Daily Archives: August 22, 2014

DNA evidence for evolution

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Last week we had another opportunity to connect with the Gene Technology Access Centre to learn about how biologists use genetic information to discover more about evolutionary relationships. Tony discussed some of the features of the ‘old world’ monkeys and the hominids – including opposable thumbs and the presence or absence of a tail. We then used a computer program, the Biology Work Bench, to compare the similarities and differences of DNA sequences between the different species. The fewer differences in DNA base pairs, the greater the similarities between species and therefor it is assumed that they are more closely related, with a more recent common ancestor.

Evolutionary biologists have been investigating the existence of a ‘molecular clock‘ for the past 40 years – the theory is that some evolutionary changes (mutations) occur at a regular rate, which gives us a powerful tool to estimate how long since different species diverged from a common ancestor. Using molecular clocks to estimate divergence dates depends on other methods of dating. In order to calculate the rate at which a stretch of DNA changes, biologists must use dates estimated from other relative (stratigraphy) and absolute dating techniques (radiometrics). There are many different methods that scientists can use to estimate the age of fossils. Read more at the Smithsonian National Museum of Natural History.