tag:blogger.com,1999:blog-8304928500646903522.post2817295759443643725..comments2024-03-28T00:11:33.489-04:00Comments on bensozia: Richard Prum on Sexual Dimorphism in BirdsJohnhttp://www.blogger.com/profile/01037215533094998996noreply@blogger.comBlogger3125tag:blogger.com,1999:blog-8304928500646903522.post-85365686489338337362021-06-30T18:14:45.764-04:002021-06-30T18:14:45.764-04:00@David
Fundamentally, evolution is just random mu...@David<br /><br />Fundamentally, evolution is just random mutations + random chance = favorable traits.<br /><br />There are lots of possible factors at play, and it would require an expert to really begin to unpack what is truly likely, but let's take a quick stab at it anyway.<br /><br />The most obvious difference is flight, which perhaps go a long way to explaining things - it's a bit hard to subject a female to sexual coercion or violence when they can just fly away from you. Of the bird species mentioned which retained penises, it's worth noting that ostriches and their relatives are all flightless, as are chickens. The one notable exception is ducks - presumably there is some factor (or factors) which make them notably different.<br /><br />One interesting factor to note is that overall, wild birds have a notably higher mortality rate of females, causing adult populations to skew male despite offspring being born at a roughly equal ratio of male to female. This is in stark contrast to mammals, where adult sex ratios skew female.<br /><br />Waterfowl in particular seem to skew very heavily male, and ducks even moreso. There is also a marked disparity among different kinds of waterfowl and ducks that correlates with mating pair bonding habits - in species that delay bonding, or which bond only briefly, populations skew much more heavily male. This is seemingly because the females do not receive as much support from their mates - females that nest, brood, rear, and molt without help from a bonded male seemingly face greater stresses and suffer severely increased mortality rates, thus causing adult males to drastically outnumber females within those species, even above the overall rate of male dominance in birds.<br /><br />Seemingly, once male dominance in adult populations within a species reaches a certain tipping point, it becomes more evolutionarily beneficial for males to retain their penises than to lose them, because rape becomes a much more necessary method of outcompeting other males in passing on genes.<br /><br />This seems to match up strongly with the fact that the species of birds who do retain penises overall do not practice monogamy and long-term pair bonding. Roughly 90% of bird species are monogamous, with similarly high percentages both lacking penises and being able to fly. The evidence for a possible connection seems strong.G. Verlorennoreply@blogger.comtag:blogger.com,1999:blog-8304928500646903522.post-83555401556048879472021-06-30T17:04:47.337-04:002021-06-30T17:04:47.337-04:00The explanation isn't much of an explanation, ...The explanation isn't much of an explanation, at least not to the layman. Another hypothesis might be the penis is extra weight during flight, so get rid of it. Look at how long it takes a duck to reach lift off :)Shadowhttps://www.blogger.com/profile/05353532874773316117noreply@blogger.comtag:blogger.com,1999:blog-8304928500646903522.post-62629920032135627742021-06-30T16:07:30.026-04:002021-06-30T16:07:30.026-04:00I suppose a question is, why didn't mammals, f...I suppose a question is, why didn't mammals, for example, evolve the same way?Davidhttps://www.blogger.com/profile/14456987412710878404noreply@blogger.com