Biological Anthropology as an Evolutionary Science

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Biological Anthropology as an Evolutionary Science

• Biological anthropology, like other life
  sciences, is founded on the mechanisms and
  operation of evolution.
• Without an appreciation of how evolution
  operates, it is difficult to understand how
  humans developed and appreciate the diversity of
  modern human biology.

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Evolutionary Background

• All life is related, via evolution, to the first
  life forms on earth. It is reasonable to believe
  that the earth and its physico-chemical makeup
  are responsible for the origins and subsequent
  evolution of all earthly life.
• Evolution represents change though there are
  many ways of characterizing this process, here it
  will be viewed as descent with modification.

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Evolutionary Background

• Although there is an abundance of evidence
  supporting the reality of evolution, there is
  still much debate about the precise mechanisms
  responsible for evolutionary change, and the
  relative importance of these mechanisms in
  explaining the diversity and patterning of
  earthly life.

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Background to the Emergence of Evolutionary Theory

• The Beginnings of Scientific Geology
• An unchanging world versus a world in constant
  change.
• Changing views of the origin and development of
  the planet.
• Fossils as time markers.
• Charles Lyell (1797-1875) Uniformitarianism

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The Earth becomes much older

• The action of uniform natural processes on the
  topography of the planet
• Uniform deposition of sediments and the
  relationships to animal fossils.
• Seriation of sediments and the visualization of
  earth history.
• Attempts at absolute dating of the origins of the
  planet.

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Linnaeus Bringing Order to the Living World

• Linnaeus (1701-1778), a Swedish botanist.
• the 18th Century, a time of great voyages, with
  many new animals and plants introduced in Europe.
• A need to systematize nature, to bring order to
  the living world.
• A need to provide names to animals and plants
  that would be universally recognized.

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The Linnaean System

• A system to bring order to the living world with
  the following features
• hierarchical placement of animals into a series
  of descending categories based on shared
  biological features.
• use of the Binomial System of nomenclature, with
  each animal receiving a genus and species name
  (i.e. Homo sapiens).

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Cuvier and Catastrophism

• Baron Georges Cuvier (1769-1832), a French
  natural historian, often seen as the founder of
  the science of comparative anatomy.
• Viewed the living world as having undergone a
  series of catastrophes, with each one totally
  destroying the previous life forms.
• Viewed animal species as fixed and unchanging
  over time.
• The development of the comparative method in
  assessing relationships amongst animals.
• The recognition of extinct life.

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Lamarck The Inheritance of Acquired Characters

• Baron Jean Baptiste de Lamarck (1744-1829), was a
  French natural historian.
• He recognized the relationship between an
  animals biology and its way of life an animal
  was adapted to its pattern of existence.
• He thought that animals change their biology each
  generation as a result of how they interact with
  their environment.

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Charles Darwin the Recognition of Natural
Selection

• Charles Darwin (1809-1882), British natural
  historian and co-developer, with Alfred Russell
  Wallace (1823-1913), of a theory of evolution
  based on the concept of Natural Selection.
• Darwin participated in a five year voyage of
  exploration during which he made observations of
  the natural world which led to his theory of
  evolution.

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The Theory of Evolution

• Darwin presented his theory of evolution, and the
  considerable evidence he had amassed to support
  it, in The Origin of Species, 1859.
• In this book, Darwin avoided all mention of
  humans, except for a cryptic sentence on the last
  page Much light will be thrown on the origin of
  man and his history.

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Humans in the Evolutionary World

• In 1863, British anatomist Thomas Henry Huxley
  (1825-1895) published his famous defense of
  evolution Evidence as to Mans Place in Nature.
  Using the comparative gross anatomy of humans and
  the African apes (chimpanzees and gorillas), plus
  the very few human fossils known at the time,
  Huxley documented the evidence for the placing
  humans in an evolutionary world.
• In 1871, Darwin published The Descent of Man, in
  which he too explored the meaning and
  implications of human evolution.

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Criticisms of Darwinian Evolution

• By the time of Darwins death in 1882, The Origin
  of Species had gone through six editions, in
  which Darwin had attempted to answer the most
  serious criticisms of his theory. In spite of
  this, by 1900, Darwinian evolution was no longer
  seriously considered by most biologists.
• Ironically, the most important criticisms, those
  dealing with the ways by which hereditary
  material is transmitted across generations, and
  the origins of new traits, were being answered by
  discoveries in the emerging field of genetics.

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Genetics and Evolution

• The first 30 years of the 20th Century were
  marked by the accumulation of enormous amounts of
  information about genetic processes.
• It was recognized by a number of genetists that
  this information provided the missing answers
  needed to support Darwinian evolution.
• In 1942, Julian Huxley (grandson of Thomas Henry)
  published Evolution, The Modern Synthesis, in
  which genetic research was utilized with
  Darwinian Natural Selection to produce the
  Synthetic Theory of Evolution, or Neo-Darwinism.

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Evolution Now

• In 1949, American scientist G. G. Simpson
  published The Meaning of Evolution, which
  presented the Synthetic Theory of Evolution to a
  wide audience.
• In 1954, J.D. Watson and F. Crick documented a
  model of the structure of the genetic material
  DNA, thus providing the basis for the emerging
  understanding of the molecular basis for genetic
  processes.
• Genetic research continues to provide more
  information about the mechanisms underlying
  evolutionary change.

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Challenges to Current Views of Evolution

• Biologists such as S. J. Gould argue that the
  process of evolution is not slow and gradual, as
  Darwin had indicated, but operates by rapid
  bursts of evolutionary change punctuated by
  longer periods of stasis, when little or no
  change occurred.
• Based on his examination of the fossil record of
  shell fish in geological deposits, Charles Lyell
  said the same thing to Charles Darwin in the
  1840s when Darwin was working on his theory.

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Evolution by Natural Selection

• Founded on three key concepts
• 1. Adaptation
• 2. Reproduction and Mortality
• 3. Variation

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Adaptation

• Animals possess biological attributes that permit
  them to follow a specific way of life.
• Animal species differ in the sorts of biological
  features they possess, and not all herbivorous
  mammals for example, have the same kinds of
  teeth.
• These specific biological features permit animals
  to be adapted to the way of life they follow.

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Reproduction and Mortality

• British naturalist Thomas Malthus (1766-1834) had
  observed that although each generation, most
  animal species produce huge numbers of sex cells,
  fertilized eggs, and young individuals, adult
  population numbers remain more or less the same
  generation after generation.
• Something was killing off the vast majority of
  young in these species before they reached
  adulthood and sexual maturity.

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Variation

• Darwin had observed that animals in a population
  are not identical in appearance but vary in all
  their features.
• It is now known that variation is present in all
  biological features, from genetic materials to
  gross anatomical features like skull shape, size
  of the teeth and limb length.

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Natural Selection

• Darwin argued that in each generation of an
  animal population, the immature individuals are
  born with biological traits that vary in their
  expression.
• Those young whose variations permit them to be
  better able to survive in the way of life
  followed by their species will have a better
  chance to survive adulthood, thus reaching sexual
  maturity.

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Natural Selection 2

• By reproducing, these favored individuals pass on
  their variations to their offspring. In time,
  the species will be characterized by animals with
  these traits.
• In contrast, those animals whose variations are
  not as adaptive will more likely die before
  reproductive maturity, and their variations will
  slowly be reduced in number in the speciesl.

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Evolution by Natural Selection

• Although Darwin called his theory Survival of
  the fittest, most biologists prefer to term it
  Reproduction of the fittest because it is clear
  that what is important is not that the animal
  reach adulthood, but that it reproduce, thus
  passing its adaptive variations on to the next
  generation.