I.1 Living systems are both the subject and object of a specific type of evolution, biological evolution

We know a number of systems in nature and human society that gradually change over time. The changes that occur can be reversible or irreversible and can occur slowly or rapidly, continuously or suddenly. Some changes can be caused by the action of the surroundings on the system, while others have their origin in the internal structure of the system.

Systems can be divided into systems with a memory and systems without a memory. Systems without a memory behave, i.e. change the combination of signals at their outputs, according to the combination of signals at their inputs at the particular moment. The behaviour of systems with a memory depends not only on the momentary combination of input signals, but also on the combination of signals that the system encountered in the past. In contrast to systems without a memory, systems with a memory can gradually change, accumulate changes, and develop. We say that they can undergo evolution (be subject to evolution, evolution can occur in them, they can be the subject/object of evolution). Systems without a memory can also change over time or, to be more precise, their behaviour can change, only if there is a change in the combination of signals arriving at their inputs. An example of a system without a memory is a solution of salt in an alternately cooled and heated vessel. When the vessel is heated, the crystals dissolve, when it is cooled, they form again. It makes no difference how many times the cycle is repeated, crystals with the same properties will always be formed. The system does not develop, does not undergo evolution.

On the other hand, human languages are an example of systems with a memory. The grammatical and phonetic changes that the language undergoes reflect not only the instantaneous effects of the external environment, such as contact with a different language, changes in social habits or the structure of society or a change in the means of communication (speech, writing, television, SMS) but also the momentary state of the language, which depends on its previous development. Thus, salt crystals cannot undergo evolution, while languages can.

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The classical Darwinian theory of evolution can explain the evolution of adaptive traits only in asexual organisms. The frozen plasticity theory is much more general: It can also explain the origin and evolution of adaptive traits in both asexual and sexual organisms Read more
Draft translation from: Evoluční biologie, 2. vydání (Evolutionary biology, 2nd edition), J. Flegr, Academia Prague 2009. The translation was not done by biologist, therefore any suggestion concerning proper scientific terminology and language usage are highly welcomed. You can send your comments to flegratcesnet [dot] cz. Thank you.