Appendix C: Chronology
Genetics, cytology, and evolutionary biology have received stimulation from both related and quite independent sciences. In many cases, the de- velopment of a particular physical instrument or technique has led to a golden age of discovery. Often research in various areas has advanced in nonsynchronous spurts, and consequently it is difficult to develop courses in genetics, cytology, and evolutionary biology from a strictly historical standpoint. The student, however, should have some idea of the chrono- logical order in which certain events having a bearing on these sciences took place.
The following chronology will fill this need, even though many experts will complain about the inclusion of some events and the omission of others. Furthermore, a decade from now some of the recent discoveries may be relegated to less prominent positions. The student should keep the following thought in mind when perusing this catalog. In science, a great unifying concept generally does not spring full-blown from the mind of a single individual. Rather, when the time is ripe, perhaps a dozen authori- ties may grope about for an explanation, and all may be on the verge of the answer.
However, often one scientist may first express the unifying concept in a clear fashion, and as a matter of convenience he or she is the one listed as the progenitor of the idea. Recently, more and more papers, reporting the work of international teams of scientists, have appeared. For example, the entries between 1989 and 1996 that describe the cloning of different human genes refer to 14 reports with an average of 25 authors each.
The entries listed between 1995 and 2004 that describe the genomes of 25 different prokaryotes have an average of 54 authors each. The consortium that sequenced the Caenor- habdites genome in 1998 contained 407 scientists! Space limitations pre- vent us from listing more than three authors in each new entry, and there- fore we regret that a large fraction of the scientists participating in such team projects fail to get the credit they deserve.
1590 Z. and H. Janssen combine two double convex lenses in a tube and produce the first compound microscope.
1651 W. Harvey puts forward the concept that all living things (including man) originate from eggs.
1657 R. de Graaf discovers follicles in the human ovary, but interprets them incorrectly as eggs.
1665 R. Hooke publishes Micrographia, in which he gives the first description of cells.
1668 F. Redi disproves the theory of spontaneous generation of maggots.
1673 A. van Leeuwenhoek sends the first of a series of letters to the Royal Soci-ety of London describing his observations with homemade microscopes.
This correspondence continues for 50 years. He is the first to see “animal- cules” (bacteria and protozoa) and red blood cells of humans and other mammals. Later he described human spermatozoa and those from arthro- pods, molluscs, fishes, birds, and other mammals.
1694 J. R. Camerarius conducts early pollination experiments and reports the existence of sex in flowering plants.
1735 C. V. Linne´ publishes the first edition of the Systema Naturae.
Sixteen editions of this taxonomic work are completed during his lifetime.
It is the 10th edition of this book (published in 1753) that serves as the starting point for the modern scientific naming of animals, as his Species Plantarum is for plants.
Linne´ originated the “Linnean” system of binary nomenclature used to this day.
His insistence on the constancy and objective classification of species posed the problem of the method of the origin of species. Linne´ invented the names that are used to this day for about 7,700 plant and 4,400 animal species, including Homo sapiens. C. Linne´ was granted nobil- ity in 1741, becoming Carl von Linne´(C. V. Linne´), and he also used the Latinized form of his name (Carolus Linnaeus).
1761-67 J. G. Kolreuter carries out crosses between various species of Nicotiana and finds that the hybrids are quantitatively intermediate between their parents in appearance.
The hybrids from reciprocal crosses are indistinguishable.
He concludes that each parent contributes equally to the characteristics of the offspring.
1769 L. Spallanzani demonstrates that the “spontaneous generation” of microor- ganisms in a nutrient medium can be prevented, provided the vessel is sealed and subjected to the temperature of boiling water for 30 minutes or more.
In 1780 he performs artificial insemination experiments with am-phibians and demonstrates that physical contact of the egg with spermatic fluid is necessary for fertilization and development.
1798 T. R. Malthus publishes anonymously An Essay on the Principle of Popula-
tion. This essay subsequently influences the thinking of both Charles Dar-win and Alfred Russel Wallace and leads them to the concept of natural selection.
Edward Jenner publishes An Inquiry into the Causes and Effects of the Vario-lae Vaccinae, a Disease Discovered in Some of the Western Countries of En- gland. Particularly Gloucestershire and Known by the Name of Cow Pox.
In it he gave the first account of vaccination with cowpox virus to prevent
smallpox. He thus establishes the principle of active immunization and ini- tiates the science of immunology.
1809 J. B. de Monet Lamarck puts forward the view that species can change
gradually into new species through a constant strengthening and perfecting of adaptive characteristics, and that these acquired characteristics are trans-mitted to the offspring.
1818 W. C. Wells suggests that human populations in Africa have been selected for their relative resistance to local diseases. He is thus the first to enunci- ate the principle of natural selection.
1820 C. F. Nasse points out that hemophilia occurs only in males, but is passed on by females, who themselves are not bleeders. The phenomenon is now called sex linkage.
1822 E. G. Saint-Hilaire suggests that the chordate body plan arose by inverting the dorsoventral axis of an ancestor whose body plan resembled that of arthropods.
1822-24 T. A. Knight, J. Goss, and A. Seton all independently perform crosses with the pea and observe dominance in the F1 and segregation of various heredi- tary characters in the F2. However, they do not study later generations or determine the numerical ratios in which the characters are transmitted.
1825 F. V. Raspail founds the science of histochemistry by using the iodine reac- tion for starch.
J. E. Purkinje discovers the germinal vesicle in the avian egg.
1827 K. E. von Baer gives the first accurate description of the human egg.
1830 G. B. Amici shows that the pollen tube grows down the style and into the ovule of the flower.
1831 R. Brown coins the name nucleus for a structure he observes within each of the cells of an orchid.
On December 27, H.M.S. Beagle sets sail from Plymouth for a voyage around the world. It carries as naturalist the 22-year-old Charles Darwin.
1835 The Beagle reaches the Galapagos Islands, on September 15, and Darwin spends five weeks surveying the plant and animal life.
1837 Darwin realizes, after he and other experts go over the collections from the Galapagos, that many species are unique to various islands. This sug- gests that the islands were colonized by a few species from the mainland, and from these evolved new species specialized to live on each of the many new environments provided. These conclusions stimulated Darwin to start accumulating data to support a theory of evolution through natural selec- tion. He makes a diagram of an evolutionary tree in his First Notebook on Transmutation of Species.
Hugo von Mohl provides the first description of chloroplasts (chlorophyll- kornen) as discrete bodies within the cells of green plants.
1838 The word protein first appears in the chemical literature in a paper by G. J. Mulder. The term, however, was invented by J. J. Berzelius.
1838-39 M. J. Schleiden and T. Schwann develop the cell theory. Schleiden notes nucleoli within nuclei.
1839 J. E. Purkinje coins the word protoplasm.
1841 A. Kolliker shows spermatozoa to be sex cells that arise by transformation of cells in the testis.
1845 J. Dzierzon reports that drones hatch from unfertilized eggs, worker and queen bees from fertilized eggs. R. Remak concludes that cell rearrangements early in vertebrate gastrulation lead to the formation of three specific tissue layers, which he names ectoderm, mesoderm, and endoderm.
1855 A. R. Wallace accumulates evidence in favor of geographical speciation during his studies of the fauna of the Malay Archipelago. He is led to doubt the dogma of the constancy of species and begins to develop a theory of evolution identical to Darwin’s. R. Virchow states the principle that new cells come into being only by division of previously existing cells.
1856 Gregor Mendel, a monk at the Augustinian monastery of St. Thomas in Bru¨nn, Austria (now Brno, Czechoslovakia), begins breeding experiments with the gar- den pea, Pisum sativum.
1858 Essays by Darwin and Wallace, which contain the theory of evolution based upon natural selection, are communicated to the Linnean Society of London at its June meeting and published in the next issue of the society’s journal.
1859 Darwin publishes On the Origin of Species.
A. R. Wallace, after studying the zoogeography of the Malay peninsula, points out that a line can be drawn defining the zone of contact between two distinct terrestrial biotas. To the east of the Wallace line the fauna is Australian, and to the west the fauna is Oriental.
1860 T. A. E. Klebs introduces paraffin embedding.
1861 L. Pasteur discovers that certain microorganisms can flourish in the absence of oxygen and that some are even poisoned by it. He postulates subsequently that fermentation is the method used by microbes like yeast to derive energy from sugar under anaerobic conditions.
1864 L. Pasteur demonstrates that air-borne microscopic bacteria and mold spores can infect sterile nutrient cultures. His essay that disproves “spontaneous gener- ation” inaugurates a new epoch in bacteriology.
1865 Gregor Mendel presents the results and interpretations of his genetic studies on the garden pea at the Bru¨nn Society for the Study of Natural Science at their monthly meetings held February 8 and March 8.
1866 G. Mendel’s Versuche u¨ber Pflanzenhybriden (Experiments on Plant Hybridiza- tion) is published and ignored.
E. Metchnikoff proposes that the pole cells of the insect embryo are the precur- sor cells of the oocyte and nurse cells.
1867 W. Waldeyer publishes the first histologic study of a developing human cancer. He describes how breast cancer develops as a localized proliferation of glandu- lar cells. They then invade adjacent tissue and reach nearby blood vessels. From here they spread throughout the body via the lymphatic and circulatory sys- tems.
1868 T. H. Huxley concludes from a study of the first specimen of Archaeopteryx that it represents the most reptilian bird, a link between flightless feathered birds and the dinosaurs.
1869 D. I. Mendeleev constructs the earliest periodic table of elements. F. Galton publishes Hereditary Genius. In it he describes a scientific study of human pedigrees from which he concludes that intelligence has a genetic basis. A. R. Wallace publishes The Malay Archipelago, the Land of the Orangutan and the Bird of Paradise. In it he reveals that the animals on the Maylay Archipelago are divided into two groups; the western species are similar to the animals found in India, and the eastern species resemble the animals of Australia.
1870 W. His invents the microtome.
1871 F. Miescher publishes a technique for the isolation of nuclei and reports the discovery of nuclein (now known to be a mixture of nucleic acids and proteins). Charles Darwin publishes The Descent of Man and Selection in Relation to Sex. In it, the theory of sexual selection (i.e., selection at mating) is first enunciated.
1872 J. T. Gulick describes variations in shell coloration among natural populations of land snails living in valleys of Oahu. He suggests that geographical isolation of small populations of such animals may be a necessary prerequisite to the formation of new species.
1873 A. Schneider gives the first account of mitosis.
1874 C. Dareste draws attention to the distinction between monozygotic and dizy- gotic twins.
1875 F. Galton demonstrates the usefulness of twin studies for elucidating the rela- tive influence of nature (heredity) and nurture (environment) upon behavioral traits. O. Hertwig concludes from a study of the reproduction of the sea urchin that fertilization in both animals and plants consists of the physical union of the two nuclei contributed by the male and female parents. E. Strasburger describes cell division in plants, and later (1884) coins the terms prophase, metaphase, and anaphase.
1876 O. Bu¨tschli describes nuclear dimorphism in ciliates. A. R. Wallace publishes The Geographical Distribution of Animals in which he describes the distinctive fauna which characterize the six zoogeographic realms of the earth. W. F. Ku¨hne discovers trypsin in pancreatic juice and coins the term enzyme.
1877 H. Fol reports watching the spermatozoan of a starfish penetrate the egg. He was able to see the transfer of the intact nucleus of the sperm into the egg, where it became the male pronucleus. He coins the term aster. E. Abbe begins to publish important contributions to the theory of microscopic optics. R. Koch develops the method used to this day for obtaining pure cultures of bacteria. L. Pasteur and his coworkers perform experiments (between 1877 and 1888) that prove that specific bacteria and viruses are the primary causes of various diseases that plague both domesticated animals and humans.
1879 W. Flemming studies mitosis in the epithelium of the tail fin of salamanders. He shows that nuclear division involves a longitudinal splitting of the chromo- some and a migration of the sister chromatids to the future daughter nuclei. He also coins the term chromatin.