“Poor Man’s Evolution”
A recently published study by HAS member Eörs Szathmáry has stirred up the interest of the scientific community. The researcher has constructed a theoretical evolutionary model describing the very early stages of evolution some 3.5 billion years ago, an era before nucleic acids took front stage. If further experiments confirm the theory scientists might find one of the missing links in early evolution.
|DNA double helix|
Evolutionary biologists have already written several chapters in the imaginary book of the origin of life, the whole story however is yet to be finished. One of the most intriguing questions, the origin of genes responsible for reproduction, is still hidden from the scrutiny of scientists. Researchers are yet to find an answer to the question of how nucleic acids took front stage in the development of life on Earth. What evolutionary processes could have led to the formation of DNA and RNA 3.5 billion years ago?
There are two major families of molecules responsible for genetic reproduction, the information storing nucleic acids, and proteins, the "labour force" of cells. Several experiments show that it's very difficult to create conditions where nucleic acids form spontaneously, although proteins form relatively easily even in pure chemical systems. This latter family of molecules however does not reproduce, i.e. cannot evolve - at least that has been the general consensus among researcher. The difficulty of such scientific discoveries stems from the fact that researchers need to use chemical methods only to identify biological systems naturally capable of forming the first evolutionary building blocks.
Entitled "Evolutions before Genes", the publication of Eörs Szathmáry laid the foundations of such a new evolutionary model describing the processes that preceded the emergence of DNA. In their recent article published in Biology Direct, Eörs Szathmáry and his colleagues re-examined the so-called Kauffman's conjecture, a theoretical model constructed in 1971, from the viewpoint of evolution. This model assumes that the self-reproduction of a purely protein based system is possible. "Imagine a chain of reactions consisting of only proteins catalyzing synthesis ways producing the same components", said to our website head of HAS-ELTE Joint Research Team of Theoretical Biology and Evolutionary Ecology, Eörs Szathmáry. The evolutionary consequences of the theory of co-author Kauffman, conceived 40 years ago, have never been studied in such detail before, and have never been experimentally validated. Furthermore, it has never been shown by mathematical means either whether such a self-reproductive network is actually capable of Darwinian evolution. "That is exactly what we did in our latest study (which reached a record number of downloads in just two weeks): could some forms of evolution take place in such cases, i.e. could multiplication, reproduction and reproductional variety exist in these Kauffman-networks? After running several simulations the answer to our question was definitely in the affirmative", the Hungarian researcher said.
Researchers placed these Kauffman-type networks into small globules, so-called protocells, and observed that after the growing networks reached a critical size, they started to divide spontaneously. "During our computer simulations we observed that the molecules inside an original globule statistically distributed between the two successors globules. We showed that this was one of prerequisites of evolvabilty", said Eörs Szathmáry pointing to one of their main findings. The scientists also studied networks with identical pools of molecules that however underwent some kind of mutation when dividing. "If we started out with type A networks that started dividing, so-called type B networks that weren't exactly similar to the type A's appeared among the new globules. Protocells producing type B networks outplaced the others in some cases. In this sense, a Darwinian natural selection took place among the networks", the researcher said.Eörs Szathmáry and his colleagues call this new model "poor man's evolution", because these networks are very simple compared to nucleic acid-based replications found in living systems today. They cannot produce such variability as RNAs. The publication of the Hungarian researcher's study is considered a sensation in the scientific community, since this new theoretical model has the possibility to bridge the gap between the chemical chaos at the early stages of the emergence of life and a later stage ruled by nucleic acids. The theory of the renowned Hungarian evolutionary biologist is still awaiting validation, since only real empirical experiments done on Kauffman-systems could confirm or falsify the poor man's evolution theory.