Talk:Dollo's law of irreversibility

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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)

I think if talking in terms of "evolution" and not individual phenotypes, expressions or instances of just anything appearing, the law is as the above poster comments true from a general sense. Anything which evolution provides existing as not recaptureable is not what the law states, rather it states the delineation of events make it so the same thing cannot exist the exact same way twice once it has "evolved" concretely, because the march of progress is indelibly marked with the process.

Evolution is only forward and devolution is a misnomer because not only is it bereft of any external valuation when changing/evolving but also because it cannot revert as if unraveling since it adheres to one single evolutionary pressure which is unbiased and cannot "change it's mind" for it changes by that one rule it continues to follow. One nucleotide mutating back and forth in genes is a possibility for example, and emulating the same characteristics in an environment between different species is common too, but the law refers rather to a specific subject undergoing the complete evolutional experience and the inability to return to states it itself held previously in the whole to it's particular self. I suppose the law works in the long term more intuitively than the short for those reasons. Nagelfar (talk) 09:29, 29 July 2008 (UTC)

Succinctly put Dollo's law works for "evolutionary adaptations", and that might be a better way to put it than just saying "evolution". Nagelfar (talk) 06:38, 30 July 2008 (UTC)

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.

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Description in template at the bottom

The template at the bottom of the page describes the rule as saying "Loss of complex traits is irreversible". That's an interesting alternative way to put it, and perhaps more accurate – but the article mentions nothing about complexity of traits. --Florian Blaschke (talk) 19:37, 21 March 2021 (UTC)