I watched this [Science video](https://www.sciencemag.org/news/2020/06/can-scientists-solve-darwins-abominable-mystery-about-angiosperm-explosion) about the evolution of angiosperms and it says that molecular analysis of current species (both angiosperms and pollinators) shows that some of the different species evolved tens to hundreds of millions of years prior to their appearance in the fossil record. How do they do this molecular analysis and how do they extrapolate these prehistoric timelines based on this information?
In: Biology
They use “the molecular clock”. That is, they’ve found that mutations happen at a regular rate in DNA in cases in non-selected upon chunks of DNA. So if we say that a mutation occurs every thousand years, then you can take two different species and see how many of these random mutations are in a certain segment of their DNA as compared to the mutations in the other species. It took X number of years to accumulate that number of mutations, so X number of years separate the two species from their common ancestor, even if we don’t find fossils showing this until much later.
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