Re: Bipedalism in different substrates

From: Jason Eshleman (jae_at_vidi.ucdavis.edu)
Date: 07/04/04 

Date: Sun, 4 Jul 2004 01:59:19 +0000 (UTC)

deowll <deowll@bellsouth.net> wrote:
>
>"Jason Eshleman" <jae@vidi.ucdavis.edu> wrote in message
>news:cc75t3$arl$1@woodrow.ucdavis.edu...
>> deowll <deowll@bellsouth.net> wrote:
>> >
>> >"Jason Eshleman" <jae@ucdavis.edu> wrote in message
>> >news:b7af43cb.0407022320.433a5f26@posting.google.com...
>> >> "deowll" <deowll@bellsouth.net> wrote in message
>> >news:<VliFc.640$bj2.438@bignews5.bellsouth.net>...
>> >> > "Jason Eshleman" <jae@vici.ucdavis.edu> wrote in message
>> >> > news:cc45su$8k5$1@woodrow.ucdavis.edu...
>> >> > > Bob Keeter <rkeeter@earthlink.net> wrote:
>> >> > > [snip]
>> >> > >
>> >> > > >No, the "arguement" against wading is that there is no real
>evidence
>> >for
>> >> > > >wading. No meaningful examples, no logic, no reason, no
>scientific
>> >> > > >"purpose" that requires hypothesizing that concept. But. . . .
>that
>> >> > > >arguement
>> >> > > >is the old standard arguement and it is totally destroyed (in some
>> >> > > >people's view) by the words "might have", "could have", and after
>> >> > > >a completely childish, and egotistically polarized exercise in
>> >rhetoric,
>> >> > > >"must have". "Must have" is the real betrayer, since those words
>> >reveal
>> >> > > >that the debater agrees that there is no evidence, but his ideas
>are
>> >> > without
>> >> > > >possible reproach, EVEN THOUGH there is no evidence. Ever use
>> >> > > >the words "MUST HAVE", Algis?
>> >> > >
>> >> > > Actually Bob, it's more complex. The argument is both that there
>> >needs to
>> >> > > be real evidence for wading *and* evidence that wading, if it
>happened
>> >> > > to any significant degree, could reasonably produce the
>morphological
>> >> > > changes we see. Neither has been adequately addressed or
>> >substantiated
>> >> > > save pure assertion backed by paranoid charges of conspiracies
>against
>> >the
>> >> > > water and all who talk about it.
>> >> > >
>> >> > > The adaptive response is still the one I have the biggest problem
>> >with.
>> >> > > That the morphology we see would result from wading *isn't* clear.
>If
>> >> > > apes can wade (a point that gets hammered out) and can and do so
>> >> > > bipedally, what changes in morphology are necessary and why?
>*THIS*
>> >> > > hasn't been adequately addressed beyond the "must haves" and "may
>> >haves."
>> >> > > [Note: other models fail to address this too. That other models
>fail
>> >to
>> >> > > address something is not a reason to follow suit.]
>> >> > >
>> >> > > The cry that this is an adaptation to avoid drowning misses several
>> >> > > points. For starters, the *best* way, actually the only one that
>> >works
>> >> > > 100% of the time (to borrow a phrase) is to stay out of the water.
>> >Don't
>> >> > > get in the water and you can't drown. As a result, to say that
>> >bipedality
>> >> > > is a response to avoid drowning means that you need to make wading
>> >> > > somewhat compulory. This is possible (e.g. a "may have"), but
>isn't
>> >> > > clear and brings us back to the initial point that you made that we
>> >need
>> >> > > to better substantiate that wading happened in the first place.
>> >> > >
>> >> > > Beyond this, it's not at all clear that the changes necessary for
>> >> > > *obligate* bipedalism [note: in an evolutionary sense, obligate
>isn't
>> >the
>> >> > > same thing as "have to stand up in particular environment because
>they
>> >are
>> >> > > "obliged to or they will drown"] result from wading. Apes have all
>> >the
>> >> > > morphological adaptations to avoid drowning by standing erect in
>> >"waist
>> >> > > deep" water just as they have the necessary tools to stand up on
>dry
>> >> > > ground. [It still seems like the resident wading proponent has
>some
>> >> > > vision of a critically stupid ape who keeps wandering into the
>water
>> >until
>> >> > > his head is submerged and then dies.]
>> >> > >
>> >> > > And so, if apes can easily stand up when the water gets too big
>> >*without
>> >> > > any additional adaptations,* what *specifically* about our
>morphology
>> >that
>> >> > > we share with the earliest clearly bipedal hominids gives a
>survival
>> >value
>> >> > > over the facultative bipedality practiced by apes? There are
>clear,
>> >> > > significantly measurable differences in our ability to move
>bipedally
>> >and
>> >> > > the ability of an ape to move bipedally over terrestrial terrains.
>It
>> >is
>> >> > > not clear that these differences would be as great in an aquatic
>> >> > > environment. *This* has to be substantiated and it hasn't been.
>If
>> >it
>> >> > > cannot be substantiated, it's totally irrelevant if apes wade
>> >bipedally
>> >> > > 100% or .0001% of the time.
>> >> > >
>> >> > Anything that causes a major portion of a population of apes to spend
>> >more
>> >> > time doing something is going to have some selection in favor of what
>> >ever
>> >> > the heck it is they are doing unless of course they don't need to.
>> >> >
>> >> > I will grant that apes are only moderately well adapted to walking
>erect
>> >and
>> >> > that if they spent more time doing it selection would favor those
>better
>> >> > adapted no matter what the reason.
>> >>
>> >> Sorry, but you're propagating one of the classic misunderstandings of
>> >> evolutionary biology. It matters not how much time you engage in an
>> >> activity if it doesn't affect survival or reproductive success. Apes
>> >> can walk around all day or not at all. In neither case will it
>> >> produce adaptive change *unless* their success at such activities
>> >> influences their reproductive success. This is a very important point
>> >> that seems to be glazed over more often than it should. The reasons
>> >> are important.
>> >
>> >Your view is reasonable if a being has unlimited time and resources. Then
>it
>> >can spend a great deal of time doing something without it affecting its
>> >reproductive success. I assume that time and resources are limited. No
>> >creature can spend a great deal of time doing anything without it
>affecting
>> >its reproductive success for good or ill.
>>
>> That's conjecture. A creature can do something all the time or not at all
>> and it won't result in evolutionary change in the lineage unless something
>> about that behavior results in change in a heritable trait. If there is
>> no heritable variation, there will be no evolution.
>>
>Which species with a population of over 300 members have no heritable
>variation and for what trait?

Is there heritable variation in automotive choices in humans?

>> If humans spend more and more time watching TV, those few who get up off
>> the couch to get it on every once in a while may well have a higher
>> reproductive success, but this doesn't mean that there will be an adaptive
>> response favoring less TV watching. That requires that there be some
>> genetic regulatory mechanism for TV watching. If the trait is entirely
>> cultural, no increase or decrease in the activity can influence
>> adaptation.
>>
>So you are stating that the choice to set and watch TV or to get it on are
>completely cultural and with no role played by biological factors?

I am not assuming a priori that there is a genetic heritable factor. If
one can demonstrate it, fine, but the null hypothesis is that it is not
under genetic regulation.

>Energy levels, attention span, sex drive, etc. are not effected by genetics
>at all?

That's not what I said. However, it has not been demostrated that there
is strong heritability of these traits. It is entirely possible that the
variation in this sort of time allocation is cultural.

>> >If a species changes its behavior so that it spends a great deal of time
>> >doing something it isn't great at it will affect the fuel budget and
>consume
>> >time it might have used doing other things and that affects everything
>else.
>>
>> Important point: selection doesn't work on the species. It works on the
>> individual. If the difference in behavior between individuals isn't
>> heritable, then it's not relevent to natural selection.

>It works on the species or they couldn't go extinct could they? Genes
>contained in units of the species get passed on or not. They become more
>common or less within the species or perhapes a now species forms.

What you are saying here is very murky. Selection works on the
individual. Individuals are the unit of selection. Populations are the
unit of evolution. Species are not selected. Members of the species are.

>Please name a behavior that you think is not in some manner effected by a
>genetic component.

I think that many behaviors aren't regulated by variable, heritable
genetic predispositions. While (virtually) all humans have the capacity
to speak, the particular language they speak doesn't have a genetic
component. I speak english and not french entirely because of where I
grew up. There is no genetic component related to that variation.
Preferences for particular types of music are largely, if not entirely
cultural and have no appreciable genetic component. Appreciation for many
asthetics are cultural, not genetic, yet these cultural variations can
greatly influence the behaviors of the individuals. The use of power
tools is not at all genetic versus using hand tools. It is a result of
cultural variation.

>> >You do not have to observe them keeling over dead after taking a hike for
>> >selection to occur within a population. In fact what happens to a given
>> >individual most likely doesn't make a lot of difference in a healthy
>> >population. It is what happens to a lot of individuals that matters and
>why
>> >one creature succeeds and another fails is always going to involve a lot
>of
>> >subtle factors that may not always be obvious even to a trained observer.
>> >
>> >That is my view. Turn about is fair play.
>> >
>> >Please explain to me how a being can spend a great deal of time doing
>> >something without it effecting reproductive success?
>>
>> It's not about whether or not the reproductive success is affected so much
>> as it's about whether or not the reproductive differentials are regulated
>> by some heritable trait. Differential reproductive success is only PART
>> of the evolutionary equation. Heritable differences related to the
>> differential success is completely required for adaptation to occur, else
>> any change will be a result of chance genetic drift.
>>
>
>If a species is still viable it has a great many heritable variables that
>can be selected for that will in some manner modify anything it does.

Huh? I have no idea what you're getting at here or what your definition
of "viable species" is. A species if viable if it's alive. It's not
viable if it's extinct. Some traits in a population are likely to be
heritable, others are not. Evolutionary change can only result from a
change in the allele frequencies related to those traits that vary. Not
all traits do vary within a species. Some do, some don't.

>That was why the old dude came up with the idea of descent with variation.
>Your hypothesis of descent without variation is rather new to me. I don't
>know how to make such a system work in practice but the computer industry
>would love to have a system that didn't mess up occasionally while storing
>or coping data so if you can think of a method go for it.

You're entirely missing it.

1) Evolution and natural selection are not synonyms. Evolution refers to
the change in a population over time. Natural selection is one (but not
the only) mechanism of this change. 2) For selection to operate, there
must be variation and this variation must be heritable. For some traits,
these conditions are met. For others, it is not. We as a species do not
possess the variation to start flying without the assistance of machines
even if every last one of us started to jump off of rooftops all day long.

You seem to be suggesting a hyper-adaptationist stance that suggests that
selection will always produce change for any characteristic. This is
simply not true and demonstrateably so with some rather simple population
genetics.

>You are right in an ideal reality but your theory requires some sort of
>"perfect" reality to be correct in practice.

I have no idea what the hell you're trying to say, but you're
understanding of evolutionary biology seems lacking.

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