When we think of life, we think of actual living things using energy from the surrounding environment to grow and reproduce. A living thing can exist simply as a one celled microorganism, or as complex as a human being. The big question is, where did it all began?
For many years, scientists have tested many different theories of the origin of life on Earth, but since it is so difficult to actually prove, or disprove them, no fully accepted theory exists. Three of the most contesting theories of the origin of life on Earth include: Life arrived from an extraterrestrial source, life originated as an autotroph, and life originated as a heterotroph.
On Earth, mostliving organisms have a carbon based chemistry and depend on water to survive. They are also made up of proteins, which are made of amino acids. Studies have shown that amino acids have been found in meteorites that have fallen from space to the Earth’s surface. Of course, there are many steps that have to take place between amino acids and actual living things, however, they are the building blocks of life.
The theory of life originating from an extraterrestrial source, or panspermia, can be dated back to about 500 B.C., when Greek philosopher Anaxagoras wrote about “seeds of life” that spread throughout the cosmos.1In the 1800s German physicist Herman Ebehard Richter was one of the first to argue the case for panspermia from a scientific standpoint.2 He stated that meteors that travel from space to the Earth’s atmosphere may pick up living cells from the air and carry them away, possibly delivering them to the Earth’s surface. This unproventheory go on to state that these living cells went on to form their own individual metabolism process. Eventually evolved into more and more complex organisms.
The second theory to be contested is the theory of life arriving on earth as an autotroph. According to Wikipedia, an autotroph is an organism that produces complex organic compounds, such as...