“Such is the essential mystery”*…
For about a billion years, life on earth was a relatively simple proposition: it was composed entirely of single-celled organisms (prokaryotes) in either the bacteria or archaea families. Then, about 2.1 billion years ago, one of those single-celled critters crawled inside another; the two merged, and a new kind of life– multi-cellular (eukaryotic) life– was born…
This inner cell—a bacterium—abandoned its free-living existence and eventually transformed into mitochondria. These internal power plants provided the host cell with a bonanza of energy, allowing it to evolve in new directions that other prokaryotes could never reach.
If this story is true, and there are still those who doubt it, then all eukaryotes—every flower and fungus, spider and sparrow, man and woman—descended from a sudden and breathtakingly improbable merger between two microbes. They were our great-great-great-great-…-great-grandparents, and by becoming one, they laid the groundwork for the life forms that seem to make our planet so special. The world as we see it (and the fact that we see it at all; eyes are a eukaryotic invention) was irrevocably changed by that fateful union—a union so unlikely that it very well might not have happened at all, leaving our world forever dominated by microbes, never to welcome sophisticated and amazing life like trees, mushrooms, caterpillars, and us.
Read the extraordinary story of how one freakish event may well account for all sophisticated life on earth in “The unique merger that made You (and Ewe, and Yew).”
* Lao Tzu
As we fill out our family trees, we might send microscopic birthday greetings to Carl Woese; he was born on this date in 1928. A microbiologist, Woese recognized and defined (in 1977) the existence of archaea as a third domain of life, distinct from the two previously-recognized domains, bacteria and “life other than bacteria” (eukaryotes). The discovery revolutionized the understanding of the “family tree” of life. And the technique he used to make it– phylogenetic taxonomy of 16S ribosomal RNA— revolutionized the practice of microbiology.