Question

The mechanisms behind the origin of life have been postulated and debated ad infinitum. Miller and Urey's experiments showed that given the probable primordial conditions, the precursors to living systems could spontaneously form. Hanczyc's work showed that a very simple system containing just a few chemicals could produce a "body" capable of primitive metabolism and movement and simplistic behavior. How do we define life, given the above facts? Are the "cells" created in a laboratory alive? Why or why not? What does this mean regarding life forms we have yet to encounter? Can we limit potential life to the conditions generally accepted in science?

Answer 1

According to Miller-Urey experiment when their whole apparatus set up was left undisturbed for about a week, they found several amino acids being formed by chemical reactions among a few chemicals like ammonia, hydrogen, water vapour etc. Thus they believed that life on earth must have formed spontaneously from abiotic conditions. Hanczyc showed that very simple chemicals when mixed together may give rise to structures like protocells which has the ability to perform very simplistic movements and show simple behaviours like recognising energy sources, self replication and self assembly to form larger, much more complex structures which are some of the characteristics of life.

Thus, the cells created in the lab although cannot be considered as completely living cells but has some life like properties which hints at how life must have originated on primitive earth approximately 4 billion years ago with its reducing atmosphere and multiple chemicals reacting among themselves deriving energy from lightening and UV rays of the sun.

Life forms on Earth must have originated in the primary conditions and no new life form can form today in natural conditions due to our oxidising atmosphere as a result of oxygen added to the atmosphere by photosynthesis. Evolution of the already existing life forms may be possible but origin of a new cell completely from chemicals of nature is not possible in natural conditions. But finding life forms in other parts of the universe is possible keeping in mind certain conditions to be present on a certain planet. A planet or a system containing potential life forms should be in a non-equilibrium state where there is an energy source for the life forms to utilise it. The system should be in a liquid state where the molecules are free to move around and interact among themselves to make or break bonds among them. The system should be able to utilise the energy available to undergo chemical reactions among themselves and transform one form of energy to another for them to survive.