Early Life Theories - Hydrothermal Vents

Blacksmoker in Atlantic Ocean
 By P. Rona (NOAA Photo Library) [Public domain], via Wikimedia Commons

It is still unclear as to how life on Earth began. There are many competing theories out there ranging from the Panspermia Theory to the proven incorrect Primordial Soup experiments. One of the newest theories is that life began in hydrothermal vents.

What Are Hydrothermal Vents?

Hydrothermal vents are structures in the bottom of the ocean that have extreme conditions. There are extreme heat and extreme pressure in and around these vents. Since sunlight cannot reach to the depths of these structures, there had to be another energy source for early life that may have formed there. The current form of the vents contain chemicals that lend themselves to chemosynthesis—a way for organisms to create their own energy similar to photosynthesis that uses chemicals instead of sunlight to make energy.

The Severest of Conditions

These types of organisms are extremophiles that can live in the severest of conditions. The hydrothermal vents are very hot, hence the word "thermal" in the name. They also tend to be acidic, which is usually harmful to life. However, life that lives in and near these vents have adaptations that make them able to live, and even thrive, in these harsh conditions.

The Archaea Domain

Archaea live and thrive in and near these vents. Since this Domain of life tends to be considered the most primitive of organisms, it is not a stretch to believe they were the first to populate the Earth. Conditions are just right in the hydrothermal vents to keep the Archaea alive and reproducing. With the amount of heat and pressure in these areas, along with the types of chemicals available, life can be created and changed relatively quickly. Scientists have also traced the DNA of all currently living organisms back to a common ancestor extremophile that would have been found in the hydrothermal vents.

The species contained within the Archaea domain are also thought by scientists to be the precursors for eukaryotic organisms. DNA analysis of these extremophiles shows that these singled cell organisms are actually more similar to a eukaryotic cell and the Eukarya domain than the other single-celled organisms that make up the Bacteria domain.

One Hypothesis Begins With Archaea

One hypothesis about how life evolved begins with Archaea in the hydrothermal vents. Eventually, these types of single-celled organisms became colonial organisms. Over time, one of the larger unicellular organisms engulfed other single-celled organisms which then evolved to become organelles within the eukaryotic cell. Eukaryotic cells in multicellular organisms were then free to differentiate and perform specialized functions. This theory of how eukaryotes evolved from prokaryotes is called the endosymbiotic theory and was first proposed by American scientist Lynn Margulis. With a lot of data to back it up, including DNA analysis that links current organelles within eukaryotic cells to ancient prokaryotic cells, the Endosymbiotic Theory links the early life hypothesis of life beginning in hydrothermal vents on Earth with modern day multicellular organisms.