Genetics of Original Sin Read Online Free

of their protein translation products. We have just seen that the information held by these molecular “words” is determined by the order, or sequence, of their molecular “letters,” their spelling, so to speak. The last few decades have witnessed the development of techniques of extraordinary efficiency for deciphering those sequences, to the point that many entire genomes have now been sequenced, including the human genome, which contains some three billion “letters,” the equivalent of about 150 volumes of the
Oxford Concise Dictionary!
This technology has revealed that genes that carry outthe same function in different organisms show many sequence similarities, many more than could be accounted for by chance. The genes are unmistakably related and are all derived from a single ancestral gene by a pathway that has involved a number of changes in sequence (mutations), somewhat like words whose spelling has changed over time.
    Not only have the sequence similarities been illuminating, by showing the single ancestry of many genes. The sequence differences have also been revealing. They have allowed the reconstruction of what is known as the “phylogenetic” (from the Greek
phylon
, race) history of the genes, that is, what amounts to their “genealogical tree,” by a technique that uses the number of sequence differences between two forms of the same gene (belonging to two different organisms) as a measure of the time that has elapsed since the two genes separated from their last common ancestor and started evolving separately. Etymological research follows a similar line.
    This method has been applied to a very large number of genes and continues to be applied more and more. Its results have confirmed—and sometimes corrected—a number of the conclusions derived from the study of fossils; especially, they have enormously enriched those conclusions. Indeed, the beauty of comparative sequencing is that it can throw light on the evolutionary history of any organism, not only those that have left fossil remnants. Fossils remain invaluable clues, of course, as illustrated by a number recently unearthed in China that have revealed several “missing links.” But the innumerable organisms, such as soft-bodied animals and, especially, bacteria and other unicellular organisms, that have disappeared without trace can be reconstituted by the magic of molecular sequencing.
    The history of life is written in the genes of extant organisms. It is written in very fine print, which it has been our generation’sprivilege to discover how to decipher. The general conclusion of all that has been learned is clear and indisputable: all known living organisms are descendants from a
single common ancestral form.
Biological evolution is an established fact
    The notoriously cautious language of science is rarely so affirmative. But, in the present case, with all the debates that surround the so-called theory of evolution, it is necessary to speak out unambiguously. Evolution is not a theory, contrary to what is often stated, sometimes even by scientists.
Evolution is a fact.
It was a theory two centuries ago, when Lamarck and Erasmus Darwin first proposed it, just as heliocentrism was a theory in the days of Copernicus and Galileo. Evolution is no longer a theory, just as heliocentrism is no longer a theory; it is a fact. The Catholic Church has recognized this with remarkable promptness, as compared to the Galileo affair. On October 22, 1996, at a meeting of the Pontifical Academy of Sciences, Pope John Paul II solemnly announced that “
evolution is more than an hypothesis.
” He did admittedly retreat somewhat to make a special case for the creation of the human soul; and his successor has retreated even further by leaning in favor of the so-called theory of intelligent design (see chapter 8 ). Nevertheless, biological evolution is not negated by the Catholic Church. Such is not