Tag Archives: Evolution

April 15, 1857 (a Wednesday)

On this date, a 3-kg carbonaceous chondrite fell at Kaba, near Debrecen, Hungary. The arrival of this meteorite was described as follows in the book The Geologist (1859) by Samuel Joseph Mackie (pp. 285-6):

About 10 pm an inhabitant of Kaba, sleeping in the open air, was awakened by a noise, different from that of thunder, as he described it, and perceived in the serene sky a luminous globe, of dazzling brightness, following a parabolic course during four seconds. This phenomenon was observed by several inhabitants of the same place. As one of them was riding out the next morning, his horse was frightened by the sight of a black stone, deeply bedded in the soil of the road, the ground around it being depressed and creviced. When dug out the meteorite weighed about 7 pounds. The finder broke off some fragments, and the remainder, weighing 5-1/4 lbs., was deposited in the Museum of the Reformed College at Debreczin.

Samples of the Kaba meteorite and the Cold Bokkeveld meteorite were examined and found to contain organic substances by Friedrich Wöhler, who inferred a biological origin. Ironically, it was Wöhler who had shown that it was possible to make organic chemicals by inorganic means. However, it was only later appreciated that complex carbon molecules can be manufactured in space by purely chemical processes.

April 6, 2006 (a Thursday)

*Tiktaalik roseae* fills in the evolutionary gap between fish and land animals.

On this date, two articles were published in the science journal Nature reporting the discovery of a fossil that might in time become as much of an evolutionary icon as the proto-bird Archaeopteryx. Several specimens of this transitional form, named Tiktaalik roseae, were found in late Devonian river sediments on Ellesmere Island in Nunavut, Arctic Canada.

References:

April 5, 1859 (a Tuesday)

Charles Darwin, aged 51

On this date, Charles Darwin sent his publishers the first three chapters of The Origin of Species, which became one of the most influential books ever published.

April 5, 1802 (a Monday)

Illustration by Felix Dujardin

On this date, the French physiologist, morphologist, and taxonomist Félix Dujardin was born. Dujardin is primarily known for his work with microscopic animal life, and in 1834 proposed that a new group of one-celled organisms be called Rhizopoda (meaning “root-foot”). This name was later changed to protozoa. In 1835, he disproved Ehrenberg’s hypothesis that microorganisms have the same organs as the more complex animals.

Also in 1835, he was the first to describe protoplasm, the jellylike material in animal cells which he called sarcode (from the Greek word σάρξ, meaning “flesh”). [Hugo von Mohl is credited with introducing the name protoplasm for it in 1846.] This substance, now called cytoplasm, was later found in living plant cells. Although the term protoplasm is rarely used any more in a strictly scientific sense, many of the notions associated with the term have survived. Thus it is still accepted that all living organisms are made largely of the same classes of substances such as salts and organic molecules, that some of these are organized into structures large enough to be seen in the microscope, and that water almost always is by far the most abundant material.

Dujardin’s written works include Histoire naturelle des infusoires (1840), Manuel de l’observateur au microscope (1842), and Histoire naturelle des helminthes (1844).

March 30, 1759 (a Friday)

A series of rock formations that Arduino categorized as "primary" and "secondary".

A series of rock formations that Arduino categorized as “primary” and “secondary”.

On this date, the Italian geologist Giovanni Arduino (1714-1795) wrote a letter to Professor A.Vallisneri the younger, in which Arduino proposed a classification of Earth’s surface rocks according to four brackets of successively younger orders: Primary, Secondary, Tertiary and Quaternary. Today, his Primary corresponds to the Precambrian and Paleozoic Era combined, his Secondary is the Mesozoic Era, and his Tertiary and Quaternary combine to form the Cenozoic Era.

March 25, 1833 (a Monday)

Jenkin

On this date, the English physical scientist and engineer Henry (Charles) Fleeming [pronounced "flemming"] Jenkin was born. No other attack on Charles Darwin’s theory of evolution has drawn more attention than Jenkin’s. Nearly every book in the history of evolution recounts the tale. It began in June, 1867 with Mr. Jenkin’s review of The Origin of Species in The North British Review (46: 277-318).

References:

  • Stephen Jay Gould, Bully for Brontosaurus: Reflections in Natural History (New York, NY: W.W. Norton & Co., 1991) 340 -353.
  • Ernst Mayr, The Growth of Biological Thought: Diversity, Evolution, and Inheritance ( Cambridge, MA: The Belknap Press of Harvard University, 1982) 512.

March 24, 1912 (a Sunday)

On this date, the American biochemist Sidney Walter Fox was born. In the 1960s at the University of Miami, Fox found that when he heated Stanley Miller’s amino acids (created through simulation experiments) to temperatures that would have been present on the volcanic primordial Earth, in conjunction with aspartic and glutamic acids (also created through simulation experiments), they formed protein-like polymers that he called”proteinoids”.

Microsphere surface.

Fox observed that when proteinoids or “thermal proteins,” are placed in water, they self-organize into microspheres or protocells, possible precursors of the contemporary living cell. Under a microscope, the microspheres look like primitive cells. In fact, artificially fossilized microspheres are indistinguishable from the earliest known microfossils that date back to about 3.5 BYA. Fox argued that RNA or DNA need not date back to the origin of life, and he showed that proteinoid microspheres exhibit growth, metabolism, reproduction (by budding), and responsiveness to stimuli – all properties of life – though without a genetic system. Although hesitant to claim that these were alive, Fox stated that they were undeniably “protoalive”. This is not an evasive answer. As Tim M. Berra says in Evolution and the Myth of Creationism (1990):

For centuries, science knew nothing intermediate between non-living and living things, but today the distinction is not at all clear. Since life evolved from non-living matter, at some point we must arbitrarily draw a line and say that everything beyond that point is alive. Viruses, for example, appear to be alive when they infect a host, but seem to be non-living when outside a host.

As a result of his monumental discovery of thermal proteins and their self-organization into protocells and that these protocells exhibit virtually all of the properties associated with life, Sidney Fox was invited to lecture widely throughout the world. Even Pope John Paul II and his advisers, on at least three separate occasions, invited Fox to the Vatican to explain his work on the synthesis of cellular life in a test tube.

March 23, 1769 (a Thursday)

William Smith's "A Geological Map of England and Wales and Part of Scotland" (1815)

William Smith’s “A Geological Map of England and Wales and Part of Scotland” (1815)

On this date, the English engineer and geologist William Smith was born. Smith was instrumental in extending the science of stratigraphy. His early work was as a miner and an engineer, for a canal-digging company. From this experience he observed the difference in rock layers. He also recognized that the same succession of fossil groups from older to younger rocks could be found in many parts of England, which he called the principle of faunal succession. He traveled the entire country to verify that relationships between the strata and their characteristics were consistent everywhere. Thus Smith created a profile of the entire country of England. His great geologic map of England and Wales (1815) set the standard for modern geologic maps. Many of the colorful names he gave to the strata are still in use today.

March 22, 1785 (a Tuesday)

Adam Sedgwick

On this date, the English geologist and paleontologist Adam Sedgwick was born. He was one of the founders of modern geology. Sedgwick was the first scientist to apply the name Cambrian to the geologic period of time, now dated at 570 to 505 million years ago. Twentieth-century research has uncovered so many excellent fossils in Cambrian sediments, especially the Burgess Shale in Canada, that this geologic period is sometimes referred to as the “Cambrian Explosion.”

Sedgwick attended Trinity College at Cambridge University, where he took holy orders in 1817. In 1818, he became Woodwardian Professor of Geology at Cambridge, despite the fact that he had no formal training in geology. His lectures at Cambridge were immensely popular; he was a spellbinding lecturer, and – breaking with the traditions of his time – his lectures were open to women, whom Sedgwick thought could make great contributions to natural history. He kept giving his famous lectures until 1871.

After passing his examinations for the Bachelor of Arts degree in January 1831, Charles Darwin began attending Sedgwick’s geology lectures, which he found fascinating. During the summer of 1831, Darwin was Sedwick’s field assistant in north Wales, and Darwin got a “crash course” in field geology from Sedgwick. This was an experience that proved valuable to Darwin over the next five years, on his round-the-world voyage on H.M.S. Beagle. During this voyage, Darwin sent geological specimens and reports to Sedgwick, who wrote approvingly to Darwin’s family:

He is doing admirably in S. America & has already sent home a Collection above all praise. – It was the best thing in the world for him that he went out on the Voyage of Discovery. . .

However, after reading The Origin of Species, Sedgwick candidly wrote to Darwin on November 24, 1859:

If I did not think you a good tempered & truth loving man I should not tell you that. . . I have read your book with more pain than pleasure. Parts of it I admired greatly; parts I laughed at till my sides were almost sore; other parts I read with absolute sorrow; because I think them utterly false & grievously mischievous– You have deserted– after a start in that tram-road of all solid physical truth– the true method of induction. . .

Sedgwick was opposed to Charles Lyell’s models of slow, gradual geological change and a more or less steady-state Earth. Instead, he followed Cuvier’s idea of multiple “catastrophes” that had destroyed much of Earth’s life. But Sedgwick did not object to evolution, or “development” as such theories were called then, in the broad sense – to the fact that the life on Earth had changed over time. Nor was he a “young-Earth” creationist – he thought that the Earth must be extremely old. Nevertheless, Sedgwick believed in the Divine creation of life over long periods of time, by “a power I cannot imitate or comprehend — but in which I believe, by a legitimate conclusion of sound reason drawn from the laws of harmonies of nature.” His problem was with the amoral and materialistic nature of Darwin’s proposed mechanism of natural selection, which Sedgwick thought was degrading to humanity’s spiritual aspirations. His letter of November 24 went on to state:

This view of nature you have stated admirably; tho’ admitted by all naturalists & denied by no one of common sense. We all admit development as a fact of history; but how came it about? Here, in language, & still more in logic, we are point blank at issue– There is a moral or metaphysical part of nature as well as a physical. A man who denies this is deep in the mire of folly. Tis the crown & glory of organic science that it does thro’ final cause, link material to moral. . . You have ignored this link; &, if I do not mistake your meaning, you have done your best in one or two pregnant cases to break it. Were it possible (which thank God it is not) to break it, humanity in my mind, would suffer a damage that might brutalize it–& sink the human race into a lower grade of degradation than any into which it has fallen since its written records tell us of its history.

Despite their differences, the two stayed friends until Sedgwick’s death in 1873.

March 21, 1925 (a Saturday)

On this date, Tennessee Governor Peay signed into law the Butler Act, “prohibiting the teaching of the Evolution Theory” in all public schools and universities and making it unlawful in public schools “to teach any theory that denies the story of the Divine Creation of man as taught in the Bible, and to teach instead that man has descended from a lower order of animals.” This set the stage for the Scopes’ “Monkey Trial” in Dayton, Tennessee during the subsequent summer.

The author of the law, a Tennessee farmer named John Washington Butler, had introduced the bill into the state House of Representatives on January 25, 1925. Ironically, he later was reported to have said, “No, I didn’t know anything about evolution when I introduced it. I’d read in the papers that boys and girls were coming home from school and telling their fathers and mothers that the Bible was all nonsense.” After reading copies of William Jennings Bryan’s lecture “Is the Bible True?” as well as Charles Darwin’s The Origin of Species and The Descent of Man, Butler decided evolution was dangerous. During the trial, Butler told reporters, “I never had any idea my bill would make a fuss. I just thought it would become a law, and that everybody would abide by it and that we wouldn’t hear any more of evolution in Tennessee.”

March 21, 1932 (a Monday)

On this date, the American molecular biologist Walter Gilbert was born. In 1980, he was awarded the Nobel Prize in Chemistry with Frederick Sanger and Paul Berg. Gilbert and Sanger were recognized for their pioneering work in devising methods for determining the sequence of nucleotides in a nucleic acid.

A Maxam-Gilbert sequencing gel.

A Maxam-Gilbert sequencing gel.

In a 1986 article (Nature 319: 618), Gilbert was the first scientist to use the term “RNA world” to refer to a possible stage in the origin of life on Earth (although the hypothetical possibility of an RNA world had already been suggested by others before him):

The first stage of [chemical] evolution proceeds, then, by RNA molecules performing the catalytic activities necessary to assemble themselves from a nucleotide soup. The RNA molecules evolve in self-replicating patterns, using recombination and mutation to explore new niches. … they then develop an entire range of enzymic activities. At the next stage, RNA molecules began to synthesize proteins, first by developing RNA adaptor molecules that can bind activated amino acids and then by arranging them according to an RNA template using other RNA molecules such as the RNA core of the ribosome. This process would make the first proteins, which would simply be better enzymes than their RNA counterparts. … These protein enzymes are … built up of mini-elements of structure.

Finally, DNA appeared on the scene, the ultimate holder of information copied from the genetic RNA molecules by reverse transcription. … RNA is then relegated to the intermediate role it has today—no longer the center of the stage, displaced by DNA and the more effective protein enzymes.

The possibility of an RNA world in the origin of life had been supported by the discovery by Thomas Cech in 1982 of the existence of naturally-occurring ribozymes.

March 15, 1806 (a Saturday)

The Alais meteorite.

The Alais meteorite.

On this date, a 6-kg carbonaceous chondrite – a type of meteorite carrying carbon-based, organic chemicals – was unequivocally identified for the first time. Its arrival on Earth was noted at 5:30 pm, outside Alais, France. The organic chemicals it carried suggested the possibility of life on whatever body was the source, somewhere in the universe. According to the observations of the Swedish chemist Jöns Jakob Berzelius and a commission appointed by the French Academy of Sciences, it “emits a faint bituminous substance” when heated. Berzelius analyzed the Alais meteorite and reported in 1833 that destructive distillation yielded a blackish substance, indigenous water, carbon dioxide gas, a soluble salt containing ammonia, and a blackish-brown sublimate, which Berzelius confessed was unknown to him.

March 13, 1720

Charles Bonnet

On this date, Charles Bonnet, a Swiss naturalist and philosophical writer, was born at Geneva, of a French family driven into Switzerland by the religious persecution in the 16th century. He made law his profession, but his favorite pursuit was the study of natural science.

Bonnet’s first published work appeared in 1745, entitled Traité d’insectologie, in which were collected his various discoveries regarding insects, along with a preface on the development of germs and the scale of organized beings. Botany, particularly the leaves of plants, next attracted his attention; and after several years of diligent study, rendered irksome by the increasing weakness of his eyesight, he published in 1754 one of the most original and interesting of his works, Recherches sur l’usage des feuilles dans les plantes; in which among other things he advances many considerations tending to show (as was later done by Francis Darwin) that plants are endowed with powers of sensation and discernment. Bonnet also studied photosynthesis in plants and noted the emission of bubbles by a submerged illuminated leaf (but see Jan Ingenhousz, who is also given credit for this observation). This very visible production of oxygen by an illuminated leaf is still used regularly in school laboratories as a way of investigating rates of photosynthesis.

Affected by his observation of the aphid, Bonnet argued, in Considérations sur les corps organisés (1762; “Considerations on Organized Bodies”), that each female organism contains within its germ cells (i.e., eggs) an infinite series of preformed individuals (Theory of Preformation), leading to an immortality and immutability of species. In his Contemplation de la nature (Amsterdam, 1764–1765; translated into Italian, German, English and Dutch), one of his most popular and delightful works, he sets forth, in eloquent language, the theory that all the beings in nature form a gradual scale rising from lowest to highest (scala natura), without any break in its continuity.

In order to explain the fossil findings of extinct species, Bonnet, in his work La Palingénésie philosophique (1769; “The Philosophical Revival”), advocated the view that Earth is periodically struck by global disasters. In these disasters most organisms die and the survivors climb the scala natura to reach new heights. According to this, mankind, the peak of evolution, would develop into angels after the next disaster, when plants would become animals, animals would become intelligent beings, and minerals would become plants. This disaster theory to explain evolution strongly influenced Erasmus Darwin (1731-1802), Charles Darwin’s (1809-1882) grandfather. This makes Charles Bonnet one of the first biologists to use the term evolution in a biological context. However, he was stuck in the preformation theory, which implied the immutability of species and precluded biological evolution.

March 13, 1832 (a Tuesday)

Rev. John Thomas Gulick

On this date, the American evolutionary biologist Rev. John Thomas Gulick was born. John Gulick continued a family tradition by attending theological school and then did missionary work in China and Japan for over thirty-five years. But he also carried on a parallel career as a naturalist and Darwinian evolutionist. Gulick had collected land snails since his teen years, and became a convert to evolutionary thinking even before reading The Origin of Species. An acute observer, he noticed that many species and varieties of snails were often restricted to very geographically-limited ranges and, as his son Addison later wrote (Scientific Monthly 18 (January 1924): 89), Gulick came

to place great emphasis upon every form of isolation or prevention of mingling, and also to emphasize the great significance for evolution of many factors that are of internal origin, such as the unknown intricacies of the process of heredity, and the effects of new choices made by the evolving creatures…

A plate of Hawaiian land snails from Addison Gulick’s book, Evolutionist and Missionary: John Thomas Gulick (1932).

In 1872, Gulick became the first person to advance the thesis that much evolutionary change is simply a result of chance variation; in other words, variation that has no effect whatsoever on survival and reproductive success can persist in a species. He came to this conclusion when observing the incredible diversity of local populations of Hawaiian land snails (Achatinella) and their seemingly random variation under apparently identical environmental conditions.

Darwin's illustration of an evolutionary tree, from The Origin of Species (1859).

In 1888, Gulick introduced terms for the two patterns of evolution that are observed: the term monotypic evolution (previously called transformation) – what today we define as “the change in gene frequencies within populations over generations” – and the term polytypic evolution (previously called diversification) – simultaneous processes, like the multiplication of species, manifested by different populations and incipient species. Darwin had been far more interested in diversification, particularly during the early years of his career. Jean-Baptiste Lamarck, in contrast, had been almost exclusively interested in transformational evolution. He stressed change in time, emphasizing transformation from what was commonly called the lower to the more perfect groups, but his mechanism – “use and disuse” and the “inheritance of acquired characteristics” – was, it turned out, erroneous.

Monotypic (left) v. polytypic evolution.

George Romanes later (1897) adopted Gulick’s terminology, distinguishing between monotypic evolution as “transformation in time” and polytypic evolution as “transformation in space.” In other words, monotypic evolution deals with the “vertical” (usually adaptive) component of change in time, while polytypic evolution deals with the “horizontal” component of change. [Today, monotypic evolution is also known as "nonbranching" evolution, or anagenesis, and polytypic evolution is also known as "branching" evolution, or cladogenesis.] This insight was largely forgotten again after 1897, until it was revived during development of the synthetic theory of evolution in the 1940s.

Gulick extended his ideas to societal evolution in human beings, which he thought was dependent on altruistic motives and a spirit of cooperation.

References:

March 7, 1854 (a Tuesday)

Charles Darwin (1855)

On this date, Charles Darwin was elected a Fellow of the Linnean Society of London.

March 7, 1930 (a Friday)

ResearchBlogging.orgOn this date, the American chemist and biologist Stanley Lloyd Miller was born. In 1953, he (under his University of Chicago mentor, Nobelist Harold C. Urey) performed a famous experiment (the so-called Miller-Urey experiment) to determine the possible origin of life from inorganic chemicals on the primeval, just-formed Earth. They passed electrical discharges (simulating thunderstorms) through mixtures of reducing gases, such as hydrogen, ammonia, methane and water, believed to have formed the earliest atmosphere. Analysis days later showed the resulting chemicals included five amino acids: aspartic acid, glycine, alpha-amino-butyric acid, and two versions of alanine. Aspartic acid, glycine, and alanine are common building blocks of natural proteins. Other compounds included urea, aldehydes, and carboxylic acids. This experiment showed that the basic molecules of life could be synthesized from simple molecules, suggesting that Darwin’s “warm little pond” was a feasible scenario.

The apparatus used for Miller's original experiment. Boiled water (1) creates airflow, driving steam and gases through a spark (2). A cooling condenser (3) turns some steam back into liquid water, which drips down into the trap (4), where chemical products also settle.

Interestingly, the 1953 Miller-Urey experiment had two sibling studies, neither of which was published. Vials containing the products from those experiments were recently recovered and reanalyzed using modern technology. The results were reported in the 17 October 2008 issue of the journal Science.

Miller relied on a blotting technique to identify the organic molecules he had created — primitive laboratory conditions by today’s standards. He would not have been able to identify anything present at very low levels.

Indiana University Biochemistry Program doctoral student Adam Johnson, Scripps Institution of Oceanography marine chemist Jeffrey Bada (the present Science paper’s principal investigator), National Autonomous University of Mexico biologist Antonio Lazcano, Carnegie Institution of Washington chemist James Cleaves, and NASA Goddard Space Flight Center astrobiologists Jason Dworkin and Daniel Glavin examined vials left over from Miller’s experiments of the early 1950s. Vials associated with the original, published experiment contained far more organic molecules than Stanley Miller realized — 14 amino acids and five amines.

The apparatus used for Miller's "second," initially unpublished experiment. Boiled water (1) creates airflow, driving steam and gases through a spark (2). A tapering of the glass apparatus (inlay) creates a spigot effect, increasing air flow. A cooling condenser (3) turns some steam back into liquid water, which drips down into the trap (4), where chemical products also settle.

However, “The apparatus Stanley Miller paid the least attention to gave the most exciting results,” said Johnson, lead author of the Science report. The difference between the published and two unpublished experiments is small — the unpublished experiments used a tapering glass “aspirator” that simply increased air flow through a hollow, air-tight glass device. Increased air flow created a more dynamic reaction vessel, or “vapor-rich volcanic” conditions, according to the present report’s authors. The 11 vials scientists recovered from Miller’s “second,” initially unpublished experiment produced 22 amino acids and the same five amines at yields comparable to the original experiment.

“We believed there was more to be learned from Miller’s original experiment,” Bada said. “We found that in comparison to his design everyone is familiar with from textbooks, the volcanic apparatus produces a wider variety of compounds.” Johnson added, “Many of these other amino acids have hydroxyl groups attached to them, meaning they’d be more reactive and more likely to create totally new molecules, given enough time.” The report’s authors bring up-to-date what is a plausible scenario for the origin of the earliest biochemical molecules on Earth:

Geoscientists today doubt that the primitive atmosphere had the highly reducing composition Miller used. However, the volcanic apparatus experiment suggests that, even if the overall atmosphere was not reducing, localized prebiotic synthesis could have been effective. Reduced gases and lightning associated with volcanic eruptions in hot spots or island arc–type systems could have been prevalent on the early Earth before extensive continents formed. In these volcanic plumes, HCN, aldehydes, and ketones may have been produced, which, after washing out of the atmosphere, could have become involved in the synthesis of organic molecules. Amino acids formed in volcanic island systems could have accumulated in tidal areas, where they could be polymerized by carbonyl sulfide, a simple volcanic gas that has been shown to form peptides under mild conditions.

Stanley Lloyd Miller

Miller’s third, also unpublished, experiment used an apparatus that had an aspirator but used a “silent” discharge. This third device appears to have produced a lower diversity of organic molecules.

“This research is both a link to the experimental foundations of astrobiology as well as an exciting result leading toward greater understanding of how life might have arisen on Earth,” said Carl Pilcher, director of the NASA Astrobiology Institute, headquartered at NASA Ames Research Center in Mountain View, Calif.

Suggested Reading:

WARNING: The creationist Jonathan Wells of the Discovery Institute has made false and misleading claims about the Miller-Urey experiment and other abiogenesis research in his book Icons of Evolution: Science or Myth? Why Much of What We Teach About Evolution Is Wrong.

February 29 (O.S.=February 18), 1792 (a Wednesday)

Karl Ernst von Baer

On this date, the Estonian-born German biologist and embryologist Karl Ernst von Baer was born. He was an important precursor to Charles Darwin and his theory of evolution.

For more than a century, scientists had attempted to determine the exact nature and location of the mammalian egg. During his research in 1826, Baer discovered the mammalian egg by identifying a yellowish spot within the ovarian follicle visible only with a microscope. He developed this idea in his 1827 treatise, De ovi mammalium et hominis genesi (On the Origin of the Mammalian and Human Ovum).

Baer studied the embryonic development of animals, discovering the blastula stage of development and the notochord. Together with Heinz Christian Pander and based on the work by Caspar Friedrich Wolff, Baer described the germ layer theory of development (ectoderm, mesoderm, and endoderm) as a principle in a variety of animal species. He summarized his findings in his two-volume textbook entitled Über Entwickelungsgeschichte der Thiere (On the Development of Animals) which he published between 1828 and 1837, laying the foundation for comparative embryology.

February 24, 1871 (a Friday)

Charles Darwin

On this date, the first edition of Charles Darwin’s The Descent of Man, and Selection in Relation to Sex was published in two volumes. The word “evolution” appeared for the first time in any of his works. This first issue was of 2,500 copies.

February 23, 1863 (a Monday)

Chamberlain and Cycads in the University of Chicago Greenhouse

Chamberlain and Cycads in the University of Chicago Greenhouse

On this date, the American botanist Charles Joseph Chamberlain was born near Sullivan, Ohio. His research into the structure and life cycles of primitive plants (cycads) enabled him to suggest a course of evolutionary development for the egg and embryo of seed plants (spermatophytes) and to speculate about a cycad origin for flowering plants (angiosperms).

Chamberlain first studied botany and zoology at Oberlin College. After spending several years as a school teacher and administrator, he entered the University of Chicago where in 1897 he received the first doctorate in botany awarded by that institution. He organized and directed the botanical laboratories at the University of Chicago (1897-1931), where, with plants collected in Mexico, Australia, New Zealand, South Africa, and Cuba, he created the world’s foremost collection of living cycads. His comprehensive work entitled Gymnosperms: Structure and Evolution was published in 1935.

February 22, 1830 (a Monday)

Geoffroy aged about 70

On this date, the historical debate that took place at the French Academy of Sciences between Georges Cuvier and Etienne Geoffroy Saint-Hilaire began.

The zoologist and historian of science E.R. Russell summed up the great biological controversy of the first half of the nineteenth century: “Is function the mechanical result of form, or is form merely the manifestation of function or activity? What is the essence of life — organization or activity?” While Cuvier founded the “functionalist” school of organismal biology, with his insistence on animals as functionally integrated wholes, Geoffroy continued the more “formalist” tradition of biology that had started with Buffon and was being continued by Goethe, Lamarck, and others.

Cuvier viewed every part of an animal as having been designed by the Creator to contribute to the animal’s functional integrity. Thus, similarities between organisms could only result from similar functions, writing in 1828, “If there are resemblances between the organs of fishes and those of the other vertebrate classes, it is only insofar as there are resemblances between their functions.” Cuvier argued that all animals could be subdivided into four and only four distinct embranchements: vertebrates, molluscs, articulates (insects and crustaceans), and radiates.

Cuvier’s viewpoint is diametrically opposed to Geoffroy’s view, which stressed the primacy of structure over function; Geoffroy wrote in 1829: “Animals have no habits but those that result from the structure of their organs; if the latter varies, there vary in the same manner all their springs of action, all their faculties and all their actions.”

Geoffrey said that unity of plan could be identified by the relative positions and spatial interrelationships of elements, rather than primarily by their shape or size. Parts may expand and contract according to their function, but topology remains unaltered, and the archetype can be traced by an unvarying spatial pattern.  He called this the principle of connections. (This is still a favored basis for recognizing anatomical homologies.)

Geoffroy wrote in 1807 (see Appel, 1987, p. 89):

It is known that nature works constantly with the same materials. She is ingenious to vary only the forms…One sees her tend always to cause the same elements to reappear, in the same number, in the same circumstances, and with the same connections.

As Charles Darwin described his work in 1859, in The Origin of Species:

What can be more curious than that the hand of a man, formed for grasping, that of a mole for digging, the leg of the horse, the paddle of the porpoise, and the wing of the bat, should all be constructed on the same pattern, and should include the same bones, in the same relative positions? Geoffroy St. Hilaire has insisted strongly on the high importance of relative connexion in homologous organs: the parts may change to almost any extent in form and size, and yet they always remain connected together in the same order.

In 1822, Geoffroy had dissected a lobster and placed it in an inverted position with respect to the ground. In this upside down orientation the lobster’s normally ventral nerve cord was located above the digestive tract, which in turn was placed above the heart. In his own words: “What was my surprise, and I add, my admiration, in perceiving an ordering that placed under my eyes all the organic systems of this lobster in the order in which they are arranged in mammals?” Geoffroy went on to argue that there was a unity of plan, or unity of composition, among animals, so that the dorsal side of the vertebrates was homologous to the ventral side of the arthropods. In 1822, he wrote that “insects formed another class of vertebrated animals, and that they were, consequently, brought under the common law of uniformity of organization”.

Thus, Geoffroy and his followers argued that all animals, vertebrates and invertebrates alike, were built on the same basic plan. Therefore, animal life could be strung into a more or less continuous, related series, rather than broken into discrete “divisions”, as Cuvier had claimed. This series implied that the history of each organism, rising in complexity from starfish to humans, could be interpreted in an evolutionary manner.

Matters between Cuvier and Geoffry came to a head in 1830, when two young naturalists, Meyranx and Laurencet, presented a comparison of the anatomy of vertebrates and cephalopods (squids, cuttlefish, and octopi), claiming that they were based on the same basic structural plan. Geoffroy enthusiastically adopted this claim as proof of the unity of plan shared by all animals; Cuvier could not reconcile it with the results of his careful anatomical research. Thus was set up one of the most famous debates in the history of biology: eight public debates between Cuvier and Geoffroy, from February to April 1830. In these debates, Cuvier showed convincingly that many of Geoffroy’s supposed examples of unity of structure were not accurate; the similarities between vertebrates and cephalopods were contrived and superficial.

Generalized protostome and chordate body plans illustrating inversion in the two lineages.

Generalized protostome and chordate body plans illustrating inversion in the two lineages.

Remarkably, Geoffroy’s idea today is supported by a growing body of molecular developmental evidence. Holley et al (1995) have demonstrated that not only do the fruit fly and frog have homologous genes that promote dorsoventral patterning, but the homologous genes have opposite effects within each animal. In fact, the genes are functionally interchangeable –- even though the product of sog ventralizes fly embryos, it dorsalizes frog embryos just like its homologue in the frog, chordin.

It would be an error to call Geoffroy an evolutionary biologist in anything like the modern sense. Archetypes were abstractions, not once-living ancestors; shared archetypal form did not necessarily indicate common ancestry. Geoffrey used the term “homologous” in its anatomical sense, meaning those parts in different animals which were “essentially” the same, even though the parts might have different shapes and functions. However, later in his career, Geoffroy published some ideas that resemble the theory of evolution by natural selection. The following quote from “Influence du monde ambiant pour modifier les formes animales” (1833) shows that Geoffroy considered that heritable changes in an organism might be selected for or against by the environment, and thus that present-day species might have arisen from antediluvian (before the Biblical Flood) species:

The external world is all-powerful in alteration of the form of organized bodies.. . these [modifications] are inherited, and they influence all the rest of the organization of the animal, because if these modifications lead to injurious effects, the animals which exhibit them perish and are replaced by others of a somewhat different form, a form changed so as to be adapted to the new environment.

But these ideas apparently were never a key part of Geoffroy’s thought. Geoffroy believed that there were limits to how far an organism might evolve, and he never developed his ideas into a complete theory, as Darwin later did.

Part of the power of modern evolutionary biology comes from its ability to synthesize elements from both schools of thought. Organismal lineages change with time, in response to changing environments, and their form constrains the functions that they can take on; at the same time, it is the ability of organisms to function in their environments that is a major component of evolutionary fitness, and form is often altered to fit a particular function. Cuvier and Geoffroy had grasped separate parts of a more complex reality.

References:

  • Toby A. Appel. The Cuvier-Geoffrey Debate: French Biology in the Decades before Darwin (Oxford University Press, 1987).
  • Stephen J. Gould, The Structure of Evolutionary Theory (Harvard University Press, 2002) pp. 298-312.
  • S.A. Holley, P.D. Jackson, Y. Sasal, B. Lu, E.M. De Robertis, F.M. Hoffmann, and E.L. Ferguson.  A conserved system for dorsal-ventral patterning in insects and vertebrates involving sog and chordin, Nature 376: 249-253 (1995).
  • Ernst Mayr. The Growth of Biological Thought: Diversity, Evolution and Inheritance (Cambridge, MA: Harvard Univ. Press, 1982) p 262.

February 20, 1835 (a Friday)

Charles Darwin by G Richmond.

On this date, a massive earthquake hit Valdivia, Chile and Charles Darwin was right in the middle of the action. While HMS Beagle tried to make anchorage at Concepcion, Darwin was dropped off at the island of Quiriquina. During his exploration of the island, he discovered areas of land that had risen a few feet due to the earthquake. Darwin was very excited about this find, as it was direct evidence that the Andes mountains, and indeed all of South America, were very slowly rising above the ocean. This confirmed Charles Lyell’s theory that land masses rose in tiny increments over an extremely long period of time. Given this fact, Darwin accepted the idea that the earth must be extremely old. The next day he went by ship to the town of Talcuhano, and from there rode by horse to Concepcion to meet up with HMS Beagle. As the Beagle sailed from Concepcion, Darwin wrote in a letter to his sister Caroline:

We are now on our road from Concepcion. The papers will have told you about the great Earthquake of the 20th of February. I suppose it certainly is the worst ever experienced in Chili [sic]. It is no use attempting to describe the ruins – it is the most awful spectacle I ever beheld. The town of Concepcion is now nothing more than piles and lines of bricks, tiles and timbers – it is absolutely true there is not one house left habitable; some little hovels builts of sticks and reeds in the outskirts of the town have not been shaken down and these now are hired by the richest people. The force of the shock must have been immense, the ground is traversed by rents, the solid rocks are shivered, solid buttresses 6-10 feet thick are broken into fragments like so much biscuit. How fortunate it happened at the time of day when many are out of their houses and all active: if the town had been over thrown in the night, very few would have escaped to tell the tale. We were at Valdivia at the time. The shock there was considered very violent, but did no damage owing to the houses being built of wood. I am very glad we happened to call at Concepcion so shortly afterwards: it is one of the three most interesting spectacles I have beheld since leaving England – A Fuegian Savage – Tropical Vegetation – and the ruins of Concepcion. It is indeed most wonderful to witness such desolation produced in three minutes of time.

February 18, 1839 (a Monday)

On this date, the English paleontologist Harry Govier Seeley was born. A man of humble origins, Seeley attended Cambridge University but quit before earning a degree. In 1859, he began working as an assistant to Adam Sedgwick at the Woodwardian Museum. For many years Seeley worked on his own, only much later in life accepting a position with King’s College.

Prior to Seeley, in the early 1840s, Richard Owen had established the order Dinosauria. Between 1866 and 1883, various authorities on dinosaurs, including Huxley, Cope, and Marsh, had produced classification schemes that attempted to bring order to the great variety of dinosaur specimens that had been and were being discovered. Marsh, in particular, had proposed to divide dinosaurs into four orders: sauropods, theropods, stegosaurs, and ornithopods; Cope had offered a different scheme. Most of the systems of classifying dinosaurs were based on the structure of their feet and the form of their teeth.

Ornithischia (above) and Saurischia (below).

However, in a paper delivered in 1887 and published in 1888, Seeley pointed out that the term dinosaur was being used for two rather different kinds of reptiles. There were those, like Marsh’s theropods and sauropods, that had a pelvis with a forward protruding pubic bone and those, like the stegosaurs and ornithopods, that had a divided pubic bone with one branch extending backwards along the ischium. Since the backward-protruding pubis is characteristic of modern birds, he called this group Ornithischia, the bird-hipped dinosaurs, and gave it the status of an order. He put the sauropods and theropods in another order he called Saurischia, or lizard-hipped dinosaurs. In the line drawing which Seeley printed with the paper, the top two figures represent the order Ornithischia, and the bottom two the order Saurischia.

Seeley not only argued for separate groups among dinosaurs, he even argued for separate origins, writing:

I see no ground for associating these two orders in one group, unless that group includes Birds, Crocodiles, Anomodonts, and Ornithosaurs; for differences of pelvic structure have been as persistently inherited as any condition of the vertebrate skeleton.

Saurischian hip (left side)

Even though Marsh had identified many characteristics common to all dinosaurs, Seeley’s interpretation held sway into the late twentieth century. In the 1980s, however, new techniques of cladistic analysis revealed that both groups of dinosaurs really did have common ancestors in the Triassic. Still, Seeley’s classification of saurischian and ornithischian dinosaurs remains intact, though, ironically, the birds have subsequently been found to descend, not from the “bird-hipped” Ornithischia, but from the “lizard-hipped” Saurischia.

Ornithischian hip (left side)

References:

  • Harry Govier Seeley, “On the classification of the fossil animals commonly named Dinosauria,” Proceedings of the Royal Society of London 43: 165-171 (1888).

February 17, 1890 (a Monday)

Ronald Fisher

On this date, the English geneticist Ronald Aylmer Fisher was born. His book The Genetical Theory of Natural Selection (1930), with its ground-breaking treatment of the concepts of fitness and dominance, was a milestone work in that field.

February 16, 1834 (a Sunday)

Ernst Haeckel

On this date, the German biologist, naturalist, philosopher, physician, and artist Ernst Heinrich Philipp August Haeckel was born at Potsdam. He is probably one of the most contentious evolutionary biologists that ever lived. He abandoned his medical practice after reading Charles Darwin’s The Origin of Species in 1859 and returned to school, studying zoology and anatomy and eventually earning a position as professor in Jena.

Haeckel embraced the pre-Darwinian notion that life formed a series of successively higher forms, with embryos of higher forms “recapitulating” the lower ones. He thought that, over the course of time, evolution of new life forms occurred by the addition of new adult stages to the end of ancestral developmental sequences. Haeckel, who was very good at packaging and promoting his ideas, coined both a name for the process – “the Biogenetic Law” – as well as a catchy motto: “Ontogeny Recapitulates Phylogeny.”

Thus, according to Haeckel, embryonic development was actually a record of evolutionary history. He expressed it this way, as quoted in Russell (1916) [1]:

The organic individual… repeats during the rapid and short course of its individual development the most important of the form changes which its ancestors traversed during the long and slow course of their paleontological evolution…

The human zygote, for instance, was represented by the “adult” stage of the protists; the colonial protists represented the advancement of development to the blastula stage; the gill slit stage of human embryos was represented by adult fish. Haeckel even postulated an extinct organism, Gastraea, a two-layered sac corresponding to the gastrula, which he considered the ancestor of all metazoan species. [2][3][4]

PZ Meyers at Talk.Origins Archive [5] writes that the Biogenetic Law as conceived by Haeckel says:

…that development (ontogeny) repeats the evolutionary history (phylogeny) of the organism – that if we evolved from a fish that evolved into a reptile that evolved into us, our embryos physically echo that history, passing through a fish-like stage and then into a reptile-like stage.

Haeckel came under fire for this embryo comparison, for excluding the limb buds of the echidna embryo.

Haeckel came under fire for this embryo comparison, for excluding the limb buds of the echidna embryo.

Haeckel was so convinced of his biogenetic law that he was willing to bend evidence to support it. In 1874, he had claimed that members of all vertebrate classes pass through an identical evolutionarily conserved “phylotypic” stage, which presumably represents the form of their most recent common ancestor. Only later in development would specific differences appear, he said.

In fact, there is a highly conserved embryonic stage among the vertebrate classes; at the late tailbud stage, vertebrate embryos of most all classes possess somites, neural tube, optic anlagen, notochord, and pharyngeal pouches. However, Michael Richardson and his colleagues (1997) [6] discovered significant differences between groups at this stage. For example, in echidnas, limb buds are already present at the tailbud stage, whereas in other species, these are not seen until significantly later.

But in his illustrations of vertebrate embryos, Haeckel deceptively omitted limb buds at an early stage of the echidna, despite the fact that limb buds do exist then, in order to make his vertebrate embryos look more alike than they do in real life. Haeckel’s motive is clear from the text accompanying his drawings: “There is still no trace of the limbs or ‘extremities’ in this stage of development…”. [7]

Near the conclusion of the Brass-Haeckel Controversy [8] of 1908, after months of vociferous and emphatic denial, in the Berliner Volkszeitung published on 29 December 1908, Haeckel apparently admitted he had altered drawings of embryos, as quoted in Haeckel’s Frauds and Forgeries (1915) [9]:

To cut short this unsavory dispute, I begin at once with the contrite confession that a small fraction of my numerous drawings of embryos (perhaps 6 or 8 per cent.) are really, in Dr. Brass’s sense, falsified – all those, namely, for which the present material of observation is so incomplete or insufficient as to compel us, when we come to prepare a continuous chain of the evolutive stages, to fill up the gaps by hypotheses, and to reconstruct the missing-links by comparative syntheses… After this compromising confession of “forgery” I should be obliged to consider myself “condemned and annihilated,” if I had not the consolation of seeing side-by-side with me in the prisoner’s dock hundreds of fellow-culprits, among them many of the most trusted observers and most esteemed biologists. For the great majority of all the figures – morphological, anatomical, histological, and embryological – that are widely circulated and valued in the best text- and handbooks, in biological treatises and journals, would incur in the same degree the charge of “forgery.” All of them are inexact, and are more or less “doctored,” schematised, or “constructed.” Many unessential accessories are left out, in order to render conspicuous what is essential in form and organisation. [ellipsis in original]

The truth is that the development of embryos does not fit into the strict progression that Haeckel claimed, but it has also been shown that ontogeny (development of a fertilized ovum through to maturity) and phylogeny (development of a species over time) are closely related. That is, similar features in embryos of different species often reliably demonstrate that the species share a recent common ancestor. This is nicely summarized by Douglas Theobald online at Talk.Origins Archive [10]:

The ideas of Ernst Haeckel greatly influenced the early history of embryology in the 19th century. Haeckel hypothesized that “Ontogeny Recapitulates Phylogeny”, meaning that during its development an organism passes through stages resembling its adult ancestors. However, Haeckel’s ideas long have been superseded by those of Karl Ernst von Baer, his predecessor. Von Baer suggested that the embryonic stages of an individual should resemble the embryonic stages of other closely related organisms, rather than resembling its adult ancestors. Haeckel’s Biogenetic Law has been discredited since the late 1800′s, and it is not a part of modern (or even not-so-modern) evolutionary theory. Haeckel thought only the final stages of development could be altered appreciably by evolution, but we have known that to be false for nearly a century. All developmental stages can be modified during evolution… [emphasis in original]

'Tree of Life' by Haeckel (1866).

‘Tree of Life’ by Haeckel (1866).

Interestingly, in 1866 Haeckel created the first evolutionary tree to incorporate all life known at the time.

Although a strong supporter and defender of evolution (especially against attacks from religious leaders), Haeckel did not share Darwin’s enthusiasm for natural selection as the main mechanism for generating the diversity of the biological world. Instead, he favored a type of Lamarckism.

According to Jean-Baptiste Lamarck (1744-1829), change in the environment causes change in the behavior of individuals; altered behavior leads to greater or lesser use of a given structure or organ. Use would cause the structure to increase in size over many generations, whereas disuse would cause it to shrink or even disappear, because physical characteristics acquired by parents during their lifetimes are passed along to their offspring. The mechanism of Lamarckian evolution is quite different from that proposed by Darwin, although the predicted result is the same: adaptive change in lineages, ultimately driven by environmental change, over long periods of time.

PZ Meyers explains in his essay why Haeckel was completely wrong:

He argued that evolutionary history was literally the driving force behind development, and that the experiences of our ancestors were physically written into our hereditary material. This was a logical extension of his belief in Lamarckian inheritance, or the inheritance of acquired characters. If the activity of an organism can be imprinted on its genetics, then development could just be a synopsis of the activities of the parents and grandparents and ever more remote ancestors. This was an extremely attractive idea to scientists; it’s as if development were a time machine that allowed them to look back into the distant past, just by studying early stages of development.

Unfortunately, it was also completely wrong.

The discoveries that ultimately demolished the underlying premises of the biogenetic law were the principles of genetics and empirical observations of embryos. Lamarckian inheritance simply does not occur… DNA is the agent of heredity, and it is not modified by our ordinary actions – if you should get a tattoo, it is not also written into the chromosomes of your sperm or ova, and there’s no risk that your children will be born with “Mom” etched on their arm. The discovery that Haeckel had taken unforgivable shortcuts with his illustrations was a relatively minor problem for his theory, because the general thrust of his observations (that vertebrate embryos resemble each other strongly) had been independently confirmed. What really scuttled the whole theory was that its foundation was removed.

Much later, Haeckel attempted to develop a comprehensive philosophical system informed by biological and evolutionary findings. This system was to encompass ethics, theology, psychology, and politics. Some authors claim that Haeckel’s work was later appropriated by the Nazis who used it as justification for their racism and nationalism. [11] Others dispute that claim. Complicating this issue is the fact that, depending on whether you disparage or praise Haeckel, you are often assumed to be either a fundamentalist Christian, opposed to evolution, or an atheist, opposed to morality.

Haeckel’s major works are The History of Creation (1868) and The Riddle of the Universe (1899). Some of the terms he coined are still in use today, including ecology, phylum, phylogeny, and Protista.

References:

  1. E. S. Russell. Form and Function (London: John Murray Ltd., 1916) p. 253.
  2. Ernst Haeckel. Generelle Morphologie der Organismen (Berlin: Georg Reimer, 1867).
  3. —————— Anthropogenie. Third edition. (Leipzig: W. Engelmann, 1879).
  4. S.J. Gould. Ontogeny and Phylogeny (Cambridge, MA: Harvard University Press, 1977).
  5. PZ Meyers. “Wells and Haeckel’s Embryos: A Review of Chapter 5 of Icons of Evolution.” The Talk.Origins Archive. Last modified 6 December 2006. Accessed on 14 July 2013 at http://www.talkorigins.org/faqs/wells/haeckel.html.
  6. Michael K. Richardson, James Hanken, Mayoni L. Gooneratne, Claude Pieau, Albert Raynaud, Lynne Selwood, and Glenda M. Wright. “There is no highly conserved embryonic stage in the vertebrates: implications for current theories of evolution and development.” Anat. Embryol. 196: 91-106 (1997). Accessed on 17 July 2013 at http://www.oeb.harvard.edu/faculty/hanken/documents/Richardson%20et%20al%201997%20Anat%20Embryol.pdf. [Archived here.]
  7. Michael K. Richardson and Gerhard Keuck, “A question of intent: when is a ‘schematic’ illustration a fraud?” Nature 410/6825: 144 (8 March 2001).
  8. “‘MAN-APES’ THE SUBJECT OF A WAR OF SCIENCE; Between Prof. Haeckel and Dr. Brass Rages a Controversy in Which Prehistoric Heads and Tails Are the Fruitful Themes.” The New York Times, 7 February 1909. Accessed on 16 July 2013 at http://query.nytimes.com/mem/archive-free/pdf?res=F30F11F83C5C15738DDDAE0894DA405B898CF1D3.
  9. J. Assmuth and Ernest R. Hull. Haeckel’s Frauds and Forgeries (Bombay: Examiner Press, 1915), pp. 14, 15.
  10. Douglas Theobald, Ph.D. “29+ Evidences for Macroevolution: The Scientific Case for Common Descent. Part 2: Ontogeny and Development of Organisms.” The Talk.Origins Archive. Last modified 17 May 2013. Accessed on 14 July 2013 at http://www.talkorigins.org/faqs/comdesc/.
  11. Daniel Gasman. “From Haeckel to Hitler: The Anatomy of a Controversy.” eSkeptic, 10 June 2009. Accessed on 14 July 2013 at http://www.skeptic.com/eskeptic/09-06-10/#feature. [Archived here.]

February 14-17, 1766 (Friday-Monday)

Title page of An Essay on the Principle of Population

Sometime on these dates, the English demographer and political economist Thomas Robert Malthus was born at Dorking, a place just south of London.

Malthus entered Jesus College, Cambridge, in 1784 and was ordained a minister of the Church of England in 1788. He earned his M.A. in 1791. He is best known for his An Essay on the Principle of Population, which was first published in 1798 and was read by Charles Darwin forty years later. This important essay first identified the geometric role of natural population increase in outrunning subsistence food supplies, prompting Darwin to explore the actual patterns of evolution.