[Marxism] human origins

["Charles Brown" <cbrown@xxxxxxxxxxxxxxxxx>]

Paul,


Thanks for your responses.

Charles

Yes, in Mayr's view, speciation is a kind of side-effect of geographic

isolation.
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However, all of this remains controversial, 60 years after Mayr. Mayr's

ideas

were for a long time the orthodoxy, but increasingly there was evidence of

other modes of speciation, in which species arose without geographic

isolation.

Chung-i Wu takes a very strong position against Mayr, and Mayr replies here:

http://www.blackwellpublishing.com/journals/jeb/

http://www.blackwellpublishing.com/specialarticles/jeb342.pdf

http://www.blackwellpublishing.com/specialarticles/jeb336.pdf



>I also wanted to throw out the thought that it is important to note that

>though there are , empirically, fewer new traits arising in the equilibria

>than in the punctuations, there _are_ new traits arising in equilibria, no
?

>The equilibria are "dynamic stabilities". Some of these arise by selection

>and some don't (following Gould's general approach). Some are
spandrel-like,

>some are genetic drift, some are not originated as adaptions, but are

>adapted to being adaptions after they arise by non-adaptive causes ( snails

>gets shells through adaptive processes; there is space under the shell as a

>"spandrel"; then the spandrel is used to store eggs, which activity _is_

>adaptive; so not-adaptive in origin , but adapted to being adaptive post

>hoc; I don't know whether the shell arises in speciation/punctuation or in

>an "equilibrium" phase)

>

>But the main point I am making is that there are new traits that arise in

>the non-speciating phases even if fewer and of non-qualitative type
changes,

>with qualitative change defined as speciating.

>

>Also,no doubt, there is some speciation in "equilibria" and some non

>speciating changes in "punctation" periods, empirically.

>

>

>

Yes, in a way it's paradoxical. We observe the great deal of variation

in natural populations,

and we know that new variation continuously appears through mutation and

recombination,

but when we look at the fossil record, the overwhelming pattern is of

stasis -- species remaining

more or less unchanged for hundreds of thousands of years -- and

similarly, when we look at living

populations, we see not a continuous band of variation, but organisms

grouped discretely as

species. It points to the existence of species as real, cohesive

entities -- they cohere over their

geographic range and over vast expanses of time. There are certainly

exceptions, but that

seems to be general rule, in my opinion.



Paul
^^^^^^



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