Bipedal Locomotion - Critique Of Anti-evolutionary Argument

Can Australopithecus afarensis please stand up? Emily A. Gatlin Ecology and Evolutionary Biology 305 Dr. Randall Small 26 February 2009

“The reason we stood up is the million -dollar question in anthropology.” -Dan Gebo

Charles Darwin. Scholar or theologian, Darwin‟s name alone conjures up a fierce reaction— respect for his brilliant originality or the defensive renouncement of his ideas. The theory of evolution or that “the adaptation of populations to their local environment was the sole cause of transmutation… [Through selecting] killing useless variations in a ruthless „struggle for existence‟” [1]. Clearly, this concept “to fight for existence” is at great odds with a religious faith espousing the compassion of an omniscient Creator who designed Earth for humans to preside over all living creatures and organisms [1]. Thus, Darwin‟s The Origin of Species (1859) initiated a dispute between religion and science that has yet to end. Today, the National Academy of Sciences describes a “creationist” as “someone who rejects natural scientific explanations of the known universe in favor of special creation by a supernatural entity” [2]. Religious fundamentalists persistently criticize attempts by paleoanthropologists, biologists and other scientists from perpetuating any scientific explanation for human origins such as evolution. Today, the struggle for the teaching of evolution within public schools is a huge issue as “intelligent design” provides another alternative to the “disbelievers” of evolution. The basic argument behind intelligent design states, “biological structures are so complex that they not have evolved through processes of undirected mutation and natural selection… [this is] irreducible complexity” [2]. Additionally, “intelligent design‟s” appeal

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stems from the claim of the “belief” 1 in the micro-molecular evolution, but mostly reject any view of macroevolution—especially if it suggests human evolution from an apelike ancestor [2]. It follows that anti-evolutionists will continue to deny vehemently any suggestion toward the idea of human evolution even if evidence within the fossil record supports an evolutionary explanation. However, it is clear that specialized derived characteristics exist within humans to distinguish us from other Homininae.2 For paleoanthropologists, one of the most hominine features is bipedal locomotion. Therefore, a clear indication for hominid evolution stems from the emergence of the anatomical structures and morphology that allow us to possess this specialized means of locomotion, bipedalism. Within the fossil record, many paleoanthropologists point to key morphological features to distinguish hominins3 from other classifications of hominoids [3]. For example, the emergence of bipedal locomotion in the fossil record exhibits a unique derived characteristic of humans and their ancestors [4]. The earliest record for hominid ancestors is the Australopithecines. Paleoanthropologists generally accept the first appearance of the Australopiths in eastern Africa approximately 5.8 million years ago (Ma.) [5]. Although the fossil record contains fragmentary remains of Australopithecines, the earliest fossils used to provide biological information are no older than 4-million-years old [6]. Using the available data, paleoanthropologists still conclude that the Australopithecines possess many anatomical features that indicate a human evolution from these apelike ancestors. For example, when Mary Leakey‟s team discovered the remains of a hominid now commonly referred to as “Lucy,” anthropologists were able to gain a higher understanding of an early hominid‟s morphological characteristics. “Lucy” (A.L. 288-14) is an Australopithecus afarensis approximately 3.18 Ma with “more detail than any comparable fossil…it includes

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Belief exists in quotations because in reality, the scientific theory of evolution is colloquially a fact and the proper terminology for scientific theory to distinguish it from belief fields (or fields not founded in research) is the word acceptance [17] 2 This is the subfamily Homininae, which consists of humans and the African large bodied apes 3 Hominins represent the taxonomic tribe Hominini (within the subfamily Homininae) which includes all species of genera Homo and Australopithecus [15] 4 This is the specimen identifier

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many of the lower-limb bones, one of the innominate5 bones, and an intact sacrum” [4]. These key morphological features provide the backdrop for L. Owen Lovejoy‟s postulate that A. afarensis lived as a committed biped [4]. Lovejoy points to many features of the postcranial morphology that strongly suggest bipedal locomotion. For example, the long femoral neck allows the lengthening from the gluteus maximus and minimus mm. that allows for the stabilization of the trunk that allow us to remain balanced while taking a step forward [4]. Additionally, the loss of the divergent big toe in “Lucy” or AL 228-1 supports a bipedal form of locomotion. In addition, D.C. Johanson and T.D. White support Lovejoy‟s hypothesis that A. afarensis exhibits post-cranial anatomy consistent with bipedalism [7]. They estimate that the humerofemoral index (limb proportions6) is around 83.9%, which is closer to our humerofemoral index of around 70% [7]. In contrast, subsequent studies at SUNY Stony Brook hypothesized using the structure of the attenuation anterior-posterior pelvis that A. afarensis did not have the correct posture to exhibit committed bipedalism and was probably more arboreal quadrupeds [8]. However, the most accepted consensus today regarding A. afarensis is primary bipedal locomotion with the preservation of some primitive arboreal quadruped features such as the curved foot and hand phalanges [9]. This curvature of the phalanges is more characteristic of lesser primates (i.e. chimpanzees)—indicating a slight reliance on arboreal quadrupedalism [9]. Nonetheless, the valgus knee (AL 124 -1a & AL 124-1b) possesses the most informative information since “human babies do not have valgus knees; this feature develops as a direct result of bipedalism” [9]. Therefore, the retention of the primitive characteristics suggests the need to escape into trees for protection and sleeping within the A. afarensis. Despite the clear anatomical evidence, creationists continue to argue against any evolutionary argument behind these features of bipedalism. Creationist Marvin Lubenow focuses his attention on the 5 6

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Innominate bone is a part of the collective primate pelvis also called the os coxae The measure of the ratio between the humerus and femur—a ratio that tends to go to 1 in lesser primates.

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aforementioned disparities for A. afarensis as a biped [10]. He argues that any feature that possesses higher similarity with a lesser primate indicates that paleoanthropologists are unable to support the evolutionary explanation. However, as mentioned previously, these apelike characteristics remain present within A. afarensis due to the need for protection—protection offered by trees. Similarly, Michael Oard also points to these features of arboreal lifestyle to argue that A. afarensis is not human [11]. He emphasizes the how cranially, the skeleton exhibits more similarities to humans and mentions the same divergences postcranially. Again, the creationist viewpoint fails to consider the environmental context surrounding A. afarensis. In order to escape a predator or sleep safely, a three-foot statured hominid in Africa clearly still needed the ability to climb trees effectively in order to survive—directly supporting Darwin‟s “struggle for existence.” Therefore, the appearance of these primitive features is direct evidence to support natural selection. Moreover, Michael Oard points to the existence of parallelism within the cladistic phylogeny if we are the descendents of A. afarensis without considering how in almost every scenario, parallelism is present within the proposed phylogeny [3]. However, the best interpretation contains the least parallelism and Oard fails to consider the parallelisms present from cranial features alone by not incorporating A. afarensis into our phylogeny. In conjunction with this misunderstanding of cladistic phylogeny and parsimony, creationist Alexander R. Williams presents a similar flawed logic [12]. Williams bases his argument on the Laetoli footprints found in East Africa by stating, Ape feet [are] like our hands, with an opposable big toe (like our thumb). Human feet are different from any in the animal world… The Laetoli footprints are clearly telling us that man was walking around as he does today when he first appeared in the fossil record. There is no sign of evolution here! [12].

Williams assumes that evolution has a distinct direction; evolution moves in a direction toward us. Nevertheless, evolution possesses no direction [13]. It is merely the most advantageous adaptations for a particular environment. Moreover, as stated earlier, evolution is rarely completely parsimonious and

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Williams tries to incorporate that any evidence for reversals demonstrates the inadequacy of evolutionary theory. However, the loss of an anatomical feature arises from another external shift (i.e. bipedalism) that arises due to natural selection. Therefore, the creationists fail to provide an adequate explanation in the context of A. afarensis behavior due to the misinterpretation of evolutionary theory and the failure to incorporate the environmental factors. Charles Darwin left behind a legacy of conflict between science and religion that continues today. Creationists continue to dispute the scientific theory of evolution despite multiple announcements throughout various secular faiths to confirm that science does not conflict with religion. Perhaps, someday, science and religion adapt to one another.

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REFERENCES Bibliography [1] Peter J. Bowler, "Darwin's Originality," Science, vol. 333, pp. 223-226, January 2009. [2] National Academy of Sciences, "Creationist Perspectives," in Science, Evolution, and

Creationism. Washington, D.C.: The National Academies Press, 2008, ch. 3, pp. 37-45. [3] Henry M. McHenry, "Homoplasy, Clades, and Hominid Phylogeny," Contempory Issues in

Human Evolution, vol. 21, pp. 77-86, 1996. [4] C. Owen Lovejoy, "Evolution of Human Walking," Scientific American, vol. 259, no. 5, pp. 118-125, November 1988. [5] Glenn C. Conroy,. New York, New York: W.W. Norton & Company, Inc., 2005, ch. 4-8, pp. 81-293. [6] C. Owen Lovejoy, , DT Rasmussen, Ed. Boston: Jones & Bartlett, 1993, pp. 1-28. [7] D. C. Johanson and T. D. White, "A Systematic Assessment of Early African Hominids,"

Science, vol. 203, no. 4378, pp. 321-330, January 1979. [8] Carol V. Ward, "Interpreting the Posture and Locomotion of Australopithecus afarensis: Where Do We Stand?," Yearbook of Physical Anthropology, vol. 45, pp. 185-215, 2002. [9] Andrew Kramer, Australopithecus afarensis Behavior, February 9, 2009. [10] Martin Lubenow. (2006, November) Answers in Genesis. [Online]. http://www.answersingenesis.org/articles/am/v1/n2/selam-from-ethiopia [11] Michael Oard, "Did Lucy Walk Upright?," TJ (Journal of Creation), vol. 15, no. 2, pp. 9-10, August 2001. [Online]. http://www.answersingenesis.org/tj/v15/i2/lucy.asp [12] Alexander R. Williams, "'Oldest' Hominid Footprints Show No Evolution," Creation, vol. 4, no. 32, p. 32, September 1993. [13] Douglas J. Futuyma, "The Origin and Impact of Evolutionary Thought," in Evolutionary

Biology, 2nd ed. Sunderland, Massachusetts: Sinauer Associates, Inc., 1986, ch. Chapter 1,

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REFERENCES pp. 1-17. [14] The Tree of Life Web Project. (1999, January) The Tree of Life Project. [Online]. http://tolweb.org/Hominidae/16299 [15] Dictionary.com. (2009) A Ask.Com Website. [Online]. www.dictionary.com [16] L.C. Aiello and P. Andrews, "The Australopithecines in Review," in The Human Evoution

Source Book, 2nd ed., R. L. Ciochon and J. G. Fleagle, Eds. Upper Saddle River, NJ: Pearson Prentice Hall, 2006, pp. 76-89. [17] Mario Bunge, "What is Pseudoscience?," The Skeptical Inquirer, vol. 9, pp. 36-46, Fall 1984.

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