Three Billion-Year-Old Genomic Fossils Deciphered

[Elmore Furth]

DNA analyses give an indication of the evolution of genes. There seems to be a rock solid set of genes that manage oxidative metabolism that developed during the Great Oxidation, the increased oxygen in the atmosphere that occurred with the development of chlorophyll.

About 580 million years ago, life on Earth began a rapid period of change called the Cambrian Explosion, a period defined by the birth of new life forms over many millions of years that ultimately helped bring about the modern diversity of animals. Fossils help palaeontologists chronicle the evolution of life since then, but drawing a picture of life during the 3 billion years that preceded the Cambrian Period is challenging, because the soft-bodied Precambrian cells rarely left fossil imprints. However, those early life forms did leave behind one abundant microscopic fossil: DNA.

The scientists traced thousands of genes from 100 modern genomes back to those genes' first appearance on Earth to create a genomic fossil telling not only when genes came into being but also which ancient microbes possessed those genes. The work suggests that the collective genome of all life underwent an expansion between 3.3 and 2.8 billion years ago, during which time 27 percent of all presently existing gene families came into being.

Because so many of the new genes they identified are related to oxygen, Alm and David first thought that the emergence of oxygen might be responsible for the Archean Expansion. Oxygen did not exist in the Earth's atmosphere until about 2.5 billion years ago when it began to accumulate, likely killing off vast numbers of anerobic life forms in the Great Oxidation.

"What is really remarkable about these findings is that they prove that the histories of very ancient events are recorded in the shared DNA of living organisms," says Alm. "And now that we are beginning to understand how to decode that history, I have hope that we can reconstruct some of the earliest events in the evolution of life in great detail."


Three Billion-Year-Old Genomic Fossils Deciphered

[Ilsa]

1. Awesome post. Are you cross-posting to GD?

I like considering what we might share with other Earth life forms. I think respect is engendered when this information is considered.

[The Doctor.]

2. Wow... that's earlier than I thought.

Thanks for posting!