamics and minimize the area of skin in contact with
the water [6 - Wheeler 1985]. If you spend much of your life
in the water surrounded by watchful and hungry predators, you
need to be able to move fast and maneuver deftly in water. The
ancient hominids, in contrast, were fairly short, bipedal
apes, with long gangly arms, who wouldn't have been able to
dog-paddle or defend themselves in the water for five minutes,
let alone spend their days diving and cavorting while swimming
after prey or one another.
(MXIII: If Jablonski had compared chimp to human
hydrodynamics, she hadn't said all that & she had
known that humans are extremely versatile in the
water. Hasn't she heard of the Moken, Ama etc.?)
In short, we didn't lose our body hair because we passed
through an aquatic phase. All the human features that this
hypothesis ascribes to a heritage of swimming and diving can
be explained far more convincingly and parsimoniously as our
adaptations to an active life in a hot and mostly open
environment.
(MXIV: Yes, in short, all antelopes & lions are naked & fat &
run on 2 legs...)
[7 "The advocates of the aquatic ape hypothesis have also
opined that habitual bipedal posture and locomotion originated
while humans were partially aquatic. Many other more
convincing hypotheses that are consistent with available facts
have been developed to account for this key innovation in
human history. George Chaplin and I have advocated a
hypothesis for the origin of bipedalism based on bipedal
social displays as efficacious methods of social control
(Jablonski and Chaplin 1993.)" p187]." Jablonski
(2006:39-41)
(MV: We're no interested in Jablonski's fantasies.
Facts please.)
Thanks a lot, Algis!
--Marc Verhaegen http://groups.yahoo.com/group/AAT
AAT = Homo littoral dispersal after the Homo/Pan split c.5 Ma.
³Aquatic Ape Theory², contrary to what many PAs still think,
is not about apes, nor about having been aquatic, nor about
australopiths. The physiological, anatomical, behavioural &
DNA differences between Homo & Pan show that our Homo
ancestors some time after the Homo/Pan split ~5 Ma lived at
the waterside (coast/lake/river). AAT says our ancestors after
the H/P split got at Java, Dmanisi, Flores... along the
waterside, not over dry & open plains. A lot PAs now agree
with a warm+wet rather than warm+dry past, eg, Wrangham's
delta hypothesis Ph.Tobias
http://allserv.rug.ac.be/~mvaneech/outthere.htm Chr.Stringer
http://www.gnxp.com/MT2/archives/003982.html