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Jim McGinn
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 Posted: Fri Aug 22, 2003 9:21 am Post subject: Seasonal Variations are Critical to Savanna Mosaic |
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pdeitik@worldnet.att.net (Philip Deitiker) wrote
[quote]. . . most people in modern paleoanthropology would argue
that if anything the transition was from an arboreal ape
to a mosaic ape,
[/quote]
Yes, or as Potts describes in his paper, Environmental
Hypotheses of Hominin Evolution, (YEARBOOK OF PHYSICAL
ANTHROPOLOGY 41:93-136 [1998]), "Essentially all textbooks
prior to 1996 explained the origin of these traits in
terms of adaptation to relatively open savanna, defined by
the presence of grass, discontinuous trees, overall
aridity, and seasonal rainfall (e.g., Klein, 1989; Wolpoff,
1980)."
Now they>ve shifted to a mosaic habitat. Mosaic habitat,
like savanna habitat, is drier and more open than the LCA>s
ancestral rainforest habitat. But it is much wetter than a
savanna habitat, has a shorter dry season, and the
vegetation therein consists of much larger patches of
woodland that grade into areas occupied by shrubs and
grasses. This also has been described as a monsoon forest
habitat.
The thing that is most conspicuously absent in discussions
by conventional theorists about either savanna habitat or
mosaic habitat is the implications associated with seasonal
dryness, or what I describe as seasonal dessication--a
severe season of dryness and scarcity of resources.
Nevertheless evidence of this phenomena has been available
for quite some time now. As Potts describes in the paper
quoted above, "The influence of short-term habitat
variation on savanna organisms, including early humans, is
discussed by Foley (1987). Foley notes that although early
hominins occupied wooded-to-open savanna, the most
significant aspect of this type of habitat is its marked
seasonality," and "Seasonality, moreover, was a consistent
part of the contexts in which hominin evolution occurred.
Seasonal variations are critical to maintaining the savanna
mosaic of Africa . . ."
Jim |
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Spiznet
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| Posted: Fri Aug 22, 2003 11:34 pm Post subject: Re: Seasonal Variations are Critical to Savanna Mosaic |
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jimmcginn@yahoo.com (Jim McGinn) wrote in message news:<
[quote]pdeitik@worldnet.att.net (Philip Deitiker) wrote
. . . most people in modern paleoanthropology would argue
that if anything the transition was from an arboreal ape
to a mosaic ape,
Yes, or as Potts describes in his paper, Environmental
Hypotheses of Hominin Evolution, (YEARBOOK OF PHYSICAL
ANTHROPOLOGY 41:93-136 [1998]), "Essentially all textbooks
prior to 1996 explained the origin of these traits in
terms of adaptation to relatively open savanna, defined by
the presence of grass, discontinuous trees, overall
aridity, and seasonal rainfall (e.g., Klein, 1989; Wolpoff,
1980)."
Now they>ve shifted to a mosaic habitat. Mosaic habitat,
like savanna habitat, is drier and more open than the LCA>s
ancestral rainforest habitat. But it is much wetter than a
savanna habitat, has a shorter dry season, and the
vegetation therein consists of much larger patches of
woodland that grade into areas occupied by shrubs and
grasses. This also has been described as a monsoon forest
habitat.
The thing that is most conspicuously absent in discussions
by conventional theorists about either savanna habitat or
mosaic habitat is the implications associated with seasonal
dryness, or what I describe as seasonal dessication--a
severe season of dryness and scarcity of resources.
[/quote]
Can we once and for all try to clearly plot the tropical biome
gradient
(i>m a big fan of using common terminology):
My first attempt:
A. tropical rainforest- wet/hot- large numbers of species/ no seasons
note: isn>t this bonobo habitat?
B. monsoon forest- wet/hot- large deciduous trees, less species/ short
dry season
note: this appears to be the Gombe environment (August/Sept dry
season)
C. woodland- wet/hot - still over 60% tree cover: longer dry season
E. treed savanna <20% tree cover
F. open savanna: few if any trees
We all see pictures of african savanna (wooded and open) stretching as
far as the eye can see to the horizon. I think it should be obvious
that the same is true for miles and miles of woodland, and miles and
miles monsoon forest (Gombe chimps have a 50 mile territory, they
never change biomes).
A territorial animal would not necessarily ever have the
opportunity/need to move from one of these biomes to another. Crossing
into another, unfamiliar biome is dangerous, it is not obvious that
this would happen. The rationale/proof of this occurring should be on
the proposers of the theories involving territorial hominids in
multiple biomes.
-Mark |
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Jim McGinn
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| Posted: Sat Aug 23, 2003 2:32 am Post subject: Re: Seasonal Variations are Critical to Savanna Mosaic |
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mark@spiznet.com (Spiznet) wrote
Mark, I snipped the above but I>m not ignoring it.
I *do* recognize the distinctions you make and I
think they are additive to the discussion. (So I
don>t want you to think I>m ignoring your input
here.) But for the time being I want to deal with
the issues raised in this last paragraph below.
[quote]A territorial animal would not necessarily ever
have the opportunity/need to move from one of these
biomes to another. Crossing into another, unfamiliar
biome is dangerous, it is not obvious that this
would happen. The rationale/proof of this occurring
should be on the proposers of the theories involving
territorial hominids in multiple biomes.
[/quote]
I>m not proposing that there was any, "opportunity/need
to move from one of these biomes to another." I>m
proposing that the climate changed, thus originating a
new (and unprecedented) biome along with a new (and
unprecedented) fauna (the Ethiopian Fauna). Like all
the other newly emerged (or soon to be newly emerged)
species of this Ethiopian fauna the shift in
climate/environment/habitat/ecosystem was thrust upon
them. Monsoon forests, in a sense, just appeared on the
scene.
Maybe it would help your understanding if you were more
cognizant of the fact that climatic change is, from the
perspective of geologic time, an *extremely* sudden
phenomena. Check out this link for more:
http://makeashorterlink.com/?A30032EA5
Regards,
Jim |
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Jim McGinn
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| Posted: Sun Aug 24, 2003 10:23 am Post subject: Re: Seasonal Variations are Critical to Savanna Mosaic |
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mark@spiznet.com (Spiznet) wrote in message news:<cb2e44af.0308231721.53ea4978@posting.google.com>...
[quote]jimmcginn@yahoo.com (Jim McGinn) wrote in message
mark@spiznet.com (Spiznet) wrote
snip
I guess I just have this view of your bipedapes peeking out of the
forest onto a treeless savannah, scurrying out to get some food in the
dry season (rooting for savanna tubers) and then scampering back into
the 60-foot tall citylike monsoon forest (just in time to escape the
sabertooth leopards IF they are well-fed enough (from have diligently
scared off all giraffes and duikers from their territorial plots.))
You are turning my hypothesis into a cartoon. (And why
in the world would they ever "scurry out" of the forest?)
Jim-
Here>s the quote as I remembered:
quote
From: Jim McGinn (jimmcginn@yahoo.com)
Subject: Group Selection This is the only article in this thread
View: Original FormatNewsgroups: sci.anthropology.paleo
Date: 2003-05-20 09:19:29 PST
At the onset of the dry season these poor A>piths failed
to prevent inmigrating large grazing and browsing mammals
from entering their lacustrine community site.
Consequently these large mammals depleted the food
resources at the community site. With the continuation of
the dry season, these situational factors caused these
A>piths to have to spend more time on the ground, away from
the relative safety of trees, foraging for food, competing
with and sometimes fighting with other neighboring bands
within their community.
end quote
Your scenario has apith>s scurrying out onto "savanna", or whatever it was.
[/quote]
Okay, I see what you>re saying. I>m just saying that when they were
in a period of poverty they had to put themselves at risk in order to
make a living. |
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