During the first half of the twentieth century, many scientists considered viruses the smallest living entities and primitive life forms somehow placed between the inert world and highly evolved cells. The development of molecular biology in the second half of the century showed that viruses are strict molecular parasites of cells, putting an end to previous virocentric debates that gave viruse...

Almost all modern proteins possess well-defined, relatively rigid scaffolds that provide structural preorganization for desired functions. Such scaffolds require the sufficient length of a polypeptide chain and extensive evolutionary optimization. How ancestral proteins attained functionality, even though they were most likely markedly smaller than their contemporary descendants, remains a majo...

A number of small RNA sequences, located in different non-coding sequences and highly preserved across the tree of life, have been suggested to be molecular fossils, of ancient (and possibly primordial) origin. On the other hand, recent years have revealed the existence of ubiquitous roles for small RNA sequences in modern organisms, in functions ranging from cell regulation to antiviral activi...

The concept of an (M,R) system with organizational invariance allows one to understand how a system may be able to maintain itself indefinitely if it is coupled to an external source of energy and materials. However, although this constitutes an important step towards understanding the difference between a living and a non-living system, it is not clear that an (M,R) system with organizational ...

Objective. To evaluate Health-Related Quality of Life (HRQoL), medication used, and Stock of Health Capital (SHC) in physically active elderly participants in Community Exercise Programs (CEPs) compared to a sedentary group. Methods. EuroQol standardized instrument was completed by physically active elderly (n = 2,185) who participated in CEPs. Common items were compared to HRQoL data of 1,874 ...

We revisit the case for the hyperthermophilic scenario for the origin of life and the last common ancestor. Evidence includes studies of phylogenetic trees, rRNA, G and C content, hyperthermophilic proteins, correlations between maximal temperature tolerances and genetic distances, saline stabilization of DNA/RNA, and the inferred climatic temperatures of the early Earth. Although some doubts r...

LESLIE E. ORGEL is senior fellow and research professor at the Salk Institute for Biological Studies in San Diego, which he joined in 1965. He obtained his Ph.D. in chemistry from the University of Oxford in 1951 and subsequently became a reader in chemistry at the University of Cambridge. While at Cambridge, he contributed to the development of ligandfield theory. The National Aeronautics and ...

The physical origin of life addresses itself to a semantic process on material grounds, in which causation toward contextualization is at work. Physically semantic process of whatever kind is specific in that every material participant is searching and modifying the material context to be fitted in. Fundamental to the physical semantics is the process of measurement proceeding internally among ...

There are diverse theories about the origin of life on Earth. Perhaps it started with an electric spark that generate amino acids and sugars from an atmosphere loaded with water, methane, ammonia, and hydrogen, and over million years, larger and more complex molecules could form. Other possibility is that molecules of life met on clay due to DNA are relatively well preserved in those conditions...

While all organisms on Earth share a common descent, there is no consensus on whether the origin of the ancestral self-replicator was a one-off event or whether it only represented the final survivor of multiple origins. Here, we use the digital evolution system Avida to study the origin of self-replicating computer programs. By using a computational system, we avoid many of the uncertainties i...