Darwinism Evolution Intelligent Design

Sexual trappings (dimorphism) may increase the likelihood of extinction, not survival

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Free Public Domain Peacock Image From geologist Julie Hollis at Massive:

Sexual dimorphism is a result of males and females diverging down different evolutionary paths through selection processes, such as competition to reproduce. These processes happen for a variety of reasons. In some cases, strong colors in male birds are a sign of health. The elephant seal’s bulbous nose allows him to roar loudly to defend his territory – and his harem. And the moose’s antlers are used to intimidate or fight other males. Sexual dimorphism is the end result of choices made by mating partners and can increase the likelihood of reproduction: I would bet on the moose with the biggest antlers, wouldn’t you?

But what about the long run? What’s the impact on survival of the species? There are conflicting theories about whether sexual dimorphism is a good plan for a species.

It turns out that sexual dimorphism correlates extremely well with increased extinction rate, with more than 99 percent of models correlating the two. But it’s not sexual dimorphism itself that’s the problem – it’s the type of sexual dimorphism. Only where males were larger or more elongate than females was the extinction rate higher. In living ostracods, larger or more elongate male carapaces are used to house larger sex organs. So by analogy, for the fossil species, males that invested more resources in reproduction did so at significant evolutionary cost. More.

A wealth of information here. Bookmark it for when we hear another Darwinian just-so tale about how the peacock evolved his big fantail via natural selection because it leads to greater “fitness” at a “cost” (fitness cost). There is no “because” when we are talking about nature alone. It is simply a history of events, one that includes eventual extinction. Correct interpretation must be done from outside the history.

Added: goodusername at 1, A common story is that sexual selection enables females to assess fitness in males. Some of us have always been skeptical. Skeptics are dubious that the females are usually able to exercise such judgment or even have much choice of mates, depending on the lifestyle habits of the species. The linked extinction story sounds more likely but it doesn’t do a lot for claims that Darwinian evolution adapts species for fitness for survival.

See also: Can sex explain evolution?

Devolution: Getting back to the simple life (Some life forms go in the opposite direction and simplify, simplify.)

and

Natural selection: Could it be the single greatest idea ever invented?

5 Replies to “Sexual trappings (dimorphism) may increase the likelihood of extinction, not survival

  1. 1
    goodusername says:

    A wealth of information here. Bookmark it for when we hear another Darwinian just-so tale about how the peacock evolved his big fantail via natural selection because it leads to greater “fitness” at a “cost” (fitness cost).

    Actually, the usual explanation is that the fantail evolved via sexual selection, despite the cost of being less adapted to the environment and decreasing the odds of survival. That’s exactly what the article says.

  2. 2
    News says:

    goodusername at 2, a common story is that sexual selection enables females to assess fitness in males. Some of us have always been skeptical. Skeptics are dubious that the females are usually able to exercise such judgment or even have much choice of mates, depending on the lifestyle habits of the species. The linked extinction story sounds more likely but it doesn’t do a lot for claims that Darwinian evolution adapts species for fitness for survival.

  3. 3

    You are aware, I hope, of the paper that put a camera on the head of a female peahen and recorded what she looked at when she met various newcomer peacocks.
    http://jeb.biologists.org/cont.....3035.short

    Spoiler alert.
    She never looked at his tail.

  4. 4
    goodusername says:

    News,

    What kind of “fitness”? If you mean health, then yes (the inability to produce bright plumage might be an indication of sickness), if you mean “fitness” as in better adapted to the environment, then no.

    Sexual selection and natural selection are often at odds. That’s why the two separate theories exist. Sexual selection will often take a sex (usually males) in a very different direction – or opposite direction – than natural selection would. For example, in cases where females are camouflaged, while the males are anything but.

    This is why sexual selection is often used as evidence against group selection (i.e. things are being selected for that are not just bad for the survival of the individual, but also bad for the population or species). This story is more evidence of that.

  5. 5
    Amblyrhynchus says:

    The linked extinction story sounds more likely but it doesn’t do a lot for claims that Darwinian evolution adapts species for fitness for survival.

    This is an odd sentiment. These results seem similar to what we already know about the evolution of (a)sexual reproduction. Natural selection can favour loss of sexual reproduction over a short-run, but those lineages that lose sex become more extinction prone. “Darwininan” natrual selection need not favour survival of the species.

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