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Which species is the most highly evolved?

EVOLUTION is defined as change over time.

ORGANIC EVOLUTION is the genetic (and phenotypic) change of living organisms over time.

  • The universe is thought to be about 10-20 billions years old.
  • Our solar system, along with earth - 4.5 billions years old
  • Life on earth first appeared approximately 4 billion years ago, with proto-humans (genus Homo) first appearing in the fossil record of the Pleistocene (about 1.8 million years ago) and humans (species Homo sapiens first showing up about 500,000 - 300,000 years ago. Modern humans (species Homo sapiens sapiens showed up around 150,000 years ago.)
    Before humans were even aware that we had been around that long, they were already trying to figure out where we had come from, and they had all sorts of creative ideas about the origins of life.

  • As long ago as 500 B.C, Greek philosophers were already toying with the idea that life was constantly changing. However, the most influential of these, PLATO and his student, ARISTOTLE, believed in an unchanging world in which all species had been created in a perfect state, with perfect interactions intact. In such a world, evolution would be counterproductive, and against the plan of The Creator.

  • The Old Testament account of The Creation fortified this idea, and even as recently as the 1700's, biology was done in a framework of natural theology--the idea that science should be dedicated to studying nature in order to figure out the Grand Plan of the Creator.
  • The early idea that living organisms could "spring" from non-living material, fully formed, is termed SPONTANEOUS GENERATION. (e.g., maggots from rotting meat; lice from sweat; eels from sea mud, etc..)

  • In 1668, FRANCESCO REDI, an Italian physician performed experiments designed to test this idea.

  • He placed rotting meat in covered and uncovered jars, and noted that maggots formed only in the uncovered jar. ("Hey! Maggots must be fly larvae!")

  • In 1676, Dutch scientist ANTON VAN LEEUWENHOEK invents the microscope, revealing a microscopic world of wigglies. Once again, interest in spontaneous generation was revived (though on a "smaller scale")
  • In the late 1700's - LAZARO SPALLANZANI performed an experiment designed to test the spontaneous generation of microorganisms. (He boiled broth in flasks, and left one covered,one uncovered; only the uncovered one produced microorganisms.)

    However, his experiments were discounted because...

  • In 1862, LOUIS PASTEUR convinced the doubting scientific community with his elegant Swan Neck flask experiments.

  • In the late 1700's, French scientist JEAN BAPTISTE LAMARCK was studying the fossil record and living organisms, and concluded that evolution was driven by the sentiments interieurs ("felt need") of organisms.
  • Also in the late 1700's, a French anatomist named GEORGE CUVIER was developing the science of Paleontology, the study of fossils.

  • Surprise! All the Early European scientists were creationists who believed that the world was made in seven days by a Supreme Being.

  • And among these creationists was a young student named Charles Darwin.) Who was this man called Darwin? Where did his ideas come from? To understand a bit more, let's look at the historical context of his work.

    People already knew about ARTIFICIAL SELECTION (humans breeding animals and plants for desired characteristics). Why should nature not operate in a similar way?

    The stage was set for the Darwininan Revolution!

    A tale of Charles Darwin.

    1809 - Darwin born in Shrewsbury, England From the very start, he loved bugs n slugs, and spent most of his time outside or reading nature books.

    His dad, a famous physician, thought that no good life could await a naturalist, and so sent young Charles, at the age of 16, off to the University of Edinburgh medical school. HATED IT.

    Dropped out after making mediocre grades

    Enrolled at Christ College at Cambridge University with plans to become a clergyman. (This isn't as weird as it sounds, since most scientists of his day were members of the clergy!)

    He fell in with the biologists and became the star pupil of Rev John Henslow, Professor of Botany.

    1831 - with the help of Darwin's uncle, Henslow convince both Captain Robert Fitzroy of H.M. S. Beagle and Darwin's dad to let Charles go on the 5-year Beagle voyage as "unpaid gentleman scholar and naturalist."

    So at the age of 22, Darwin set sail. While the Beagle's crew mapped South American coastlines, he went ashore and collected every living things he could lay his hands on.

    1836 - Darwin returned to England, settled down and got married and wrote up all his work.

    1858 - Darwin was nearly scooped by Alfred Wallace, a young British scientist studying plants in Malaysia. (Alarmed at Darwin's failure to publish his ideas, his friend Charles Lyell had warned him about this possibility!)

    Lyell and some colleagues presented both Wallace's and Darwin's work at the meetings of the Linnaean Society of London on July 1, 1858. Wallace's and Darwin's ideas were identical, but Darwin's had been written first, and with much more completeness than Wallace's. Today, Darwin is given credit as the Father of the Theory of Evolution by means of Natural Selection.

    Darwin made some profound observations, from which he inferred some brilliant conclusions...

    SO WHAT IS THIS THEORY OF NATURAL SELECTION, ANYWAY? It can be broken down into four basic tenets, or ideasS Note that EVOLUTIONARY FITNESS is nothing more and nothing less than DIFFERENTIAL REPRODUCTION due to organisms' differing abilities to cope with environmental limitations.

    The popular phrase "survival of the fittest" that's often ascribed to Darwin was a phrase originally used by Herbert Spencer, (27 April 1820 - 8 December 1903) an English philosopher, in his 1851 work Social Statics. (The phrase was later used by Social Darwinists, but that's another story.) The phrase "survival of the fittest", when applied in the colloquial sense, is not truly meaningful when applied to Darwin's theory.

    The fittest organisms are those that leave the most genes to the next generation, nothing more and nothing less. Survival doesn't always ensure fitness, and fitness doesn't always ensure survival.

    Any trait exhibited by an organism may be

    A trait can be classified into one of these three categories only in the context of the environment in which the organism exists. Hence, evolutionary fitness is determined by the environment, and organisms are selected to "fit" the environment in which they forage, seek mates, escape predators, destroy pathogens, etc.

    A SPECIES is a group of similar organisms that can mate to produce fertile, viable offspring. Different species are, by definition, REPRODUCTIVELY ISOLATED from one another.

    Scientists who study the processes and mechanisms that lead to such speciation events are EVOLUTIONARY BIOLOGISTS.
    Over the course of the next few weeks, we will be studying Zoology in the context of Evolution, the change in genetic composition of populations over time.

    To understand a little more about how evolution works, let's refer to this GENETICS PRIMER.

    Genetics is only one area of BIOLOGY, and like all other areas of biology, it is a NATURAL SCIENCE.

    The Natural Sciences (Physics, Chemistry, Biology, Geology, etc.) are all governed by the necessity of their adherents to utilize

    The Scientific Method add to the knowledge of their field.

    The Scientific Method is a precise set of rules followed by researchers/investigators in the natural sciences.

    The difference between a Miracle and a Fact
    is exactly the difference between a mermaid and a seal.

          -- Mark Twain
    As eminent German philosopher Karl Popper wrote in his famous essay, Science as Falsification, it is vulnerability to falsification--not constant verification--that is the mark of truly powerful theory.

    The Scientific Method consists of the following steps...

    "The process known as the Scientific Method outlines a series of steps for answering questions, but few scientists adhere rigidly to this prescription. Science is a less structured process than most people realize. Like other intellectual activities, the best science is a process of minds that are creative, intuitive, imaginitive, and social. Perhaps science is distinguished by its conviction that natural phenomena ,m including the processes of life, have natural causes--and by its obsession with evidence. Scientists are generally skeptics." (from Biology by Neil A. Campbell

    So don't confuse The Scientific Method with Science, in general. And also note that if something is outside the realm of scientific testability, the wise scientists will not presume that it is not true, or that it does not exist. It is simply outside the realm of Science, and may not be answerable with the Scientific Method.

    As we tour through the scientific discoveries of genetics this semester, recall a couple of definitions (that will serve you well in your own fields, too!):

    A common theme in scientific endeavors is the use of HYPOTHETICO-DEDUCTIVE reasoning: The formulation of hypotheses (a tentative answer to a question) and the execution of experiments from which one may deduce a general answer to the hypothesis.

    Important aspects of hypotheses...

    The only part of Darwinian thought that's "theoretical" is that evolution has occurred by means of natural selection. Scientists do not question that evolution has occurred (all physical evidence clearly says that it has), but only how it has occurred. And Darwin's hypothesis was that it has occurred by means of NATURAL SELECTION.

    Also remember that in science, the term THEORY has a very precise meaning that is quite different from the colloquial use of the term.

    A THEORY is an hypothesis whose predictions have stood up to thorough and rigorous testing with experiments and observations. Such has been the case with Darwin's hypothesis, and so it has been elevated to a THEORY.

    Still, neither a hypothesis nor a theory can be "proven" with the scientific method, and a good scientist refuses to let even the most powerful theory become DOGMA (something held as an established, unquestioned opinion). New evidence should always be examined with an open mind, as even a powerful theory is always subject to modification and revision.

    (Note: A theory that is ultimately proven to hold true in all cases becomes a LAW. There are very few laws in natural science, most of them in Physics, such as the Laws of Thermodynamics.)