First off, do plant and animal souls even exist? A scientific examination can answer this question, but I’m not so sure it’s accurate. A strictly biological investigation seems to answer the question, What is life? rather than What is a soul or principle of life? According to "History of Life through Time" (Regents of the University of California, 2008), it appears that life on our planet began around 3.7 billion years ago, the origin of life might be a good place to start.
Some scientists believe that over billions of years, pre-biotic environmental conditions on Earth were such that ongoing evolutionary adaptation resulted in the formation of an extremely basic cell. Aleksandr Oparin suggested in his book, The Origin of Life on Earth (1938) that from a primordial soup of organic molecules in an atmosphere of hydrogen, not oxygen, the first cells spontaneously formed in the lakes and seas of the Earth as it cooled. The cells that survived had developed the ability to reproduce.
However, astrophysicist Paul Davies doubts this entire theory. “Because even the simplest living cell is immensely complex, the odds of such a thing forming by chance are virtually zero” ("Living with Aliens" in The Guardian, 2005). He feels that some sort of life principle is at work guiding matter to reach a living state Davies’ opponents are quick to point out that the odds, however small, are not actually zero. Theoretically, all it took was just one occasion!
Being Alive Scientifically
Although there are many variations on this theme, the critical attributes of being alive on planet Earth are usually described by scientists from a biological standpoint. Some non-living creatures possess one or several of the attributes discussed below, but not all of them.
Gelderblom's "Structure and Classification of Viruses" (Medical Microbiology, 1996) says that all living things except viruses are made up of tiny cells. Where amoeba and paramecium consist of a single cell, a horse, a tree, a human being consists of trillions of cells.
Regardless of size, living organisms are ordered not only at the cellular level, but also at the molecular level. Here, creatures are structured by tissues, organs, and systems (digestion, circulation, nervous, lymph) which are in themselves organized, but all these unique systems are so structured as to preserve the integrity of the total being: a mouse, a tulip, a planaria, a human, an amoeba. "Life" (New World Encyclopedia, 2009) claims the following ordering principles for living things.
1. Living things have a common basic chemistry: They are water and carbon based.
2. As a living creature grows in size, it develops more fully and begins to age.
3. To ensure survival, a living thing is able to maintain a balance within its individual parts and systems.
4. Living things reproduce themselves.
5. Living beings respond in some way to environmental stimuli.
6.In order to keep on existing, a living being must interact with its environment for energy to maintain its own internal organization, to grow, and to reproduce.
7. Organisms are able to adapt to the environment within certain limits.