The Yucatan, Mexico impact, which is believed to have led to mass extinctions including that of the dinosaurs, occurred at the end of the Cretaceous, about 65 million years ago. See Perkins 2003a; Kerr 2002c; Mukhopadhyay et al. 2001; Becker et al. 2000; ScienceDaily; Kyte 1998; Alvarez 1997.
On the dinosaurs, see Makovicky et al. 2005; Zimmer 2005a; Lambert et al. 2001; Padian and Currie 1997; and "The Paleontologist's Tale, note 27. According to the Institute for Creation Research (ICR) and Answers in Genesis (AiG) (the world's two leading young-Earth creationist organizations), dinosaurs were contemporaneous with man and were included with the animals on Noah's ark, "then gradually disappeared in post-flood centuries due to climate changes and other possible causes" (DeYoung 2002; Ham 2003). However, the ICR has cited accounts of a creature called Mokele-mbembe in Africa as evidence that some dinosaurs may still exist in remote jungles of the world (W. Gibbons 2002).
2 On the evolution of mammals, see Bininda-Emonds et al. 2007; Kielan-Jaworowska et al. 2004; Gore 2003; Wyss 2001; Murphy et al. 2001; Pennisi 2001f; Ming et al. 2006. On the evolution of the order Cetacea (whales, dolphins, and porpoises), see Spoor et al. 2002; ScienceDaily; Gingerich et al. 2001; Stokstad 2003; Rose 2001; Thewissen et al. 2001; Harder 2001a; see also "The Biologist's Tale," note 38.
On primates, see de Waal 2001; Matsuzawa 2001; Franzen et al. 2009; and Science 316:215-246 (featuring rhesus macaque research). It is estimated that primates diverged from other mammals over 80 million years ago (Tavare et al. 2002). The higher primates, or anthropoids, include monkeys and the hominoids (superfamily Hominoidea, or apes and man, with man being the only surviving hominid [family Hominidae]). (On use of the broader term "hominin," see Berger 2001.) On anthropoid origins, see Jaeger and Marivaux 2005.
3 These are the "main events" outlined in Lewin 1997, 32-33. See Zimmer 2005c and Jim Foley's "Fossil Hominids" on the human family tree. Bipedalism may have evolved many times in vertebrate history. The extinct ape Oreopithecus bambolii, which lived on a Mediterranean island from 9 million to 7 million years ago, is believed to have walked on two legs. (See Bower 1998a and Kohler and Moya-Sola 1997.) The long-held theory that bipedalism and the first hominids arose when tree-dwelling apes, possibly due to climatic change, moved out into open savannas, has been called into question by the discoveries of 6-million-year-old Orrorin tugenensis (see note 11) and nearly 6-million-year-old Ardipithecus kaddaba (see note 8), both claimed to be hominids who lived in wooded environments (Balter and A. Gibbons 2001; Woldegabriel et al. 2001).
4 Sarich and Wilson 1967; Wood 2002; A. Gibbons 2002a; Haile-Selassie 2001. For a study suggesting two divergences between man and chimpanzee, with hybridization (interbreeding) in between, see Patterson et al. 2006.
5 The Toumai ("hope of life") skull (Sahelanthropus tchadensis), found in Chad in 2001, with more specimens found subsequently, is a disputed candidate--along with Orrorin (note 11) and Ardipithecus kaddaba (note 8)--for oldest known hominid. (See Brunet et al. 2005, 2002a, 2002b; Wood 2002; Gibbons 2005a, 2005b and 2002d; Wolpoff et al. 2002; Bower 2002a; Parsell 2002; see also note 26.)
6 See Bower 1993a; Simons 1989; Nickels 1986.
7 Johanson 1996; Johanson and Maitland 1981. Paleoanthropologist Donald C. Johanson (1989, 20) nicknamed his three-million-year-old australopithecine Lucy because a tape of the Beatles' "Lucy in the Sky with Diamonds" was playing in camp during the specimen's discovery (Johanson 1989, 20). On a juvenile female A. afarensis found in 2000 at Dikika, Ethiopia, the most complete partial skeleton of a hominid child yet found, see Alemseged et al. 2006.
8 Leakey et al. 1995 and 1998; Bower 1995; Culotta 1995b.
Tim D. White and Meave Leakey (wife of Richard Leakey) are among paleoanthropologists who hypothesize that Australopithecus afarensis ("Lucy") evolved from Australopithecus anamensis (dating from 3.9 to 4.2 million years ago), and that A. anamensis evolved from Ardipithecus ("ground ape") ramidus (Bower 1998c; White et al. 2006), a 4.4-million-year-old fossil hominid discovered by White in Ethiopia (White et al. 1994 and 1995; see special Science issue on "Ardi," 10/2/09). In 2004 White and his colleagues announced the new hominid species Ardipithecus kaddaba (previously the subspecies Ardipithecus ramidus kaddaba), after finding new specimens in Ethiopia (Haile-Selassie et al. 2004). Dating from 5.6-5.8 million years ago, Ardipithecus kaddaba is arguably the oldest known hominid after the divergence of man and chimp (between 6 and 8 million years ago) (Begun 2004). White's colleague Yohannes Haile-Selassie (2001) has questioned the hominid status of 6-million-year-old Orrorin (see note 11).
Later Australopithecus species, living as late as one million years ago, include A. africanus, A. aethiopicus, A. robustus, and A. boisei. In 1999 Tim White and colleagues announced the discovery in Ethiopia of a new species, 2.5-million-year-old A. garhi, which they believe descended from A. afarensis and is possibly an ancestor of early Homo (Asfaw et al. 1999; Groves 1999; Culotta 1999a; ScienceDaily). There is disagreement as to whether A. bahrelghazali (3 to 3.5 million years old), discovered in Chad by Michel Brunet in 1993 (Brunet et al. 1995), is really a new species and not a variant of A. afarensis (A. Gibbons 2002e). On the Sterkfontein cave specimen called Little Foot (2.2 million years old), see Walker et al. 2006.
9 Gish 1995a, 262. Retired ICR vice president Duane Gish (1986) has said it's "silly" to argue about whether the australopithecines are transitional forms, since "even evolutionists argue about that." See also note 15 below.
10 Futuyma 1979, 78. Johanson (1989, 20-21) calls all fossil finds "miraculous" because of the odds against them.
11 On the disputed hominid status of Orrorin ("original man" in northwestern Kenyan dialect, also called "Millenium Ancestor," the bones having been found in 2000), see Balter 2001a. For a study supporting bipedal locomotion of Orrorin "at the dawn of the human lineage," see Galik et al. 2004; for a critique and response, see Ohman et al. 2005 and Galik et al. 2005. On Ardipithecus, see note 8 above.
12 On the 3.5-million-year-old hominid Kenyanthropus platyops, with its surprising combination of small molars and flat face (unlike Lucy from the same period), see Leakey et al. 2001; Balter 2001c; Bower 2001b; ScienceDaily. Tim White questions whether Kenyanthropus is "a valid taxon" or "simply an early Kenyan variant of A. afarensis" (White 2003).
13 The oldest known Homo fossil (no species assigned) is a 2.3 million-year-old partial upper jaw discovered in Ethiopia. (See Bower 1996.) The oldest known stone tools, also found in Ethiopia, are over 2.5 million years old (Semaw et al 1997).
14 Homo habilis was found by Louis and Mary Leakey at Tanzania's Olduvai Gorge in the 1960s. The first specimen was about 1.75 million years old. See Leakey 1984.
15 The australopithecines, says Gish (1995a, 261-262), "were simply apes," and H. habilis was "just another variety" of australopithecine. Some experts have indeed argued that H. habilis, based on small brain size and other features, should be reclassified from Homo to Australopithecus (Wood and Collard 1999; Brooks and Potts 2000; see also Blumenschine et al. 2003). But the fossils in question are nonetheless hominids, not "simply apes." (See Jim Foley on creationist arguments regarding the australopithecines and H. habilis.)
16 Isaiah 6:9; Matthew 13:14; Mark 4:12; Acts 28:26. "The so-called 'ape-men'," argued the late creationist leader Henry Morris (1995b, 31), "can all be shown to be either remains of extinct apes or of true men, probably all living after the Flood."
17 Java Man, the first fossil specimen (a skullcap) of Homo erectus, was discovered by Eugene Dubois in 1891. The Javenese H. erectus lineage apparently remained isolated, with its morphological distinctiveness intensifying, over a period of about a million years. In 2001 a skull was discovered in Java that is "intermediate between that of earlier and later Javenese Homo erectus" (Baba et al. 2003).
The bones of Peking Man (Homo erectus) were lost during World War II. This has led some creationists (e.g., Keith 1982, 5) to suggest that Peking Man was a hoax (a la Piltdown Man, called "the greatest hoax in the history of science" [Blinderman 1986; see Carroll 2002 and Gee 1996]). But casts of the Peking Man bones still exist as do many other H. erectus specimens, including more from the Peking area (Eldredge 1982, 125-131). On Peking Man, see Boaz and Ciochon 2004.
18 There is fossil evidence of H. erectus in Asia and Kenya as early as 1.8 million years ago (see Curtis et al. 2000; Huang et al. 1995; Wood and Turner 1995; Culotta 1995a; Swisher et al. 1994; Bower 1994 and 2001c; Shreeve 1994; Brown et al. 1985 [on Turkana Boy]). The oldest known human presence in northeast Asia, indicated by stone tools in north China dating from 1.66 million to 1.32 million years ago, imply a long yet rapid migration from Africa (Zhu et al. 2004).
19 Balter and Gibbons 2000, quoting paleoanthropologist Peter Andrews.
20 If H. erectus were nicely groomed and put on a subway, says Ernest Conrad (1986, 32), "people would not only notice, they would move to the other end of the car."
21 This is the view stated in the ICR's quasi-official textbook Scientific Creationism (H. Morris 1985, 174). Retired ICR vice president Gish (1995a, 304), however, has argued that H. erectus specimens "are definitely from the ape family with no link of any kind to Man."
22 Futuyma 1982, 111. On evidence that humans are still evolving through natural selection of genes, see Voight et al. 2006 and Wade 2006; see also Evans et al. 2005 and Balter 2005a.
23 The French anthropologist Marcellin Boule constructed the Neanderthal stereotype from a skeleton with arthritis in the neck, jaw, and spine (Conrad 1986, 26; Gould 1988, 20).
On Neanderthal Man, see Klein 2003; Balter 2004b and 2001e; Bower 2004a; Culotta 2005a; Tattersall 1999; Foley 1996-2005; Gore 1996; and note 24 below. On analysis of DNA from Neanderthal fossils, including evidence that Neanderthals and ancestral humans split between around 500,000 and 370,000 years ago, see Green et al. 2006 and Noonan et al. 2006. Clear evidence that Neanderthals practiced cannibalism 100,000 years ago has been found in a French cave (Defleur et al. 1999; Culotta 1999b; Bower 1999e). On the degree to which Neanderthals and early modern humans may have mated, see Culotta 2005b.
24 On the question of which Homo species introduced intentional burial, see Harder 2001b.
On whether or not the Neanderthals could speak, ICR president John Morris calls them "descendants of Noah--a language group that migrated away from Babel," who "were as human as you or I" (1997).
In 1998 researchers reported that the hypoglossal canal, a bony tube at the bottom of the skull through which the hypoglossal nerve passes from the brain to the tongue, shows enlargement in fossil hominids as old as 400,000 years, suggesting that Neanderthals as well as other early Homo species had the ability to speak (Bower 1998b). It is generally agreed that humans had the necessary brain capacity and mouth and throat anatomy necessary for spoken language more than 150,000 years ago, but not until 40,000 years ago was there a "creative explosion" in language-suggestive behavior such as burials, living sites, and art and personal adornment (Holden 2004 and 1998). On perhaps the oldest known jewelry, 75,000-year-old beads from South Africa made of perforated shells, see Henshilwood et al. 2004 and Holden 2004. On evidence from the Skhul cave in Israel (see note 26) that shells worn as beads may date back 100,000 or more years, see Vanhaeren et al. 2006 and Balter 2006a. On cave art, dating back 30,000 years, see Valladas et al. 2001. On pigment possibly used for body coloring 164,000 years ago, see Bower 2007.
On the evolution of language, see Deutscher 2005; Holden 2004b; Pennisi 2004a; Christiansen and Kirby 2003; and Hauser, Chomsky, and Fitch 2002; see also Premack 2004 and Bever and Montalbetti 2002. On the possible role in the emergence of speech and language of the regulatory gene FOXP2, the present human version of which dates back no more than 200,000 years, see Balter and Gibbons 2002. For studies on the origin of the Indo-European language family (including English and the Germanic, Slavic, and Romance languages), supporting the theory that Indo-European languages expanded and evolved with the spread of agriculture from Anatolia (central Turkey) beginning around 8,000 to 9,500 years ago, see Balter 2004, Balter and Gibbons 2003, and Gray and Atkinson 2003. On the evolution of agriculture, see Bower 2005a and "The Geologist's Tale," note 21.
Whether or not they could speak, the Neanderthals may have had rhythm. See musicologist Bob Fink's Neanderthal Flute, and Wong 1997, on possibly the world's oldest known musical instrument, made from a bear thigh bone as much as 82,000 years ago, found at a Neanderthal campsite in Slovenia. (See also Science 276:203.) For the dissenting view that the so-called flute is a bone with holes that were gnawed by some animals, see Bower 1998e, which includes Fink's rebuttal.
25 Beginning in 1987, studies of mitochondrial DNA (mtDNA), inherited only through the female line, led to the much-publicized hypothesis that the most recent common ancestor of all modern humans was a woman ("mitochondrial Eve") living in Africa between 100,000 and 200,000 years ago (Cann et al. 1987; Brown 1990; Vigilant et al. 1991). (On how mutations in mtDNA allowed humans to adapt to colder climates as they migrated out of Africa, see Ruiz-Pesini et al. 2004.)
In 1997, two teams of scientists reported that tracing back the Y chromosome (the male sex chromosome, passed from fathers to sons) led them to what may be called "Y chromosome Adam," a man who lived in southern Africa in the same time frame as the hypothetical "mitochondrial Eve" (see Gibbons 1997b; see also Bower 2000b on a later Y chromosome study).
Fossil support for these genetic studies now exists, thanks partly to three near-modern human skulls found near the village of Herto in Ethiopia by Tim White and colleagues, and argon-potassium dated to between 154,000 to 160,000 years ago. Intermediate between more archaic human fossils and anatomically modern man, the Herto hominids were named Homo sapiens idaltu (idaltu meaning "elder" in the local Afar language), and according to the discoverers "represent the probable immediate ancestors of anatomically modern humans" (White et al. 2003; see also Clark et al. 2003; Stringer 2003; and Wilford 2003). In addition, fossil remains of two early H. sapiens individuals found along Ethiopia's Omo River in 1967 have now been given a radiometrically determined age of 195,000 years, making the Omo fossils "the earliest well-dated anatomically modern humans yet described" (McDougall et al. 2005).
This combined genetic and fossil evidence lends strong support to the "out of Africa" or "replacement" model of human origins, according to which modern humans evolved in Africa, from which they then migrated about 100,000 years ago or less, replacing Homo species in other regions. (See note 26 on the possible late coexistence of two or more Homo species.) The opposing view is the "multiregional" model, according to which modern humans evolved in various parts of the world, after early humans left Africa almost two million years ago. (On the out-of-Africa vs. multiregional models, see Wolpoff et al. 2001; Balter 2001a; Holden 2001; Pennisi 2001a; Balter 2001b; Wong 1999 and 1998; Stringer and McKie 1997; Bower 1999a; and note 26 below.)
Two mtDNA studies of aboriginal inhabitants of Malaysia and the Andaman and Nicobar Islands indicate a single successful migration of anatomically modern humans out of Africa about 65,000 years ago, taking a southern route via India to Australia, with an offshoot of this migration moving north to enter the Levant and Europe (Macaulay et al. 2005; Thangaraj et al. 2005; Forster and Matsumura 2005; see also Olivieri et al. 2006 and Goebel 2007). The Malaysian mtDNA study also yields a time for the most recent common ancestor of all humans (TMRCA, a woman or mitochondrial Eve) of about 200,000 years ago (Macaulay et al. 2005; Wade 2005a). (See also Ke et al. 2001, A. Gibbons 2001a, ScienceDaily, and Templeton 2002 for other genetic evidence supporting the "out of Africa" model.)
Even if the evidence is now heavy on the out-of-Africa side (regardless of whether the migration initially went north or south), the debate isn't over. For example, if dating estimates are confirmed that the Liujiang skull (a H. sapiens fossil found in China) is 111,000 to 139,000 years old, the out-of-Africa proponents must explain how modern humans leaving Africa 100,000 or less years ago reached eastern Asia so rapidly (see Shen et al. 2002 and Bower 2002c). As for the Herto hominids, multiregionalist Milford Wolpoff says, "All the specimens show is that there was a trend of evolution in Africa toward modernity, just as there was in China and Europe" (Wilford 2003). (The oldest known fossil of a modern human in Europe, a jawbone found in a cave in Romania's Transylvanian Alps in 2002, is at least 35,000 years old, based on radiocarbon dating [A. Gibbons 2003a].)
See also Roberts 2002 on fossilized, anatomically modern human footprints, found at Langebaan, South Africa, over 100,000 years old. A pair of human footprints found at Nahoon Point in South Africa, and carbon-14 dated in 1964 at about 30,000 years, has been tentatively redated at about 200,000 years by a new experimental technique called thermoluminescence (TL) (Science 282:1635). (The oldest known human footprints are 325,000 to 385,000 years old, found in southern Italy [Mietto et al. 2003]. The oldest known hominid footprints, found in 1978 by Mary Leakey's team at Laotoli in Kenya, are 3.5 million years old [Leakey 1984].)
26 Fossils from Java suggest that H. erectus lived as late as 27,000 years ago in Southeast Asia (Swisher et al. 1996; A. Gibbons 1996b). There is dispute as to whether or not small-bodied Homo floresiensis, who lived on the island of Flores in Indonesia from as early as 95,000 until as recently as 12,000 years ago, was a modern human--either a now-extinct species of dwarfs (nicknamed "hobbits"), or H. sapiens, resembling pygmies, with microcephaly (pathologically small heads) (A. Gibbons 2007b and 2004; Brown et al. 2004; Jacob et al. 2006; Morwood et al. 2005 and 2004; Falk et al. 2005 and 2006; Martin et al. 2006; Wilford 2006b; Dalton 2004; Bower 2004b; Brumm et al. 2006).
Thus H. erectus, little Flores Man (possibly branching from H. erectus), Neanderthal Man, and early modern man (H. sapiens) were all alive on Earth contemporaneously as late as 27,000 years ago. (On the earliest Australians including Mungo Man, a human skeleton 40,000 years old, see Dayton 2003 and ScienceDaily. On the presence of humans 30,000 years ago in the Siberian Arctic, see Pitulko et al. 2004 and Stone 2004. On the first Americans, arriving via a theoretical land bridge from Asia no earlier than 18,000 years ago, according to a Y-chromosome study, see Seielstad et al. 2003. For a complex theory of American origins, see Gonzalez-Jose et al. 2003. For a genetic study indicating that the founding population for the New World was fewer than 80 individuals [approximately 1% of the ancestral Asian population], see Hey 2005. On marks from human butchering found in woolly mammoth bones near Kenosha, Wisconsin, and dating back 13,500 years, 2,000 years before the so-called Clovis hunters crossed the Bering Strait into America, see Falk 2004. (On the Clovis dating, see Waters and Stafford 2007.) On Kennewick Man, who lived around 9,000 years ago in the American Northwest, see the Kennewick Man Virtual Interpretive Center. On the oldest known civilization in the Americas, a monument-building cultural complex that according to radiocarbon dating flourished in the Norte Chico region of Peru between 5,000 and 3,800 years ago, see Haas et al. 2005 and Mann 2005.)
Interestingly, Neanderthals and early modern humans lived in caves in what is now Israel that were as close as 100 meters apart, but at different times in different climatic conditions (the modern humans from as early as 110,000 to 92,000 years ago in the caves of Qafzeh and Skhul, and the Neanderthals from about 70,000 to 50,000 years ago in the caves of Amud and Kebara) ( A. Gibbons 2003b). (The Qafzeh and Skhul fossils would obviously be of modern humans who ventured out of Africa prior to the theorized migration of 65,000 years ago [see note 25 above and Macaulay et al. 2005].)
These studies support the "bushy" view of human evolution, which sees hominid species as separate, at times coexistent branches, as opposed to the traditional linear view (one hominid species evolving into another) (Wood 202; Gould 1997; Tattersall 1998; Johanson and Edgar 1996). The mosaic nature of the chimp-sized Toumai skull (Sahelanthropus, see note 5), about 7 million years old and arguably the oldest known hominid, suggests early hominid diversity (Wood 202). The discoveries of Sahelanthropus, Ardipithecus, and Orrorin indicate that early hominids were geographically more widespread than previously thought (Brunet et al. 2002). The differing hominid species A. afarensis (Lucy) and Kenyanthropus platyops (see note 12) lived in the same time period (between 3 and 4 million years ago), and Meave Leakey, the discoverer of Kenyanthropus, says "I personally believe we'll find more" (Gugliotta 2001). Fossils intermediate between late H. erectus and archaic H. sapiens, the latter appearing about 500,000 years ago, include a skull found near Heidelberg, Germany in 1907 and classified as Homo heidelbergensis (Foley 1996-2003). The bushy view seems to get even bushier with H. antecessor, a species announced in 1997 based on 800,000-year-old hominid fossil remains found in Spain. Its discoverers believe H. antecessor may be the common ancestor of the Neanderthals and modern humans (Bermudez et al. 1997; see also A. Gibbons 1997a and Kunzig 1997). On H. georgicus, see Gabunia et al. 2002 and A. Gibbons 2003c; on H. cepransensis, see Schwartz 2004.
Tim White cautions against an overeagerness to name new hominid species. He argues that "the metaphor of an early hominid bush seems seriously misplaced," based on "a populist zeal for diversity" (White 2003). White cites, for example, Kenyanthropus, which he suggests may be an australopithecine (White 2003; see note 12 above), and believes that Sahelanthropus, Orrorin, and Ardipithecus kaddaba, three rivals for the title "oldest known hominid," may be variations within a single genus (Haile-Selassie et al. 2004). See also note 8 on the australopithecines.
27 See "The Biologist's Tale," lines 63-69, note 7.
28 See "The Biologist's Tale," lines 101-135.
29 Ruse 1982, 5. I have substituted "baboons" for Ruse's "orangutans" for the sake of meter. Not that orangutans would be any less offended by Ruse's question.
30 Gould 1987, 68.
31 The late geneticist Theodosius Dobzhansky (1973), one of the giants of modern evolutionary theory (see "General Prologue," note 4), was a theist who doubted that God would plant false evidence of evolution as if "deliberately to mislead sincere seekers of truth." See "The Astronomer's Tale," notes 26-27. On Dobzhansky, see "General Prologue," notes 3-4.
32 Lewin 1997, 59.
33 Moore 1976, 81.
34 Wilson 1985, 130. See "The Philosopher's Tale," lines 318-324.
35 Lorenz 1966, 238.
36 Paleontologist George Gaylord Simpson was, like Dobzhansky (note 31), one of the founding fathers of the modern synthesis (see "General Prologue," note 4). The "statement" recalled is actually a condensed merger of two passages from Simpson's writings (1964, 25 and 1967, 311). On the effects of human activity on evolution, see Palumbi 2001. For a futuristic view of human and artificial intelligence, see Kurzweil 2005.
Philosopher of science Michael Ruse has cautioned against making evolution-based moral judgments or value statements such as Simpson's. Ruse distinguishes between this "popular" kind of evolutionism that creationists might with some justification call "a kind of secular religion," and "professional evolutionary biology," which is "no more a secular religion than is industrial chemistry." Ruse argues that "we who cherish science should be careful to distinguish when we are doing science and when we are extrapolating from it, particularly when we are teaching our students" (Ruse 2003b).