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Happy Darwin Day

Happy Darwin Day

In celebration of Charles Darwin’s 206th birthday, here is a post on how species continue to evolve to this day. Speciation caught in the act! 


Originally shared by Rajini Rao

Evolution of a Species

Assortive Mating: The diversity of lifeforms on our planet is central to evolution. But how do new species form? A key step is assortive mating, when individuals use physical or vocal cues to choose mates that resemble themselves. Perhaps natural selection favors offspring from similar matings. Eventually, the populations diverge genetically to the extent that the hybrids are unfit, and separate species emerge.

Caught in the act? Take the curious case of the Australian Gouldian finch (Erythrura gouldiae). There are black and red head color morphs (see image) that prefer to mate with like types. This preference is genetic, as chicks reared by foster parents of different type still prefer to mate with their own head color morph. In fact, the head color and mating preference are tightly linked on the sex chromosome Z (males are ZZ and females are ZW in birds). This lack of “sexual imprinting” is unusual, since most birds get their cues from rearing parents.

Hybrid drama: Both head color types coexist in the same geographical area. Shrinking and unequal populations mean that mates of the same type can be hard to find (the bird is endangered). The birds seem to “make the best of a bad situation” and breed with different head color morphs anyway. But there is a steep price to pay : more than a third of the offspring die. The mortality rate is worse in female chicks, nearly half fail to survive. Curiously, the mothers seem to control for this by producing broods with more males. So, if they are tricked into thinking that their mate is of a different head color  (using bird make-up!) they produce biased broods! All of this suggests that the Gouldian finch may be in the process of splitting into species, unless it becomes extinct before then 😦

▪ Images (National Aquarium):

▪ H/T Mindy Weisberger whose post on the phosphorescence beads marking the gouldian finch chick’s mouth ( set me off on this evolutionary hunt!

▪ Further readings by Sarah R. Pryke ▶



Join the Conversation


  1. No it isn’t. The diversity of life on this planet is breathtaking, so many species diverging in so many different ways can easily boggle the mind. I hope one day to understand it all, but until that happens, its best to preserve these species for future generations.


  2. I had no idea my little cage bird was a member of an endangered species! He’s been locally bred, though. I adore him. His lady died within the first year. Old, horrible story I won’t tell again.


  3. I swear, we sciencey folks really need to come busting into your churches and telling you all you’re fools and listening to nonsense, see how you like it!

    Leave us alone, you ignorant cowards, and go pray to your altars.


  4. Science is essentially observational analysis of interaction. (natural and fabricated) 

    God is the essence of spirituality as a function of belief.

     Science is defined with metrics; and, God has no metric with which to define.

    This is a false belief.

    Linguistics tells the story, however, metrics defined linguistics. Be not confused, that the two should be separate. For one was discovered, as the other, given a name.

    Peace to all.


  5. Gee who would think someone as “smart” as you Ann, wouldn’t even know you’re keeping an endangered bird caged. I thought scientists were supposed to be open minded, since after all, None of us living now were there at the creation”big bang”. Calling people names when you weren’t there is pretty egotistical, in your own words, ignorant.(by the way Evolution is still just a theory-get it?)


  6. +coleen Mitchell, They’re just one of the many captive bred finches available from local breeders. Why, I wonder, can’t they also do this in Australia? They seem to breed well enough to supply all the pet stores! At any rate, he’s quarantined because he and his mate brought with them a disease that decimated my flock and left me waiting for the survivors to die naturally. I cannot breed nor sell a one of them and I won’t cull them.


  7. Let’s focus more on what the post says rather than fighting over science and religion. If somebody wants to fight go to some other forum or send pm to each other rather than spamming here.


  8. …and God will “repay” you in heaven. Because in heaven the first(rich/powerful) will be last(in heaven) and the least(slaves/poor/sick) will first! It takes more faith to believe that something came from nothing(the Universe) than to logically believe a Creator designed it. 2nd law thermodynamics


  9. Burden of proof is always on the person claiming something exists. The fact that you dont understand that speaks towards your lack of understanding here. You have lost credibility by saying something so rediculous.


  10. Ian Evans

    The question should be does god exist? If so, where? And…what has he been doing? Very simple questions…and the answer would change the human existence forever.

    Real or not…is a the state of mind…tooth fairy, lochness etc


  11. I read and understood the first paragraph ‘assortive mating’, but am stuck at second paragraph! That is ‘caught in the act’. Can someone please read and explain it ? I understood the part that birds have Z chromosomes (which I never knew and it’s awesome to know!) but not able to push beyond it. So, could someone please explain? Just the second paragraph: ‘caught in the act’.


  12. Michael Logue Great than when you quite calling me stupid perhaps you can gather the best in your field to come up and prove creation wrong which I offer you. Or just say it stupid without trying out of fear of being made wrong. You have your theory today cause you have cheated and eliminated the most important text.

    -Oh as a eye witness to a UFO and records which place that type ship here 7,500 years ago during the “War In Heaven” and a film of the ship I saw landed filmed. You might not be so correct or arrogant when I finish with you and your kind.

    Let’s Go.


  13. Ian Evans this is not a forum for discussing the Bible, God, Satan or creationism. We are here for discussion of science, as exemplified by the questions and comments from Mohan Pathak and Ross Marks (many thanks to you both!). Our role as moderators is to keep the conversation on topic, and about science. Anyone continuing to derail the scientific conversation will be blocked. This includes you. 


  14. Science on Google+

    On the discussion of science: You can use both methods. Darwinism and/or Creationism. Both are “Scientifically” valid. By just blocking the people like me (Who will gladly follow the rules of debate) you are not allowing peer review. While I will respect you as modulators: Set the rules and I will follow. So long as both sides get equal treatment: I don’t care. I am leaving for an encampment this afternoon and will be incapable to respond to your response. I await your reply.


  15. tommy northam, I suspect that my response is a waste of time but here goes. This post is about evolution, not on the origin of life, please stay on topic. If you are interested in how simple molecules can come together to form self replicating biochemicals, look up abiogenesis and RNA world. There’s even a Wiki entry on it. Look it up. 


  16. tommy northam you asked, “where did that original organism come from, and how did it obtain the breathe of life?”  Arien Huckeba suggested that for earth at least, panspermia could explain how complex biochemicals could have seeded self replicating forms. I told you that abiogenesis explains how biological life arose from self replicating biochemicals, with RNA being a key molecule. What else do you need to know? 


  17. As I suspected, a waste of my time :/

    There are plenty of peer reviewed publications on the topic, especially on RNA world, but you’re not going to bother. Just a troll. 

    We don’t engage with creationists here, blocked. 


  18. Fascinating, thanks Ross Marks . This excerpt is a helpful conclusion: “What we see are two diverged lineages, but we can’t know whether they will continue their evolutionary divergence and go on to form two “full species”, totally incapable of exchanging genes, that deserve different Latin names.  It’s possible that they will maintain their status as somewhat distinct lineages, but that gene flow will be enough to keep them from achieving full reproductive isolation.”


  19. Humans are more self aware (by far) than any other species, yet we are as tied to the law of assortative mating as ever.

    A perfect example that we are not as in control of our own destiny as we like to think so.


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