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This question already has an answer here:

Male pattern baldness is a common genetic trait. With a distinctive pattern/ density gradent (as apposed to general old age thinning as the body ages)

Hair has an advantage of protection from the sun/weather. So to lose it in a distinctive pattern (and lose that advantage) appears to have a reason*; and as it is a genetic trait, it seems like it would have been something that was selected for (or it would be more likely to be selected out). So why is it better to develop pattern baldness as someone gets older?

So what might be the biological/evolutionary advantage to developing baldness?

Traits get selected for good and bad reasons(in retrospect), however I am interested in the reason why this particular trait has been selected.

* Lets assume that there is a specific cause (causes) and it is not just a leftover evolutionary artifact.


The related question: Why do some bad traits evolve, and good ones don't? provides some interesting background, but doesn't specifically address the What causes in this question.

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marked as duplicate by David, Bryan Krause, Remi.b evolution Apr 20 '18 at 21:46

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

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    $\begingroup$ You need to show some evidence in support of your premise that a trait "looks" selected. $\endgroup$ – swbarnes2 Apr 20 '18 at 21:21
  • $\begingroup$ @swbarnes2 I never said "looks" , but I have taken what you on board said and have rewritten to better layout my premise, with evidence for it. $\endgroup$ – DarcyThomas Apr 21 '18 at 6:43
  • $\begingroup$ @david Can you please remove the duplicate. As per the 3rd paragraph in this meta post biology.meta.stackexchange.com/questions/3116/… This question is about "specific hypothesis" In other words this is not a 'Why does evolution...' question; but a 'What caused this evolution...' question. $\endgroup$ – DarcyThomas Apr 23 '18 at 21:33
  • $\begingroup$ "Appears to have a reason" is not any different from "appears selected". Not every trait you find distinctive has been specifically evolutionary selected for. $\endgroup$ – swbarnes2 Apr 23 '18 at 22:02
  • $\begingroup$ @swbarnes2 The question is: there appears to be a reason What is the reason. If you think that the answer is "There is no reason" then put that as a answer and it can be voted on along with other answers of: "The reason is XYZ", "The answer is ABC" $\endgroup$ – DarcyThomas Apr 23 '18 at 22:07
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Baldness would appear to be a trait on display. That being said, hair loss can be selected against the opposite condition (full head of hair), or selected by way of precise pattern deemed attractive. So, male pattern baldness evolution for mate selection purposes is probably a factor in play. But, either way, hair loss appears to have both its advantages and disadvantages as far as both fitness and mate selection is concerned.

Similarly, in terms of fitness, the advantage/disadvantage you state is the immediate positive advantage of hair as a protectant. The immediate advantages of hair diminish as one grows older, making age apparent. Old age is disadvantageous in itself (older can mean less fit). Hence, the immediate advantage for a protection against the elements decreases and becomes less relevant to survival as one grows older. Please see the references below.

https://en.wikipedia.org/wiki/Mate_choice

https://en.wikipedia.org/wiki/Evolution_of_ageing

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  • $\begingroup$ "Questions like this are in the domain of mate selection (or choice) in biology" - citation needed. It is not at all clear that the answer to OP's question has anything to do with mate selection, unless you can cite evidence that it is. $\endgroup$ – Bryan Krause Apr 20 '18 at 21:42

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