how did life begin on earth?
Answers
Answer:
The earliest known life-forms are putative fossilized microorganisms, found in hydrothermal vent precipitates, that may have lived as early as 4.28 Gya (billion years ago), relatively soon after the oceans formed 4.41 Gya, and not long after the formation of the Earth 4.54 Gya.
Answer:
In discussions about the origin of life, an important first step is clarifying what is meant by life. The first forms of life on Earth were probably very different from what we would call life today. It may be tempting to think of life as anything containing the DNA double helix so familiar to us. However, the main property required for early life is self-replication. The earliest self-replicating systems could have been made out of DNA, RNA, or some other basic building blocks. The key feature of such systems would have to be the ability to gather chemicals from the local environment and make copies of themselves.
All life on Earth contains carbon as an essential elemental building block.2 Carbon is the simplest element capable of forming the remarkably complex molecules that are so prevalent in life forms. Therefore, it is likely that carbon was involved from the beginning. Compounds containing carbon are generally categorized as organic; and exploring the natural mechanisms that create complex organic compounds is a main focus in research on the origins of life.
The Earth is approximately 4.6 billion years old. All evidence suggests that the Earth was inhospitable to life for the first 700 million years, largely because it was so hot. However, the Earth gradually cooled, and 4 billion years ago it became more hospitable. Within little more than 100 million years, the first single-cell life forms appeared.3 Where did these organisms come from? And what were their capabilities?
Although we do not know the path that led to these early bacterial forms, it seems likely that DNA had emerged as the information molecule by this time. Microbiologist and physicist Carl R. Woes suggests there was a considerable amount of lateral gene transfer among the first forms of bacteria called archaebacteria.4 Lateral gene transfer, which is the movement of genes from one bacterium to another, would have enabled the exchange of genetic material, and it would therefore expedite the process of diversification of biological function acted upon by natural selection. How these first organisms ever developed in the first place is the topic of the following discussion.
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