(Fwd) pol-cien : RV: Fw: NY Times Article: What Only the E

Gorojovsky Gorojovsky at arnet.com.ar
Sat Sep 8 09:38:51 MDT 2001

Dear friends and comrades,

It is long since I had the time to get involved in philosophical debate on the 
marxism list, particularly debates on the relation between dialectics and 
biology/ecology. However these things are still of my interest, and maybe 
something that I got from a friend may spark some discussion here which I will 
shamelessly profit from while lurking.

------- Forwarded message follows -------
From:           	"Ovidio Núñez" <onunez at impsat1.com.ar>
To:             	<pol-cien at ccc.uba.ar>
Subject:        	pol-cien : RV:     Fw: NY Times Article: What Only the Embryo Knows
Date sent:      	Fri, 7 Sep 2001 16:40:38 -0300

>What Only the Embryo Knows
>Thomas Henry Huxley designated three men as the finest intellects of
>19th century natural history: his dear friend Charles Darwin; his
>most worthy opponent Georges Cuvier; and Karl Ernst von Baer, who
>discovered the mammalian egg cell in 1827 and wrote the founding
>treatise of modern embryology in 1828. Of these three, posterity
>has largely forgotten von Baer, who suffered a severe mental
>breakdown in the 1830's, but then recovered and moved to Russia
>(not uncommon for a German-speaking Estonian national), where he
>enjoyed a distinguished second university career, largely in
>anthropology and lasting well into the 1870's.
>In 1828, von Baer enunciated the central principle of
>embryological development, later known as "von Baer's law" and now
>regarded as the correct interpretation of Ernst Haeckel's famous
>(and erroneous) claim that "ontogeny recapitulates phylogeny," or
>that the successive forms of embryology repeat the adult stages of
>a lineage's evolution, with the gill slits of an early human
>embryo representing an ancestral fish and the later tail an
>ancestral reptile, for example.
>By contrast, von Baer proposed a principle of progressive
>specification and differentiation: One can first tell that an
>embryo will become a vertebrate and not some sort of invertebrate,
>then a mammal and not another kind of vertebrate, then a carnivore
>and not a rodent or ruminant, then a dog and not a cat, and finally
>Buster the Beagle and not another breed.
>Von Baer summarized his principle in an epigram: "The development
>of the organism is the history of growing individuality in every
>respect." In other words, successive narrowing and determination of
>parts as complexity coagulates. No turning back after the blueprint
>becomes finalized from a broad mass of initial potential. For an
>appropriate literary metaphor, think of Lot's wife or Omar
>Khayyam's lines: "The moving finger writes; and having writ, moves
>Von Baer's law epitomizes the central issue, unfortunately rarely
>discussed and little understood, in our current debate over
>embryonic stem cells. The very structure of material reality
>imposes a principle of trade- offs in both nature and human
>affairs: One always gives something in order to gain. In
>particular, we usually pay for complexity by surrendering
>flexibility, and von Baer's law encapsulates the embryological
>version of this structural generality.
>In genetic terms that von Baer could not know, each cell of our
>body contains a full set of genes. But embryological
>differentiation into a specialized adult role--as a brain cell,
>liver cell or heart cell, for example--leads to a "freezing" or
>"turning off" of most of this potential apparatus, leaving active
>only those few components regulating the specialized adult form and
>function. The cells of the earliest, undifferentiated embryo
>(little more than a clump of identical units in appearance)
>maintain full capacity to develop in any direction; that is, all
>their genes remain potentially active and recruitable.
>The irony of the trade-off, explicitly recognized by von Baer
>nearly 200 years ago, inheres in the evolved surrender of this
>embryonic flexibility as development proceeds toward our maximal
>complexity. Cut a planarian flatworm in two, and the tail end
>regenerates a head while the head end regrows a tail. For in this
>simplest of bilaterally symmetrical invertebrates, with minimal
>differentiation of internal organs, all cells retain the embryonic
>potential to build any part of the body. This capacity for
>regeneration--the ability of cells at a wound site to
>"dedifferentiate," or return to a state of early embryonic
>flexibility--becomes progressively lost in animals that evolve
>greater adult complexity by von Baer's universal process of
>"locking in," with increasing specialization of parts. We have, in
>short, traded regenerative capacity for the undeniable evolutionary
>advantages of maximal complexity.
>For this reason, we must use embryonic stem cells if we wish to
>pursue a large body of enormously important, highly promising and
>deeply humane research in how specific tissues and organs grow from
>the broad potential of early cells derived from the fertilized
>ovum. Speaking personally, I do not grant the status of a human
>life to a clump of cells in a dish, produced by fertilization in
>vitro and explicitly destined for discard by the free decision of
>the man and woman who contributed the components. But I also have
>no desire to offend the sensibilities of those who disagree. Thus,
>if I could derive cells of similar flexibility in a different way,
>I would gladly do so, even at considerable extra time and expense.
>Unfortunately, von Baer's law, and nature's broader structural
>rules of trade-off between complexity and flexibility, give us no
>alternative to embryonic stem cells for now, and the research is
>important and far more than merely theoretically lifesaving.
>(Moreover, if we hope to find ways to dedifferentiate adult cells--
>and therefore learn to recover the requisite flexibility from cells
>derived without offense to anyone--then we must experiment with
>embryonic cells in order to understand and control the mechanism of
>their broad potentiality).
>As an old man, from his Russian periphery, von Baer made the
>famous and rueful remark that all new and truly important ideas
>must pass through three stages: first dismissed as nonsense, then
>rejected as against religion, and finally acknowledged as true,
>with the proviso from initial opponents that they knew it all
>along. Genetic technology has brought us through the first stage.
>Our current debate on stem cells resides in von Baer's second
>stage, with the religious views of a clear, if powerful, minority
>setting an unfortunate opposition to one of the most vital avenues
>of beneficial research in our time. The third stage will arrive,
>and we will marvel that we ever rejected a pathway toward knowledge
>so imbued with life-saving capacity. May this third stage come
>soon, as our understanding differentiates further into a true and
>humane grasp of the virtues of flexibility.
>Stephen Jay Gould is a professor of zoology at Harvard

------- End of forwarded message -------

Néstor Miguel Gorojovsky
gorojovsky at arnet.com.ar
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