Allegrao Agiato: The Origin of Life. 41
2 Gya, more or less simmultaneously with teh rise of oxygen in the Earth’s atmosphere and the appearance of an efficient oxidative metabolism. Simple nucleated and nonnculeated cells were citizens of Rodina. Life in the form of our singlecelled ancestors rode the diverging continents and was undoubtedly shaped in yet-unknow ways by these long, ancient crustal wanderings.
The modern eucaryotic cell arose through invasion by expert bacterial metabolizers that bacame the cell’s mitochondria, and for plants, through invasion by blue-green cyanobaterya that envolved into the oxygen-generating chloroplasts. Microbes
often ingest smaller creatures that they intent to digest. In the descent of eucaryiotic creatures like us, the intended prey very occasionally took up residence instead of becoming lunch. The mitochondrion and chloroplast can, as resultr, be placed on the Big Tree alongside ordinary easily recognizable bacteria and blu-green cynobacteria. (See Chapter 3 for more of the story.)
Deaspite the dramat eucaryotic elaboration, it is more than a billion years later at 0,6 Gya, that the earliest multicellular animals can be found: the simple saucerlike creatures called Edicara, named after the Edicara Hills in Australia. About 0.54 Gya modern complex multicellular animals left fossils (in
the Burgess Shale of vthe Canadian Rockies) that distantly resemble modern multicellural forms.
From a human point od view, only about 500 million years now intervence before another crucial innovation. Only 0,006 Gya (6 million years ago), having come out ofv the sea and diversified, a small band of exceptional African apes began dangerous experiments with language and technology. About 0,00001 Gya, descendants of the upwardly mobile, now relatively hairless ape invented agriculture and took up a settled