Wednesday, September 25, 2013

Luigi Luca Cavalli-Sforza, Genes, Peoples and Languages (2001)

Information is typically packaged.  The smallest unit of information (something like a bit) (see August 23, 2009 and August 17, 2009 posts) has limited meaning (information value) on its own.  Aggregating, absorbing, connecting, colliding, and communicating with other units of information expands the information value associated with the package of bits.  These packages of information include small subatomic units, electrons, atoms, chemical compounds, photons, waves of sound and light, proteins, genotypes, cells, organs, phenotypes, letters, words, songs, books, and culture. (See November 27, 2010 post).

Information migrates.  (See May 20, 2012 post)  It is in nearly constant motion.  And when it is in motion, information can be altered and its meaning changed.  (See August 15, 2011 and  August 23, 2009 posts).  Sometimes information is degraded by change; sometimes information is enhanced. Information moves with its package; the package migrates, and information moves along.  Genes, Peoples and Languages is about the movement of genetic information in the package of a phenotype and the scientific quest to track the movement and transformation of modern human genes over the course of roughly one hundred thousand years.  And along the way, as a result of natural selection, and in some geographic areas, genetic drift, the information in this genetic package was edited and revised from the general population that preceded it:  hair texture and color changed, skin color changed, small genetic changes enabled humans to digest milk, immunized them from diseases such as malaria in certain areas, morphologies changed, and so on. 

This research supports the Out of Africa hypothesis:  that modern human origins begin on the African continent approximately 100,000 years ago, likely in southern Africa; that intra-continental African migration ensued northward along East Africa in the thousands of years afterward; and the first migration of homo sapiens out of Africa occurred roughly 50-60,000 years ago to the Arabian peninsula and the Levant, likely along the coast, and ultimately to southern Asia (India), southeast Asia, and Oceania (Australia) about 45,000 years ago.   And about the same time that modern humans were reaching Oceania, migrations out of the Levant northward in the direction of Europe, and later in the direction of central Asia and ultimately to North America roughly 15,000 years ago. What should not be forgotten in this focus on modern human migration is that a similar migratory path may have been taken over a million years earlier by homo erectus.

Cavalli-Sforza sees a parallel between genetic evolution and cultural evolution. The units and type of information as well as the means of information transmission in these two circumstances, however, are radically different.   Speech acts (including rituals) and language are the means of transmitting cultural information, and Cavalli-Sforza treats linguistic evolution as a type of cultural evolution.  But genes and culture do not co-evolve. As mentioned in an earlier post, "Language is a social institution, and social institutions and culture evolve, albeit at a different and faster pace than biological evolution."  (August 31, 2009 post). Language changes can occur as a result of migration and conquest of another's territory.  Cavalli-Sforza documents this in a number of cases.  Religion is another attribute of culture that likewise can change as a result of migration and conquest.  (See May 12, 2010 post).  And ideas can change as a result of migration and conquest.  (See May 20, 2012 post).  "There is a fundamental difference between biological and cultural mutation," writes Cavalli-Sforza.  "Cultural mutations may result from random events, and thus be very similar to genetic mutations, but cultural changes are more often intentional or directed to a very specific goal, while biological mutations are blind to their potential benefit.  At the level of mutation, cultural evolution can be directed while genetic change cannot."   Later he adds, "We must note a significant difference between biological and linguistic mutation.  A genetic mutant is generally very similar to the original gene, since one gives rise to another with only a small change.  Words vary in more complicated ways.  The same root can change meaning.  One word can have may unrelated senses.  One could try to establish greater similarities between genes and words taking into account all of the peculiarities, but it is not clear that would be useful."  The curious aspect of Cavalli-Sforza's discussion of biological and cultural evolution and transmission is the absence of any discussion of the evolutionary debate about whether evolution operates on genes, phenotypes, or groups that has laced this subject for several decades now.  (See November 4, 2009, November 30, 2009, September 12, 2012, and September 17, 2012 posts).  References to Richard Dawkins, memes, and Edward Wilson are not to be found.  Cavalli-Sforza's discussion on this subject is disjointed, and one wonders how he would treat the subject of the unit of information on which evolution operates.

1 comment:

  1. It was great article. Here you mention the effects of mutations which may occur and help to avoid expect health problem with Original Gene test.