A harsh economy
Virtually every living being forms part of the stock of biological material which is
recycled to provide fuel for the functioning of new beings.
It would be like if you were to build a small metal box, and instead of buying raw
materials, such as metal plates, screws and other parts, you dismantle a computer to
obtain the components from it to assemble the small box. With the amount of electronic
waste these days, the idea seems quite promising. At least, the cute robot Wall-E,
from the Walt Disney film (2008), lived very comfortably reusing parts and components
creatively, in a world full of junk.
Organisms with a nervous system have the possibility of being mobile and at the same time, are able to
obtain their fuel from more complex biological material. On the other hand, those organisms which have
no nervous system, which includes most of the vegetable kingdom, are not mobile, and must obtain their
fuel by synthesising substances from basic chemical compounds. Some increase the complexity of molecules
and others decrease it. A plant is essentially a chemical laboratory that collects soil molecules and
energy from the sun to produce nutrients they need.
The survival of an organism with a nervous system is achieved by the assimilation of parts of another,
so as to obtain its biological fuel (proteins and other complex molecules). It is more economical to
break down another living being into processable parts than synthesise this material from more elementary
chemicals as plants do.
Such is nature!
I believe the reason is an economic one.
Life originates from molecules that become increasingly more complex. This is the reason why most
primitive living things, such as amoebae, which are unicellular, have no opportunity to synthesise
protein, so the only way to obtain it is by catching a paramecium, another unicellular organism, and
break it down by injecting acids into it. This is the cheapest way to get hold of fuel if the species
has the ability to move around.
There is no aim of annihilation of another being in this action nor is there a competitive element,
but it is simply cost-effective: breaking down molecules is less expensive, than synthesising them
(obviously meaning the cost in terms of time and energy).
The more complex organisms have many other chemical processes that allow them to extract the fuel,
but they always do it using existing organisms, almost never using basic chemicals from which they
could synthesise the fuel they need.
For example, some animals use honey, milk or the nectar that had been extracted from plants by another
animal, without the need to destroy the bees, cows or plants, respectively. Others feed only on the
blood of other species.
There are also those who take advantage of organisms that have already died, as with the case of
scavengers. Others use the waste of more complex beings, worms for example.
There are of course exceptions.
Some bacteria extract mineral substances directly from inorganic materials, such as the bacteria
Thiobacillus ferrooxidans which produce chemical changes in the minerals, which then serve as
nourishment, and so there is no host to use or kill.
Another exception is found with some animals such as some monkeys and macaws, which occasionally
eat soil for its mineral content, but this behaviour is assumed to occur because these animals need
certain minerals to compensate for the intake of some vegetables containing toxic substances. In
other words, the intake of soil is rather like the consumption of medicines by humans.
We humans do basically the same things in that we kill and process the cows, the tilapia (a type
of edible fish) and crab for the sole purpose of breaking down their molecules and to extract from
them those ones which are useful to us. It is important to understand though that due to our human
ability to invent solutions for many of our needs, we also use other "tools" about which I have
elaborated further in another publication "Art and Nothingness" (2012).
In this way we have devised many ways to synthesise some of our food from other organisms without
having to kill them.