Über die Autorin bzw. den Autor

Daniel J. Fairbanks is a distinguished university professor, research geneticist, artist, and author. He is the coauthor (with A. Franklin, A.W.F. Edwards, D.L. Hartl, and T. Seidenfeld) of The Mendel-Fisher Controversy, and (with W. R. Andersen) of Genetics: The Continuity of Life in addition to numerous journal articles.

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RELICS OF EDEN

Prometheus Books

Contents

Preface.........................................................................7Introduction....................................................................11Chapter 1 Fusion...............................................................17Chapter 2 McClintock's Masterpiece.............................................31Chapter 3 Bogus Genes..........................................................47Chapter 4 Solving the Trichotomy...............................................61Chapter 5 Darwinian DNA........................................................73Chapter 6 A Spectacular Confirmation...........................................87Chapter 7 Diversity............................................................103Chapter 8 The Tree of Life.....................................................121Chapter 9 "When Faith and Reason Clash"........................................133Chapter 10 Abandoning the Dichotomy.............................................161Introduction to the Appendices..................................................173Appendix 1 The Story of NANOG and Its Pseudogenes...............................177Appendix 2 Nine Inversions......................................................189Appendix 3 From Darwin to the Human Genome: A Brief History.....................207Glossary........................................................................245Bibliography....................................................................253Index...........................................................................269

Chapter One

Images of evolution abound, often depicting humans with apes and monkeys. The idea that we are related to other primates gripped the public almost from the day Darwin first published the Origin of Species. On June 30, 1860, just a few months after the first edition of Origin of Species was released, Samuel Wilberforce, the bishop of Oxford, and Thomas Henry Huxley, a staunch supporter of Darwin, engaged in a brisk exchange during a meeting at Oxford University. Years later, Isabella Sidgwick famously recounted the incident with more than a bit of embellishment:

The Bishop rose, and in a light scoffing tone, florid and fluent, he assured us there was nothing in the idea of evolution; rock-pigeons were what rock-pigeons had always been. Then, turning to his antagonist with a smiling insolence, he begged to know, was it through his grandfather or his grandmother that he claimed his descent from a monkey? On this Mr. Huxley slowly and deliberately arose. Aslight tall figure stern and pale, very quiet and very grave, he stood before us, and spoke those tremendous words-words which no one seems sure of now, nor I think, could remember just after they were spoken, for their meaning took away our breath, though it left us in no doubt as to what it was. He was not ashamed to have a monkey for his ancestor; but he would be ashamed to be connected with a man who used great gifts to obscure the truth. No one doubted his meaning and the effect was tremendous. One lady fainted and had to be carried out: I, for one, jumped out of my seat.

Huxley's own recollection, although less spirited than Ms. Sidgwick's, captured the excitement of the moment:

If then, said I, the question is put to me would I rather have a miserable ape for a grandfather or a man highly endowed by nature and possessed of great means of influence and yet who employs those faculties and that influence for the mere purpose of introducing ridicule into a grave scientific discussion -I unhesitatingly affirm my preference for the ape. Whereupon there was inextinguishable laughter among the people -and they listened to the rest of my argument with the greatest attention.

Almost a century and a half later, emotions still run high whether one accepts or scorns the idea of an evolutionary relationship between humans and apes. Setting emotions aside, what does science tell us about the relationship? Specifically, does our DNA hold solid evidence that humans and great apes share common ancestry? This chapter highlights some of the clearest and most powerful evidence, all within a single human chromosome.

HUMAN AND GREAT-APE CHROMOSOMES ARE STRIKINGLY SIMILAR.

The DNA of most organisms, including humans, is contained within structures called chromosomes. Each chromosome is a coiled-up molecule of DNA with proteins that stabilize it. When a cell is about to divide in two, the chromosomes condense into compact structures that are easy to observe with the help of a microscope. Each compact chromosome has a constricted region called a centromere, with very specific DNA sequences in it. The centromere serves a critical role in helping direct the chromosome to its proper position when cells divide. The ends of each chromosome are called telomeres and they, too, contain highly specific DNA sequences.

Each time a chromosome replicates, a bit of telomere DNA erodes away, but a protein called telomerase restores the eroded ends to reconstitute the telomeres. Thus, telomeres function as buffer zones to protect the important DNA within the chromosome from erosion. If not for telomeres and telomerase, our chromosomes would progressively erode inward from the ends until they could no longer function. As we'll see momentarily, these structural features-centromeres and telomeres-offer a compelling clue about our evolutionary history.

If we compare human chromosomes to those of the great apes (chimpanzee, gorilla, and orangutan), one glaring difference stands out: the human genome has one fewer chromosome than the genomes of the great apes. Chimpanzee, gorilla, and orangutan genomes each have twenty-four chromosomes, whereas the human genome has twenty-three. Some opponents of evolution pounced on this difference, claiming that it disproves common ancestry between humans and apes. At one time the difference seemed to justify the traditional classification of great apes into a single family called the Pongidae and humans as the sole surviving species of a different family called the Hominidae. However, DNA analysis eventually shattered that classification (as we'll see later).

In 1982, Jorge Yunis and Om Prakash published what is now viewed as a landmark article in the journal Science. Their work confirmed the findings of several earlier studies in exquisite detail: chromosomes from humans, chimpanzees, gorillas, and orangutans are highly similar and can be aligned with one another. More recently, the human and chimpanzee genome projects confirmed and greatly amplified this comparison, showing that not just the chromosomes but the DNA within the chromosomes of humans and chimpanzees is strikingly similar in both sequence and organization, usually with at least 98 percent identity. All researchers comparing human and chimpanzee chromosomes, and the DNA in them, arrived at the same overall conclusion: every human chromosome, except one, has a matching chimpanzee chromosome. The exception is human chromosome 2, which matches two different chromosomes in chimpanzees as well as in the other great apes.

HOW DID HUMAN CHROMOSOME 2 ORIGINATE?

The two chimpanzee chromosomes that match human chromosome 2 are called 2A...