Why Has the Origin of Life Not Yet Been Solved?

Let us think about the reasons from the viewpoint of research Methodology.

bottom-up approach

Top-down approach

Researchers into the origins of life are working to recreate the environment of primitive Earth 4 billion years ago. This is the bottom-up approach.

In contrast, the top-down approach tries to discover the origins of life from the basic life systems of the present day.

We believe that the origin of life cannot be elucidated by either a top-down approach or a bottom-up approach alone, and that joint research between the two is necessary.

Dr. Ikehara describes the dilemma in the following way.

“The bottom-up approach is of course quite important, because many events, which might occur on the primitive Earth; could be elucidated. However, the riddle of the origin of life can not be made clear only with the bottom-up approach, because it is difficult to understand how even the core life system, composed of three main members or gene, tRNA(genetic code) and protein, was established. Another reason may be that many researchers have had a too deep interest in prebiotic synthesis of organic compounds such as nucleotides on the primitive Earth.”

Now, let us explain the top-down approach and　 the bottom-up approach!

The top-down approach started with the question of how genes with completely new functions are generated.

Dr. Ikehara describes his good fortune in this way.

“I have accidentally explored the study on the origin of life through a top-down approach, as I started with my studies from a question of how and from where an entirely new gene can be created on the present Earth. Consequently, I could reach the novel establishment process of the fundamental life system and of the origins of protein, the genetic code and gene, owing to the top-down approach.”

Now, let us use a diagram to explain the difference between the bottom-up approach and the top-down approach.

Source: Towards Revealing the Origin of Life, P.232, Fig. 10.3

＊The evolutionary steps from the birth of Earth to the modern organisms, which are deduced by connecting the two results obtained by bottom-up approach (upper blue right arrows) and top-down approach (lower red left arrows). The main evolutionary steps, which were deduced by GADV hypothesis, are drawn in the figure. Bold arrows and thin arrows show the steps deduced from the two approaches with a higher and a lower reliability,- respectively. It can be seen in the figure that the number of steps, which were deduced from the bottom-up approach, is smaller than the number of steps deduced from the top-down approach. It can be also understood from the figure that there are no large discrepancies in the whole evolutionary steps, which are deduced from the two results obtained by bottom-up and top-down approaches.

Reference: Ikehara K(2021) Towards Revealing the Origin Of life. Springer Nature