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On Tue, 19 Sep 2000 20:42:07 -0700 hemidactylus@my-Deja.com (Scott
Chase) wrote:
>
>--
>
>On Wed, 20 Sep 2000 09:52:32 John Wilkins wrote:
....
>>Likewise, splitting does not mean that selection has occurred, as most
>>speciation occurs through allopatric isolation and subsequent drift.
>>
>Can the concept of drift be applied fruitfully within the sphere of
>cultural evolution?
I would have thought so. There is a general averaging effect of
variation in human populations such that we can treat variation as
effectively random. Curves that are biased are thus the sort of curves
we'd expect to see if there were selective transmission going on. So as
a first approximation, variation in populations is "random". This means
that as populations get smaller, the deviation of a single variant
behaviour will increase in likelihood. Hence, stochastic sampling
effects (ie, drift) will occur in the absence of strong selective
biasing.
This is a point first made by David Rindos, to my knowledge.
>>
>>There is another distinction that must be made firmly in this matter
>if
>>memetics is not to repeat the confusions of taxonomy for the past 250
>>years: the difference between *why* something is a separate lineage,
>and
>>whether we can *tell* that it is. This is the difference known as the
>>history-character split in taxonomy. For example, sibling or cryptic
>>species may be indistinguishable to a human taxonomist, but yet be
>>evolutionarily distinct.
>>
>>So, if we can tell the difference, then there may be one; if we
>cannot,
>>there may still be one.
>>
>On the other hand, aren't there instances where the differences noticed
>by the layperson or even the investigator are greater than the degree
>of evolutionary distinction? Perhaps two populations within a species
>or even individuals within a population are different enough to make
>someone assume they are members of distinct groups. At a present loss
>for good examples, I'd just offer the case of morphological variation
>within domestic dogs versus the relative lack of cladogenetic
>distinction. For the most part the various breeds of dogs can
>interbreed, with some exceptions due to size. Also dogs can interbreed
>with wolves (coyotes too?)
>
>There may be examples of species or populations which are polymorphic
>and having individuals apparently quite distinct from each other, yet
>having only minor genetic differences.
>
>So, perhaps, if we can tell the difference, what we see might not
>correspond to a significant difference as far as evolutionary
>separation goes (ie- the large visible or surface difference is
>negligible or minimal within a certain deeper context).
If you are classifying in terms of *morphology* then in many species
with strong sexual dimorphism you can classify males of one species in a
different taxon to the females, and the females of many species in a
single taxon (eg, in birds or butterflies). Moreover, morphological
classification can result in making obvious subspecific variants
different species despite ecological vicariance and reproductive
community. This is why phenetics failed in the end to provide a
theory-neutral species concept - it was too unstable and
counter-intuitive. The result is that on cladistic grounds one assumes
taxa at the terminal nodes rather than tries to establish them, although
recent phylogenetic species concepts (Mishler and Theriot, Donaghue and
others) define species as minimally monophyletic groups (ie groups that
cannot be cladistically divided further).
The objection to the cladistic conception is that it treats species as
typological unities (ie, ignores subspecific demic variation). The reply
to that is that they only define a species in terms of universal
characters not variable traits, which only members of the species share
(autapomorphies). If a species lacks autapomorphies then it is a
"pseudospecies". Of course, here again is the diagnosis versus cause
confusion. If a species is different to some other species, it must have
some *causal* differences even if we can't know about them (yet), so it
has autapomorphies by definition.
>>
>>In biology, adaptive evolution results in the shifting of the
>>frequencies of alleles in populations.
>>
>So does non-adaptive drift, which can fix alleles or remove alleles
>from a population.
True. Careless of me.
>>
>>In this way, by analogy, carriage
>>making may shift to car making but remain within the same population
>of
>>professionals. But when car making becomes an isolated tradition, then
>>it becomes a distinct cultural species. IOW, the critical thing for
>>speciation is lineage splitting, not adaptation.
>>>
>>>Had Martindale shown that the _reason_ man creates art has evolved
>over
>>>the eons?
>>
>>I would have thought that was irrelevant to the evolution of culture.
>In
>>the same way, it is irrelevant to speciation that the sun continues to
>>shine and be the source of energy input into ecology, or that
>graviation
>>and tectonic plate movement continue to be the background to
>biological
>>evolution. Human "nature" (ie, biology) is the background to cultural
>>evolution.
>>
>>
>And "human nature" *may* channel cultural evolution along biased
>directions, though the depths of the various "canals" may vary and some
>sorts of cultural phenomena may not have a deep correpondence to
>discrete epigenetic biasings. These balls may roll quite freely. Maybe
>an analogy with a magnet in a pinball machine would suffice (off the
>top off my head).
EO Wilson and Lumsden refer to this as "culture on a genetic leash", but
I think that memes can exceed the normal biases of genes so long as the
overall configuration is still viable (ie, things that are biologically
inviable may suceed in a culture of, for instance, medical technology).
Genes do not rigidly determine developmental outcomes (and memes do not
rigidly determine behavioural outcomes neither).
>
>Scott "still hasn't gotten around to hunting down Waddington's
>_Strategy of the Genes_, tsk, tsk" Chase
So many books, so little reading time...
--John Wilkins, Head, Graphic Production The Walter and Eliza Hall Institute of Medical Research Melbourne, Australia <mailto:wilkins@WEHI.EDU.AU> <http://www.users.bigpond.com/thewilkins/darwiniana.html> Homo homini aut deus aut lupus - Erasmus of Rotterdam
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