Evolution And The Genes

We will use an example to illustrate the enormous evolutionary power of the genes to transfer information from generation to generation. If a chimpanzee would try to write this book by randomly using a computer keyboard, the chimpanzee would not have been able to write the volume even if it had started at the big-bang 15 billion years ago: but if we could control the first attempt to write the volume and use the signs that were correct for the second round and so on, then 1/40 of the volume would be correct in the first round (assuming 40 different signs), (39 x 39)/(40 x 40) would still be incorrect after the second round, (39 x 39 x 39)/(40 x 40 x 40) after the third round and so on. After 500 rounds—which may take a few years—there would be only 5 "printed" errors left, if we presume that 1 volume contains 600,000 signs. To write the volume would probably require 600,000 seconds or approximately about 1 week. To make 500 rounds would then take 500 weeks or about 9 years.

The biochemistry of organisms is determined by the composition of a series of enzymes that again are determined by the genes. Successful organisms will be able to get more offsprings than less successful organisms and as the gene composition is inherited, the successful properties will be more and more represented generation after generation. This explains that the evolution has been towards more and more complex organisms, which have new and emerging properties; see for instance Figure 2.2, where an evolution index is plotted versus time. The index is found as the product of the number of marine families and the /3-value of the most developed organism at a given time. It is presumed generally that the development of the number of species follows the same pattern as the development of the number of families. The /3-value has been

400,000 200,000 0

0 100 200 300 400 500 600

Time (million years ago)

Figure 2.2 An evolutionary index is plotted versus time. The calculation of the index is explained in the text.

0 100 200 300 400 500 600

Time (million years ago)

Table 2.1 Time of emergence applied to calculate the evolution index shown in Figure 2.2

Ma Animals emergent

500-550 A wide spectrum of invertebrates

475 Primitive fish

400 Fish

375 Amphibians

300 Reptiles

200 Mammals

30 Monkeys

10 Apes

1 Human presented in J0rgensen et al. (2005). The applied ^-values are shown in Table 1.1, Chapter 1. Table 2.1 gives the time of emergence applied in Figure 2.2.

The genetic code is a language or an alphabet. In the first hand, it is a constraint on the living organisms that has to follow the biochemical code embodied in the genes. As an alphabet is a constraint for an author (he has to learn it and he is forced to use it if he wants to express his thoughts), so the genetic code is a constraint for the living organisms. But as the alphabet gives a writer almost unlimited opportunities to express thoughts and feelings, so the genetic code has given the living organisms opportunity to evolve, becoming more and more complex, more and more creative and more and more adaptive to constraints that are varying in time and space. The need for heritage of useful properties has, in the first hand, been constraints. The genetic code has, however, not only solved the problem associated with these constraints, but it has also been able to give the living organisms new emergent properties and enhanced the evolution.

The evolution is formed by the constraints as the challenges for the organisms are originated in steadily changed life conditions. The organisms have been forced to provide most possible growth by a wide spectrum of changeable life conditions. Due to mutations and, later in the evolution, sexual recombinations, new solutions to the survival in a changeable world have been provided and if there, among the new solutions, were better solutions than the previous ones, the information has been stored in the genes and can be used in the future. This image of the evolution is in accordance with Monod's description of evolution as a result of chance and necessity. The chance or random element of the evolution is the steadily varying life conditions and the necessity is the survival, because without survival there would be no continuation.

The genetic code contains the combination of four amino bases in blocks of four. The genetic code opens therefore for 4 x 4 x 4 x 4 combinations, but the code is used to select slightly over 20 amino acids, which implies that the code contains redundant signals.

It does not matter anything for the efficiency of the code system; but it seems to indicate that the genetic code itself has an element of randomness.

New constraints are needed to give the evolution a kick from time to time. It has, therefore, probably been an advantage for the evolution that the Earth has been witness



Specific exergy = exergy/biomass

Figure 2.3 Holling's four phases of ecosystems, described in terms of biomass vs. specific exergy. The presentation is inspired by Ulanowicz (1997).

to several enormous nature catastrophes, as for instance, when an asteroid probably hit the Earth 65 million years ago and thereby created new conditions and therefore new challenges. New solutions may often not have a chance as long as old solutions are dominant. Only elimination of old solutions can give a new and different start. The evolution is dependent on catastrophes from time to time—volcanic eruptions, hurricanes and sudden climatic changes. Compare with Holling's cycle (Holling, 1986); see Figure 2.3.

About 5 million years ago the climate in Africa changed dramatically. The precipitation was reduced significantly and the rain forest in East Africa was replaced mainly by savanna. This was a new challenge to the apes: it would be more beneficial for the apes in the savanna to be bipedal. That started the evolution towards the modern man, Homo sapiens. The evolution towards a bigger brain volume was probably also or at least partially started randomly: man became carnivorous and the brain growth needed a wide spectrum of amino acids and at the same time hunting required a bigger brain because successful hunting required a co-ordinated team work—the tribe formed therefore an information network to facilitate the communication (exchange of information) among the members of the tribe and the hunting team.

The relationship between the random changes in the life conditions or the constraints and the evolution means that if we would repeat the evolutionary process, for instance, since the Cambrian Explosion, it would inevitably follow the same ecological principles—the same ecosystem theoretical propositions, but it is not at all certain that the final results would be the same due to the role of randomness. This issue is touched on further by the discussion of Drake's equation in the Second Movement.

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