Deep-Sea Microorganism Hasn't Evolved For Over 2 Billion Years

sfcrazy writes: Evolution is a natural process — everything evolves over a period of time, depending on the environment. But now scientists have discovered an organism which hasn't evolved for over more than 2 billion years. That's almost the half of the life of the Earth. "The scientists examined sulfur bacteria (abstract), microorganisms that are too small to see with the unaided eye, that are 1.8 billion years old and were preserved in rocks from Western Australia’s coastal waters. Using cutting-edge technology, they found that the bacteria look the same as bacteria of the same region from 2.3 billion years ago — and that both sets of ancient bacteria are indistinguishable from modern sulfur bacteria found in mud off of the coast of Chile." Scientists say the extreme stability of the environment around the organisms made further adaptations unnecessary.

Comments

uhhh

[bob.lansdorp]

Just because a fossil looks similar does not mean it hasn't evolved. Most evolution happens on the molecular scale, if you looked at the genomes I guarantee they would be different.

Re:uhhh

[Phronesis]

Just because a fossil looks similar does not mean it hasn't evolved. Most evolution happens on the molecular scale, if you looked at the genomes I guarantee they would be different.

The paper in PNAS discusses this at length. It clearly states that it would be very nice to be able to check DNA, but that defining species in microbes is about phenotypes, not genotypes, and the important thing is that there is no sign of speciation (that is, two separate populations, separated in space, did not diverge.

The morphology-based “concept of hypobradytely does not necessarily imply genomic, biochemical, or physiological identity between modern and fossil taxa," a claim of extreme evolutionary stasis—a lack of speciation over billions of years—would be strengthened not only by discovery of additional fossil communities but by firm evidence of their molecular biology. Although speciation-based evolution occurs at the phenotypic rather than genotypic level of biologicenvironmental interaction, the biomolecules underlying such change are not preserved in the rock record in which such assessment can be based only on indirect proxies and inferences of physiology based on isotopic analyses

However, the article noted, it's possible that this interpretation is wrong and that what they saw was two separate populations that underwent convergent evolution rather than one population that was separated and remained static or that there might have been significant biochemical evolution that did not change the morphology.

Moreover, large-diameter (“giant”) sulfur bacteria of differing phylogenetic lineages can exhibit similar morphologies and patterns of behavior suggesting convergent evolution of morphologic “look-alikes” adapted to a same or similar function. Although it remains to be established whether such morphological “mimicry” is exhibited also by the more narrow 10-m-diameter sulfur bacteria described here—the two modern sulfur bacterial taxa of similar dimensions being aerobes rather than anaerobes like the Duck Creek and Turee Creek fossils—it remains conceivable that the marked similarities between the two mid-Precambrian communities and their modern counterparts could be an example of the so-called Volkswagen Syndrome, a lack of change in organismal form that masks the evolution of internal biochemical machinery

Visual only

[Tablizer]

They seem to be going by visual appearance. There may be loads of DNA changes that affect metabolism chemistry and behavior that wouldn't be detectable by visual inspection of fossils. Looks can be deceiving.

Also in the TFA: "If they were in an environment that did not change but they nevertheless evolved, that would have shown that our understanding of Darwinian evolution was seriously flawed."

It's possible for a chance mutation or set of mutations to "discover" a new feature even in a stable environment. There are probably always better designs in highly remote combinations of mutations.

Re:Why Evolve?

[Rob Y.]

If they reproduce asexually, then evolution has to count only on random mutations and copying errors. Sexual reproduction intentionally mixes up the genes so you get new combinations all the time. Evolution based on random mutations that still produce a viable organism is closer to monkeys at typewriters.