Hyatt, Alpheus

Hyatt, Alpheus

(b. Washington, D. C., 5 April 1838; d. Cambridge, Massachusetts, 15 January 1902)

invertebrate paleontology, zoology.

Alpheus Hyatt, an influential evolutionist and co-founder of the neo-Lamarckian theory, was the descendant of an old Maryland family. After a year at Yale, he went to Harvard in 1858 to study with Louis Agassiz. He graduated from the Lawrence Scientific School of Harvard in 1862. He married Ardella Beebe (1867) and after serving in the Union army during the Civil War became professor of zoology and paleontology at the Massachusetts Institute of Technology, a position he held until 1888. In 1877 he was appointed professor of biology at Boston University and remained there until his death. He became custodian in 1870 and curator in 1881 of the Boston Society of Natural History. In 1875 Hyatt was elected to the National Academy of Sciences. He founded the marine laboratory at Annisquam, Massachusetts (later moved to Woods Hole), and was a co-founder of the American Society of Naturalists.

Although he was primarily a prolific specialist on the systematics and evolution of ammonoids (“Genesis of the Arietidae” [1889]) Hyatt also published extensive works on gastropods and bryozoans and wrote an important treatise on North American sponges (1877). He was working on the evolution and zoogeogrphy of Hawaiian tree snails at the time of his death. It is as an evolutionary theorist, however, that he is best known. He was among the gifted group of students who broke with their mentor Agassiz and embraced evolutionary theory soon after 1859.

Hyatt was not a Darwinian. He granted natural selection an executioner’s role in removing the unfit, but he did not see how it could create the fit. Moreover, he thought he could detect repeated patterns on directed change in the fossil record that could not be the result of adaptation to changing environments. He believed that evolution could lead to increasing complexity of organization only if variation were intrinsically directed toward advantageous states (rather than being random in direction, as the Darwinians thought).

To produce this variation, he accepted the Lamarckian postulate that organisms could pass on to their offspring the advantageous characters that they had acquired during their lifetimes. Hyatt and the vertebrate paleontologist E. D. Cope were the leading exponents of this so-called neo-Lamarckian school. They believed that most important new characters arose from the mechanical activity of animals themselves (for example, that the astragalus of eventoed ungulate animals developed from pressures of contact in sustained running) and that this is why structure is so well adapted (in an engineer’s sense) to function. Hyatt’s extended argument (1894) for the origin of the ammonites’ “impressed zone”—that it arose from pressures of contact with its own outer whorls—was surely the most influential case ever made for this belief.

It is often said that the neo-Lamarckians accepted only this side of Lamarckism, rejecting or ignoring Lamarck’s perfecting principle and his distinction between vertical progress up the ladder of life and horizontal side-branches as adaptations to specific environments (eyeless moles and long-necked giraffes). This interpretation is not correct. Both Hyatt and Cope distinguished progressive evolution, which they regarded as the addition of stages to an ancestral ontogeny, from specific alterations of existing ontogenies. The mechanism of addition, and therefore o evolutionary progress, is the principle of recapitulation. Cope and Hyatt both formulated this principle independently in 1866, the same year that Haeckel announced it in his Generelle Morphologie der Organismen. (While the evolutionary interpretation was new, the principle dates back to ancient Greek science.) The addition of new stages depends upon a “law of acceleration” that “makes room” for them by shortening ancestral ontogenies. The law of acceleration operates continuously to transfer the adult stages of ancestors to earlier and earlier steps of a descendant’s ontogeny (with new steps being added at the end of growth). Thus, the sequence of embryonic stages parallels the sequence of ancestral adults, and phylogeny can be read from ontogeny. Hyatt used this principle of recapitulation (often incau-tiously as an absolute a priori) to reconstruct the history of ammonoids.

But since it is not natural selection, what determines the sequence of new stages in phylogeny? In attempting to answer this question, Hyatt made his most imaginative and original contribution to evolutionary thought—his “old age” theory (see especially his 1880 work). Species, as individuals, have a determined cycle of youth, maturity, and old age leading to extinction. Early in its history, a species adds the vigorous features of its phyletic youth and prospers. Later it adds the degenerate features of its phyletic senescence (the incorporation of inadaptive states, an anti-Darwinian tenet) and eventually succumbs. This theory of “racial senescence” was fairly popular, especially among paleontologists, until the formulation in the 1930’s of the “modern synthesis” of evolutionary theory.

BIBLIOGRAPHY

See “On the Parallelism Between the Different Stages of Life in the Individual and Those in the Entire Group of the Molluscous Order Tetrabranchiata,” in Memoirs of the Boston Society of Natural History, 1 (1866), 193-209; “Revision of the North American Poriferae,” ibid., 2 (1875-1877), 399-408, 481-554; “The Genesis of the Tertiary Species of Planorbis at Steinheim,” in Anniversary Memoirs of the Boston Society of Natural History (1880); “Genesis of the Arietidae,” in Memoirs of the Museum of Comparative Zoology at Harvard College, 16 (1889); “Phylogeny of an Acquired Characteristic,” in Proceedings of the American Philosophical Society, 32 (1894), 349-647.

An obituary notice by W. K. Brooks is in Biographical Memoirs. National Academy of Sciences, 6 (1909), 311-325.

Stephen Jay Gould