Genetic Atlas

Researchers trace the mixing of human populations using DNA.

By | February 17, 2014

NICHOLAS RAYMOND, FREESTOCK.CAUsing the genome to understand human migrations and population admixture throughout the ages is complicated, but could potentially clarify or reveal historical events. An international team of researchers has now used genetic information to create an atlas of the mixture of different populations during the last 4,000 years. Their work was published last week (February 14) in Science.

“In some sense, we don’t want to talk to historians,” coauthor Daniel Falush of the Max Planck Institute for Evolutionary Anthropology in Leipzig, Germany, told The New York Times. “There’s a great virtue in being objective: you put the data in and get the history out. We do think this is a way of reconstructing history by just using DNA.”

Falush and his colleagues examined modern genomes using a technique called chromosome painting, which identifies the ancestry of segments of chromosomes. By comparing a modern population’s painted chromosomes, the researchers could infer where and when its ancestors may have interbred. They sampled genomes of nearly 1,500 individuals from 95 populations from around the world. Their analyses revealed more than 100 admixture events, including several in populations in the Mediterranean and the Near East that could have resulted from the Arab slave trade between 890 and 1754 CE. The authors plan to use more modern and ancient genome samples in the future to give an even clearer picture of human population movement and mixing.

“They’ve developed a sophisticated statistical method for making inferences about human history,” Joshua Akey from the University of Washington in Seattle, who was not involved in the work, told Nature News. “Such advances are critical if we are going to read the stories of our past written in our genomes.”

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Avatar of: James V. Kohl

James V. Kohl

Posts: 475

February 17, 2014

Estrogen receptor α polymorphism in a species with alternative behavioral phenotypes appears to link ecological variation to nutrient-dependent pheromone-controlled chromosomal rearrangements and diversity of morphological and behavioral phenotypical traits in "morphs" of white-throated sparrows. The article also seems to pit experimental evidence of biologically-based cause and effect, which is exemplified in differences in parental feeding behavior, against statistical representations of what might otherwise be considered mutation-driven evolution in the context of speciation. Simply put, the "morphs" do not seem to result from mutations.

The use of their detailed series of experiments may extend what they have shown across the vertebrate genome via what is currently known about the conserved molecular mechanisms of epigenetically-effected physical landscapes of DNA in the organized genomes of other model organisms. That could help others understand human migrations and population admixture in the context of ecological adaptations in vertebrates and invertebrates. For example, their model organism has the potential to clarify the role of  the achiral glycine substitution in the gonadotropin releasing hormone decapeptide, which is similar to a nutrient-dependent mating pheromone in a yeast species.

In my model, that amino acid substitution appears to link the past 400 million years of vertebrate "evolution" to what is actually nutrient-dependent pheromone-controlled ecological adaptation sans mutations. The relatively rapid changes in the white-throated sparrows suggest that species do not mutate into other species, but that they quickly ecologically adapt as experimental evidence from other species appears to indicate. 

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