Why did life begin on earth using an anaerobic mode of metabolism?
1.o no one knows how life on earth began.
2. the presence of Oxygen makes a biogenesis unlikely.
3. Oxygen is not believed to have existed in the early history of the earth
No one knows how life began. The idea that life began using anaerobic metabolism is an unproven assumption.
If life began totally by natural means then the presence of Oxygen would make the a biotic synthesis of organic molecules unlikely due to the oxidizing power of Oxygen. So it is believed that life started before the presence of Oxygen in the atmosphere.
If there was no Oxygen present then the only form of energy metabolism would be anaerobic fomentation. ( anaerobic means without Oxygen). The idea that the first life used anaerobic metabolism is based on the assumption that life occurred totally by accidental naturally means.
It is believed that the early earth had no Oxygen because that is only way that life could have occurred by natural causes. The Miller Urey experiments on the a biotic origin of life are based on the assumption that the early earth was a reducing atmosphere without Oxygen. This is believed despite evidence that there has always been Oxygen in the atmosphere.