Tag Archive | "human evolution"

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Genetic History: Some Have Made Their Mark

Posted on 15 January 2014 by Jerry

Genome sequencing is rapidly advancing our knowledge of genetic contributions to the human species.   Recent genetic studies indicate interbreeding between Africans who initially migrated around the world and made up the largest part of the modern human genome, with Neanderthals, Denisovans, and an as yet unknown branch of hominid that contributed to our genetic code.

This new knowledge is demonstrating the evolutionary tree of modern humans includes new ancestral groups.  We see their presence in our genetic code.  This is becoming readily apparent from largely mitochondrial DNA, as well as nuclear DNA, extracted from archeological sites widely distributed in Africa, Siberia, Northern Germany, and Eurasia.

A recent article in Nature shows a likely gene flow that puts the contribution of the unknown ancient population in perspective.  It is from a recent article in the January 2, 2014 issue of nature magazine by Ewan Birney and Jonathan K. Pritchard.  It contains a chart showing first the genetic input of an unknown archaic population was followed by the main human tree splitting into two, with modern Africans separated from Neanderthals and Denisovans and a later branching to two separate  directions for Neanderthals and Denisovans.

This article stated “One surprise was the first clear evidence for interbreeding between Neanderthals and modern humans; another was the discovery of a second type of archaic hominin in Eurasia in addition to Neanderthals.  This group has been dubbed Denisovans.”  Continuing, the article states, “Most provocatively, Prufer et al. find evidence for levels of gene flow into Denisovans of sequence that is different from that of any known group, implying that there is at least one more, so far undiscovered, archaic-hominin group.”

This new information suggests some unusual conclusions can be drawn.  We have dramatically expanded our abilities to extract genetic information from all sorts of ancient remains.  The genetic material used for these studies is from single individuals in the distant past in each population group.  It is clear their presence and existence is indelibly inscribed in our own genetic code.  This knowledge of them has survived the passage of time.  These individuals, who ever they were, have created a lasting impact.

Use the following links to obtain more information regarding this subject matter or to access the source documentation.

http://www.nature.com/nature/journal/v505/n7481/full/nature12847.html

http://www.nature.com/nature/journal/v505/n7481/full/nature12886.html

http://www.cbc.ca/news/technology/neanderthals-incest-interspecies-sex-revealed-by-genome-1.2474245

http://uk.news.yahoo.com/neanderthal-bone-highlights-human-inter-breeding-190309785.hmtl#VaOhuje

http://discovermagazine.com/2013/march/14-interbreeding-neanderthals#.utwoy5udc6u

 

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Bonobos and Chimpanzees: How Close are our Closest Relatives?

Posted on 24 June 2012 by Jerry

It is difficult to be precise when comparing three different animal genomes, each with billions of base pairs, to assess similarity.  Scientists at the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, have however completed sequencing the DNA of a contemporary bonobo and have declared it the second great ape with which human beings share 99.6% of their DNA.  This mirrors an assessment in 2005 when researchers studied the chimpanzee genome.

This finishes sequencing of the genomes of the three most related of the great apes; the human being, chimpanzee, and the bonobo.  Their common genetic ancestry shows that human beings, chimpanzees and bonobos took separate evolutionary paths more than four million years ago, with chimpanzees and bonobos diverging from each other in a more recent timeframe of one to two million years.

What is intriguing about these findings is not the great similarity but rather the differences.  Researchers found that there is about 1.6% of human DNA that is shared with the bonobo that is not found in the chimpanzee.  Conversely, they found about the same proportion of human DNA that is shared with the chimpanzee that is not found in the bonobo. 

While chimpanzees are found throughout equatorial Africa, bonobos are only found in the Democratic Republic of Congo.  The population of bonobos was thought to be isolated from chimpanzees with the formation of the Congo River which may have physically separated the two groups more than a million years ago.

There are some notable behavioral differences between the two species.  Male chimpanzees are territorial and dominant.  The males compete aggressively for rank dominance within the group, and sex. They cooperate to defend their territory and attack other groups.  Bonobo males, on the other hand, are subordinate to the females and do not compete aggressively for dominance rank.  In addition, they are playful and show almost continual sexual behavior including with same sex partners.  They do not form alliances with each other and there is no evidence of aggression with other groups.  

Researchers would like to know if their genetic differences can explain the very different behavior of the three animals. What makes the bonobos playful, the chimpanzees aggressive, and the humans cerebral?

Background: In Beyond Animal, Ego and Time, Chapter 16 – Transcending Egocentricity argues that our outdated belief in meaningful differences between groups of human beings is persuasively contradicted by their known genetic similarities.  It states “For these reasons we have to allow perceived human differences to slip away as insignificant and inconsequential.” The results of this research further demonstrate the evolutionary ancestry of human beings and show the behavioral similarities between related species.

Use the following links to obtain more information on the topics in this article:

http://www.nature.com/nature/journal/vaop/ncurrent/full/nature11128.html

http://news.sciencemag.org/sciencenow/2012/06/bonobo-genome-sequenced.html

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