Seeds of Hierarchy 201
and the needs imposed by completeness and coherence once we abandon the
myopia of regarding "organized adaptive complexity" (Dawkins, 1986) as the only
focus for evolutionary explanation (with all else arising by extrapolation
therefrom).
WEISMANN'S ARGUMENT ON LAMARCK AND THE ALLMACHT
OF SELECTION
I first learned about August Weismann in high school biology as the man who
"disproved" Lamarckism by cutting off mouse tails for numerous generations and
noting the fully retained tails of all offspring (a good example of terrible teaching
based upon the myth of crucial experiments as the source of all insight in science).
Weismann did perform these experiments (1888, in 1891, pp. 431-461), but they
(by his own admission) did little to combat Lamarckism, which is, as supporters
parried, a theory about the inheritance of functional adaptations, not of sudden and
accidental mutilations.
Weismann's strong anti-Lamarckian argument does not rest upon an
experiment, or an empirical observation at all. The rejection of soft inheritance
arises as a logical deduction from Weismann's most distinctive contribution— his
theory of inheritance and the continuity of germ-plasm (1885, in 1891, pp. 163-
256). If germ-plasm is "immortal" (by passage across generations) and soma-plasm
limited in existence by the death of each multicellular organism; and if germ-plasm
is sequestered early in ontogeny ("locked away" as the guardian of posterity, and
protected from all somatic influence); then Lamarckian inheritance becomes
structurally impossible because acquired somatic adaptations cannot affect the
protected germ plasm. Weismann wrote in his Allmacht paper (1893, p. 608):
"Nature has carefully enclosed the germ-plasm of all germ-cells in a capsule, and it
is only yielded up for the formation of daughter-cells, under most complicated
precautionary conditions."
Once Lamarckian inheritance becomes impossible, Weismann's argument for
the Allmacht of selection proceeds in four logical steps. This fourfold development
will strike most modern scientists as curious and unsatisfactory, for the sequence
not only requires no empirical contribution, but actively denies the possibility of
effective input from this conventional source of scientific affirmation. The
argument breaks no rules of logic, but several of its premises are (to say the least)
not self-evidently true.
- Adaptation is ubiquitous in nature; explaining adaptation therefore becomes
the chief goal of evolutionary theory. As "the greatest riddle that living Nature
presents to us" (1909, p. 18), Weismann identified "the purposiveness of every
living form relative to the conditions of its life, and its marvelously exact
adaptation to these" (loc. cit.).
I believe it can be clearly proved that the wing of a butterfly is a tablet on
which Nature has inscribed everything she has deemed advantageous to the
preservation and welfare of her creatures, and nothing else (1896, p. 5).