When I first studied mitochondria, back when I was a high school student, I didn’t appreciate their importance or their origin. I got a lot smarter recently, especially after reading "The Energetics of Genome Complexity," by Nick Lane and William Martin, in the October 21, 2010 edition of Nature (available online only to subscribers). I now realize that Mitochondria are organelles that generate energy in the form of ATP, and that without mitochondria, humans wouldn't exist. Lane and Martin begin their article by asking: "Bacteria made a start up virtually every avenue of eukaryotic complexity, but then stopped short. Why?” As I indicated, in this article, I learned many things about mitochondria. I have inserted excerpts from the Lane/Martin article in several locations. Mitochondria formerly existed as their own independent life form (they were proto-bacteria), but they now reside within other cells. This combining of mitochondria happened only once about four billion years ago and all eukaryotes descended from that symbiotic occurrence. All Eukaryotes had mitochondria (or once did but lost them).

All eukaryotes share a common ancestor, which arose from prokaryotes just once in 4 billion years. Genomic chimaerism points to the origin of eukaryotes in an endosymbiosis between eukaryotes. All eukaryotes either possessed mitochondria, or once did and later lost them, placing the origin of mitochondria and the eukaryotic cell as possibly the same event.

The host mitochondria were also prokaryotes. This was determined by Russian botanist Konstantin Mereschkowski in 1905 and, as you might expect, he was not believed. [More . . . ]