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This does not mean that all of the manifestations of intelligence are motivated by sex. However, sexual selection can favor the evolution of intelligence-related traits even when they are motivated by things other than sex, such as a true love of one’s fellow humans, or a sublime sense of aesthetics. One might expect that, after many generations of sexual selection, all variability in fitness indicators would have been eliminated. The inferior traits would have died out, leaving only males and females with superior characteristics that the other sex finds appealing. But this point is never reached. If this point were approached, the fitness indicators would no longer be reliable. The whole point of a fitness indicator is that it reveals which individuals are superior in their health and potential fitness. If variability in one fitness indicator is eliminated, more variation in that indicator may evolve, or sexual selection may seize upon some other trait as a fitness indicator. Sexual selection never finishes its job. This is exactly what human intelligence looks like—a set of traits that has evolved to absurd lengths and keeps diversifying into new forms. What remains unexplained is how intelligence began to evolve in the first place. The evolution of a little intelligence would create a demand for more, particularly through sexual selection. But how did it get started? Miller explains that sexual selection frequently produces characteristics that have no survival value. Intelligence could therefore have gotten started quite by chance, after which it evolved explosively by sexual selection. While natural selection may be unable to favor a partly evolved trait, sexual selection would be able to do so. Although humans are uniquely high in intelligence, they are not unique among animals in the evolution of increased intelligence over time. Paleontologist Simon Conway Morris points out that intelligence, although less than that of humans, has evolved in cetaceans such as dolphins, and even in cephalopod mollusks such as the octopus. An octopus has a level of intelligence that, while below that of a human, takes human investigators by surprise. For example, an octopus can learn how to perform a complex task by watching another octopus perform it. The dolphin brain is structurally different from the human brain, as dolphins rely on sound much more than on sight, but it is approximately as large as the human brain and has even more of the convolutions that provide cortical surface areas for the integration of neurons involved in thought. In fact, dolphin brains may be superior to human brains in some aspects. A dolphin will allow half of its brain to sleep at a time, so that it can continue swimming while sleeping. This partial independence of the two brain hemispheres, which is one of the contributors to human intelligence, is more developed in dolphins than in humans. The discovery of high levels of intelligence in nonhuman species raises questions about animal rights. Moreover, the evolution of intelligence in humans has occurred at least twice and possibly more often. Although Neandertals did not have art or religion, they did have brains as large as those of modern humans, and they evolved independently from Homo HeiDelbergensis ancestors. There is even some evidence that Homo erectus in Asia evolved slightly larger brains than their African Homo ergaster ancestors before becoming extinct (see Homo erectus). intelligent design According to Conway Morris, the independent evolution of intelligence in mollusks, cetaceans, and two (possibly three) human lineages is an example of the pattern of convergence that he says pervades evolutionary history. Human intelligence is a many-faceted and extremely complex thing. Its current operation is not fully understood, therefore its evolution cannot be fully understood. Undoubtedly, many processes were at work in the evolution of intelligence. For example, one must not underestimate the central role that religion played in human evolution, including the evolution of intelligence (see religion, evolution of). Because intelligence is equally developed in all races, it seems certain that human intellectual abilities were fully evolved before Homo sapiens began to disperse from Africa more than 50,000 years ago. All of subsequent prehistory, and all of human history, has consisted of the cultural development of the human mind, using the biological abilities that had evolved prior to that time. Further Reading Bouchard, Thomas J., Jr., et al. “Sources of human psychological differences: The Minnesota study of twins reared apart.” Science 250 (1990): 223–229. Conway Morris, Simon. Life’s Solution: Inevitable Humans in a Lonely Universe. Cambridge: Cambridge University Press, 2003. Evans, Patrick D., et al. “Microcephalin, a gene regulating brain size, continues to evolve adaptively in humans.” Science 309 (2005): 1,717–1,720. Marcus, Gary. The Birth of the Mind: How a Tiny Number of Genes Creates the Complexities of Human Thought. New York: Basic Books, 2004. Mekel-Bobrov, Nitzan, et al. “Ongoing adaptive evolution of ASPM, a brain size determinant in Homo sapiens.” Science 309 (2005): 1,720–1,722. Miller, Geoffrey. The Mating Mind: How Sexual Choice Shaped the Evolution of Human Nature. New York: Doubleday, 2000. Miller, Greg. “The thick and thin of brainpower: Developmental timing linked to IQ.” Science 311 (2006): 1,851. Ridley, Matt. “Intelligence.” Chap. 6 in Genome: The Autobiography of a Species in 23 Chapters. New York: HarperCollins, 1999. Rumbaugh, Duane M., and David A. Washburn. Intelligence of Apes and Other Rational Beings. New Haven, Conn.: Yale University Press, 2003. Trewavas, Anthony. “Aspects of plant intelligence.” Annals of Botany 92 (2003): 1–20. Available online. URL: http://aob.oupjournals.org/cgi/content/full/92/1/1. Accessed September 7, 2005. Wynne, Clive D. L. Do Animals Think? Princeton, N.J.: Princeton University Press, 2004. intelligent design Intelligent design (ID) theory is minimalist creationism. It is a theory that claims there is irreducible complexity of biological systems and structures. According to this view, biological systems consist of many interacting components, none of which can work unless all the other components are present and operational. It is a form of creationism because, the defenders of intelligent design theory admit, only an intelligent Creator could have brought irreducibly complex systems into existence; irreducibly complex systems cannot be produced by a series of evolutionary steps.
intelligent design However, ID theorists like to distance themselves from oldfashioned creationism. The most popular statement of this position has been Darwin’s Black Box, by Michael J. Behe, a biochemist at Lehigh University. Most of the following discussion is based upon Behe’s book. According to Behe, gone from ID are all the arguments that creationists usually present about gaps in the fossil record, young age of the Earth, and the Flood of Noah. Although most adherents of ID accept many or all of the tenets of creationism (for example, Jay W. Richards, a senior fellow at the Discovery Institute in Seattle, Wash., still uses the “gaps in the fossil record” argument), the debate sidesteps these issues. Few ID theorists accept the historical facts of human evolution; but their publications generally do not address it. Instead, it is enough for them to point out that human (and other) biochemistry is too complex to have arisen by evolution. Evolutionary scientists point out that the fossil record really does provide evidence that evolution occurred; Behe indicates that paleontology does not matter. Evolutionary scientists, starting with Darwin (see appendix, “Darwin’s ‘One Long Argument’: A Summary of Origin of Species”) and continuing through modern evolutionary scientists (see Dawkins, Richard), point out the existence of intermediate stages in the evolution of the eye from the simple eyespot of a protozoan; Behe indicates that does not matter either. In his discussion of the bombardier beetle, Behe admits that other beetles have similar, and simpler, systems of defense; not surprisingly, Behe indicates that this does not matter either. All that matters, in his argument, is irreducible complexity on the biochemical and cellular level. Behe’s examples of irreducibly complex systems include vision in a retinal cell; the explosive defense mechanism of the bombardier beetle; cilia and flagella (the whiplike mechanisms by which many single-celled organisms propel themselves); blood clot formation; and the mammalian immune response. According to ID arguments, in order for evolution to produce biochemical complexity, uncountable billions of cells would have to die over the course of billions of years. As a matter of fact, that is exactly what happened during Precambrian time. Almost 80 percent of evolutionary history occurred when life on Earth was primarily microbial. It looks from the Precambrian fossil record as if nothing much was happening, but this is because the significant events were taking place on a molecular scale that no fossil could reveal. ID has two components, and there are major problems with both. First, there is the recognition of “irreducible complexity.” The recognition of irreducible complexity involves a fallacy that Richard Dawkins has called “the argument from personal incredulity.” Ever since the design argument in the early 19th century (see natural theology), creationists have argued that “I do not see how this could have evolved, therefore it could not have evolved.” ID theory has simply continued this argument, at a biochemical and cellular level. This is no more convincing than when atheists claim, “I do not see how there could be a God, therefore God does not exist.” In fact, Behe’s argument is what could be called “the argument from personal omniscience.” It takes three forms: • Behe makes it sound as if he assumes the omniscience of famous biochemists. Behe points out that Stanley Miller (see Miller, Stanley) has been doing origin-of-life simulations since 1953, the Journal of Molecular Evolution has been in print since 1971, and the most prominent biochemists in the world after all these years still have not figured out how complex systems might have evolved by gradual steps. Surely, if Stanley Miller cannot figure it out, then it could not have happened—which assumes the omniscience of Stanley Miller. • Although Behe does not really consider himself omniscient, he did claim that ID theory (which everyone associates with him) is as important a contribution to science as anything contributed by Newton or Einstein. • Behe makes it sound as if his readers are also omniscient. He describes a complex biochemical system, then he asks readers if they can imagine how it could have evolved in gradual steps. If they cannot, then it could not have happened that way. Behe and other ID theorists also recognize irreducible complexity on the basis of biochemical and cellular systems as they now exist. They claim that simpler biochemical systems would not work, and would be of no use to the organisms even if they did: • Behe cites the flagella of some eukaryotic cells as an example of irreducible complexity. However, there are some eukaryotic cells whose flagella lack one or more components yet still function. The sperm of eels, for example, lacks the central axis found in most eukaryotic flagella. • Behe simply asserts that a system simpler than the irreducibly complex ones would be of no use to an organism. He uses the human immune system as an example. However, the phytoalexin response, by which plants fend off infection by fungi, is much simpler, and quite useful to the plant. Behe even cites an article by David Baltimore regarding the simpler, but still very effective, immune response of sharks, then disregards it. • Behe overlooks the possibility that intermediate structures may have arisen as exaptations, having been useful for some other purpose than that which they now serve (see adaptation). Second, ID has difficulty with the process by which complexity has been generated. ID theorists usually insist that the only two alternatives for explaining what they call irreducible complexity is either gradual evolution or intelligent design, both from scratch. Problems with this approach include: • Substitutability of components of systems. One creationist book from before the ID era, entitled Evolution: Possible or Impossible?, made arguments such as this: living cells use 20 different kinds of amino acids; the insulin protein has 51 amino acid residues, therefore the chances against the random origin of insulin are 20 51 . The chance of one in 20 51 essentially represents impossibility. Therefore, an insulin molecule could not have evolved in a single step. However, no evolutionary scientist believes that insulin arose in a single step. In addition, not all 51 amino acids have to
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ENCYCLOPEDIA OF Evolution
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Encyclopedia of Evolution Copyright
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Contents Foreword ix Acknowledgment
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Foreword The theory and facts of ev
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IntroduCtIon What you do not know a
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other issues coming along with it.
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adaptation Adaptation is the fit of
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from the allometric patterns of gro
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considered as an example. (The taxo
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English) were a resounding success,
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Some Centers of the Evolution of Ag
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helps the DNA insert into the host
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Even within a single patient, HIV e
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then into the insect body; carbon d
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chromosomes (they are diploid) whil
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genetic basis. About 35,000 years a
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emained dormant and sprouted after
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Further Reading Wise, Steven M. Rat
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Because the DNA of many archaebacte
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Koi and goldfish have been bred tha
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Barringer Crater, Arizona, was form
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y a silent wall of darkness advanci
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Skeleton of “Lucy,” the Austral
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Further Reading Alemseged, Zerxenay
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acteria, evolution of Examples of t
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0 Bates, Henry Walter advantage. Th
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ehavior, evolution of In another sp
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ig bang make nests with horizontal
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iodiversity How Much Do Genes Contr
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iodiversity Biodiversity (as indica
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0 biogeography Another problem with
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iogeography Biogeography of Selecte
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iogeography their species through d
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iology design) or adaptation to the
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iology D. Response to environment.
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0 birds, evolution of • The foot.
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irds, evolution of • doves and pi
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Burgess shale early career. By heat
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Burgess shale jointed legs, Anomalo
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Cambrian period occurred when anima
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0 Cenozoic era opens the way to an
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Chicxulub Pritchard, J., and Dolph
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cladistics The above examples used
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coevolution descent, and that scien
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coevolution Coevolution of Organism
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0 coevolution What Are the “Ghost
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coevolution What Are the “Ghosts
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commensalism Wilson, Michael. Micro
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continental drift was an animal tha
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continental drift During geological
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0 convergence bee-pollinated flower
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convergence Both birds and bats hav
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creationism explained these observa
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creationism used to justify militar
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creationism • In the early 21st c
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00 Cretaceous period however, other
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0 Cro-Magnon evolution had occurred
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0 Cro-Magnon areas, perforated shel
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0 Cuvier, Georges Cuvier held stron
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0 Darwin Awards Darwin Awards “Th
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0 Darwin, Charles forever. It would
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Darwin, Charles and animals did hav
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Darwin’s finches has its own uniq
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Dawkins, Richard ate the pulp. More
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developmental evolution Part II. In
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0 Devonian period gene from an inve
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dinosaurs what DeVries thought were
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diseases, evolution of • Thyreoph
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disjunct species have happened? Som
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DNA (evidence for evolution) genes,
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0 DNA (evidence for evolution) seco
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DNA (raw material of evolution) DNA
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DNA (raw material of evolution) The
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Dobzhansky, Theodosius Mice have tw
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duplication, gene prominent brow ri
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0 ecology Second, organisms can con
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Eldredge, Niles they possess no str
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eugenics grieving, or experiencing
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eugenics because government officia
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eukaryotes, evolution of of the sor
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0 Eve, mitochondrial within cells,
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evolutionary ethics the ability to
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evolutionary ethics Can an Evolutio
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evolutionary medicine Can an Evolut
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evolutionary medicine variable in t
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0 extinction past (a genetic bottle
Page 181 and 182: fishes, evolution of his obvious vi
Page 183 and 184: Flores Island people Christopher St
Page 185 and 186: fossils and fossilization The grain
Page 187 and 188: founder effect Further Reading Fort
Page 189 and 190: 0 Gaia hypothesis nitrogen oxide (N
Page 191 and 192: Galton, Francis constituted a premi
Page 193 and 194: gene pool Cocos Island is too small
Page 195 and 196: Gould, Stephen Jay animals, and the
Page 197 and 198: Gray, Asa he had long accepted Lyel
Page 199 and 200: 0 group selection used the carbon t
Page 201 and 202: gymnosperms, evolution of began per
Page 204 and 205: Haeckel, Ernst (1834-1919) German E
Page 206 and 207: The initial divergence between homi
Page 208 and 209: Although Homo ergaster, the presume
Page 210 and 211: tions were spreading through Africa
Page 212 and 213: Selected Examples of Homo heidelber
Page 214 and 215: sunlight of tropical regions, and t
Page 216 and 217: win, Hooker could not pay his own w
Page 218 and 219: gene transfer from a bacterium, per
Page 220 and 221: to evolutionary science. He also ap
Page 222 and 223: Examples of Intergeneric Crosses Re
Page 224 and 225: ice ages The term ice ages usually
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Page 228 and 229: migrated into Europe and displaced
Page 230 and 231: ence their intelligence. There is a
Page 234 and 235: e exactly the right ones. Bovine in
Page 236 and 237: Van Till, Howard J. “E. coli at t
Page 238 and 239: food particles with whiplike struct
Page 240 and 241: would readily interbreed and produc
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Page 244 and 245: isotopes When evaporation from the
Page 246: Java man See Homo erectus. Johanson
Page 249 and 250: 0 Kenyanthropus chemist Henri Becqu
Page 251 and 252: language, evolution of is not consi
Page 253 and 254: language, evolution of Italian, Por
Page 255 and 256: Lascaux caves Some of the original
Page 257 and 258: Leakey, Richard Richard Leakey, in
Page 259 and 260: 0 life history, evolution of it inv
Page 261 and 262: life history, evolution of is: sele
Page 263 and 264: life history, evolution of Why Do H
Page 265 and 266: life history, evolution of Why Do H
Page 267 and 268: Linnaean system The tree of life us
Page 269 and 270: 0 living fossils admired. The genus
Page 271 and 272: Lysenkoism about evolution. When Da
Page 273 and 274: Malthus, Thomas intelligent design)
Page 275 and 276: mammals, evolution of the reptilian
Page 277 and 278: markers another precocious and crea
Page 279 and 280: 0 Mars, life on • The spacecraft
Page 281 and 282: Maynard Smith, John producing a 200
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meiosis Zoology. He became director
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Mendel, Gregor of the fertilized eg
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Mendelian genetics an American gene
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0 Mendelian genetics the environmen
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microevolution Stanley Miller did o
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missing links Batesian mimicry. Nam
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mitochondrial DNA Hominin skulls ha
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molecular clock these scientists di
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0 mutualism function of the protein
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natural selection Fact 1. Populatio
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natural selection Three types of na
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natural theology different kinds of
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Neandertals different species of hu
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0 Neolithic Neandertals lived short
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new synthesis In contrast to progen
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noncoding DNA Some regulatory molec
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origin of life they refer to life t
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origin of life Are Humans Alone in
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00 origin of life It is often said
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0 Origin of Species (book) ribose);
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0 Orrorin ———. On the Origin
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0 Paley, William in the Chordata) e
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0 peppered moths There remained som
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0 Permian extinction produced in la
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Permian period upon the exploitatio
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Piltdown man found in slightly diff
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plate tectonics The Earth’s surfa
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population Percent of Mammal Genera
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0 population genetics Vandermeer, J
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population genetics If allele A is
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Precambrian time at least some gene
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progress, concept of arboreal prima
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promoter Each chromosome contains t
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0 punctuated equilibria and persist
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punctuated equilibria Gradualism wa
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Quaternary period epoch of the Quat
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ecapitulation would cause some of t
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eligion, evolution of pathogens nev
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0 reproductive systems Catkins of m
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eproductive systems Scobell has inv
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eproductive systems fact, there is
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eptiles, evolution of Blanckenhorn,
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esistance, evolution of ineffective
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0 respiration, evolution of There i
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Sagan, Carl (1934-1996) American As
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tain features are universally recog
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The testing of hypotheses accumulat
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the results are sufficiently intere
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een wrong: His hypothesis of the co
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Comparison of Inherit the Wind with
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and others form more complex struct
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endonuclease gene is then used as a
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e able to do the same thing. Second
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mosomes come in groups of five rath
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eliminated—that is, if sexual rec
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one, free of parasites, is likely t
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nesses of resource acquisition and
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Zahavi, Amotz. The Handicap Princip
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and it is not happening extensively
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this, too, is a genetically based u
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monkeyflowers of the genus Mimulus)
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Further Reading Abrahamson, Warren
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comes from the unfertilized egg, ra
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of the bacteriophages. Therefore, h
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technology Technological and Cultur
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thermodynamics • Plants. The flow
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thermodynamics return to their orig
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00 Triassic period more resulting l
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unconformity An unconformity is a g
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sissippi River is getting shorter e
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ago. This was the birth of the Sun.
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0 vestigial characteristics algae.
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Wallace, Alfred Russel (1823-1913)
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genetic inferiority of the lower cl
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that point onward he questioned the
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Carl R. Woese pioneered the use of
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Darwin’s “One LOng argument”:
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the young seedlings must compete wi
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Traits can reappear after even hund
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ated: It has been an advantage in o
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chapter 10. On the imperfection of
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out in competition with the species
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languages. Linguists classify all R
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My theory has been much maligned. T
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Index Note: Boldface page numbers i
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asexual propagation 370-371 Ashfall
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Bryan, William Jennings creationism
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ird evolution 62-63 cladistics 72-7
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divergence molecular clock 278-279
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extinction 159-160. See also mass e
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Gondwana (Gondwanaland) 68, 84, 86,
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Huxley, Julian S. 200 eugenics 146
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Mendelian genetics and 268 Spencer,
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Origin of Species (Darwin) 433-434
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ocean currents 179, 207 Oceanian re
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polar cells 368 Polkinghorne, John
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Sanger, Frederick 55 Sanger, Margar
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spores 264, 370 spotted hyena (Croc
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useless characteristics 409 Ussher,
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