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How biomolecules from deep time can help to reconstruct the tree of life

 Ginkgo biloba, the only existing species of an ancient group of seed plants Photograph: Herve Lenain/Alamy

By Susannah Lydon

Applying spectroscopy techniques to tricky fossil leaves enables researchers to work out their evolutionary relationships

The tree of life is almost entirely composed of dead branches. The species which exist on the Earth today are the tips of a very exclusive set of branches – the ones which happen to have representatives alive now, at the same time as human beings with the technology to divine their gene sequence. By comparing how similar their gene sequences are, we can classify living organisms according to their shared ancestry.

This doesn’t help us one little bit in classifying the long dead branches with no modern survivors. Actually, that’s not completely fair, because we can combine the modern way of working out shared ancestry using molecular data with the way we did it before sequencing became commonplace: comparative morphology. If you have discovered an extinct organism, but have good evidence from fossils that its physical characteristics are sufficiently well understood for it to be placed within an established group, then all well and good. That’s basically our current best method for building a tree of life that incorporates both extinct and living organisms. But what if there was a third way?

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Wednesday, September 20, 2017