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Russell Gray and Quentin Atkinson, of the University of Auckland in New Zealand use the rate at which words change to gauge the age of the tree's roots - just as biologists estimate a species' age from the rate of gene mutations.The differences between words, or DNA sequences, are a measure of how closely languages, or species, are related.Years later, a ruler declares one of those copies the definitive manuscript, and a rush is on to make many copies of that version — so whatever changes from the original are in this presumed important copy become widely disseminated.Scientists attempt to date genetic changes by tracing back to such spread, using a statistical model that assumes genes have a certain mutation rate over time. So suggests new research that tracked changes in two genes thought to help regulate brain growth, changes that appeared well after the rise of modern humans 200,000 years ago.That the defining feature of humans — our large brains — continued to evolve as recently as 5,800 years ago, and may be doing so today, promises to surprise the average person, if not biologists."The genetic evolution of humans in the very recent past might in some ways be linked to the cultural evolution," he said.Other scientists urge great caution in interpreting the research.
Some linguists believe that Kurgan horsemen carried them out of central Asia 6,000 years ago.
That the genetic changes have anything to do with brain size or intelligence "is totally unproven and potentially dangerous territory to get into with such sketchy data," stressed Dr.