Evolutionary progress

Three billion years ago, life on Earth consisted of single-celled organisms, but now there is a tremendous variety of complex multi-celled creatures. It may seem obvious that there is progress in evolution, but the topic has inspired much controversy. Ruse (1997) argues that many evolutionary theorists have implicitly or explicitly supported the notion of progress in evolution. Gould (1997) argues that there is no progress in evolution.

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History of the idea of evolutionary progress

Prominent historical figures who have championed some form of evolutionary progress include Alfred Russel Wallace, Herbert Spencer, Pierre Teilhard de Chardin, and Henri Bergson. Even Charles Darwin seems to have believed in some form of progress (Darwin, 1859):

[Chapter 10] The inhabitants of each successive period in the world's history have beaten their predecessors in the race for life, and are, insofar, higher in the scale of nature; and this may account for that vague yet ill-defined sentiment, felt by many palaeontologists, that organisation on the whole has progressed.

[Chapter 14] As all the living forms of life are the lineal descendants of those which lived long before the Silurian epoch, we may feel certain that the ordinary succession by generation has never once been broken, and that no cataclysm has desolated the whole world. Hence we may look with some confidence to a secure future of equally inappreciable length. And as natural selection works solely by and for the good of each being, all corporeal and mental endowments will tend to progress towards perfection.

Ruse (1997) presents a detailed and carefully researched survey of the idea of progress in evolutionary biology. He argues that belief in evolutionary progress is still prevalent among evolutionary biologists today, although it is often denied or veiled. Ruse (1997) writes, "A major conclusion of this study is that some of the most significant of today's evolutionists are progressionists, and that because of this we find (absolute) progressionism alive and well in their work." He claims that progressionism has harmed the status of evolutionary biology as a mature, professional science.

Reformulating the question

In examining the issue of evolutionary progress, the first step is to define progress. Ayala (1988) defines progress as "systematic change in a feature belonging to all the members of a sequence in such a way that posterior members of the sequence exhibit an improvement of that feature." He argues that there are two elements in this definition, directional change and improvement according to some standard. Whether a directional change constitutes an improvement is not a scientific question; therefore Ayala suggests that science should focus on the question of whether there is directional change, without regard to whether the change is "improvement". This may be compared to Gould's suggestion of "replacing the idea of progress with an operational notion of directionality".

Dawkins, on the other hand, proposes that Darwinian evolution is fundamentally progressive if progress is simply defined as "an increase, not in complexity, intelligence or some other anthropocentric value, but in the accumulating number of features contributing towards whatever adaptation the lineage in question exemplifies." [1]

Evolutionary theorists agree that there are local trends in evolution, such as increasing brain size in hominids, but these directional changes do not persist indefinitely, and trends in opposite directions also occur (Gould, 1997). Evolution causes organisms to adapt to their local environment; when the environment changes, the direction of the trend may change. The question of whether there is evolutionary progress is better formulated as the question of whether there are any largest-scale trends in evolution (McShea, 1998). That is, is there a consistent directional change throughout the history of life on Earth?

See also

• Largest-scale trends in evolution
• Evolution
• Evolutionary biology
• Full House: The Spread of Excellence From Plato to Darwin
• Michael Ruse
• Stephen Jay Gould
• Francisco J. Ayala

References

• Ayala, F.J. (1988). Can "progress" be defined as a biological concept? In Evolutionary Progress, ed. M Nitecki, pp. 75-96. Chicago: University of Chicago Press. ISBN 0-226-58693-6

• Darwin, C. (1859). On the Origin of Species By Means of Natural Selection, or, the Preservation of Favoured Races in the Struggle for Life.

• Gould, S.J. (1997). Full House: The Spread of Excellence from Plato to Darwin. New York: Harmony. ISBN 0-609-80140-6

• Korotayev, Andrey (2004). World Religions and Social Evolution of the Old World Oikumene Civilizations: A Cross-cultural Perspective, First Edition, Lewiston, New York: Edwin Mellen Press. ISBN 0-7734-6310-0.  (on the applicability of this notion to the study of social evolution).

• Alexander V. Markov, and Andrey V. Korotayev (2007) "Phanerozoic marine biodiversity follows a hyperbolic trend" Palaeoworld 16(4): pp. 311-318.

• McShea, D.W. (1998). Possible largest-scale trends in organismal evolution: Eight "Live Hypotheses". Annual Review of Ecology and Systematics, 29, 293-318. DOI 10.1146/annurev.ecolsys.29.1.293

• Ruse, M. (1997). Monad to Man: The Concept of Progress in Evolutionary Biology. Harvard University Press. ISBN 0-674-58220-9