From
the time of ancient Greeks to the early Christian era, concepts of evolution
were openly discussed. This dialog ended during the Middle Ages and was
replaced by the dogma of Biblical scriptures, including the fixed and
unchanging nature of living organisms since creation. With the discovery and
mounting accumulation of fossils in the 1700s, a number of prominent
naturalists began questioning whether life-forms were fixed since creation or
had evolved.
Although
the theory of the inheritance of acquired characteristics is inextricably
linked to Lamarck, it was first explored by the ancient Greeks and expanded by
a leading eighteenth-century intellectual, Erasmus Darwin, grandfather of
Charles, in his two-volume Zoonomia (1794–1796). Here, the Earth’s age was
described in millions of years, in contrast to Irish Bishop Ussher’s 1654
calculation that creation was in 4004 BCE.
Jean-Baptiste
Lamarck was a soldier in the French army, an acclaimed botanist, and, in his
time, the foremost expert on invertebrates (a term he coined). In his most
famous work, Philosophie zoologique (1809), he argued that rather than living
beings evolving from a series of successive catastrophies and recreations,
there were gradual alterations. He theorized that as the environment changed,
organisms needed to change to survive. If a body part was used more than
previously, that part would increase in size or strength during its lifetime
with the enhancement transmitted to the offspring. So, for example, if a
giraffe stretched its neck to reach higher leaves, its neck would increase in
length. Its progeny would inherit the longer neck and, with continued
stretching, would make it still longer over generations. Similarly, he
contended that wading birds would have evolved long legs by stretching them to
remove their bodies from water. By contrast, disused body parts would shrink
and disappear, thus explaining how snakes lost their legs.
Long
before his death, Lamarck’s theory was challenged and rejected by religious and
scientific communities; he died blind, in poverty, and seemingly unremembered.
More recently, Lamarckism has been reexamined in terms of epigenetics, where
traits are inherited by mechanisms not involving genes.
No comments:
Post a Comment