Evolution is the process of merging opposite trends

It seems that evolution into multicellular organisms is due to the interaction between different selective trends when changing the level of organism?

The evolutionary step from a single-celled multicellular organism has been accompanied by the division of labor, the development stage and the organization of the creature of the organism. Although this is one of the essential stages of life history, the understanding of this process is too sketchy. While observing the interactions of different primary bacterial populations in the laboratory, the author (Paul B. Rainey) proposed the mechanism of evolution at a higher level of organism as after.

(Photo: J. KAPUSTA / IMAGES.COM, Sinhocvietnam) In multicellular organisms, basic entities (cells) have to give up fertility as independent units that follow control like is part of a larger organization. The difficulty of biologists now is how to explain 1) how a cell population becomes a unified entity capable of reproducing itself, or 2) evolutionary mechanism and selective properties how nature has changed between the level of organization of a single entity and of a group of unified entities.

Current theories especially emphasize the process of cooperation. This hypothesis is built from experimental observations of bacterial populations with simple non-differentiated cell groups. These groups come from mutant cells that produce a cell binder and make the daughter cells after division not separate but form a membrane of adherent cells. This membrane forms the interface between the liquid and the air above, thus reducing the amount of oxygen in the environment. Cell-binding properties have become beneficial in exchanging oxygen between cells in the environment.

Although the generation of association groups is a beneficial feature, these cell groups are only relatively short-lived. The reason is simply because the natural selection process continues at the level of individual cells. In particular, natural selection favors beneficial mutations, which no longer produce adhesives but enjoy adhesives from other individuals in the group. Since there is no effective mechanism to inhibit or eliminate these smart individuals, the entire population becomes progressively degraded.

The success of multicellular bodies is that they have effective mechanisms to control smart individuals for the benefit of the collective. Control of each unit is not directly related to natural selection pressures on a group. The bottom line is that new emerging groups do not have the ability to differentiate reproduction. In other words, although the microorganisms in a group continue to divide, the whole group is unable to produce the next generation, similar to somatic cells (soma), and becomes end point in terms of evolution.

Volvox Group, though multicellular, has only two main types of cells, immortal somatic cells and genital cells.

So, what mechanism builds the evolutionary path of multicellular properties? Cooperation is necessary but not enough. This evolutionary process requires group-based reproduction and effective enforcement of individuality at the lower levels of organization. Moreover, all three of these events are required to take place almost simultaneously.

Cao Xuan Hieu

According to Paul B. Rainey (2007) Evolution, Unity from conflict, Nature, Vietnamese Biology