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The case against evolution
As a result of recent investigations on the sex chromosomes and chromosome numbers in mammals, Theophilus S. Painter reaches the conclusions that polyploidy cannot be invoked to explain evolution within this class. After giving a table of chromosome numbers for 7 out of the 9 eutherian orders, Painter concludes: The facts recorded above are of especial interest in that they indicate a unity of chromosome composition above the marsupial level and effectively dispose of the suggestion that extensive polyploidy may have occurred within this subclass. In the marsupials the chromosome number is a low one and in the opossum is 22. At first sight it might appear that the eutherian condition might have arisen from this by tetraploidy. There are two objections, however. In the first place the bulk of the chromatin in marsupials is about the same as in the eutheria, using the sex chromosome as our measure. In the second place, polyploidy could scarcely occur successfully in animals with X-Y sex chromosomes, as most mammals possess, because of the complication occurring in the sex chromosome balance (Science, April 17, 1925, p. 424). As the X-Y type of sex chromosomes occurs widely not only among vertebrates, but also among insects, nematodes, and echinoderms, Painters latter objection excludes evolution by polyploidy from a large portion of the animal kingdom. ......Buy Now (To Read More)
Ebook Number: 68574
Author: O'Toole, George Barry
Release Date: Jul 21, 2022
Format: eBook
Language: English
Publisher: The Macmillan Company
Publication Date: 1925
Publisher Country: United States
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