Re: Bipedalism in different substrates

From: NA Sides (nas_at_sonic.net)
Date: 08/24/04 

Date: Tue, 24 Aug 2004 15:00:47 GMT

On Mon, 23 Aug 2004 17:51:45 +0100, "Paul Crowley"
<slkwuoiutiuytciuyik@slkjlskjoioue.com> wrote:

>> I've been through this whole discussion already with Algis. Human
>> beings can hike for long distances through such territory.
>
>Nonsense. Of course they can't. Humans
>can only travel through such territory by
>cutting paths with pangas or machetes as
>they go along -- a desperately slow, and
>usually hopelessly uneconomic method.

Human beings demonstrably do live and hike for long distances in a
variety of different type habitats. You seem to think open forest is
"full of branches and other obstacles at a height of two feet" that
must be hacked through with machetes. This is true of some types of
dense tropical rainforest, but it's not my experience with regard to
most areas within either seasonal tropical forest or temperate forest.
And pygmies even lived in deep forest and were able to get around
without machetes. Apparently their smaller size allowed them to do so
more easily. They didn't live in areas where they couldn't move easily
and forage successfully. The same would apply to brushland situations.
I don't know about the African equivalents to chaparral scrub, but
moving through dense chaparral can be extremely difficult.
Proto-hominins wouldn't have occupied such territory.

<snip>

>All the above is either irrelevant or nonsense
>or both. How would 'dual-function' mothers
>carry their infants when travelling? You say
>that they would walk bipedally -- presumably
>carrying the infants in their arms. But that is
>a FAR less effective system than the
>quadrupedal one, where the infant hangs on
>underneath. The mother has her hands free at
>all times and can go through low bush, forage,
>fight, climb, or react instantly to whatever
>might happen. If the mother-infant dyad is
>capable of standard quadrupedal motion, there
>is no reason why they would switch to bipedal
>locomotion --and many reasons why they
>would not.

Infants probably wouldn't have been carried all that much in the
mother's arms. They may have ridden on her shoulders, clinging to her
fur. Almost everyone has carried children on his or her shoulders.
It's easy, and it's a natural way for the child to ride. It's
plausible that proto-hominin infants would have had a grasping reflex
similar to that of chimp infants and that even small infants could
have ridden on one shoulder while holding on the mother's hair or fur.

>You will NEVER see a mother-infant dyad in
>modern apes moving bipedally -- except in
>highly peculiar circumstances and for very
>short distances. That very obvious fact is
>ignored by all standard PA types (and by the
>likes of Algis) since the model (or all hominids
>and hominoids) that fully occupies their
>brains is exclusively male.

Chimps are quadrupeds. Proto-hominins would have been primarily
bipedal. Obviously this transition in locomotory modes would have
entailed ancillary behavioral changes as well.

<snip>

>> The lemurs of Madagascar represent a unique set of related species
>> that apparently have diverged on that island, in a process of adaptive
>> radiation, from a common ancestral stock.
>
>Or, more likely, they represent a set of
>primates which at one time ranged over
>the whole of Africa -- so that Madagascar
>is, to some extent, a living museum. In any
>case, Madagascar is much larger than the
>kinds of islands we were discussing.

Africa is bigger, too. A river was apparently enough a barrier to
separate the ancestors of chimps and bonobos. Even without such
barriers, distance and habitat preference could have played a major
role in limiting gene flow between populations.

>> The honeycreepers of Hawaii
>> are another case exhibiting clear ecological specialization and
>> population segregation according to diet and habitat preference.
>
>I know nothing about these species -- but
>(a) they moved into new unexploited habitats
>with almost zero competition; and (b) even
>if what you say is true, it has no relevance
>to the creation of new niches on continents
>for large, highly mobile hominoids.

I think that proto-hominins probably wouldn't have had that much
competition in their generalist niche. Unlike specialists, generalists
can coexist with a considerable degree of niche overlap as long as
each of the competing species has its own areas of foraging
"strength." Competition might have come from suids and baboons, but
the situation would have been somewhat akin to that in the USA where
raccoons and opossums can coexist in the same areas. Chimp-like apes
might have competed in some areas, but for the most part the
proto-hominins, occupying ecotone type areas, wouldn't have penetrated
very far into the deep-forest habitat preferred by those apes. The
forest-apes' habitat preference would have itself constituted an
isolating mechanism. The apes living in the rain forest "good
neighborhoods" would have kept to their own plush territories while
those populations out there in regions that were changing due to the
long-term climatic shift, might have been forced to adjust their
behavior and develop new skills such as weapon and more extensive tool
use. Apparently their was a shift to a greater dietary meat component.
These kinds of conditions can bring about speciations.

>> The
>> various species and subspecies of Galapagos finches apparently also
>> arose through adaptive radiation within that archipelago. Birds
>> originating on one island obviously have in some cases migrated or
>> been blown by storms between one island and another and this has
>> contributed to the variety of species within some archipelagos. But
>> this kind of geographic isolation is just one factor,
>
>It is more than 'just one factor'. It is the
>overwhelmingly dominating one, that
>makes your use of such species as
>'examples' hopeless, and absurd beyond
>words.

Tell it to the lemurs.

<snip>

>As I keep saying, there is little problem
>about the maintenance; but there is a
>major one about the speciation.

Your saying it doesn't make it true. You seem to think all species
originate through the appearance of genetic or morphological isolating
mechanisms. Yet some fish and some avian and canid species are
interfertile and produce fertile offspring with closely related
species. In our previous discussion in the thread "Thermoregulation
and Predation in Homo," I gave you the example of documented insect
speciation, that of the apple/haw fly, which apparently is fully
interfertile with its parent haw fly species but which doesn't mate
with haw flies because its preferred food is available at a different
time. There is temporal, rather than geographic, isolation.

<snip>

>> Now here you are ready to dismiss, because it hasn't extended for
>> "several centuries, at a minimum," the longest continued and most
>> rigorously done study of evolution in action.
>
>How long would it take for a new mammalian
>species to emerge? How long would it take
>for a new hominoid species to become
>established? How could it happen? Anyone
>who expects some observations of bird
>populations over a few decades to yield
>relevant answers is a fool.

The total population of ground finches on Daphne Major ranged from
something over a thousand to about four hundred, depending on habitat
conditions (which were climate related) from year to year. If the
subspecies were going to merge, they could have done so in one or two
seasons. Yet they retain their separate identities for millennia. This
is partly due to the fact that birds usually have a greater chance of
survival if their phenotype is close to the population mean for one or
the other of the subspecies. Their fitness is higher if they have the
morphological and behavioral "tools" to make their living in one of
the several different ecological niches. In most seasons intermediate
individuals are less fit.

Granted this is a different situation than that on Cocos Island where
members of a single morphologically homogeneous and behaviorally
flexible finch species occupy the various different specialized
"trades." Could proto-hominins, who probably were also behaviorally
flexible ecological generalists, have arisen on an isolated island in
a situation analogous to that of Cocos Island? I don't see why not.
It's a possibility. I've never argued this point with you. In fact, I
believe our initial encounter occurred after I proposed a similar idea
myself (but without your speculations about guarding of waterholes
etc., and without all your stuff about how their descendants were
supposed to occupy seaside valleys and guard their perimeters from
incursions by predators). Dump all those implausible claims that you
want to add on, then island origins is one possibility.

Although there's no evidence for it beyond the existence of
Oreopithecus (which wasn't a hominin), one could assume this is a case
of convergence. On the other hand you have Sahelanthropus who lived,
apparently, in an ecotone type situation in a vegetated perilacustrine
belt between a lake and desert. This vegetated region may have
constituted an isolated "island" surrounded by a "sea" of desert that
would prevent any gene flow with hominoids elsewhere.

>> Sorry about your emotional distress. Let me clarify the statements
>> that disturbed you. I don't deny that some form of geographical
>> isolation is usually required to bring about speciation,
>
>When did you last see that mentioned in
>any discussion of the hominid speciation
>in a learned journal? What is _thought_
>to have been the minimum period? How
>is it _thought_ to have been achieved?
>(I emphasise 'thought' because you know
>as well as me that there is none.)

Way back there a year ago in that thread I keep referring you to, I
gave you the example of the Faeroe Island house mouse, "which
occurred in less than 250 years after man brought the creature to the
island."

http://www.talkorigins.org/faqs/speciation.html

>> Our own ancestors, the Miocene apes that gave rise to hominins, would
>> have been, to some extent at least, behaviorally flexible ecological
>> generalists like the Cocos finches, but they weren't restricted to a
>> single small island.
>
>How do you know?

Actually I don't know. The island would have to have been larger, but
it's possible that hominins did emerge on an island. Right now,
however, my money is on the "island" formed by the vegetated
perilacustrine belt around ancient Lake Chad and surrounded by desert.

>> Due to long-term aridification, the
>> continent-wide rain-forest was thinning in some regions and breaking
>> up into patchy forest, woodland, wooded-grassland and more open
>> grassland mosaics.
>
>Yawn. This mythical 'drying period' serves
>modern PA people in much the same manner
>as the 'fluvian period' (i.e. the Great Biblical
>Flood) served Victorians. It can explain
>everything and can be hypothesised for any
>time that happens to be convenient, and
>extend over any period that is desired. It can
>be theorised to recur as often as the theory-
>maker requires. It's not unlike Marc's (and
>Algis's?) periods of immersion into water --
>a general-purpose 'solution' to all problems.

I've said it before, Paul: you are like unto a certifiable net loon.
You can believe that humans require more salt than horses and cattle
and that 60 grams of salt a day causes no ill effects and you can
easily dismiss all the paleoclimatic and paleoecological data for
Miocene aridification. You're as good at ignoring uncongenial facts as
are Algis and Verhaegen. And yet every once in a while you come up
with an interesting argument. 'Tis a strange phenomenon that I haven't
completely figured out yet.

>> Some apes, those that inhabited areas that retained
>> their ancient rain-forest character, would have retained more of the
>> ancestral characteristics. Our hominin ancestors would have descended
>> from populations in different areas that were undergoing more habitat
>> change.
>
>Ridiculous. There has been plenty of
>'habitat change' in the last 15 Kyr. How
>many species benefited from it all?
>How many new species emerged?
>Can you show any parallels between
>your hypothesised ancient period of
>'habitat change' and THIS very-well-
>understood one? Any parallels at all?
>No matter how remote? No? Presumably
>the idea that you ought to be able to do
>so, has never occurred to you.

http://www.talkorigins.org/faqs/faq-speciation.html

<snip>

NAS

>Paul.

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