The Edge of Evolution by Michael J. Behe

Author:Michael J. Behe [Behe, Michael J.]
Language: eng
Format: mobi
Publisher: Simon & Schuster, Inc.
Published: 2007-06-04T23:00:00+00:00

9

THE CATHEDRAL AND THE SPANDRELS

HOW DEEP GOES DESIGN?

Up until now we have examined molecular structures and processes and have drawn a tentative line marking the molecular edge of Darwinian evolution. Most protein-protein interactions in the cell are not due to random mutation. Since cells are integrated units, it’s reasonable to view cells in their entirety as designed. But keep in mind that accidents do happen, so there are Darwinian effects, of some degree, everywhere. For example, just as automobiles may accumulate dents or scratches over time, or have mufflers fall off, but nonetheless are coherent, designed systems, so, too, with cells. Some features of cells of course result from genetic dents or scratches or loss, but the cell as a whole, it seems, was designed.

Now it’s time to look at higher levels of biological organization. There are several major classes of cells, which include the simpler prokaryotic cells of bacteria and the more complex eukaryotic cells of creatures ranging from yeasts to humans. Were just the simpler, prokaryotic cells designed? Could the more complex eukaryotic cells have evolved from them over time by unintelligent processes? In other words, given the simpler, designed cells in the distant past as a starting point, is it biologically reasonable to think that random mutation and natural selection could reach the more complex cells?

No. Eukaryotic cells contain a raft of complex functional systems that the simpler prokaryotes lack, systems that are enormously beyond Darwinian processes. For example, the cilium discussed in Chapter 5, which contains hundreds of protein parts, and IFT, the system that constructs the cilium from the ground up, both appear in eukaryotic cells, but not in prokaryotic cells. And the cilium isn’t the only difference. As the evolutionary developmental biologists Marc Kirschner and John Gerhart exclaim in The Plausibility of Life, “enormous innovations attended the evolution of the first single-celled eukaryotes one and a half to two billion years ago.”1 The innovations include such fundamental features as sexual reproduction (meiosis and recombination), the organization of DNA into chromatin, and the provisioning of a cellular protein “skeleton.” Of course, the two kinds of cells share a number of similar systems, such as the genetic code. Nonetheless, just as it’s reasonable to view a motorcycle as a different sort of system from a bicycle, because eukaryotic cells contain multiple complex systems that prokaryotes do not, it’s reasonable to view eukaryotes as integrated, designed systems in their own right,

So design extends beyond the simplest cells at least to more complex cells, which is the biological level of “kingdom.” Does it go further? Although prokaryotes are single-celled organisms, not all eukaryotes are. Eukaryotes include not only single-celled organisms such as yeast and malaria, but also multicellular organisms: plants, and animals from jellyfish to insects to humans. So does design stop at the eukaryotic cell, or does it extend to multicellular organisms? More pointedly, given a generic, designed, eukaryotic cell in the distant past, is it biologically reasonable to think that over time the rest of life developed from it entirely by unintelligent processes? This chapter answers that question.

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