Claudius Denk
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 Posted: Thu Jul 31, 2008 10:26 pm Post subject: An ecology based approach to understanding human origins |
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An ecology based approach to understanding human origins
New species don>t just spring up out of the blue. They are part and
parcel to new biomes (ecosystems). Likewise new biomes don>t just
spring up out of the blue, they are the result of changes in
environments/climatic conditions.
Here>s the way speciation works. Ecosystems experience a change in
climate. The change in climate causes a period of extreme stress
whereupon a whole set of niches disappear and a whole new set of
niches appear. New species either find their way to a new niche (and
this almost always involves a whole host of new adaptations and new
behaviors being achieved simultaneously rather than just one or two
adaptations) or they go extinct.
The gradualistic, just-so-story approach to understanding the origins
of new species, an approach to which all paleoanthropologist
subscribe, is an archaic approach that was developed in the nineteenth
century when ecological ignorance was the rule. We know better now.
Species evolve in a punctuated fashion. (If you don>t know what this
means then I suggest doing some research on a concept called
punctuated equilibrium.) And, like I said above, they evolve a whole
host of strategies and traits at once to fit the lifestyle
requirements of the new niche. Consequently hominid evolution could
only have produced the dramatic shift to bipedalism if it coincided
with a complete shift to a new lifestyle that involved the
requirements of a new niche in a new ecosystem.
What is this new ecosystem and what is this new niche?
In the light of this understanding it becomes obvious what steps a
scientist should take with respect to assessing what took place 8 to
10 mya in Africa with the emergence of this new ecosystem. Obviously
we>d want to be explicit about what factors are in this new habitat
that were not in the old habitat. These new and different factors
should introduce new and different problems which they, our earliest
hominid ancestors, must overcome if they are to survive and
reproduce. Only after we have an explicit picture of the ecological
problems/opportunities in the new niche should be venture to begin
hypothesizing what shift in behavior best explains the evidence.
I>m going to employ a very simple analytical method to attempt the
ends I describe in the above paragraph. I>m going to subtract the
factors in the ancestral habitat from the factors in the new habitat.
(See the "Formula" below.) The idea here is to focus on the factors
in the new environment that did not exist in the ancestral
environment. And we want to be as explicit as possible so that we get
an idea of what would have been the implications of these new factors,
and implications of implications.
The data we will employ for this analysis is the following:
Source: http://www.sfu.ca/archaeology/dept/fac_bio/skinner/arch131/lecture5.htm
THE ANCESTRAL HABITAT: The Tropical Forest biome: tends to be hot and
humid with a 70 meter high rain forest canopy with high precipitation
up to 250 cm rain annually. In this canopy habitat there are few
predators with a great variety of food in the form of fruit, insects.
Tends to be ecologically complex with many species of life but few
individuals of anyone species; treeshrews, prosimians, pongids, NW
monkeys, most OW monkeys, mandrill baboon (but on forest floor),
orangutans and gorillas and gibbons. Group Size tends to be quite
small usually less than 20.
THE NEW HABITAT: Woodland Savannah biome: tropical arid with seasonal
rainfall and woodland along stream margins where primates tend to live
with some venturing out into savannah; some lemurs, chimps, baboons,
Macaques; grass is primary food source with nutrients locked up in
tubers and bulbs. In this habitat there are lots of grazers, browsers
and predators; the latter hunting in social packs (lions, hyenas,
dogs); consequently the primates tend to show group defence strategies
with well defined social roles which ensure protection of young; group
sizes tend to be larger with 20 to 40 (or even up to 100) in some
baboon troops
Formula: THE NEW HABITAT minus THE ANCESTRAL HABITAT equals WHAT IS
DISTINCTIVE ABOUT THE NEW HABITAT
* CLIMATE *
THE NEW HABITAT: tropical arid with seasonal rainfall
Minus
THE ANCESTRAL HABITAT: tends to be hot and humid with high
precipitation up to 250 cm rain annually.
equals:
What I see here is the appearance of a monsoon climate. Much of the
year, maybe even most of the year, it would have been very similar to
the climate in the Tropical Forest biome (hot, humid, daily rain and
relatively little fluctuation in these conditions). However, for
large stretchs of months every year, upwards of six months, the rain
stops. This produces dessication (dryness) and the implications of
dryness: a tendency for temperatures to fluctuate between hot during
the day and cold during the night.
* ENVIRONMENT *
THE NEW HABITAT: woodland along stream margins. Treeless, savanna
habitat in the surrounding areas. Primates tend to live with in
woodland along stream margins where, some venturing out into treeless
savannah; some lemurs, chimps, baboons, Macaques.
Minus
THE ANCESTRAL HABITAT: Forest canopy 70 meters high. (Note: little
sunshine makes it to the ground.) This rainforest habitat would have
been extensive, continuous, and relatively uninterrupted by treeless
habitat.
equals:
Treed habitat would have been more patchy and isolated at locations
close to sources of perrenial water, lakes, rivers, streams, areas
with high ground water. (Note: the size of these remaining patches of
treed habitat would have, firstly, varied greatly from patch to patch
and, secondly, these patches might have been larger than we tend to
assume. It was considerably wetter back then that it is now in
Eastern Africa.)
* FOOD *
THE NEW HABITAT: Grass is primary food source with nutrients locked up
in tubers and bulbs.
Minus
THE ANCESTRAL HABITAT: forest canopy (extensive, continuous and
uninterrupted by treeless habitat. A great variety of food in the
form of fruit, insects.
equals:
I think there would have continued to be fruit and insects in these
remaining patches of treed habitat. However, with the disappearance
of the canopy there would have been more sunlight hitting the ground
within these patches. This would have produced more foodstuff on the
ground, such as tubers, bulbs, and even grasses for our primate
ancestors.
* PREDATION *
THE NEW HABITAT: Lots of predators. They have a tendency to hunt
social packs (lions, hyenas, dogs).
Minus
THE ANCESTRAL HABITAT: Few predators
equals:
Obviously our ancestors now found themselves in a much more hostile
habitat. One that is populated by predators bigger than they
themselves.
* INTERSPECIES COMPETITION *
THE NEW HABITAT: In this habitat there are lots of grazers, browsers.
We also find some lemurs, baboons, Macaques; primates tend to show
group defence strategies with well defined social roles which ensure
protection of young; group sizes tend to be larger with 20 to 40 (or
even up to 100) in some baboon troops.
Minus
THE ANCESTRAL HABITAT: Tends to be ecologically complex with many
species of life but few individuals of anyone species; treeshrews,
prosimians, pongids, NW monkeys, most OW monkeys, mandrill baboon (but
on forest floor), orangutans and gorillas and gibbons. Group Size
tends to be quite small usually less than 20;
equals:
This new habitat has a lot more competition from grazers and browsers,
which did not exist in the ancestral habitat. Also we see a relative
explosion of social stratetgies/adaptations in all species in this new
habitat. The competitive nature of this new habitat tends to be
relatively more group vs. group.
Comprehensive Analysis:
The next step is to put all of this together and see if we can paint a
larger picture of how these implications would have effected our
chimpanzeelike ancestors.
The following factors were precipitated out of the post quoted above:
(1) The Emergence of Monsoon Climate: Warmer and wetter than is
the climate currently at this region of Africa but with a
distinct and severe dry season.
(2) The Emergence of Grassland Habitat: The dissipation of the
rainforest and emergence of grasslands and resulting patchiness of the
remaining forest habitat, which persisted at locations where water
was perrenially available (rivers, streams, lakes, areas with high
ground water).
(3) The Emergence of Mosaic of Habitats: The resulting spatial mixture
of grassland and forest habitat produces an environment that is less
predictable from location to location or from one point in time to
another than had been the rainforest habitat.
(4) The Emergence of the Ethiopian Fauna: relatively large,
intelligent, and fast moving (quadrupedal) browsing and grazing
mammals; and large, intelligent, fast moving predatory mammals that
prey upon these large browsing and grazing mammals.
(5) The Emergence Ground based foodstuffs: With the disappearance of
the forest canopy came a shift of foodstuff toward the ground, tubers,
bulbs, and even grasses, in and in the vicinity of the remaining
patches of forested habitat.
(6) The Emergence of Social Strategies: primates, grazers, browsers,
predators and mammals in general.
When we put all of these factors together we get a sense of a very
different habitat than the rainforest habitat. Most notably it is the
inclusion of a severe dry season that puts a sense of foreboding in
the environment. The onset of a period of dryness may have been
especially unforgiving to the primates in this biome, including our
chimpanzeelike ancestors, in that being adapted to arboreality they
were less able to travel from one isolated forested location to
another. Consequently, if the foodstuff in at these locations--
regardless of whether it is up in trees or on the ground--becomes
depleted then this does not bode well for their survival through the
depths of the dry season.
Complicating the situational factors in the above paragraph would have
been the seasonal migration of browser, grazers, and the predators
that followed them. With the onset of seasonal dessication we would
expect these animals to generally migrate from the more dessicate
grassland and into the treed patches. This supposition, in conjuction
with the fact that foodstuff, tubers, bulbs, and grasses, were now
more prevalent on the ground than it had been in the rainforest
habitat, indicates there would have been dramatic competition between
the primates at these treed patches and the inmigrating browsers and
grazers during these periods of seasonal dessication. And this
competition may have been especially dramatic for our chimpanzee-like
ancestors in that they were generally more preadapted to ground
conditions than were other primates and, consequently, were more
dependent on the availability of ground based and low-branch
foodstuffs than would have been the smaller primates that could more
readily find food and avoid predators in the higher branches.
The picture that is starting to emerge in the above paragraphs is one
whereby our chimpanzee-like ancestor>s fate was more closely linked
with the relative level of scarcity/abundance at their particular
treed patch. The inclusion of predators in this scenario, most
notably large and intelligent predators that employ social hunting
strategies, provides us, IMO, even more of a reason to hypothesize
this linkage. Firstly, the strategy of primates to avoid predation
involves trees as refuge. Not only does this supposition serve as a
rationale for the conjecture that they were isolated at these treed
patches, as indicated above, but it provides us an understanding of
why the selective factors of this scenario would have been so closely
linked with the relative level of scarcity/abundance at their
particular treed patch. When the resources at a particular treed
patch (community site) became depleted the primates therein would have
little choice but to spend more time foraging and, consequently, more
time away from the trees thus becoming more vulnerable to predators.
Predators are always looking for vulnerabilities. It seems likely
they would have noticed that the primates at one treed patch were
easier pickings and, consequently, they would have concentrated their
efforts at these treed patches. Consequently, the primates at treed
patches (community sites) that are more depleted would be more likely
to be decimated by predation. Those at treed patches (community
sites) that were relatively more abundant--regardless of causal
factors underlying this relative abundance--would tend to be ignored
by predators.
Given these situational factors, what adaptations/behaviors would we
expect to emerge for our chimpanzee-like ancestor? Would this or
would this not indicate a shift to communal territorialism and its
associated mob oriented, stick wielding, rock throwing aggression as
indicated in my Ecological Gatekeeper Hypothesis?
Ecological Gatekeeper Hypothesis
I started thinking about migration in the context of the environmental
assumptions of my hypothesis: seasonal dessication, spatial polarity
of resources (patches of forest that persist near sources of perrenial
water, lakes, ponds, streams, rivers, areas of high ground water).
(For a more comprehensive description of the environmental assumptions
of this hypothesis see a post I put on this newsgroup recently
entitled: Questions Regarding Selective . . . ) Then I asked myself
what kind of migrational patterns would I expect given these
assumptions. The answer was obvious. During periods [of] increasing
dessication and resulting scarcity there would be a tendency for all
of the species in this environment to begin to migrate toward and into
these treed havens, our ancestor>s "community sites." And with the
onset of the rainy season they would migrate back out again. Then I
started thinking about how all of this would appear from the
perspective of our earliest, recently rainforest dwelling, prehominid
ancestors. Every year their patches of remaining forest, their
"community sites," got overrun with other species. Many of these
species would have competed directly with them for food and thus would
have caused the depletion of resources at a time when these resources
were increasingly scarce, the dry season. Other herbivores may not
have directly competed with them, but all of them brought predators
with them: lions, tigers, hyenas, dogs, etc. The negative implications
are obvious. When these inmigrating species had depleted the resources
at these community sites they would simply migrate over to other less
depleted areas (other community sites). But our tree dwelling
ancestors, being less mobile, had fewer options. They were now left
vulnerable to starvation and/or predation. Lacking the ability to run
fast, they didn>t have much choice but to stay put, wait out the
predators, and hope the rains returned. Surely their population would
often have been decimated as a result. Among a number of other
adaptations, which I will get to shortly, I predict that territorial
based peskiness will have begun to be selected among our chimpanzee-
like ancestor. This would have been a direct result of the above
described factors associated with migration. The reason I believe this
scenario predicts the relatively rapid adaptation of territorial based
peskiness behaviors among these still tree dwelling apes is because
apes that have such predisposition will tend to harass any other
animals that it percieves to be trespassing on its territory. This
will act as a deterent to these inmigrating species who--all other
things being equal--will follow the path of least resistance to their
migratory goals. If one patch of forest is associated with pesky
apes-- regardless of the fact that these pesky apes may be mostly
harmless to them--and another patch of forest is relatively free of
pesky apes then the inmigrating individuals would follow the path of
least resistance to the patch that is relatively free of pesky apes.
More specifically, how and why do I contend that these above mentioned
implications predict the rapid adaptation of territorial peskiness
amongst our earliest prehominid ancestors? I think the answer to this
question is fairly obvious. The members of community sites that
reduced inmigration, even if only marginally (let>s say, for example,
they reduced it by only 10%), would increase their own community>s
probability of surviving through and, at one and the same time, reduce
the probability of survival of those who reside at other, neighboring,
community sites who, lacking territorial based peskiness behaviors,
would now have to deal with more inmigration and, of course, more of
the negative implications thereof: more depletion of resources, more
predators, and more resulting decimation. This comprises a classic
group selectionist scenario: behavior that increases one>s own
communities survival decreases the survival of other communities. This
is not to say that the members of these respective communities would
have had the ability to recognize that they were competing against
other communities on a community vs. community basis. In fact it seems
unlikely--especially in the earliest years of hominid evolution--that
they would have even had the ability to recognize that they were
members of communities. Regardless of wether they were capable of
realizing it, apes that had whatever behavior and/or morphology that
would enable or cause them to dissuade other species from migrating
into their community site would have a tremendous selective advantage
over those that lacked such. The more their behavior dissuaded
inmigration the greater the selective advantage to their own community
and the greater the selective disadvantage to neighboring communities.
It is, of course, normal to be hesitant about asserting group
selective factors such as those that I have asserted here. But in the
context of this scenario this hesitancy is, I contend, completely
unwarranted. ?This contention is based on the group selective
implications of the two factors mentions above, 1) the patchiness of
the remaining forested habitat which divided our ancestors up into
"communities" between which gene flow (interbreeding) was greatly
reduced, and 2) the fact that the grim reaper,seasonal dessication,
focussed on whole communities whose territorial resources at their
community sites had become, for whatever reason, deplete. So, the
selective realities of our ancestors shifted from those of the
chimpanzee lifestyle--focussed only on being successful individuals
and members of successful breeding groups (bands, extended family
units)--to those of the A>pith lifestyle--focussed on being successful
individuals and members of successful breeding groups AND on being
members of communities that successfully effect the preservation of
resources at their community sites in the face of the onslaught of
multi-species inmigration to their community sites. It is also
important to point out that there is a positive feedback aspect
associated with inmigration. Specifically this has to do with the
herding or grouping instincts of the inmigrating species: if one or a
few members of an inmigrating species is able to infiltrate a
community site then the probability is higher that more members of the
same species, and/or members of ecologically related species, will
follow. When this aspect is considered in conjunction with the fact
that this scenario clearly indicates the community as the group entity
that is being selected, it is apparent, I contend, that the better a
community is at closing the gate of its ecosystem--sealing its
borders--the more likely the members of the community will survive the
grim reaper of this habitat, seasonal dessication (the dry season). In
the context of these peculiar selective factors, we can start to ask
ourselves what other adaptations, in addition to territorial
peskiness, would we expect to evolve? This can be more explicitly
delineated in the context of what is mentioned in the above paragraph:
what additional behaviors or morphologies would cause/enable these
chimpanzee-like territorially pesky apes to be better able and/or more
inclined to "close the gate" and effectively seal the borders of their
community sites? I propose the following: Cooperation (in the context
of mob oriented harassing behaviors): The tendency to confront and
attempt to prevent inmigrating species collectively rather than just
individually. This would involve collecting into larger groups from
neighboring and other closely situated "properties" (see below) within
a community site and confronting inmigrating species: throwing rocks,
sticks, and generally making a big racket. As I envision it, this
would involve the same kind of emotion based behaviors that we
currently associate with a mob mentality, including sports fanaticism.
Communicativeness: The ability to communicate the relative level of
threat associated with potential inmigrating species so that mobs can
form at vulnerable infiltration points quickly and efficiently. This
also involves such behaviors as cheering, booing, and other behaviors
that would tend to draw attention of other members of a community to
such events. Consciousness: Awareness of the meaning of emotional
outbursts that they might see or hear in the distance so that one
might be excited into being additive to whatever mob oriented
activities are taking place in one>s vicinity. Awareness of the
property of others due to the implications of the, below mentioned,
selective benefits of property oriented communal territorialism.
Property Oriented Communal Territorialism (rather than just communally
oriented territorialism): Property oriented communal territorialism
involves a community being comprised of subgroups each of which has
its associated property in the context of the larger community site.
The reason, I contend, that we would predict property oriented
territorialism is because this would, firstly, cause them--by way of
their percieved incentive--to spread out to the different infiltration
points of the community site so that they will be in position to
better effect the collective sealing of the community sites borders.
Secondly, property oriented territorialism will give them the
percieved incentive to defend "their" property. (Which, as indicated
above, could also include calling out to one>s neighboring property
holders for assitance to effect a mob and/or responding to one>s
neighbors call for assistance.) The particular group that I envision
as the entity that maintains ownership of the different intracommunal
"properties" of a community site would be based upon the band or
extended family unit, similar in size and composition to that of the
bands that extant chimpanzees tend to form. Gamesmanship: I think it>s
possible that the behavior that is indicated in this hypothesis was to
they themselves little more than a game. ?Those who were passionate
about the game achieved the survival of themselves and their whole
community (by way of driving off inmigrating species). (In other
words, we>re descended from sports enthusiasts.) Also, this scenario
gives us a sense of how and why we evolved to be so controlling of
other species. It even suggests how we began to develop our weapon
oriented hunting skills and inclination, not to mention our weapon
oriented and mob oriented approach to intraspecies conflicts (war). (I
can foresee there being "Hunting Hypothesis," variants of this
hypothesis.) Additionally, this scenario is the perfect setup for the
scenario in my larger hypothesis (which I now realize is much more
dependent upon the pre-existence of a community), which better
explains the evolution of other hominid traits, such as our political,
ideological nature, our attentiveness to dance, art, storytelling, and
other artistic, our economic predisposition for trade, our complex and
logic oriented languages, and our pursuit of knowledge and truth.
However, the beginning of the dynamics in my greater hypothesis (the
Intraspecies Capitalism stuff which is very difficult to explain), may
have to be pushed forward in time all the way up to the transition to
homo. But this may be a good thing in that it better coorelates to the
growth of brain capacity in the homo lineage (which, as you know, is
greatly lacking in the A>pith lineage). |
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