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Wednesday, August 31, 2011

THE DEBATE OVER HUMAN ORIGINS: Evolution and Polygenism

This is the next part of my examination of human origins. In this part, I give a quick summary of the theory of evolution involving humans (with a, I think, fascinating digression to discuss Neanderthals). Then I explain some aspects of polygenism. More to come!

Polygenism has its roots in the evolutionary theory of man’s origins. The traditional evolutionist account holds that the human species (Homo sapiens) evolved from the same simian ancestors that produced the “great apes.” Along the path to humanity, one finds a host of characters, all ancestors in the evolutionary family tree. The first, a sort of great-great-grandfather for humanity, is Australopithecus afarensis, the first bipedal primate. It lived about 3.3 million years ago (the oldest fossil of this species, nicknamed the Dikika Baby, dates to that time).[i] Part human, part ape, Australopithecus features a body structured for walking, like a modern human body, but with arms designed for climbing. It’s skull bears a closer resemblance to an ape than a man, and scientists now agree it is, at best, a human ancestor, but not a human.[ii] Australopithecus’ evolutionary descendents, according to the current scientific theory, are a series of progressively more human creatures, each one giving a small contribution to the development of the human race: Homo habalis chipped pebbles into tools; Homo ergaster developed more elaborate tools, as well as forming “a family structure in which fathers protected and provided for the mothers of their children.”[iii] Homo erectus developed weapons, putting stones on sticks. Following this line of descent, Homo erectus’ descendents eventually evolved into two branches: the Neanderthals (Homo neanderthalis) and modern humans (Homo sapiens).[iv]

Though often cited as such, due in large part to their human-like body and their apparent ritual of burying their dead, recent evidence proves that Neanderthals were not ancestors of modern humans. A debate still rages over the exact relation between humans and Neanderthals. Some scientists argue that the Neanderthal is a separate species from the modern human (hence the scientific name Homo neanderthalis), while others argue that the Neanderthal is a sub-species or race of humans (whose scientific name would be Homo sapiens neanderthalis). Scientists who support the two species theory point to the genetic differences between Neanderthals and modern humans, information unavailable prior to the sequencing of the Neanderthal genome.[v] The project found “3 million base pair differences between Neanderthals and Homo sapiens,” far fewer differences than that of a human and its closest genetic match, a chimpanzee.[vi] At the same time, there is also evidence of interbreeding between modern humans and Neanderthals. A recent study found that “Between 1% and 4% of the Eurasian human genome seems to come from Neanderthals,” providing equally compelling evidence that the Neanderthals and humans are of the same species.[vii]

Homo sapiens share many traits with earlier hominids, but there is one unique, crucial difference: Homo sapiens can talk. Anthony Zimmermann notes that the earlier hominids “could not have spoken a human language as fluently and as richly articulate as we are able to do. Our advanced type of speech organs would not have fit into their skeletal forms.”[viii] Verbal communication is a key to proving man’s rationality and immortal soul.

The evolutionary process described above assumes a theory of polygenism. Scientists normally list two supports for a polygenetic origin of the human race: “A) One human pair would be too narrow a base genetically for mankind and would imply a genetic weakness of an inbreeding type” and “B) The emergence of any new species normally takes place in numerous individuals about the same time.”[ix] Evolution does not provide a model for individual specimens arising alone, as a theory of monogenism requires. Adaptations happen in groups. These changes often happen in specified places where the conditions are most ripe for adaptation, and because of this, most scientists follow the theory of monophyletism, that is, that Homo sapiens evolved in one isolated region of the world, in one specific population, and from that population spread throughout the world. Support for Monophyletism comes from the discovery of “mitochondrial Eve,” the most recent common female human ancestor who lived in Africa about 143,000 years ago, as well as the “Y-chromosomal Adam,” the most recent common male human ancestor who lived in Africa about 60,000 years ago. Both individuals lived in East Africa, supporting monophyletism; at the same time, scientists could use the discovery as evidence for polygenism. As Dr Gareth Leyshon notes,

There may have been other women accompanying Mitochondrial Eve; their sons would breed with Eve’s daughters and produce offspring with Eve’s mitochondrial DNA. The other women would also produce daughters, but no humans alive today are descendents of these daughters down the purely female line. . . . And similarly, other men could have been around at the time of “Y Chromosome Adam”; any line of descent from them including a female would lose their Y chromosome. All we know for sure is that no direct male lines of sons survive from these fellow men.[x]

The genetic “Adam” and “Eve” are not the Biblical Adam and Eve. In fact, the genetic “Eve” might represent one individual of thousands sharing a similar genetic makeup, thereby lending credence to polygenism.[xi]

Polygenism’s disregard for God’s hand in creation has placed this theory at odds with many Christians. Those that oppose this theory usually cite the story of Creation in Genesis as a counterargument. There is a fear in some circles that a truth of science will somehow counter a truth of faith. The Catholic should hold no such fears, for, in the words of Bl. Pope John Paul II, “We know that the truth cannot contradict the truth.”[xii] Any truth of science compliments Theology, the Queen of Sciences. One should not fear comparing the theory of evolution to the Creation account, for in doing so the truth shines forth.

[i] Christopher T. Baglow, Faith, Science, and Reason: Theology on the Cutting Edge (Woodridge, IL: Midwest Theological Forum, 2009), 242–243.

[ii] Ibid., 251.

[iii] Ibid., 252.

[iv] Ibid.

[v] Baglow, 252; Fiorenzo Facchini, “Man, Origin and Nature,” translated by Barbara Zanotti and Eva Bruno, available at http://www.disf.org/en/Voci/121.asp, accessed 7/7/11.

[vi] Jacqui Hayes, “DNA find deepens Neanderthal mystery,” Cosmos Online (16 November 2006), available at http://www.cosmosmagazine.com/news/853/dna-find-deepens-neanderthal-mystery, accessed 7/8/11. Humans and Chimpanzees differ by 30 to 50 million base pairs (Ibid.).

[vii] Paul Rincon, “Neanderthal genes ‘survive in us,’ BBC News (6 May 2010), available at http://news.bbc.co.uk/2/hi/science/nature/8660940.stm, accessed 7/8/11.

[viii] Anthony Zimmerman, Evolution and the Sin of Eden: A New Christian Synthesis (Lanham, MD: University Press of America, 1998), 12.

[ix] Ervin Nemesszeghy and John Russell, Theology of Evolution, vol. 6, Theology Today, ed. Edward Yarnold (Notre Dame, IN: Fides Publishers, 1971), 52.

[x] Gareth Leyshon, “The Problem of Original Sin in an Evolutionary System,” (2011), available at www.drgareth.info/Polygenism.pdf, accessed 7/12/11.

[xi] Jozef Zycinski, God and Evolution: Fundamental Questions of Christian Evolutionism, trans. by Kenneth W. Kemp and Zuzanna Maslanka (Washington DC: CUA Press, 2006), 205.

[xii] John Paul II, “Message to the Pontifical Academy of Sciences: On Evolution” (Rome: 22 October 1996), available at http://www.ewtn.com/library/PAPALDOC/JP961022.HTM, accessed 7/8/11.

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