HOME

 

 

    NEWS

INTERVIEWS

RESOURCES

ABOUT

View by:

 SUBJECT

 THEME

QUESTION

  TERM

 PERSON

   EVENT

In general, as pointed out above, those features and behaviors that are considered adaptations are explained teleologically. This is simply because adaptations are features that come about by natural selection.

Among alternative genetic variants that may arise by mutation or recombination, the ones that become established in a population are those that contribute more to the reproductive success of their carriers. "Fitness" is the measure used by evolutionists to quantify reproductive success. But reproductive success is usually mediated by some function or property. Wings and hands acquired their present configuration through long-term accumulation of genetic variants adaptive to their carriers. How natural selection yields adaptive features may be explained with examples where the adaptation arises as a consequence of a single gene mutation.

One example is the presence of normal hemoglobin rather than hemoglobin S in humans. One amino acid substitution in the beta chain in humans results in hemoglobin molecules less efficient for oxygen transport. The general occurrence in human populations of normal rather than S hemoglobin is explained teleologically by the contribution of hemoglobin to effective oxygen transport and thus to reproductive success.

A second example, the difference between peppered-gray moths and melanic moths is also due to one or only a few genes. The replacement of gray moths by melanics in polluted regions is explained teleologically by the fact that in such regions melanism decreases the probability that a moth be eaten by a bird. The predominance of peppered forms in nonpolluted regions is similarly explained.

Not all features of organisms need to be explained teleologically, since not all come about as a direct result of natural selection. Some features may become established by random genetic drift, by chance association with adaptive traits, or in general by processes other than natural selection. Proponents of the neutrality theory of protein evolution argue that many alternative protein variants are adaptively equivalent. Most evolutionists would admit that at least in certain cases the selective differences between alternative amino acids at a certain site in a protein must be virtually nil, particularly when population size is very small. The presence in a population of one amino acid sequence rather than another, adaptively equivalent to the first, would not then be explained teleologically. Needless to say, in such cases there would be amino acid sequences that would not be adaptive. The presence of an adaptive protein rather than a nonadaptive one would be explained teleologically; but the presence of one protein rather than another among those adaptively equivalent would not require a teleological explanation.

To return to the previous topic, click on your browser's 'Back' button.

Topic Sets Available

AAAS Report on Stem-Cells

AstroTheology: Religious Reflections on Extraterrestrial Life Forms

Agency: Human, Robotic and Divine
Becoming Human: Brain, Mind, Emergence
Big Bang Cosmology and Theology (GHC)
Cosmic Questions CD-ROM Preview...
Cosmic Questions Interviews

Cosmos and Creator
Creativity, Spirituality and Computing Technologies
CTNS Content Home
Darwin: A Friend to Religion?
Demystifying Information Technology
Divine Action (GHC)
Dreams and Dreaming: Neuroscientific and Religious Visions'
E. Coli at the No Free Lunchroom
Engaging Extra-Terrestrial Intelligence: An Adventure in Astro-Ethics
Evangelical Atheism: a response to Richard Dawkins
Ecology and Christian Theology
Evolution: What Should We Teach Our Children in Our Schools?
Evolution and Providence
Evolution and Creation Survey
Evolution and Theology (GHC)
Evolution, Creation, and Semiotics

The Expelled Controversy
Faith and Reason: An Introduction
Faith in the Future: Religion, Aging, and Healthcare in the 21st Century

Francisco Ayala on Evolution

From Christian Passions to Scientific Emotions
Genetic Engineering and Food

Genetics and Ethics
Genetic Technologies - the Radical Revision of Human Existence and the Natural World

Genomics, Nanotechnology and Robotics
Getting Mind out of Meat
God and Creation: Jewish, Christian, and Muslim Perspectives on Big Bang Cosmology
God, Humanity and the Cosmos: A Textbook in Science and Religion
God the Spirit - and Natural Science
Historical Examples of the Science and Religion Debate (GHC)
History of Creationism
Intelligent Design Coming Clean

Issues for the Millennium: Cloning and Genetic Technologies
Jean Vanier of L'Arche
Nano-Technology and Nano-ethics
Natural Science and Christian Theology - A Select Bibliography
Neuroscience and the Soul
Outlines of the Science and Religion Debate (GHC)

Perspectives on Evolution

Physics and Theology
Quantum Mechanics and Theology (GHC)
Questions that Shape Our Future
Reductionism (GHC)
Reintroducing Teleology Into Science
Science and Suffering

Scientific Perspectives on Divine Action (CTNS/Vatican Series)

Space Exploration and Positive Stewardship

Stem-Cell Debate: Ethical Questions
Stem-Cell Ethics: A Theological Brief

Stem-Cell Questions
Theistic Evolution: A Christian Alternative to Atheism, Creationism, and Intelligent Design...
Theology and Science: Current Issues and Future Directions
Unscientific America: How science illiteracy threatens our future
Will ET End Religion?

Current Stats: topics: >2600, links: >300,000, video: 200 hours.