 |
Science Frontiers ONLINE No. 54: Nov-Dec 1987 |
|
| 
|
Instances Of Observed Speciation
Creationists have long maintained that no one has ever observed the creation of a new species in nature. C.A. Callag han has sought to counter this attack on evolution with a paper bearing the above title. Her concluding paragraph is: "I have cited several instances of ob served speciation that can be used as illustrative examples in the classroom. They should also silence at least one common creationist argument against evolution."
The paper begins with the well-worn peppered-moth story; but Callaghan quickly dismisses this, as the creationists do, as merely an example of variation within a species. We now quote the lead sentences from her discussions of the next two candidates:
"An incipient neospecies of Drosophila may have developed in Theodosius Dobzhansky's laboratory sometime between 1958 and 1963 in a strain of D. paulistorum....""A probable instance of a naturally emerging plant species was discovered on both sides of Highway 205 at a single locality 25.5 miles south of Burns, Harney County, Oregon...."
We have inserted underlining beneath the two words that greatly weaken the paper. In short, the biologists are not really sure that speciation occurred in these two cases. The reasons for doubt are also presented.
The paper concludes with a discussion of allopolyploidy in plants, in which the chromosomes of a sterile hybrid are doubled, giving rise to a fertile variety. Allopolyploidy has been observed in primroses, tobacco, cotton, and other plants.
And that's it; two questionable examples and allopolyploidy. (Callaghan, Catherine A.; "Instances of Observed Speciation," American Biology Teacher, 49:34, January 1987.)