I have devoted my whole life to the study of Nature, and yet a single sentence may express all that I have done. I have shown that there is a correspondence between the succession of Fishes in geological times and the different stages of their growth in the egg that is all. It chanced to be a result that was found to apply to other groups and has led to other conclusions of a like nature.
Louis Agassiz, 1869
One of the great scientists of his day, and one of the "founding fathers" of the modern American scientific tradition, Louis Agassiz remains something of a historical enigma. A great systematist and paleontologist, a renowned teacher and tireless promoter of science in America, he was also a lifelong opponent of Darwin's theory of evolution. Yet even his most critical attacks on evolution have provided evolutionary biologists with insights.
Biography of Agassiz
The son of a minister, Jean Louis Rodolphe Agassiz was born on May 28, 1807 in the village of Môtier, in the French-speaking part of Switzerland. Agassiz was educated in the universities of Switzerland and Germany as a physician, like many naturalists of the time. He studied with prominent German biologists, including Oken and Döllinger. These men were followers of Naturphilosophie, a German Romantic philosophy that sought metaphysical correspondences and interconnections within the world of living things. Though Agassiz later renounced this philosophy, he was never quite able to free himself from its influence. Receiving his medical degree from the University of Erlangen in 1830, he went to Paris on December 16, 1831 to study comparative anatomy under Cuvier, the most famous naturalist in Europe. Cuvier was so impressed with Agassiz's work on fossil fishes that he turned over to Agassiz his own notes and drawings for a planned work on fossil fishes. Cuvier died on May 13, 1832, yet although their relationship lasted only months, Agassiz always considered himself an intellectual heir of Cuvier. For the rest of his life, Agassiz promoted and defended Cuvier's geological views and his classification of the animals. With the publication of his vast work on the fossil record of fishes, Poissons fossiles, Agassiz's reputation began to grow in the scientific community.
After Cuvier's death, Agassiz took up a professorship at the Lyceum of Neuchatel in Switzerland, where for thirteen years he worked on many projects in paleontology, systematics, and glaciology. Agassiz took up the study of glaciers in 1836 and was guided by colleagues Ignatz Venetz and Jean de Charpentier to examine the geological features of his native Switzerland. Agassiz noticed the marks that glaciers left on the Earth: great valleys; large glacial erratic boulders carried long distances; scratches and smoothing of rocks; mounds of debris called moraines pushed up by glacial advances. He realized that in many places these signs of glaciation could be seen where no glaciers existed. Previous scientists had variously explained these features as made by icebergs or floods, but following the lead of others, Agassiz became a powerful proponent of the theory that a great Ice Age had once gripped the Earth, and published his ideas in Étude sur les glaciers in 1840. His later book, Système glaciare (1847), presented further evidence for this theory, gathered all over Europe. Agassiz later found even more evidence of glaciation in North America.
In 1846, Agassiz came to the United States on a lecture tour; he was a huge popular success and his expertise was widely recognized and celebrated. In 1848 he accepted a professorship at Harvard. He immediately set about organizing and acquiring funding for a great museum of natural history. In 1859 his dream came true with the founding of the Museum of Comparative Zoology, which opened its doors in 1860. This was the first publicly funded science building in North America. Agassiz labored for support of science in his adopted homeland; he and his colleagues urged the creation of a National Academy of Sciences, and Agassiz became a founding member in 1863. Agassiz was also appointed a regent of the Smithsonian Institution in 1863. He campaigned constantly for funds and resources for American science, and for his research projects in particular and the funding grew and grew (although it never seemed quite enough for all that Agassiz wanted to do and although Agassiz himself never quite finished most of his grand projects).
Agassiz's scientific thought
Agassiz stayed loyal to Cuvier's classification, which divided the animal kingdom into four embranchements (branches): Vertebrata, Insecta, Vermes (worms) and Radiata (radially symmetrical animals). Within each embranchement the classes could be ranked from lowest to highest; the orders in each class could be similarly ranked, and so on down to the species level, with Homo sapiens sitting at the very top of the scale of life. The cornerstone of Agassiz's biological thought was his belief that the gradation from low to high forms, in any taxon, paralleled the order of appearance in the fossil record, the order of stages in the organisms' development, and the distribution and ecology of the taxon. The "lowest" forms were first found lowest in the rock record, their morphological features appeared earliest in embryonic development, and they are distributed today at the highest latitudes. Agassiz summed up his thought in his Essay on Classification, first published in 1851:
… the phenomena of animal life correspond to one another, whether we compare their rank as determined by structural complication with the phases of their growth, or with their succession in past geological ages; whether we compare this succession with their relative growth, or all these different relations with each other and with the geographical distribution of animals upon the earth. The same series everywhere!
Darwin, and many others after him, accepted these parallelisms as providing evidence for evolution. Darwin wrote in The Origin of Species that "this doctrine of Agassiz accords well with the theory of natural selection," although he was writing somewhat ironically because he did not agree with Agassiz's belief of a strict "parallelism." Haeckel in particular invoked the "recapitulation of phylogeny by ontogeny" in support of evolution. But Agassiz was no evolutionist; in fact, he was probably the last reputable scientist to reject evolution outright for any length of time after the publication of The Origin of Species. Agassiz saw the Divine Plan of God everywhere in nature, and could not reconcile himself to a theory that did not invoke design. He defined a species as "a thought of God." As he wrote in his Essay on Classification:
The combination in time and space of all these thoughtful conceptions exhibits not only thought, it shows also premeditation, power, wisdom, greatness, prescience, omniscience, providence. In one word, all these facts in their natural connection proclaim aloud the One God, whom man may know, adore, and love; and Natural History must in good time become the analysis of the thoughts of the Creator of the Universe ….
Agassiz was a staunch creationist; he taught that after every global extinction of life God created every species anew. This differed from the view of Cuvier, who recognized extensive and sometimes apparently quite abrupt changes in fossil faunas and their environments. Cuvier did not think that God re-created life; he thought that new species migrated in from elsewhere as climates and environments changed.
Agassiz's works on living and fossil fishes and on glaciers have remained classics. His work on glaciers revolutionized geology, and drove another nail in the coffin of the Biblical Flood as a serious scientific hypothesis. He trained and influenced a generation of American zoologists and paleontologists, including Alpheus Hyatt, William Healey Dall, David Starr Jordan, Nathaniel Shaler, and Edward S. Morse. He left a mark on the development and the practice of American science, and brought science to "the man in the street" as no one else had before. People from all over the world read his books, sent him specimens, and asked his advice. By the time of his death, on December 14, 1873, he was the most famous scientist in America, and although he actually published few major scientific works after he emigrated, his popular books and public lectures made him extremely well-known and respected by the public. Scientifically, however, he was being left behind by his absolute rejection of evolution and his insistence on glaciers as a major force that shaped geology worldwide.
Agassiz was also being left behind by his racist attitudes, which were extreme even for his day. In the early and mid-1800s there was considerable scientific debate about the origins of humans and of human races, and about just how different human groups were. This debate concerned all groups of plants and animals how do you tell how much difference constitutes a species? and was an important avenue of inquiry. Unlike Darwin and others, who thought that humans all belonged to one species and that their populations had differentiated through time as they spread geographically and adapted to new environments, Agassiz could not accept that all groups of humans belonged to the same species, and he argued vehemently for the inferiority of non-white human groups. He was not alone in this; several prominent scientists saw populational differences as major and discontinuous, and used various statistical and other arguments to support this. But Agassiz was also physically revulsed by the idea that all humans were equal. In this feeling he was not alone, but increasingly he was seen as the product of a bygone age himself.
His philosophy of nature, aiming to understand the Divine Plan, is the last great expression of the old school of natural theology, started by men like John Ray almost two hundred years before. Natural theology had once inspired countless scientists, including Darwin and his forerunners, but by the time of publication of The Origin of Species it had largely run out of steam, unable to offer any real explanation for natural phenomena except "God made it that way." Within Agassiz's lifetime, and much to his grief, most of his students including his son Alexander, a well-known naturalist in his own right became evolutionists, though not necessarily Darwinians.
Agassiz's idea of the "three-fold parallelism" that the order of appearance of animals in the fossil record largely mirrors the order of appearance of their morphological features during the development of animals, and that this in turn mirrors the arrangement of their phylogenetic relationships was not strictly accepted even in his day, although many facts are consistent with it. Like many biological generalizations, there are too many exceptions to its principles to use it as a strict guide. And we must remember that Agassiz did not accept evolution, so the explanation of why these patterns would make sense to modern biology would have been anathema to him. Still, the general concordance of patterns that he noticed and described stimulated much research in his day. It would not be correct to say that today's "comparative biology" and "evolutionary developmental biology" (or "evo-devo") owe a great debt to Agassiz, but at least he saw the grand scheme of many of its patterns, despite his refusal to accept evolution.