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paoloferrari
09-14-2017, 08:27 PM
When ancient fossil DNA isn't available, ancient glycans may help trace human evolution

http://popular-archaeology.com/issue/summer-2017/article/when-ancient-fossil-dna-isn-t-available-ancient-glycans-may-help-trace-human-evolution

"Ancient DNA recovered from fossils is a valuable tool to study evolution and anthropology. Yet ancient fossil DNA from earlier geological ages has not been found yet in any part of Africa, where it's destroyed by extreme heat and humidity. In a potential first step at overcoming this hurdle, researchers at University of California San Diego School of Medicine and Turkana Basin Institute in Kenya have discovered a new kind of glycan—a type of sugar chain—that survives even in a 4 million-year-old animal fossil from Kenya, under conditions where ancient DNA does not.

While ancient fossils from hominins (human ancestors and extinct relatives) are not yet available for glycan analysis, this proof-of-concept study, published September 11 in Proceedings of the National Academy of Sciences, may set the stage for unprecedented explorations of human origins and diet."

"Glycans are complex sugar chains on the surfaces of all cells. They mediate interaction between cells and the environment, and often serve as docking sites for pathogens. For millions of years, the common ancestors of humans and other apes shared a particular glycan known as Neu5Gc. Then, for reasons possibly linked to a malarial parasite that exploited Neu5Gc as a means to establish infection, a mutation that probably occurred between 2 and 3 million years ago inactivated the human gene encoding the enzyme that makes the molecule. The loss of Neu5Gc amounted to a radical molecular makeover of human ancestral cell surfaces and might have created a fertility barrier that expedited the divergence of the lineage leading to humans"

maria_gencove
09-29-2017, 04:01 PM
Very cool.