Evolution News

Another whack at the “sex paradox”

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This time from The Scientist :

In 1886, German evolutionary biologist August Weismann proposed that sexual reproduction reshuffles genes to create “individual differences” upon which natural selection acts. Additional ideas have emerged since Weismann’s hypothesis: sex rids the genome of deleterious mutations; sex rapidly introduces beneficial mutations; sex helps organisms dodge parasitic infections. Yet these evolutionary justifications for sex have remained hypotheses because there is not enough evidence to suggest that any of them provide enough of a benefit to surmount the exquisitely high costs of sex, which include the time and energy it takes to find a mate, the passage of only half of one’s genes to the next generation, and the breaking apart of favorable gene combinations. (See “Why Sex?”)

More than 99 percent of multicellular eukaryotes reproduce sexually and have evolved elaborate ways to do so, including behavioral, physiological, and biochemical adaptations. So there must be some enduring benefit. But despite years of observing, theorizing, and experimenting, researchers have been unable to pin down exactly what that might be. “Why sex evolved is very hard to answer,” says Timothy James, who studies sex in fungi at the University of Michigan in Ann Arbor. “[Many] evolutionary biologists are trying to understand why it’s so rarely lost, even though it’s so costly.”

A current trend is to study the few organisms that are capable of reproducing both ways, including yeast and pond (bdelloid) rotifers. The article is most informative about tests done on the various theses but in the end,

And so the paradox of sex lives on. “We still really don’t know the answer to this very most basic question,” says Mark Welch. “We don’t know why sex exists.”

Unless it exists simply because the life forms prefer it. 😉

One problem with studying the few creatures that can reproduce both ways is that the ability exists in such a tiny minority of life forms, it’s not clear that retaining asexual reproduction provides a broad general benefit.

See also: Bdelloid rotifer uses horizontal gene transfer (HGT), dispenses with sex

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6 Replies to “Another whack at the “sex paradox”

  1. 1
    Robert Byers says:

    god created sex, for animals, to make them want to reproduce. Reproduction was the agenda. how else reproduce?
    With people its a issue of identity and soul and the rest is secondary.

  2. 2
    Acartia_bogart says:

    If you examine most protozoans, sexual reproduction is not something that is optional, it is an absolute necessity. When grown in culture, they reproduce asexually for numerous generations but the population, regardless of how favourable the environment, will senesce and die unless a sexual phase is undertaken.

    What is interesting is that this does not always require another organism. Some protists will undergo a process called autogamy. This involves all of the nuclear processes that take place during conjugation, but it takes place within a single cell. So, it is obviously something related to the meiotic process that is important, not necessarily the sharing of genes with another member of the species.

  3. 3
    bornagain77 says:

    You just got to love these moments of honesty by materialists and Darwinists:

    “We don’t know why sex exists.”

    Goes well with:

    “Huffington Post announces Universe shouldn’t exist.”

    They better watch it, they are treading dangerously close to philosophical/Theistic waters:

    A few notes:

    Why is There Something Instead of Nothing?
    https://www.youtube.com/watch?v=8-ZleERg4mY

    Not Understanding Nothing – A review of A Universe from Nothing – Edward Feser – June 2012
    Excerpt: A critic might reasonably question the arguments for a divine first cause of the cosmos. But to ask “What caused God?” misses the whole reason classical philosophers thought his existence necessary in the first place. So when physicist Lawrence Krauss begins his new book by suggesting that to ask “Who created the creator?” suffices to dispatch traditional philosophical theology, we know it isn’t going to end well. ,,,
    ,,, But Krauss simply can’t see the “difference between arguing in favor of an eternally existing creator versus an eternally existing universe without one.” The difference, as the reader of Aristotle or Aquinas knows, is that the universe changes while the unmoved mover does not, or, as the Neoplatonist can tell you, that the universe is made up of parts while its source is absolutely one; or, as Leibniz could tell you, that the universe is contingent and God absolutely necessary. There is thus a principled reason for regarding God rather than the universe as the terminus of explanation.
    http://www.firstthings.com/art.....ng-nothing

    “The ‘First Mover’ is necessary for change occurring at each moment.”
    Michael Egnor – Aquinas’ First Way
    http://www.evolutionnews.org/2.....first.html

    Richard Dawkins interview with a ‘Darwinian’ physician goes off track – video
    Excerpt: “I am amazed, Richard, that what we call metazoans, multi-celled organisms, have actually been able to evolve, and the reason [for amazement] is that bacteria and viruses replicate so quickly — a few hours sometimes, they can reproduce themselves — that they can evolve very, very quickly. And we’re stuck with twenty years at least between generations. How is it that we resist infection when they can evolve so quickly to find ways around our defenses?”
    http://www.evolutionnews.org/2.....62031.html

    i.e. Since successful reproduction is all that really matters on a neo-Darwinian view of things, how can anything but successful reproduction be realistically ‘selected’ for? Any other function besides reproduction, such as sight, hearing, thinking, etc.., would be highly superfluous to the primary criteria of successfully reproducing, and should, on a Darwinian view, be discarded as so much excess baggage since it would slow down successful reproduction.

    How did the sexes originate? Why is it that the vast majority of living things require a “male and female” to reproduce? If evolution were true – doesn’t it make much more sense that EVERY living organism was self-replicating and required no useless energy expenditure? When did the first male get here? When did the first female get here? How? Why? Wouldn’t they have had to appear fully functional and at the same time in order for the next generation of organisms to arrive? Of course, they would. So, how is it that the first male and female for almost 2 million living organisms arrived together and fully functional so that reproduction could take place? “Sex is the QUEEN of evolutionary biology problems.”
    Dr. Graham Bell – In his book, ‘The Masterpiece of Nature’

    Ian Juby’s sex video – (Can sexual reproduction plausibly evolve?) – video
    http://www.youtube.com/watch?v=Ab1VWQEnnwM

  4. 4
    mahuna says:

    When we moved into our house, there was a pair of holly bushes in front. You have to have a pair because holly, a mere plant, exists as male and female. And this is not like many other plants where all individuals have both sexual organs and gain something by cross pollination. A single holly bush would simply never reproduce. And there doesn’t seem much chance that the plants experience anything like the thrill of mating that animals do.

    So, why do single sex plants exist? The path for evolution by random chance seems impossible, and there doesn’t appear to be any clear advantage over normal plants. I mean, the world hasn’t been taken over by holly bushes.

    The thing that makes the most sense is it was a slow Tuesday, and the Design Team had just finished doing Coconut Palms or something, and Joe says, “Hey, guys. How about we make a PLANT that needs a partner to reproduce?”

  5. 5
    Acartia_bogart says:

    Most flowering plants, even though the same plant contains both sexes, there are mechanisms in place to reduce the probability of self fertilization.

  6. 6
    Mung says:

    Mechanisms are designed. They don’t just come about by sheer dumb luck.

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