THE EVOLUTION OF ORGANIC EVOLUTION By Edward L. Crisp, Ph.D.

 

INTRODUCTION

• The ancients Greeks had some thoughts on evolution (but not much was passed on to later generations).
• During the Middle Ages, and even from the time of Aristotle, not much thought on organic evolution.
• In fact, Aristotle believed that species were fixed (immutable) and cound not change.
• Also, traditional interpretations of the bible (particularly during the Dark Ages and Middle Ages and prior to the 1700's) stressed the immutability of species.
• During the 1700s attitudes toward organic evolution started to change (at least by some naturalist).
• Erasmus Darwin (1731-1802) (Charles Darwin's grandfather) was the first to actually propose an idea of gradual evolution of organisms.
• Jean Baptist de Lamarck (1744-1829) - Botanist and geologist.  Lamarck proposed the "Inheritance of Acquired Characteristics" and was the first person who was taken seriously relative to concepts of organic evolution.  Giraffe example:  the giraffe's neck became longer with time because the parents stretched their neck to get the higher leaves, and the longer necks were passed on to the next generation, etc.  Actually, not too crazy an idea for his time, remember there was no concept of genetics then..

CHARLES DARWIN AND ALFRED RUSSEL WALLACE

• Charles Darwin (1809-1882) and Natural Selection -  From: The C. Warren Irvin, Jr., Collection of Charles Darwin and Darwiniana at http://www.sc.edu/library/spcoll/nathist/darwin/darwin.html (this is a nice website, it would be worth your time to visit this website).
  •      Charles Darwin, an English naturalist (GO TO THIS SITE TO READ ABOUT DARWIN), conceived many of his ideas on organic evolution while serving as a naturalist (1831-1836) on the British ship, the HMS Beagle.  Darwin first published his book Voyage of the Beagle in 1839, with the popular version in 1845.  In this publication, Darwin demonstrated that evolution had occurred in the past and was still occurring in his time.  His study of the different adaptations of finches on the Galapagos Islands is a classic.  However, after returning from his voyage on the HMS Beagle, and for many studious years following, Darwin still did not have an acceptable mechanism for evolution.  However, by about 1838, based on his studies of domestic breeding (artificial selection) and the reading of an essay by Thomas Malthus on population growth, Darwin was starting to formulate his ideas on natural selection (even though he still did not know how traits were actually transmitted and retained in a population of interbreeding organisms)
  • .
  • Alfred Russel Wallace (1823-1913)
  • (From:  Alfred Russel Wallace (1823 - 1913) is one of the forgotten fathers of modern science http://www.iol.ie/~spice/alfred.htm)
  •      During the summer of 1858, Alfred Russel Wallace (also an English naturalist), then on a collecting expedition in Indonesia, wrote a note to Darwin outlining his ideas on a mechanism for evolutionary change, the mechanism being "NATURAL SELECTION BY MEANS OF SURVIVAL OF THE FITTEST".  Darwin was shocked, he had been thinking along the same lines himself and now it appeared that Wallace was going to publish his ideas before Darwin could publish.  At the urging of Charles Lyell and Joseph Hooker, friends of Darwin and fellow members of the prestigious Linnaean Society of London, it was arranged for Darwin and Wallace to independently present papers at the same session of the Linnaean Society in 1858, outlining their ideas on evolution by means of natural selection.  Darwin published his famous On the Origin of Species by Means of Natural Selection (usually shortened to The Origin of Species) the following year, 1859.  (An online version of Origin of Species is located at this website: Online Literature Library - Charles Darwin - The Origin of Species ).  (Another website that you may find interesting, and which discusses evolution, is my Paleobiology of Dinosaurs site at:  GEOLOGY 307. Check out parts of lectures 2, 3, and 4).
  •      Darwin believed that natural selection was a very gradual process involving natural selection and minute mutations which were advantageous to the organism.  Many followers of Darwin today (Neodarwins) also believe in gradualistic evolution.  However, fairly recently several noted paleontologists and evolutionary biologists have questioned gradualism and have proposed that evolution may have occurred by "jumps and leaps" followed by very slow evolutionary change for long periods of geologic time.  This concept, known as the Punctuated Equilibrium Model of Evolution, has spread rapidly in scientific circles since Stephen Gould of Harvard University and Niles Eldridge of the American Museum of Natural History published several articles on the subject in 1971 and 1972 (Gould and Eldridge have enhanced ideas orginally suggested by Ernest Mayr of Harvard in the 1950s and 60s).  Steven Stanely, of John Hopkins University, is also an adament disciple of the Punctuated Equilibrium Model and preaches the theory eloquently in his book The New Evolutionary Timetable...Fossils, Genes, and the Origin of Species (1981).

THE DARWIN-WALLACE MODEL OF ORGANIC EVOLUTION BY NATURAL SELECTION

• 1.  There is natural variation among the individuals of a population of a given species.  This variation controls characteristics such as color (like flower color), size, shape, and many other morphologic and physiologic characteristics.  Darwin and Wallace were not aware of genetics, but they assumed that characters must be controlled by traits within the organisms that could be transmitted to the offspring (i.e., the traits were inheritable).
• 2.  Certain variations are more beneficial to the organism than others and those variations will give the organisms that have them a selective advantage in the stuggle for existence.
• 3.  Most organisms produce many more offspring than can survive to maturity.  Of course this is to help ensure that some of the offspring have the beneficial variations that will allow them to reach maturity.
• 4.  Those individuals of a population that have the more beneficial variations are the ones most likely to survive to sexual maturity and pass on their favorable combinations of variable characteristics.
• How would Darwin and Wallace explain the evolution of a long neck in the giraffe?
• Note:  After publishing The Origin of Species, Darwin did not argue for his theory.  He left that
• to others, most notable Thomas Henry Huxley (1825-1895) ("Darwin's Bulldog"). (Check out his site relative to Huxley: Thomas Huxley , 
• and this one: Huxley From Devil's Disciple to Evolution's High Priest - Adrian Desmond )  Of course Darwin's book made a real stir in Victorian England.