This work is the product of a class assignment plus many additional hours of research and composition. There's not much information floating around on Hyatt- so I thought I'd upload the paper. It's very brief, incomplete, a bit dated, and represents an unfinished project. Web search engines collect the amateur efforts (mine) along with the professional. I have no scientific or philosophical axe to grind here. This essay owes much to the works of Peter Bowler, and does not offer radically original perspectives. But I hope I have simplified and condensed Hyatt's unusual evolutionary ideas in a manner which makes them more approachable. Read it with a critical eye.
The elaboration of several non-Darwinian evolutionary theories during the period 1865-1940 (e.g., neo-Lamarckism and orthogenesis) has evoked little reflection from historians of biology until the past decade. Peter Bowler, the preeminent historian of these ideas, has attributed the deficiency in part to the myopia of the emergent "Darwin industry" which, not surprisingly, has focused most attention on the genesis of those elements of Darwin's thought now considered fundamental tenets of the modern synthesis. As he has noted in the preface to "The Non-Darwinian Revolution", at least one of his critics has asked the question, "Every one in the field [professional historians] knows that much late nineteenth-century evolutionism was non-Darwinian, so why make such a fuss about it?" (Bowler, 1988, ix). Bowler has claimed that the vigorous growth of late 19th century non-Darwinian evolutionism- defined broadly by a shared opposition to the existence or primacy of the role of natural selection in evolution- constitutes strong evidence against the orthodox perception that Darwin commenced a radical conceptual revolution in 19th century biology. While Darwin undoubtedly catalyzed the rapid and near-total conversion of the scientific community to evolutionism, that facet of the theory considered integral to Darwin's success by students of the modern synthesis, natural selection, appears to have been largely irrelevant.
Bowler and others have argued that Darwin's immediate success rested heavily on extra-scientific factors, namely the skillful dissemination and presentation of his theory through a close circle of scientific colleagues- Huxley, Gray, Hooker, etc.. Although the theory of natural selection was a topic of debate from the outset, it would be little exaggeration to claim that most of the newly converted were content with buttressing the case of evolutionism against special creation without adopting a clear stance for or against natural selection. T. H. Huxley was little concerned with the causes of evolution in his defenses of evolution; Asa Gray resorted to theistic speculation to bolster his belief in progressive evolution. At the birth of Darwinism, evidence supporting natural selection as the primary mechanism of evolution did not appear convincing to all and Lamarckian and orthogenetic theories would become viable (and in some countries and scientific disciplines, preferred) alternatives to natural selection for the next half-century. With few exceptions, support for Lamarckism eroded only after its fundamental incompatibility with Mendelian inheritance became evident during the first decade of the 20th century.
Clearly, any discussion of non-Darwinian evolutionism must come to terms with the question of what ideas Darwinism comprises as a biological theory. Because Darwin himself eventually conceded a greater role for Lamarckian adaptive mechanisms in later editions of the "Origin", a broad interpretation might seem warranted. But such an argument is irrelevant to the present context (see Hull, 1985, for a discussion of Darwinism as a historical entity.). The definition Bowler adopts is not his own, but apparently that of the Modern Synthesis: Darwinism implies that evolution is divergent in pattern and proceeds by adaptation through the mechanism of natural selection. Regardless of whether one accepts this working definition as a description or a caricature of the view held by the majority of modern Darwinists, one does not need to probe deeply into the scientific literature to discover a tradition which has adopted this definition. A cursory examination of recent introductory textbooks (admittedly, favorite straw men) reveals a common pattern in the analysis of the comparative reception of Darwinism. Most texts examine Lamarckism and orthogenesis from a simplified, didactic perspective in the attempt to elucidate basic tenets of modern theory. Historical context is usually lacking, as one might expect from introductory treatments. In one noteworthy example a chapter is devoted to the development of evolutionary thought, and a large segment of the period under consideration here is eulogized as the "Romantic Period (1860-1903)." The authors portray it as follows:
"The Romantic Period was characterized by extreme enthusiasm for Darwinism, together with an uncritical acceptance of whatever data were claimed to support Darwinism. Negative evidence was given little weight (in contrast to Darwin's own practice) and absurd extremes of interpretation in order to make observed facts fit Darwinian theory were quite common. Leaders of this group in England included T.H. Huxley, Herbert Spencer, and George Romanes; in the United States David Starr Jordan and Asa Gray were the leaders...The German evolutionists of the Romantic Period were more strictly Darwinian than their English and American colleagues in the sense that they were generally more thorough and careful collectors of data." (Dodson and Dodson, 1985, p. lll, 113)
One cannot fail to appreciate the methodological difficulties inherent in any attempt of an "objective" historiography of the scientific reception of Darwinism. The extent of the historical supremacy of selectionism has evidently varied among scientific disciplines, yet no focused analysis of these trends has been attempted. Furthermore, the historical judgments have often been derived from a restricted analysis of a few "dominant" personalities of the period rather than from a broader examination of the reception of a particular theory within a scientific discipline. Bowler's ground-breaking study (1983) was a major effort aimed at surmounting some of these obstacles. Several studies now exist which address these movements, but the historiography has been approached from different perspectives and varies in the depth of analysis (e.g., Pfeifer, 1965, 1974; Gould, 1977; Bowler, 1977, 1979, 1983, 1988; Rainger, 1981, 1985, 1986; Reif, 1983, 1986; Desmond, 1982; Richardson and Kane, 1988).
I hope to examine more closely the development and fate of late 19th and early 20th century orthogenesis in American invertebrate paleontology. I intend to devote primary attention to the evolutionary concepts put forward by the American invertebrate paleontologist, Alpheus Hyatt, originator of idea of racial senescence, and to the subsequent adoption or modification of this theory in the works of the paleontologists James P. Smith, Charles Beecher, Amadeus Grabau, and Robert T. Jackson (see bibliography for a partial list of their published works in this area). While Hyatt is generally grouped with Cope and Packard as a co-founder of the neo-Lamarckian movement in America, his "old age" theory is more aptly described as a precursor to later orthogenetic ideas (e.g., evolutionary momentum and over development, racial disease) owing to its decidedly non-adaptive and linear evolutionary predictions. No recent study has examined Hyatt's work closely, although Donovan (1973), Gould (1977), Bowler (1983), and Richardson and Kane (1988) have presented general and largely overlapping summaries of his theoretical contributions. A large body of valuable paleontological commentary exists but has received little attention from historians. Because I have not had access to any of Hyatt's unpublished manuscripts or correspondence (The Alpheus Hyatt Autograph Collection, Maryland Historical Society [Lurie, 1960]), this preliminary study, like all preceding, will rely on his published works alone. Rainger (1981) provides a brief but useful survey of the works of Hyatt, Smith, Beecher, Grabau, Jackson, and other American Paleontologists of this period. Raymond (1941) remains the best source for the (invertebrate) paleontological literature on racial senility and orthogenesis.
Perhaps a more fruitful (yet formidable) avenue of inquiry would be an investigation into the basis of the apparent "convergence" toward similar orthogenetic theories in the largely independent spheres of German and American paleontology during the first decades of the 20th century. Reif (1983, 1986) has provided a first look at the development of distinctly non-Darwinian evolutionary theories (e.g., typostrophism) in German paleontology but has not commented on the possibility of a historical or derivative relationship between Hyatt's racial senility theory and the similar concept of "typolysis" developed in the works of Beurlen and Schindewolf. The similarities beg for an explicit investigation into just how isolated these two communities were during this period. There undoubtedly existed similar philosophical commitments to the developmental approach to evolutionary causes. Perhaps more telling is the fact that several American invertebrate paleontologists received their doctorates at German universities (e.g., James P. Smith, W. B. Clark, and John Mason Clarke were students at Gottingen). To what degree this training influenced their subsequent intellectual commitments to orthogenetic theories remains to be studied.
Not long after Darwin published "The Origin of Species" in 1859, an abundant store of embryological and natural history studies was reinterpreted in light of evolutionary theory. The idea that the recapitulation of progressive tendencies occurred during organismal development had already been seeded by the Naturphilosophen in the first half of the century  (Gould, 1977), and this conception was quickly given evolutionary expression through Haeckel's biogenetic law (1866), and the law of "acceleration of growth," formulated independently by the American paleontologists E D. Cope (1866)  and Alpheus Hyatt (1866). Evolution proceeded by the regular, terminal addition of stages to individual growth, each of which was pushed back (accelerated) in development until becoming a fixed, heritable stage. Variation was perceived as ordered and directed, and evolution generally proceeded in a linear manner.
As originally conceived by Cope and Hyatt, there was no adaptive purpose to these additions, and the sequence of ontogeny and phylogeny had a purely "formal" goal (Bowler, 1983). Cope would later abandon this deterministic explanation in favor of an adaptive, Lamarckian mechanism of addition, and he would become the most forceful voice of American neo-Lamarckism. Hyatt would follow Cope's lead, but only to a point. Throughout his career, Hyatt stressed the importance of studying the entire ontogeny of the individual- not confining investigations to the embryo, but extending them to the periods of the adult and old age. Within this framework, Hyatt emphasized senescence as a distinct, maladaptive phase in the individual's ontogeny and consequently, in a group's phylogenetic history. The present essay will be restricted to a general discussion of this peculiar "old age theory" (Packard, 1902) and will emphasize Hyatt's original (1866), and as I will argue, persistent, deterministic and orthogenetic formulation.
Alpheus Hyatt (1838- 1902) was educated at Harvard and studied under Louis Agassiz, a mentor whose influence was evidently crucial in shaping Hyatt's views on the parallelisms between individual development and the history of the fossil record (Gould, 1977; Bowler, 1983; Richardson and Kane, 1988). In one of his later papers, Hyatt gave direct credit to Agassiz for several of these principal ideas:
"...I must have got directly from him [Agassiz], subsequently to 1858, the principles of this branch of research, and ...I soon began to find that the correlation of the epembryonic [post-embryonic] stages and their use in studying the natural affinities of animals were practically an infinite field for work and discovery." (1897, pg. 216)
Agassiz was influenced by the Naturphilosoph, Oken, while a student in Germany, and remained committed to a view of nature as progressive, orderly, and goal-directed. Under this influence, he developed his theory of the three-fold parallelism evident among developing embryos, living forms, and the hierarchy of the fossil record. Whereas Agassiz remained a staunch anti- transformationalist until his death, Hyatt quickly  adopted Darwin's theory of descent, but with it he retained Agassiz' essential theory:
"Although within a year after the beginning of my life as a student under Louis Agassiz I had become an evolutionist, the theoretical position altered in no essential way the conception I had first received from him, nor the use we both made of them in classifying and arranging forms." (1897, pg. 216)
Hyatt's lifelong concern with investigating the entire ontogeny of the individual was reflected in the organisms he chose to study -- the fossil nautiloids and ammonoids of the molluscan order Tetrabranchiata. Hyatt was appointed honorary curator of the Museum of Comparative Zoology in 1865 and until his death was in charge of the fossil cephalopod collection (Brooks, 1909). The record of life preserved in these fossils was such that Hyatt would proudly proclaim:
"...[They] have structural peculiarities which make them the most favorable subjects now known for the specific study of the problems and laws of evolution of forms in time....The shell in these is so built that it preserves in the fossils...the embryo, the young shell, and all the stages to full grown. Then passing into old age, it shows in the senile period, a series of retrogressive transformations, often reversing its adult condition and aspect." (1884, pg. 122)
Hyatt's clearest and most idealistic expression of evolutionary senescence appeared in his first major paper (1866) in which he discussed the phylogenetic progress and decline of the nautiloid and ammonoid tetrabranchiates. Through Hyatt's perspective, these two suborders represented morphologically "polar" and "opposing" lineages through time. I have constructed a diagrammatic clade histogram (Figure I) from Hyatt's estimates of species diversity in an attempt to illustrate his reconstruction of the progression and decline of both suborders through the Paleozoic and Mesozoic eras.
Fig. 1: Clade histogram model of Hyatt's view of tetrabranchiate evolution.
Representing the first pole in time were the "aberrant" nautiloids, straight (uncoiled) and smooth shelled, which appeared first and in greatest diversity during the Silurian. They subsequently declined before reaching extinction in the Jurassic. The "normal" nautiloids, discoidal (coiled) and having external ornamentation on the shell, expanded from few species in the Silurian to their greatest number in the Carboniferous. They declined in the Triassic leaving only the two extant species of Nautilus. Meanwhile, during the Jurassic, the "normal" ammonoids, discoidal in form and highly ornamented, marked the order's period of greatest expansion ("zenith") but subsequently declined rapidly in the Cretaceous. Finally, the second and last pole was represented by the seemingly youthful-appearing "aberrant" ammonoids, straight and smooth-shelled. These expressed greatest diversity in the Cretaceous but the same period also marked the near total demise of the entire order. Hyatt compared these "four great epochs of expansion" with the "four periods of the individual":
"The first epoch of the order is especially the era of the rounded and in the majority of species, unornamented shells with simple septa; the second is the era of ornamentation, and the septa are steadily complicating; in the third the complication of the septa, the ornamentation, and the number of species, about twice that of any other epoch, all combine to make it the zenith of development in the order; the fourth is distinguished from all the preceding as the era of retrogression in form and partially in septa. The four periods of the individual are similarly arranged and have comparable characteristics... the first is smooth and rounded; the second tuberculated and the septa more complicated; the third was the only one in which the septa, form and ornamentation simultaneously attained the climax of individual development; the fourth, when amounting to anything more important than the loss of a few ornaments, was marked by retrogression of the whorl to a more tubular aspect, and by the partial degradation of the septa." (1866, pg. 200)
Fig. 2: Specimens illustrating Hyatt's stages of evolution (graphic by rlg)
In the first paragraph Hyatt is not referring to the progression and decline of a lineage within the order (as Richardson and Kane, 1988 mistakenly indicate), but to the life of the order itself, and this clearly reflects an idealistic interpretation of the fossil record. One can trace the life of the order, from youth to old age, as a single progressive and retrogressive continuum (Figure I, line A--> D), but this is evidently a correlation only because the four lineages appear to be independent at their periods of greatest expansion- there exist no real connections among them at these times as there does exist among the ontogenetic stages of the individual. Hyatt would admit this himself later in the paper, precisely because the phylogenetic history of the order was not that of a single "chain of being":
"....we have in the same formation, and side by side, embryonic, adult, and old age forms [species], and among the Nautiloids the old age forms actually precede in the Silurian the great display of the fully ornamented adult forms of the Carboniferous. I can only claim, therefore, that there is a correspondence between the manifestations of decline in the individual and in the degradational features of the group...."(1866, pg. 207)
However, judging from Hyatt's later works, it appears that this analogy was simply too "wonderfully harmonious and precise" (1866, pg. 195) to be discarded as a mental construct void of meaning.
Hyatt noted a second important pattern in the ontogeny of individuals within each of the four lineages from which he would deduce the law of acceleration of growth. In the youthful aberrant nautiloids, the adult form of the shell and septa was identical to that of the young individual. In the normal ammonoids, however, a more complex pattern emerged. In the early representatives of this lineage, the open-coiled young resembled the aberrant nautiloids, but the adults developed a close-coiled form. Complication of the septa and ornamentation would likewise distinguish the adult portion of the shell from the young. Hyatt noted that within this lineage,
"...each successive species adds something to the increment of complication and there are no visible traces of a failing vitality... either in the individual or the group to which it belongs." (1866, pg. 201)
However, in the later representatives of the normal ammonoids, at the height of the order's development, the first evidences of senility appeared in the adult individuals:
"...in the same manner that the individual begins to show signs of decay during the adult period do the ammonoids begin to produce individuals and species with well-marked senile characteristics. Doubtless...the parts were effected by the decline of the vital powers of the individuals among the earlier series..".(pg. 201)
And finally, in the aberrant ammonoids, the young and adult form of the shell and septa would appear again "precisely the same." Hyatt sought a mechanism to explain this pattern and proposed recapitulation by the law of acceleration of growth. This law of "concentration", as he termed it in this paper (pg. 203) could account not only for the progressive phase of increasing complication of form, but also for the retrogressive phase of decline of the Tetrabranchiata:
"...when the same law acts on some series whose individuals alter the skull in old age...[the] old age characteristics in due course of time or structure become embryonic, and finally affect the entire growth and aspect of higher [descendent] members of the series." (pg. 203)
The morphologically polar forms resemble one another (straight and smooth shell) because acceleration during the declining phase of the group is so intense as to "pass entirely over the stages of growth corresponding to the adult periods of preceding or lower species" (pg. 203). The paradox becomes evident: the death of the order is signaled by the appearance of youthful-looking (but senile) forms. In a later paper (1889), Hyatt would codify this intense acceleration phase as the "law of mechanical replacement." In essence, Hyatt argued that the adult characters of the paracme phylogenetic stage (i.e., at the zenith of the group) were actually lost as the gerontic characters were accelerated to the earlier stages of development during the declining phase of the group. Throughout his subsequent papers, Hyatt would defend the explanatory value of acceleration of growth with regard to the appearance of juvenile-like features in old age species. He forcefully opposed (Hyatt, 1896) the alternative mechanism, abbreviated development ("retardation") espoused by both Cope and Haeckel, especially when applied to the cephalopods; Retardation suggested that Hyatt's old age characters were truly juvenile- somatic development was simply abbreviated.
While the law of acceleration suggested a basic mechanism of concentration and fixation of heritable characters, it did not account for how characters were terminally added to ontogeny ; moreover, how could the addition of senile characteristics to the ontogeny of the later ammonoids occur? As previous studies (Bowler, 1983; Gould, 1977), have noted, Hyatt's early papers reveal no evidence of his later, Lamarckian views. Hyatt emphasized the pattern of evolution over process. His references to increases and decreases in "vital powers" (see above) only allude to some internally driven, predetermined unfolding of progressive and retrogressive evolution (As Richardson and Kane  have clarified, the trends towards increasing complexity were not necessarily considered adaptive at this stage of his work, and his frequent use of the adjective "progressive" should be interpreted in this light.). As late as 1871, in a brief note opposing natural selection (Hyatt, 1871), it appears that Hyatt had not yet absorbed Cope's Lamarckian perspective even though he mentions Cope's work in this note). In it he concurs with St. George Mivart's comment that "the view here advocated regards the whole organic world as arising and going forward in one harmonious development similar to that which displays itself in the growth of each individual" (pg. 148). In reference to his 1866 paper Hyatt continued, "This was the view advocated by the speaker [Hyatt] some four years previously..." Hyatt's subsequent adoption of a Lamarckian concept of character acquisition (see Hyatt, 1882, 1884, 1889 and especially 1893) has been well documented in the secondary literature (Gould, 1977) and is relevant to his theory of evolutionary senescence only with respect to the somewhat ambivalent statements it forced from him  . As an example, Hyatt's general review of cephalopod evolution (1884) contains two implicit hypotheses of cause for the addition of senile characteristics. The first, clearly Lamarckian in nature, argues that unfavorable external factors influenced retrogression:
"The facts show that some general physical cause acted simultaneously, or nearly so, over the whole known area of the world...[and] acted on the type so as to cause the successive generation of the larger part of the shells to become distorted... In extreme cases they became straight again." (pg. 147, 148)
In order to retain the indispensable orthogenetic component of phylogenetic senescence, Hyatt was forced to postulate the occurrence of a very widespread and "unfavorable" period in the Earth's history. But further in the text, Hyatt alludes to his earlier views of an internal, pre-determined retrogression:
"The evidence is very strong that there is a limit to the progressive complication which may take place in any type, beyond which it can only proceed by reversing the process and retrograding." (pg. 148)
Hyatt appears to have attempted an uneasy synthesis of these two hypotheses. In "The Genesis of the Arietidae" (1889), Hyatt formulated two laws revealing possible mechanisms underlying retrogressive evolution: 1) the law of evolution of geratologous [senile] forms and 2) the law of succession in catagenesis [retrogression]. Essentially, the first law suggests that unfavorable surroundings act to trigger an internal, heritable propensity (second law) to degeneration. After a group had lost its "vital powers to adapt", there was a heritable tendency towards degeneration which accelerated the pathological effects of the environment.
Many of Hyatt's writings have been judged difficult to interpret . Darwin would admit in a letter to Hyatt that "I have never been able to grasp fully what you wish to show, and I presume this must be owing to some dullness on my part" (10 Oct. 1872, quote from Dexter, 1979). H. F. Osborn would remark that Hyatt's theories "...were rendered unnecessarily mysterious and difficult to comprehend through the inveterate American love of word-making" (1909). Hyatt clearly influenced the research programs of several American invertebrate paleontologists who used his principles of recapitulation to reconstruct phylogenetic histories for the brachiopods (Beecher), pelecyopods (Jackson), gastropods (Grabau), and the cephalopods (Smith, ref., also see Raymond , 1938 for a more extensive list). The old age theory would fade during the early 1900's, owing in part to its vitalistic component, and Mendelian genetics, but also to rise of non-adaptive orthogenetic theories postulating the existence of periods of over- development just prior to phylogenetic extinction (Bowler, 1983, Jepsen, 1949).
Beecher, C.E. 1891. Development of the Brachiopoda, part I. Amer. J. Sci. 3rd ser, 41:343-357.
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Haeckel, Ernst. 1866. Generelle Morphologie der Orginismen: Allgemeine Grundzuge der organischen Formen-Wissenschaft, mechanisch begrundet durch die von Charles Darwin reformirte Descendenz-Theorie. 2 Vol. Berlin: Georg Reimer, 1036pp.
Hyatt, Alpheus. 1866. On the parallelism between the different stages of life in the individual and those in the entire group of the Molluscus order Tetrabranchiata. Mem. Boston Soc. Nat. Hist. 1: 193-209.
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 Some Naturphilosophers (e.g., Meckel) did promote a causal relationship between developmental history and the transformation of organisms through time. Mayr (1982 p. 382) argues that essentialism, over-speculation, and a predominant interest in functional questions limited the successful elaboration of a theory of species transformation in pre-Darwinian Germany. However, the conjoining of essentialism and evolutionism did not disappear with the advent of Darwin's theory (Hyatt's evolutionism is a prime example). Essentialism was not so much antagonistic to evolutionism as it was to natural selection.
 Several studies suggest that Cope's ideas were first expressed not in 1866 (Trans. Am. Phil. Soc. 13: 398.), but 1868 in the paper "On the origin of genera." Gould (1977) and Richardson and Kane (1988) are exceptions in citing the 1866 paper.
 Winsor (1991 p.41) argues that Hyatt's early papers reveal only the application of Agassiz's law of parallelism- with no explicit reference to species transformation. I've read the 1866 paper closely and Winsor's perspective is perhaps defensible from a reading of this paper alone, but it seems clear that Hyatt is discussing (albeit foggily) process, as well as pattern in the 1866 paper. Hyatt's own testimony is also at odds with Winsor. (see e.g., Hyatt , p. 216; , p. 48 -discussed in this paper)
 Hyatt never suggested why he emphasized the peaks in species diversity within the 4 lineages. Only here does a [spurious] correlation with ontogeny arise. The peaks in diversity would suggest a peak in a lineage's "propensity to speciate" only- and seem irrelevant to the temporal sequence of origin of the four morphological stages Hyatt is defining. Hyatt is, in effect, granting biological properties to large taxonomic units. Hyatt consistently granted importance to this superficial sequence of transformation even while conceding- upon close inspection- that it was not founded in reality. His adoption of process hypotheses to explain observed patterns seem very secondary in importance to that pattern. Because evolutionary patterns were predetermined- investigating the process generating that pattern became less a focus than the primary task of phylogenetic reconstruction. This perspective was evidently the product of a paradigm foreign to Darwin. Gould characterizes Hyatt and Cope as "incessant students of evolution's cause" [1977, p. 184, footnote], but Hyatt seems to have subordinated process to pattern.
 Hyatt states this clearly in letter to Samuel Scudder, 1873 [see Dexter, 1979]; Relevant to timing of his adoption of Lamarckian views. The Steinheim Planorbis studies may have been a product of, or a stimulus to develop his Lamarckian ideas.
 Cope apparently did not adopt (publicly) an explicitly Lamarckian perspective until the mid (?) 1870's- my comment here is likely invalid.
 Because Hyatt accepted direct environmental induction as a means of acquisition of senile characters, his thinking here resembles that of Geoffroy Saint-Hilaire rather than Lamarck. Hyatt discusses three possible causes in his 1897 paper. He does not seem to view them as interdependent hypotheses.
 After 1866, Hyatt seemed to abandon his defense of the racial cycle at the ordinal level and defended it in the context of specific lineages- those with true phyletic succession.
 Additional quotes: Donovan (1973): Hyatt's views were "...formulated in great detail with little attempt at conciseness of expression..." Also, both Brooks (1909 p.319) and Mayer (1911, p. 144) voiced similar criticisms.