Richard Goldschmidt (1878 Germany – 1958 USA) , geneticist, professor at the University of Munich and later University of California, Berkeley. Member of the National Academy of Science and in 1953 Elected President of the Ninth International Congress of Genetics. “Brilliant but unorthodox geneticist” according to Richard Milner (1990) (1).
In Goldschmidt’s view the gradual accumulation of small mutations was sufficient for microevolution, but insufficient for macroevolution. For speciation (macroevolution), a different mechanism is required. In The Material Basis of Evolution (1940), Goldschmidt proposed systemic mutation – “a change of intrachromosomal pattern” – and developmental macromutations, popularly known as the “Hopeful Monster” hypothesis.
“The change from species to species is not a change involving more and more additional atomistic changes, but a complete change of the primary pattern or reaction system into a new one, which afterwards may again produce intraspecific variation by micromutation.” [The Material Basis of Evolution, pp.205/206.] (2)
In 1945 Goldschmidt published an interesting paper “Mimetic Polymorphism, a Controversial Chapter of Darwinism” (3). Darwinian explanation of mimicry in butterflies realm had already been criticised by Punnet (author of the Punnet’s square) and Heikertinger (see my entry about Heikertinger). Goldschmidt agreed with Punnett that selection of small mutants was unable to explain the origin of polymorphic mimicry.
The photo shows, on the bottom three rows, unpalatable butterfly model species in the family Danaidae (left) and palatable mimetic forms of female Papilio dardanus (right), an African swallowtail species. At top left is the Papilio dardanus male; at top right is a non-mimetic, male-like female of the same species. The polymorphic, female-limited Batesian mimicry was first described by Roland Trimen (1869). (4)
I will avoid quoting lengthy passages where scientific arguments against Ford’s hypothesis of modifiers take place as well as passages where intercrossing and other experiments are described to support Goldschmidt’s arguments.. Those crucial parts are of course indispensable, but are too “technical” for the purpose of first information. Anyway I recommend everyone to read the paper. See the first page (3).
Important point is that R.Goldschmidt rejected natural selection as the source of evolution of mimicry, but admitted that it could maintain already established resemblances. Richard Goldschmidt saw following difficulties in neodarwinian explanation of the origin of polymorphic mimicry (3):
“The first diffculty of the Darwinian theory, which as well known to Darwin himself, is the problem of the first step. If this does not produce a sufficient similarity with the model to deceive predators it has no selective value; but how can a small variation achieve such a minimum resemblance?
Darwin and Wallace overcame this difficulty by assuming that originally there was only a small difference between mimic and model
and that afterwards the present type was simultaneously built up in both. A powerful argument (already realized by Darwin) against this view can
be derived from the so-called mimicry rings. As already mentioned, it happens “that a given species in a given locality may serve as a model for several other species belonging to unrelated groups.” In such a ring palatable and presumably unpalatable forms may be united. If now the Darwinian explanation of a slow accumulation of variations toward the warning pattern in both model and mimic, originally not very different, is applied, it follows that the ancestors of the members-e.g., one ring from Ceylon specified by Punnett as a Danaine Dads plexippus, a Nymphaline Hypolimnas misippus (here only the female is involved), a Satyrine, Elymnias undularis and a fritillary, Argynnis hyperbius-have been more or less alike. Such an idea would hardly appeal to anybody. This is still less the case if the sexual differences are also taken into account. Thus Punnett does not see any solution of such cases except by the saltation theory. He is also opposed to an intermediate view, that by a single mutation first a rough-hewn resemblance is brought about that is later perfected by selection of (small variations). In his opinion this requires that selection continues operating, because otherwise the likeness would gradually deteriorate by regression.
This is not considered to be the case.”
“There is another important point which is passed over in discussions. There exist cases in which both sexes are mimics. This shows that here the male also profits from mimetic advantage. In the majority of cases, however, the males are non-mimetic. Did they not need protection which is only needed by the egg-laying female? Why, then, are some males mimetic? Or does the mechanism of sex-controlled inheritance prevent the modifiers from acting in the male? If so, why have not male sex-controlled modifiers been selected if the male also needs protection? In some instances there are found non-mimetic and mimetic females. One should expect the non-mimetic females to dissappear. In P. memnon there are two types of non-mimetic females and one mimetic. Polymorphism is thus present in the same species with and
without mimicry, but the modifiers of two non-mimetic forms are not counter selected against. At least we should expect the non-mimetic
females to have that remote resemblance. It would not be dificault to invent some kind of explanation for these occurrences, as has been done
by statistical deliberations. But it is difficult to see why the simple explanation which does not re quire new hypotheses from case to case is rejected. If the second non-mimetic female is a mutant, why not the third mimetic one? But let us not continue with such general argumentation but analyze the factual basis as well as the logic of the opposing theories.”
“ In my opinion, the origin of the mimetic pattern requires a similar genetic situation. The ancestral form must have had a type of pattern determination parallel to that present in seasonal dimorphic forms. This means a developmental system which can be switched into a very different
one by one simple lever:. in this case a mutation. The mutant must be such as to affect the primary patterning processes; it can change the pattern
thoroughly because the proper developmental system is already available. Small wonder therefore that mimetism is about as rare as extreme
seasonal dimorphism, and that it is confined to a few nearly related members of a few systematic groups (see above). I cannot see how such
conclusions could be avoided in the face of the reported facts.”
“After reporting and discussing the significant facts, we came to the conclusion that Punnett’s interpretation of mimetic polymorphism by
mutation (saltation) agrees better with the facts than Fisher’s neo-Darwinian theory. We have tried to prove this by scrutinizing in every detail
both the logic and the factual basis of the controversial theories discussed by the former authors, as well as by studying many other aspects not
discussed before. Among the facts pertaining to the situation under scrutiny we have given equal weight to those taken from the fields of genetics
and evolution and to those of an embryological character. Such an all-round analysis has shown neither any need for the application of the more
complicated explanation of the neo-Darwinists, nor any reason for abandoning the simpler solution, which fits all the known facts.”
So we can see that Richard Goldschmidt mentioned also problems that neodarwinian school has still failed to address plausibly:
1) why in the case of Papilio Dardanus are all males non-mimetic
2) why non-mimetic female morphs are sometimes more abundant than mimetic morphs?
As far as I can judge Goldschmidt’s concept of saltation in the case has not been rejected. Richard Dawkins still insists on small steps, but experts in the field speak something else ( F.Nijhout 2003) (5):
Batesian mimicry is believed to originate by means of an initial mutation that has a sufficiently big effect on the phenotype to give a passable resemblance to a protected model, followed by the accumulation and selection of mutations in modifier genes that progressively refine the mimicry.
Compare it with interpretation of Richard Goldschmidt’s hypothesis (1):
He suggested that a relatively small change might have a large effect on the phenotype, especially through “controlling” genes which mediate the expression of the organism’s blueprint.
Edward Goldsmith: Richard Benedict Goldschmidt
Richard Goldschmidt: “Mimetic Polymorphism, a Controversial Chapter of Darwinism”
The Quarterly Review of Biology, Vol. 20, No. 2. (Jun., 1945), pp. 147-164.
The Quarterly Review of Biology, Vol. 20, No. 3. (Sep., 1945), pp. 205-230.
H. Frederik Nijhout:
Polymorphic mimicry in Papilio dardanus: mosaic dominance,
big effects, and origins H. Frederik Nijhout
EVOLUTION & DEVELOPMENT 5:6, 579–592 (2003)