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Author Topic:   why is the lack of "fur" positive Progression for humans?
Dr Jack
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Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 190 of 202 (561525)
05-21-2010 4:26 AM
Reply to: Message 189 by RAZD
05-20-2010 8:51 PM


Re: Mr Jack (and anyone else): Sexual Selection for Apparent Bareness
I agree that the dimorphism between the sexes is down to sexual selection. Or, at least, it is involved in sexual signalling. The large beard of males probably serves a similar function to a Lion's mane.
I'm unconvinced by the argument that hairlessness* of humans represents sexual selection.
What I really don't buy is your argument-from-recent-porn.
* - Yes, technically we're not hairless. You know what I mean.

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 Message 189 by RAZD, posted 05-20-2010 8:51 PM RAZD has replied

Replies to this message:
 Message 195 by RAZD, posted 05-22-2010 11:01 PM Dr Jack has replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 191 of 202 (561526)
05-21-2010 4:28 AM
Reply to: Message 189 by RAZD
05-20-2010 8:51 PM


Neotony vs. paedomorphism
This would suggest that the selection for vellus hair in women is part of the neoteny selection for young appearing females.
Humans, male and female, are not neotenous. We have numerous paedomorphic traits (acquired at different points in our evolution) but the relative paedomorphy of traits reflects differing selective pressures through human evolution not a neotony event.

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 Message 189 by RAZD, posted 05-20-2010 8:51 PM RAZD has seen this message but not replied

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 193 of 202 (561530)
05-21-2010 6:03 AM
Reply to: Message 192 by Dr Adequate
05-21-2010 5:52 AM


Re: Neotony vs. paedomorphism
This is a fine distinction; and I'm not convinced by your selectionism. It is at least plausible that (hormonal?) changes favored because they produced one selectively advantageous pedomorphic trait could as a side-effect have induced another which was neutral or even somewhat disadvantageous.
It is plausible for that to happen, yes, almost all genes have multiple effects. However, the differing timing of the various paedomorphic traits means that there has been no overall neotony of the human form but rather multiple incidences of paedomorphy.
Hairlessness could be non-adaptive, but I find it unlikely. If hairlessness was a neutral trait we'd expect it to be more randomly distributed through populations.

This message is a reply to:
 Message 192 by Dr Adequate, posted 05-21-2010 5:52 AM Dr Adequate has replied

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Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 197 of 202 (561769)
05-23-2010 4:34 AM
Reply to: Message 195 by RAZD
05-22-2010 11:01 PM


Re: Mr Jack (and anyone else): Sexual Selection for Apparent Bareness
Neoteny\paedomorphy\tomatoe quibble. Meaning is the same in the end.
No, it isn't. The two are distinctly different in the genetics behind them, the protein changes that produce them and the overall effect on the organism one should expect.
In Neotony the changes usually result at the production end of the signals producing adult features and form, whereas paedomorphy results from alterations to the response to existing signalling. Neotony means that childlike features in one area are very likely to correlate with childlike features in another because they both have the same cause; paedomorphy doesn't share this feature.

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 Message 198 by Blue Jay, posted 05-24-2010 10:49 AM Dr Jack has replied
 Message 201 by RAZD, posted 06-13-2010 3:39 PM Dr Jack has not replied

  
Dr Jack
Member
Posts: 3514
From: Immigrant in the land of Deutsch
Joined: 07-14-2003
Member Rating: 8.7


Message 199 of 202 (561916)
05-24-2010 10:56 AM
Reply to: Message 198 by Blue Jay
05-24-2010 10:49 AM


Re: Paedomorphosis
Yeah, I wouldn't use the Encyclopedia Britannica as a source for biological terminology. Paedomorphosis can refer to changes in individual features or to the entire organism; neoteny refers to change in the entire organism. Humans are not neotenous; they are paedomorphic for certain traits.

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 Message 198 by Blue Jay, posted 05-24-2010 10:49 AM Blue Jay has replied

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