By now, this kind of thing shouldn’t even be a surprise:
A collaborative study between the groups of Toni Gabaldón, ICREA researcher at the Institute for Research in Biomedicine (IRB Barcelona) and the Barcelona Supercomputing Center (BSC-CNS), and Berend Snel at the University of Utrecht, has concluded that the first cell to incorporate a mitochondrion (considered the key step to the increased complexity of eukaryotic cells) already presented eukaryote-like complexity in structure and functions. This scenario serves as a bridge between the signs of complexity observed in some archaeal genomes and the proposed role of mitochondria in triggering eukaryogenesis.
“The acquisition of mitochondria was considered either to be the crucial first step or the last step in the development of eukaryotic cell complexity,” explains Gabaldón. “Our findings show that it was indeed a crucial event, but that it happened in a scenario where cell complexity had already increased.”
For roughly the first half of the history of life on Earth, the only forms of life were the relatively simple cells of bacteria. “Eukaryotic cells are larger, contain more DNA and are made up of compartments, each with their own task,” explains first author Julian Vosseberg. “In that sense, you could compare bacterial cells with a tent, while eukaryotic cells are more like houses with several rooms.”
How and when organisms traded the tent for a house is still a mystery, as there are no intermediate forms. One important moment in evolution was the origin of mitochondria, a component of eukaryotic cells that function as their ‘power plants.” Mitochondria were once free-living bacteria, but during evolution, they were absorbed by the ancestors of today’s eukaryotic cells. As gene duplication probably drove the increase in cell complexity, the researchers attempted to reconstruct the evolutionary events based on these genetic changes.Institute for Research in Biomedicine (IRB Barcelona), “Timeline of early eukaryotic evolution unveiled” at Phys.org
Already complex? No intermediate forms? Where have we heard that before.