A teacher says, “Okay, class. Today we’re going to be talking about the tenses. If I say ‘I’m beautiful,’ which tense is it?”
Little Johnny raises his hand and says, “Obviously past tense, Miss.”
Oldest fossilsIn 1977, American paleontologist Elso S. Barghoorn of Harvard announced the discovery of Pre-Cambian spherical one-celled algae microfossils (named Eobacterium) 3.4 billion years old, earth's earliest life forms. Barghoorn, with J. William Schopf, studied the ancient chert (a flintlike or quartz-like rock) of the Fig Tree formation in Transvaal, South Africa. Rubidium and strontium ratios in the chert are used to establish the age of the rock, and the fossils contained in it. The fossils are a kind of Prokaryotes, organisms with simple cell wall containing organic chemicals, and examples of cell division are visibile in the remains. A huge number of varieties exist today. They all produce oxygen; and, in the Precambrian period, began to change the earth's primoidal reducing atmosphere to the oxygenated one we have today. |
