The theory of abiogenesis proposes that the first cells originated from non-living matter through a series of chemical reactions. This process is thought to have occurred around 3.8 billion years ago on Earth.
There are several lines of evidence that support the theory of abiogenesis. For example, experiments have shown that simple organic molecules, such as amino acids and nucleotides, can be formed from inorganic components under conditions similar to those on early Earth. Additionally, the discovery of microfossils and the similarities between all living cells suggest a common origin for life.
The first cells likely obtained energy through chemical reactions with their environment. This process, known as chemosynthesis, involves using inorganic molecules, such as hydrogen sulfide or methane, to produce energy-rich organic compounds. These early cells may have also used the energy from sunlight, a process known as photosynthesis.
It is believed that the first cells did not have DNA as we know it today. Instead, they may have used RNA, a simpler molecule that can both store genetic information and catalyze reactions. Over time, DNA evolved as a more stable and efficient way to store genetic information.
The first cells likely reproduced through a process called binary fission, where a single cell divides into two identical daughter cells. This process is still used by many single-celled organisms today. As cells evolved and became more complex, sexual reproduction and other forms of cell division developed.