Wednesday, May 15, 2019

"Eukaryogenesis, how special really?"

Eukaryogenesis, how special really?

Another interesting article.

Abstract

Eukaryogenesis is widely viewed as an improbable evolutionary transition uniquely affecting the evolution of life on this planet. However, scientific and popular rhetoric extolling this event as a singularity lacks rigorous evidential and statistical support. Here, we question several of the usual claims about the specialness of eukaryogenesis, focusing on both eukaryogenesis as a process and its outcome, the eukaryotic cell. We argue in favor of four ideas. 

  • First, the criteria by which we judge eukaryogenesis to have required a genuinely unlikely series of events 2 billion years in the making are being eroded by discoveries that fill in the gaps of the prokaryote:eukaryote “discontinuity.”
  • Second, eukaryogenesis confronts evolutionary theory in ways not different from other evolutionary transitions in individuality; parallel systems can be found at several hierarchical levels.
  • Third, identifying which of several complex cellular features confer on eukaryotes a putative richer evolutionary potential remains an area of speculation: various keys to success have been proposed and rejected over the five-decade history of research in this area.
  • Fourth, and perhaps most importantly, it is difficult and may be impossible to eliminate eukaryocentric bias from the measures by which eukaryotes as a whole are judged to have achieved greater success than prokaryotes as a whole. 

Overall, we question whether premises of existing theories about the uniqueness of eukaryogenesis and the greater evolutionary potential of eukaryotes have been objectively formulated and whether, despite widespread acceptance that eukaryogenesis was “special,” any such notion has more than rhetorical value.

Context: reading of David Quammen's "The Tangled Tree: A Radical New History of Life".

Comments (4)

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It is at least plausible that Eukaryotes arose at the same time as oxygen levels in the atmosphere reached values high enough for mitochondria to be useful (2 gigayears ago).
2 replies · active 306 weeks ago
Did chloroplasts have anything to do with rising oxygen levels?
If I correctly understand the evolutionary history, chloroplasts originated about a billion years ago when eukaryotes engulfed cyanobacteria. The first oxygen revolution is roughly another 1 billion years older, and was produced by the cyanobacteria who had already been conduction photosynthesis for something like another billion years. It took that billion years to oxidize the iron in the oceans, producing banded iron formations. Once that job was done, it started increasing atmospheric oxygen. Eukaryotes with chloroplasts could have been involved in subsequent oxygen increases before the Cambrian. See, e.g., https://en.wikipedia.org/wiki/Geological_history_...
Interesting thanks; could have implications for SETI.

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