Evidence and Implications: Replacement Model

Evidence for the Replacement Model

In this post, I explain the Replacement Model. As a refresher: proponents of this model maintain that AMH actually emerged out of Homo heidelbergensis in Africa about 200, 000 to 150, 000 years ago, and left Africa as recently as 60, 000 to 40, 000 years ago.

http://www.politicalforum.com/current-events/206817-hints-earlier-human-exit-africa.html

 There is archeological and DNA evidence to support the Replacement Model.

The oldest evidence of AMH presence was discovered in Africa. Border cave, near the border between South Africa and Swaziland, yielded fossil remains of AMH dating back to 200, 000 years ago.

View from the mouth of Border Cave

http://en.wikipedia.org/wiki/Border_Cave

Excavations were initiated in 1940 by W. E. Barton. Raymond Dart realized that the bone remains discovered were extremely old. Further excavations were conducted in 1941 and 1942, then in the 1970's by Peter Beaumont. This last expedition yielded a complete infant skeleton as well as the remains of at least 5 hominins.

An aside: they found as many as 69, 000 artifacts, including an artifact later named the "Lebombo bone", a piece of baboon fibula marked by a number of notches thought to represent lunar phases (cool!).

Lebombo Bone, dated to 37, 000 years ago 

http://fyeahblackhistory.tumblr.com/post/26033197671/knowledgeequalsblackpower-the-lebombo-bone-the

Evidence for AMH presence in other parts of the world only begins to appear 60, 000 to 50, 0000 years later in the archeological record. The archeological record thus far does seem to support the Replacement Model, because it clearly indicates that AMH originated in Africa.

Geneticists have used AMH mitochondrial DNA to determine our place of origin. According to them, "the geographic region in which modern people have lived the longest should have the greatest amount of genetic diversity". Turns out, Africa has the world's greatest genetic density. These geneticists therefore conclude that "Mitochondrial Eve" would have lived in Africa 200, 000 to 100, 000 years ago. This evidence also seems to support the Replacement Model.

Eve might have looked something like this

http://www.bradshawfoundation.com/journey/reconstructed-eve.html

Implications of the Replacement Model 

(1) Neanderthal extinction by violence

AMH may have played a major role in Neanderthal downfall as they spread rapidly throughout the world.  Steven Churchill of Duke University is particularly interested in a particular Neanderthal male found at Shanidar Cave in Iraq.

Shanidar 3's fatal rib injury 

Churchill and his team advance that the rib wound was caused by a thrown spear. Only AMH used projectile weapons; Neanderthals are thought to have hunted at close range (sometimes with horrific consequences). It seems that a AMH was directly implicated in the death of this particular individual. 

Alternatively, AMH may have eaten Neanderthals (!). Fernando Rozzi says that a particular Neanderthal jawbone shows evidence of flesh removal, while the teeth might have been used to make a necklace. 

Remnants of a yummy Neanderthal meal?  

http://www.ablogabouthistory.com/2009/05/18/early-humans-may-have-butchered-and-eaten-neanderthals/

(2) AMH outcompeted Neanderthals 

Some archeologists have argued that AMH outcompeted Neanderthals, who after all lived in very similar ecological niches. In an earlier post, I discussed two factors that may have given AMH an edge over Neanderthals: the division of labor and anatomical differences. 

Other hypotheses abound. 

This article says that AMH's longtime partnership with dogs may have "helped humans by transporting meat and other supplies from one place to another, removing an energy burden from their masters which would have given them an advantage when hunting". Proponents, like Pat Shipman, believe that AMH's use of dogs was essential to their success. 

Another article summarizes the recent discovery of the oldest microliths in South Africa. They date back to 71, 000 years ago, and would have been used to make projectile weapons. While these represent our first evidence of microliths, the trend did not actually take root until after 40, 000 years ago. Nonetheless, it's been argued that this early innovation might have eventually allowed AMH to out compete Neanderthals.

Bibliography 

• "Border Cave - Wikipedia, the free encyclopedia." Wikipedia, the free encyclopedia. N.p., 1 Aug. 2012. Web. 9 Nov. 2012. <http://en.wikipedia.org/wiki/Border_Cave>.
• Collins , Nick . "Dogs 'helped man out-compete with Neanderthals' - Telegraph." Telegraph.co.uk - Telegraph online, Daily Telegraph, Sunday Telegraph - Telegraph. N.p., 16 Mar. 2012. Web. 9 Nov. 2012. <http://www.telegraph.co.uk/science/evolution/9269523/Dogs-helped-man-out-compete-with-Neanderthals.html>.
• Darling, David . "Lebombo bone." The Worlds of David Darling. N.p., n.d. Web. 9 Nov. 2012. <http://www.daviddarling.info/encyclopedia/L/Lebombo_bone.html>.
• Harrell, Eben. "CSI Stone Age: Did Humans Kill Neanderthals? - TIME." Breaking News, Analysis, Politics, Blogs, News Photos, Video, Tech Reviews - TIME.com. N.p., 24 July 2009. Web. 9 Nov. 2012. <http://www.time.com/time/magazine/article/0,9171,1913769,00.html>.
• McKie, Robin. " How Neanderthals met a grisly fate: devoured by humans | Science | The Observer ."  Latest US news, world news, sport and comment from the Guardian | guardiannews.com | The Guardian . N.p., 16 Mar. 2009. Web. 9 Nov. 2012. <http://www.guardian.co.uk/science/2009/may/17/neanderthals-cannibalism-anthropological-sciences-journal>.
• O'Neil, Dennis. "Early Modern Homo sapiens ." EVOLUTION OF MODERN HUMANS: A Survey of the Biological and Cultural Evolution of Archaic and Modern Homo sapiens. Behavioral Sciences Department, Palomar College, San Marcos, California, n.d. Web. 8 Nov. 2012. <http://anthro.palomar.edu/homo2/mod_homo_4.htm>.
• Wong , Kate. "Arrowheads Hint at How Humans Overtook Neanderthals - Business Insider." Business Insider. N.p., 8 Nov. 2012. Web. 8 Nov. 2012. <http://www.businessinsider.com/arrowheads-hint-at-how-humans-overtook-neanderthals-2012-11>.