This is the sort of thing that makes me laugh:
britannica.com
This unity reveals the genetic continuity and common ancestry of all organisms. There is no other rational way to account for their molecular uniformity when numerous alternative structures are equally likely. The genetic code may serve as an example. Each particular sequence of three nucleotides in the nuclear DNA acts as a pattern, or code, for the production of exactly the same amino acid in all organisms. This is no more necessary than it is for a language to use a particular combination of letters to represent a particular reality. If it is found that certain sequences of letters--planet, tree, woman--are used with identical meanings in a number of different books, one can be sure that the languages used in those books are of common origin.
Genes and proteins are long molecules that contain information in the sequence of their components in much the same way as sentences of the English language contain information in the sequence of their letters and words. The sequences that make up the genes are passed on from parents to offspring, identical except for occasional changes introduced by mutations. To illustrate, assume that two books are being compared; both books are 200 pages long and contain the same number of chapters. Closer examination reveals that the two books are identical page for page and word for word, except that an occasional word--say one in 100--is different. The two books cannot have been written independently; either one has been copied from the other or both have been copied, directly or indirectly, from the same original book. Similarly, if each nucleotide is represented by one letter, the complete sequence of nucleotides in the DNA of a higher organism would require several hundred books of hundreds of pages, with several thousand letters on each page. When the "pages" (or sequence of nucleotides) in these "books" (organisms) are examined one by one, the correspondence in the "letters" (nucleotides) gives unmistakable evidence of common origin.
The arguments presented above are based on different grounds, although both attest to evolution. Using the alphabet analogy, the first argument says that languages that use the same dictionary--the same genetic code and the same 20 amino acids--cannot be of independent origin. The second argument, concerning similarity in the sequence of nucleotides in the DNA or the sequence of amino acids in the proteins, says that books with very similar texts cannot be of independent origin.
If they had a common author, they would not be of independent origin either, so it proves little. Similarly, to say that there tends to be a close relationship among various living things says no more than that most of the permutations of the genetic code were employed....... |
