Claim CA210:
A true science must make predictions. Evolution only describes what
happened in the past, so it is not predictive.
Source:
Response:
- The difference in predictive power between evolution and other sciences
is one of degree, not kind. All theories are simplifications; they
purposely neglect as many outside variables as they can. But these
extraneous variables do affect predictions. For example, you can
predict the future position of an orbiting planet, but your prediction
will be off very slightly because you can not consider the effects of
all the small bodies in the solar system. Evolution is more sensitive
to initial conditions and extraneous factors, so specific predictions
about what mutations will occur and what traits will survive are
impractical. It is still possible to use evolution to make general
predictions about the future, though. For example, we can predict that
diseases will become resistant to any new widely used antibiotics.
- The predictive power of science comes from being able to say things we
would not have been able to say otherwise. These predictions do not have
to be about things happening in the future. They can be
"retrodictions" about things from the past that we have not found yet.
Evolution allows innumerable predictions of this sort.
- Evolution has been the basis of many predictions. For example:
- Darwin predicted, based on homologies with African apes, that human
ancestors arose in Africa. That prediction has been supported by
fossil and genetic evidence (Ingman et al. 2000).
- Theory predicted that organisms in heterogeneous and rapidly
changing environments should have higher mutation rates. This has
been found in the case of bacteria infecting the lungs of chronic
cystic fibrosis patients (Oliver et al. 2000).
- Predator-prey dynamics are altered in predictable ways by evolution
of the prey (Yoshida et al. 2003).
- Ernst Mayr predicted in 1954 that speciation should be accompanied with
faster genetic evolution. A phylogenetic analysis has supported
this prediction (Webster et al. 2003).
- Several authors predicted characteristics of the ancestor of
craniates. On the basis of a detailed study, they found the fossil
Haikouella "fit these predictions closely" (Mallatt and Chen
2003).
- Evolution predicts that different sets of character data should still
give the same phylogenetic trees. This has been confirmed informally
myriad times and quantitatively, with different protein sequences, by
Penny et al. (1982).
- Insect wings evolved from gills, with an intermediate stage of
skimming on the water surface. Since the primitive surface-skimming
condition is widespread among stoneflies, J. H. Marden predicted that
stoneflies would likely retain other primitive traits, too. This
prediction led to the discovery in stoneflies of functional
hemocyanin, used for oxygen transport in other arthropods but never
before found in insects (Hagner-Holler et al. 2004; Marden 2005).
With predictions such as these and others, evolution can be, and has
been, put to practical use in areas such as
drug discovery and
avoidance of resistant pests.
- If evolution's low power to make future predictions keeps it from
being a science, then some other fields of study cease to be
sciences, too, especially archeology and astronomy.
Links:
Wilkins, John. 1997. Evolution and philosophy: Predictions and
explanations. http://www.talkorigins.org/faqs/evolphil/predict.html
References:
- Hagner-Holler, Silke et al. 2004. A respiratory hemocyanin from an
insect. Proceedings of the National Academy of Science USA 101:
871-874.
- Ingman, M., H. Kaessmann, S. Paaba and U. Gyllensten. 2000.
Mitochondrial genome variation and the origin of modern humans.
Nature 408: 708-713 . See also: Blair Hedges, S. 2000. A start for
population genomics. Nature 408: 552-553. See also:
Thomson, Jeremy, 2000 (7 Dec.).
Humans did come out of Africa, says DNA. Nature Science Update,
http://www.nature.com/nsu/001207/001207-8.html
- Mallatt, J. and J.-Y. Chen. 2003. Fossil sister group of craniates:
Predicted and found. Journal of Morphology 258(1): 1-31.
- Marden, Jim, 2005. Flap those gills and fly: Comment (#46024: 10/29).
http://pharyngula.org/index/weblog/comments/flap_those_gills_and_fly/P25/#c46024
- Oliver, Antonio et al. 2000. High frequency of hypermutable
Pseudomonas aeruginosa in cystic fibrosis lung infection.
Science
288: 1251-1253. See also Rainey, P. B. and R. Moxon. 2000. When
being hyper keeps you fit. Science 288: 1186-1187. See also:
LeClerc, J. E. and T. A. Cebula. 2000. Pseudomonas survival
strategies in cystic fibrosis (letter), 2000. Science 289: 391-392.
- Penny, David, L. R. Foulds, and M. D. Hendy. 1982. Testing the theory
of evolution by comparing phylogenetic trees constructed from five
different protein sequences. Nature 297: 197-200.
- Webster, Andrea J., Robert J. H. Payne, and Mark Pagel. 2003.
Molecular phylogenies link rates of evolution and speciation.
Science 301: 478.
- Yoshida, T., L. E. Jones, S. P. Ellner, G. F. Fussmann
and N. G. Hairston Jr. 2003. Rapid evolution drives ecological
dynamics in a predator-prey system. Nature 424: 303-306.
Further Reading:
Rainey, Paul. 2003. Evolution: Five big questions: 4. Is
evolution predictable? New Scientist 178(2399) (14 June): 37-38.
created 2001-2-18, modified 2005-11-3