Talk:Evolution of biological complexity

Minor comment regarding the lead
I'm just wondering if The evolution of complexity is a common area of confusion in popular conceptions of evolution is the best lead sentence. Shouldn't we be describing the evolution of complexity here, as opposed to its rate of confusion? Cheers, darkliight[&pi;alk] 21:01, 30 May 2007 (UTC)

Orthogenesis
I notice that this other article seems to be on a related subject. Am I mistaken?--Filll 23:05, 10 August 2007 (UTC)


 * Good addition, thanks. Tim Vickers 23:16, 10 August 2007 (UTC)


 * Believe it or not, I have lots more in a rough draft on my machine. I might get around to cleaning it up and then we can maybe put some of that material in one article or the other. This subject seems to be an endless source of fascination for assorted cranks and new-age kooks of one type and another.--Filll 23:45, 10 August 2007 (UTC)

what do we mean by "trend toward increasing complexity?"
This article repeatedly implies that the phrase "trend toward increasing complexity" can only refer to a "trend toward increasing average complexity," and is therefore "illusory." But couldn't the phrase just as easily refer to a trend toward increasing maximum complexity, which as the article already explains, is not illusory at all? If there's no citation that says "increasing complexity" has to refer to increasing average complexity, then I think we should reword several phrases in the article, so we don't seem to flatly deny something and then say it can be true after all. --Allen (talk) 17:16, 28 June 2008 (UTC)
 * P.S. Even if we do always mean "average" complexity, then we still have to say what kind of average we mean, right? Even the "passive trend" example shown looks like an illustration of increasing mean complexity over time (not that that's its most important feature).  --Allen (talk) 17:20, 28 June 2008 (UTC)

The article discusses both possibilities, the passive model, where the maximum increases, but the mode stays constant, and the active model where both the mode and the maximum increase. The term "complexity" can refer to either the maximum or the average of a population, or to a trend in a specific lineage. One of the problems is that this is such an ill-defined concept. Tim Vickers (talk) 17:50, 28 June 2008 (UTC)
 * I agree that the article discusses the passive model, but my problem is with the language the article uses when it isn't discussing the passive model. I was trying to imply that the article should be changed, but I can't tell if you agree.  Here are some examples:
 * "If it were generally true that evolution tended to move towards increasingly complex organisms, evolution would possess an active trend towards complexity."
 * What does this sentence mean? Does the passive model not, in at least one sense, embody a trend toward increasing complexity?
 * "Any apparent trend in complexity over the history of life is due to our sampling bias in concentrating on a few large organisms and ignoring the large majority of smaller organisms."
 * "In this hypothesis, any apparent trend towards complex organisms over the history of life is an illusion resulting from concentrating on the small number of large, complex organisms that inhabit the right-hand tail of the complexity distribution and ignoring simpler and much more common organisms."
 * An "illusion" due to our "sampling bias"? Sure, if one only considers the mode.  But is there something illegitimate about considering the maximum?  And that's not even considering that some people presumably hold to this "active model" (which I don't know anything about).  Let me know if you agree that these sentences are problematic.  If you do, I think we can reword the article fairly easily. --Allen (talk) 20:54, 28 June 2008 (UTC)
 * P.S. Looking more closely at the history, I see you are pretty much the sole author of the article, including these passages.  So let me also say I think you did a great job overall, and thank you for writing about this topic.  --Allen (talk) 21:01, 28 June 2008 (UTC)
 * Thanks, but I agree that this was written to be a bit self-contradictory, what do you think of the new version? Tim Vickers (talk) 01:15, 29 June 2008 (UTC)
 * I don't think you wrote what you probably intended. You wrote, "Any increase in the maximum level of complexity is not due to an active direction towards complexity over the history of life but is due to our sampling bias..."  But the increase in the maximum level of complexity is a real consequence of the passive model, not an artifact of our bias.  I almost suggested what I thought would be a better wording, but really I'd recommend removing this sentence and the next altogether.  I think these two sentences, even if reworded, would still be hard to understand before reading the next section, and without them we'd still be left with a good introduction.  As for the other two sentences I mentioned, here's what I'd recommend:
 * Instead of "If it were generally true..." (and its following sentence): If evolution possessed an active trend toward complexity, then we would expect to see an increase in the mode complexity among all life, as shown to the right.
 * In the sentence beginning "In this hypothesis...", we could simply replace "apparent trend towards complex organisms" with "apparent trend in mode complexity of organisms".
 * Using the word "mode" does make the writing more technical, but I don't see any other way to be precise and correct except to try to explain the concept of mode each time we need it. What do you think?  --Allen (talk) 01:55, 29 June 2008 (UTC)
 * OK, how does draft 2 look to you? Any better? Tim Vickers (talk) 02:34, 29 June 2008 (UTC)
 * Yes! Thanks. :-)  --Allen (talk) 04:22, 29 June 2008 (UTC)