Talk:Dollo's law

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Is Dollo's law not spurious?

When we talk about "returning" to a previous evolutionary state in what sense can we say that we have returned or not? If we are talking about an exact recapitulation of a former state then this must be true; things don't exactly repeat themselves to the best of our knowledge, the universe is supposed to become increasingly disordered.

However if Dollo's law was applied loosely it would clearly be erroneous, an organism can evolve a trait, the trait can disappear and it can return. This could be a matter of gene expression switching on and off over evolutionary history. I'm no genetic expert but surely this must have happen rather many times before!

In a sense the commonly mooted principle of neotony regards adults which resemble the young of their precursors. To quote from wikipedia (Neoteny)

flightless birds—physical proportions resemble those of the chicks of flighted birds; humans—with traits such as sparse body hair and enlarged heads reminiscent of baby primates. dogs—which share many physical features with the immature wolf; these same traits were found during the development of the tame silver fox

Yes, today it is generally assumed the "law" isn't one.--MWAK 07:06, 1 March 2007 (UTC)

[edit] 2nd Law of Thermodynamics

The last sentence, "This logic, however, conflicts with the second law of thermodynamics which states that all chemical processes, evolution included, are not reversible, i.e. evolution is irreversible as defined by the arrow of time." is in error. It shows a misunderstanding of the 2nd Law of Thermodynamics.

The 2nd Law is talking about a closed system, in which energy can not be added. In an open system, which the Earth is, energy can be added which can reverse a chemical process.