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Ever wonder how livings things came from non-living things? We will explore what conditions on early Earth
may have created life from non-living items.
Primitive Earth
The origin of life on Earth is a highly curious thing. In fact, many scientists have dedicated their entire lives to
finding out how life came to be on Earth. There are a few
key experiments that we will look at in order to gain an
understanding of how scientists have best hypothesized
how life started on Earth, but let's first take a trip back in
time - about four billion years ago.
Primitive Earth was very different than the way things are
now. There were probably many oceans and seas with
many hot vents at the bottom of these waters and quite
a bit of volcanic activity on land. The atmosphere most likely contained water, methane, ammonia, and
hydrogen, unlike our current atmosphere, which is mostly nitrogen and oxygen.
Stages of Early Life on Earth
Now that we have an idea of what Earth may have looked like, let's take a look at what steps scientists have
hypothesized led to early life. It is agreed by scientists that there are four main stages to how life came from
non-living things.
The first step is that small organic molecules - such as amino acids that make proteins and nucleotides that
make DNA - were made. While these organic molecules are found in living things, they aren't actually living
things themselves but are really just specific combinations of elements.
The second step is that these small organic molecules joined together to form larger molecules. The small
molecules are called monomers since they are made of just one unit. However, when they join together, they
create polymers that have many repeating units. You may be able to remember this because of the prefixes.
'Mono' means 'one' - like in the words monorail and monocle - while 'poly' means 'many' - like in polygon and
polymorph. You can also think of it as putting paperclips together in a long chain. Each individual paperclip is a
monomer, but the entire long chain of paperclips is a polymer.
The third step of early life on Earth is when things start to get a little tricky. The polymers that were formed
from the monomers grouped together to form protobionts. Protobionts are very important to understanding
early life. The name protobionts literally means 'early form of life,' but they are basically small droplets with
membranes that are able to maintain a stable internal environment. They are similar to the cells with which we
are familiar in that they can reproduce, metabolize, and even respond to their environments. Many experiments
have shown that these pre-cell structures can spontaneously form.
The fourth step is that these simple protobionts evolved to pass on genetic information. Protobionts are
capable of replicating - that is, they can make new protobionts. However, cells, which are the basic unit of life,
are unique in that they can reproduce and pass on genetic information from one generation to the next,
metabolize matter and energy, and can evolve. These simple cells created from complex molecules that were
created from simple molecules then continued to evolve into a wide variety of life forms.