Encyclopedia of Evolution.pdf - Online Reading Center

complex organisms came into existence only later. This is
abundantly demonstrated by the fossil record (although this
could not be the case if the fossils were the products of a single
gigantic flood; see creationism). The controversy is over
whether this pattern should be called “progress.” Is progress
simply something that happened to occur, or is it something
that had to occur? That is, is progress a side effect, or is it a
process? Progress has been recognized in both the complexity,
and the diversity, of organisms.
Progress as a process within evolution. The concept that
progress is part of the process of creation predates evolution.
Catastrophists (see catastrophism) believed in a series
of creations in which each new era had more complex and
diverse organisms than the previous era. With the ascendancy
of evolutionary science, the notion of progress, as a necessary
and built-in process, was not abandoned. Some people (see
Spencer, Herbert) assumed that evolutionary change had to
be progressive. This notion has been perhaps best characterized
in the 20th century in the writings of philosopher-scientists
Henri Bergson, Pierre Teilhard de Chardin (see Teilhard
de Chardin, Pierre), and Pierre Lecomte du Noüy.
When evolutionary scientists began to understand how
the process of evolution actually worked (see modern synthesis),
they could find no mechanism that could generate
inevitable progress. Henri Bergson wrote that there was a
mysterious “life force” (élan vital) that caused evolutionary
progress. In a famous retort, evolutionary biologist Julian
Huxley (one of the architects of the Modern Synthesis; see
Huxley, Julian S.) said that someone who knew nothing
about engines might assume that a train running on its tracks
was propelled by a mysterious “élan locomotif.” Although
the concept keeps coming back in some popular writings,
evolutionary scientists have abandoned progress as a process,
simply because nobody can think of how such a process could
actually occur on the molecular level.
Progress as a result of evolution. Most observers will
admit the overall pattern of progress that has resulted from
evolution. However, they attribute this to natural selection
acting upon random variation. It occurs because there
are more ways for evolutionary diversification to produce
greater complexity than there are ways for it to produce
greater simplicity; that is, there are more possible complexities
than there are simplicities. Paleontologist Stephen Jay
Gould strongly denounced the concept of progress, claiming
that life today, as it has been for the last three and a half
billion years, is dominated by the bacterial mode (see bacteria,
evolution of). Bacteria constitute the overwhelming
share of the mass, diversity, and history of life. Complexity
has evolved in multicellular organisms, against this bacterial
background. This has occurred by means of what he called
the “drunkard’s walk,” in which random stumbling results in
progress because the drunkard bounces off of one wall and
keeps going but can no longer continue if he falls into the
gutter. What scientists call progress has resulted not so much
from an increase in the mean level of complexity, as from an
increase in the variance of complexity, with one direction (the
direction of simplicity) truncated. Most observers believe that
Gould was making a distinction without a difference; what
promoter
Gould described is, in fact, what most evolutionary scientists
would call progress that has resulted from natural selection
acting on random variation.
Some evolutionary scientists have claimed that progress
is an inevitable product of evolution. A recent example
of this is Simon Conway Morris, a British paleontologist
who figured prominently in the interpretation of Cambrian
fauna (see Burgess shale). He claimed neither miraculous
creation nor a mysterious élan within evolutionary history.
He pointed out that progress has occurred because there
are only a certain number of evolutionary pathways that
will work. Because light provides a good source of information
about the environment, it is no surprise that vision,
even acute vision with complex eyes, will evolve over and
over during evolutionary history. The evolution of complex
eyes from simple eyespots is progress, but it has resulted,
over and over again in separate lineages, because natural
selection has favored it in each case. Another example he
provides is the evolution of intelligence: It has evolved separately
in hominins and cetaceans, because natural selection
has favored it in both cases, and evolved separately in Homo
sapiens and Homo neanderthalensis, for the same reason (see
intelligence, evolution of; Homo sapiens; Neandertals).
Progress is inevitable, because natural selection has
caused a convergence of adaptation upon a relatively small
number of workable solutions to problems of survival (see
convergence). As a result, wherever life may have a chance
to evolve for a long time in the universe, Conway Morris
claims, it is inevitable that something resembling a human
being would come into existence.
Evolutionary scientists will continue to study the processes
by which complex adaptations have evolved and converged,
regardless of whether the result of such processes is
eventually considered to be progress or not.
Further Reading
Bergson, Henri. Creative Evolution. Translated by Arthur Mitchell.
New York: Henry Holt, 1911. Reprint, New York: Dover, 1998.
Conway Morris, Simon. Life’s Solution: Inevitable Humans in a
Lonely Universe. London: Cambridge University Press, 2003.
Dixon, Dougal. After Man: A Zoology of the Future. New York: St.
Martins, 1981.
du Noüy, Pierre Lecomte. Human Destiny. New York: Longmans,
Green and Co., 1947.
Gould, Stephen Jay. Full House: The Spread of Excellence from Plato
to Darwin. New York: Harmony Books, 1996.
Ruse, Michael. Monad to Man: The Concept of Progress in Evolutionary
Biology. Cambridge, Mass.: Harvard University Press,
1996.
Teilhard de Chardin, Pierre. The Phenomenon of Man. New York:
Harper, 1959. Reprint, New York: Harper Perennial, 1976.
Ward, Peter, and Alexis Rockman. Future Evolution: An Illuminated
History of Life to Come. New York: Henry Holt, 2001.
promoter A promoter is a position on a chromosome that
indicates the beginning of a gene. A gene is the DNA that
instructs the cell how to make one or more proteins or protein
components (see DNA [raw material of evolution]).