Evolution of a Species

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): http://aqua.org/explore/animals/gouldian-finch

▪ H/T Mindy Weisberger whose post on the phosphorescence beads marking the gouldian finch chick’s mouth (http://goo.gl/Zw8tv) set me off on this evolutionary hunt!

▪ Further readings by Sarah R. Pryke ▶ http://goo.gl/Tngj1


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83 Responses to Evolution of a Species

  1. Rajini Rao says:

    Thanks, Marie and Roland 🙂

  2. Arnav Kalra says:

    Interesting. Thanks for sharing. 🙂

  3. Thank you for this treasure Rajini   🙂

  4. Rajini Rao says:

    Terry Hallett , glad you enjoyed it. Something to read while waiting for the robins, right?

  5. Thomas Kang says:

    Rajini Rao I’m curious what you think about the kin selection vs. group selection debate. Do you find one hypothesis more compelling than the other? I only have a faint clue as to what the key arguments are, so I’m curious to hear your opinion.

  6. Rajini Rao says:

    Do you have a link as a starting point, Thomas Kang , so we’re on the same page? I’d love to look into it.

  7. anami rizvi says:

    This is original snap. ….or restored

  8. Rajini Rao says:

    anami rizvi , photos were taken from the link cited in the post (National Aquarium) and combined into one image.

  9. Rajini Rao says:

    Yes, indeed Carl Brown . So what do you see beyond the colors? 🙂

  10. Thomas Kang says:

    Rajini Rao No, not really. In the updated version of The Selfish Gene, Dawkins leans heavily toward kin selection as the best explanation for evolutionary development, and he barely stops short of ridiculing group selection as the main basis for evolution, for instance in birds.

    He goes into great detail using game theory models to buttress his arguments. I have a pretty good understanding of game theory so I was able to follow most of what he was saying, but I still couldn’t discern why that offered a more compelling explanation for kin selection as opposed to group selection.

    I know that E. O. Wilson is at the other end of the debate, arguing that group selection is the driving factor in evolution. I should mention that most of this takes place, I think, in the context of the evolution of altruistic behavior, but the arguments may well extend beyond the question of altruistic behavior.

    This is muddy territory for me, so I can’t really even pinpoint the key issue, other than my muddled attempt here. In spite of being a bit clueless with respect to the crux of the debate, I did find Dawkins’s explanation of kin selection as the driving force for altruism convincing to an extent, but he lost me when it came to altruism among siblings, and even worse, among more distant relatives, particularly when he incorporated the percentages of shared genes among various kin as part of the game theory argument. For instance, I believe that he started going into arguments along the lines of how many cousins being the equivalent to how many siblings, on the basis of the percentages of shared genes. I thought that was a bit strange because it seemed to pose problems with the idea that the gene is the central unit in Darwinian selection, and I had the feeling that he was trying to force an explanation to fit parts of reality that don’t quite fit into the selfish gene model.

    I’ve probably butchered everything here (1) because I don’t have a complete grasp of the crux of the debate, (2) because my readings are superficial, and (3) because I really don’t know enough biology to even hazard a decent evaluation of the arguments of either side. I feel as if I have an intuitive grasp of evolutionary biology, and I know that I’m particularly receptive to evolutionary biological arguments when they align with my intuitions, but the actual testing of hypotheses is the stuff that really counts, and this is where I’m mostly clueless because my exposure to the hard core testing of the fine points is pretty close to zero.

    I don’t even know how much of what I just wrote would even make sense to someone who studies this for a living. There’s a cognitive bias known as the Dunning-Kruger effect, which basically states that people who are ignorant in a particular field tend to overestimate their own knowledge and skill level, in large measure because they are too ignorant as to the extent of their ignorance. The point of writing all of the above is so that you — or anyone else — can point out blind spots and fill out the empty gaps that I don’t even know are there.

  11. Thomas Kang says:

    What triggered these memories was the part above about there being a high price to pay for birds that try to make do with what’s available under inferior circumstances. Even though this doesn’t really impinge on the question of altruistic behavior, at leas as far as I can see, it reminded me of the issue because (again, as far as I can recall) Dawkins went into some detail calculating the net gains and losses in terms of an individual bird being able to pass on its genes to the next generation.

  12. The Beak of the Finch, by Jonathan Weiner, describes a similar circumstance, this time with respect to Darwin’s finches on the Galapagos.


    There is an absolutely amazing chapter in which Weiner describes what happened after a decade of drought.  Different populations of finches began specializing on distinct food sources.  They evolved adaptations making them more efficient at exploiting them.  The biologists watching saw them changing, saw them poised on the cusp of speciation — and then the rains came and everything went back to normal.  Oh well.  But it’s still inspiring to learn that if we look carefully we can see the forces of Creation in real time.

  13. Between writing chapters and this is like a refreshing dive in the pool. Great post Rajini Rao and excellent thread.

  14. Rajini Rao says:

    David Ratnasabapathy , thanks for the introduction to the Beak of the Finch. This comment from the Amazon website explains exactly why I fell in love with the story of the Gouldian finch: “natural selection is neither rare nor slow: it is taking place by the hour, and we can watch”. 

    Thomas Kang , you know more than I do on this topic 🙂 My knowledge is heavily tilted to the molecular and cellular aspects of biology. I’ll leave a book review by Jerry Coyne here, that made sense to me: http://goo.gl/TgwMv  and get back to you on this later.

  15. Rajini Rao says:

    David Amerland , good luck with the writing! I feel much the same as you do when writing: it’s good to take a mental break to read something totally different 🙂 

  16. Thomas Kang says:

    +Thomas Kang , you write as if you know more than I do on this topic.

    FTFY. ^^

  17. OEL M says:

    Mutations and hibridizations happen in this planet but I don’t believe evolution created the Jurasic. Genetic science says that a monkey never will become a man unless the help come from the aliens themselves. All the Jurasic animals that grew here are but the remanents germs of a celestial colision in the past. Later they were changed, srinking in size, and form due to earth cicles around the sun. That croc out there were a giant monster but now he was srinked in size. The sheep, bull, cow, horse, dolphin…by name a few are not from this world. Many accient animals were fossilized. Some changed in size due earth cicles around our sun. Darwin was wrong. Sumerian account talk about aliens and what happened here and how all begun. Sumerian accounts demolish the absurd theories of Darwin. Our scientific books about our solar system and evolution would be questioned. We have not science but pseudo- sciences that are sold in the market as science. The true science would demolish everthing man wrote about universe and evolution. Man can not compete with the techology from advanced aliens and life forms. It is like a donkey wanting to learn math. 

  18. Thomas Kang says:

    From the Coyne piece:

    Such helping behavior seems hard to evolve by conventional selection, since it’s easily subverted by cheaters who accept help but don’t reciprocate. That’s where group selection comes in. If our ancestors lived in small bands containing different proportions of helpers and cheaters, those bands with more helpers could thrive and spawn similar groups. It’s this differential proliferation of groups, Wilson claims, that has made humans so cooperative.

    Group selection isn’t widely accepted by evolutionists for several reasons.

    Dawkins goes into this in quite detail, citing Robert Axelrod’s book The Evolution of Cooperation, which is a seminal work in multi-player game theory. The integrity/viability of groups is heavily influenced by the relative percentages of “altruists” and “free-riders” (or “cheaters/opportunists”). For instance, one could make theoretical calculations as to the relative percentages of honest vs. rogue editors in Wikipedia to determine the ultimate viability of the site as a reliable source of information (“group viability).

    Dawkins engages in fairly heavy mathematical calculations with differing percentages among various species of birds, then extrapolates from this why he believes that kin selection is a better explanatory hypothesis for the evolution of altruism in bird species. What I found particularly intriguing was how some birds developed idiosyncratic strategies for survival. If I recall correctly, cuckoos not only lay their eggs in the nests of different species of birds, thus free-riding on the efforts of the dupes, but when the chicks hatch they kick over the eggs of the host species from the nests, effectively killing off all the other rivals. Shakespearean betrayals in the bird kingdom make for amazing drama!

  19. OEL M says:

    Hahaha…who taugh the humans to do wars? It is what they were doing for centurias. Are not they? Wars, slavery, sexual orgies, incest, royalty… all that was not an invention from man. Man doesn’t invented all that. They were taugh for the aliens themselves. They taugh man how to kill and do wars. Still we do wars. Humans were taugh by some type of alien-warrior- mind culture. They taugh man how to do weapons, do sexual orgies and incest. They brought slavery. Egipt copied all that from the aliens. Later Greece and Roma did the same.

  20. Rajini Rao says:

    LEONEL MAZA , this is a science post, not science fiction

  21. Thomas Kang says:

    LEONEL MAZA I’m curious, are you basing your ideas on your intuition and/or personal beliefs, or on historical or scientific evidence?

  22. Thomas Kang says:

    I’m not sure what Sumerian accounts might have to do with aliens, but I’m curious which Sumerian accounts you’re referring to. I’d love to read them.

  23. Rajini Rao says:

    I’m afraid I stopped reading at sentence #2: “Genetic science says that a monkey never will become a man unless the help come from the aliens themselves.” 😀

  24. Thomas Kang says:

    I find it interesting that both religious fundamentalists and scientists agree that monkeys did not actually evolve into human beings. What I don’t understand is why fundamentalists should believe that this is what scientists believe, when they don’t.

  25. OEL M says:

    Hahaha…if you read sumerian accounts you probably will not be the same again. Are you ready to do an incredible time journey? Then..fasten seat belt, buckle up! Go online and read THE LOST BOOK OF ENKI by Zachary Sitchin. No for idiots. There are all exposed. This is not a fairy tale. It is a wonder and every year by passin by the scientific and geneticist are giving the reason to the sumerians accounts. I know everthing about how all begun. Thank to those clay tablets. Since I read all the sumerian accounts I never was the same. They talk about the aliens and they are the nightmare of all nightmares! 

  26. Rajini Rao says:

    Robert Pratt we’ll have to make do with exogenesis and aliens instead 🙂

  27. Thomas Kang says:

    The only Sumerian account of anything I ever read that I can recall is the Enuma Elish, for an introductory class in world history taught long ago by William H. McNeill who is a brilliant historian (http://goo.gl/y28iA). I still have The Readings in World History series, and I just pulled the first volume, The Origins of Civilization, from my bookshelf so that I can read a bit of the Enuma Elish tomorrow.

    It’s fascinating literature, but I wouldn’t want to base my science on it. 

  28. LEONEL MAZA, you might find this helpful.


    The Outline of Science by J. Arthur Thomson.  I confess I haven’t read it myself, just checked the table of contents and skimmed the first few pages, but I think you’ll find it rewarding.  It was published in 1922 but that’s not serious, not in your case at any rate.

    A perusal of Darwin’s Origin would be exceedingly worth your while too.


  29. Great post!  Now I have another example of sympatric speciation.  The Hawthorne apple example is getting rather stale  (http://evolution.berkeley.edu/evosite/evo101/VC1eSympatric.shtml

  30. Rajini Rao says:

    Free, online sources? Wow, thanks for the links David Ratnasabapathy . Excellent resources..I’ll be checking them out too. 

  31. Thomas Kang, while it is indeed true that monkeys are just as evolved as us, isn’t it also true that our common ancestor more closely resembled a monkey than it did a human?  Fur coat, prehensile tail, hands on the ends of its legs, habitat in trees… If I saw it in a zoo I’d call it a monkey.

    Honest Creationists are profoundly ignorant.  Saying we didn’t come from monkeys confuses and misleads them, I think, without educating them.

  32. Rajini Rao says:

    Shannan Muskopf , that Evolution 101 web site is great, thanks! If there are any papers of Dr. Pryke that you would like (from the link to the abstracts), I’ll check if they are in our University subscription. I’ve skimmed a bunch, they are very well written (although they got too complicated for me pretty fast!). 

  33. Rajini Rao, I so wish more books explaining science to laypeople were available online.  Of course there are plenty of amazing websites exploring single subjects; but what I’m looking for are resources similar to those which educated kid-me.  After all, I know those work 🙂  Something like, dunno, the Ladybird “How it works” series of books; and the “Science Library” series; and the “Tell Me Why” books. So enthralling they were. And so informative that, read carefully, they made science class at school vastly more comprehensible.

  34. Thanks, Rajini Rao , but I’m afraid if they are too complicated for you, they’re going to be way over my head (and my students).   I do love that website though and reference it frequently.   If you find something that would be a good read for high school level students, I would love to see it. 

    Oh, I also meant to ask if you knew what caused the high mortality rates of the “hybrid chicks”.

  35. Thomas Kang says:

    David Ratnasabapathy Thanks for the correction. I suppose I should have said apes, particularly the great apes, rather than monkeys. I tossed out the word indiscriminately in my eagerness to point out an irony.

    Origin of Species is also available for free on the Kindle, and I happen to be in the middle of it now. The breadth of Darwin’s knowledge of the development of so many different plant and animal species is very impressive, even putting aside his ability to tie these threads together into a coherent theory, which is mind blowing. He mentions numerous animal species that I’ve never even heard of.

  36. Thomas Kang says:

    I just finished the first tablet of Enuma Elish, which is only a half dozen pages long. What I find particularly interesting about Enuma Elish is the obvious similarities of the creation myth with the Book of Genesis. The introduction outlines both the similarities and differences in the two myths of creation, as well as those in the respective conceptions of god, and so on.

    Very interesting stuff, though it’s a bit unsettling to learn that millions of people today base their conception of science on this sort of thing.

  37. OEL M says:

    Of course must be similarities but all sacred books came from the original sumerian but they are not originals despite they have some similiarities. The interesting thing is that all gods from all sacred books were the same sumerian gods under other names, disguise and eras. They had very long longevity. So the sumerian God Enlil was Osiris en Egipt, was Jehova in hebrew, was Jupiter in Roma, Zeus in Greece and so on….it is, a good example how the sumerian gods have been messing up with the humans. I have Enuma Elish book. But there are other book named THE LOST BOOK OF ENKI by Zachary Sitchin. The increible sumerian accounts are not for everybody to understad. They demolish all scientific manuals about how the solar systen was created, how the earth came into being, what happened during the anunnaki expedition to this planet, what they were looking for, and for what reason had to create man. In reading that book is the same like going in a time machine. The tale were written in clay tablets around 6, 000 years ago. The sumerian talk about the aliens. It was an increible tale never heard. May be the wonder of wonders. They talk about who constructed the piramids, who was that anunnaki hero that was carved on the top of mars montain with laser beams and NASA only discovered that face from Mars with their Viking satelites around year 1967….incredible!

  38. Thomas Kang says:

    If I may I ask, LEONEL MAZA, I’m curious how you can be certain of the following:

    (1) that the stuff you mention was actually the creation of the ancient Sumerians, and not Zachary Sitchin.

    (2) that even if the material above was mentioned by the ancient Sumerians, what basis they had for confirming such statements as factual truths as opposed to conjectures of the imagination, myths descended down from their own culture, or even metaphorical musings by a few scholar priests.

    (3) that the above should be more compelling than the predictions of the Mayans, or Nostradamus, or L. Ron Hubbard, who has an equally large, if not larger, following than Zachary Sitchin, at least in the West.

    (4) that any of this should have greater factual or logical basis than what science can confirm through concerted, and logical, attempts at falisfication.

  39. Kawthar A says:

    Oh..Thex Dar mentioned some time ago that, these are the birds that ViewSonic use in their logo.

    Beautiful share Rajini Rao 🙂

  40. Thomas Kang says:

    It also looks like the tiny Angry Bird that doesn’t do crap to bust the bricks, but that could be because I’ve only played a few times and don’t know my Angry Birds.

  41. thanks a lot Rajini Rao , is it that this can be used to generalize in the context of formation of perhaps other species too?

    it’s more of simple understandable (except technicalities)article that help to understand things and buildup on it,that’s why i found your posts very informative

  42. Ms rajini rao, u r cruel. U r showing delicious dishes to us but not feeding us. It is bad.

  43. Assortive mating is not the answer to evolution, prefer gene mutation as the better logic, dont think a woman could ever mate with a horse and produce a super species…lol

  44. Amul Dsilva says:

    Creator s fantastic colour combination

  45. Thomas Kang, I meant no correction!  You’re right, we really didn’t come from modern monkeys.  A Creationist who understands evolution to mean that humans evolved from monkeys is technically wrong. 

    I just think he’s more right than wrong.

  46. Thomas Kang says:

    Hi, David Ratnasabapathy That’s okay. Even if you didn’t mean any correction, I appreciate any opportunity to identify mistakes or inexact statements in my own thinking or writing. If it weren’t for stuff like that, my thoughts would stay muddled, and my writing would not have the clarity I want it to have. ^^

  47. I totally second that, Thomas Kang.  Participating in online discussions, particularly on the losing side, has vastly honed my understanding.

  48. Thomas Kang says:

    I believe in arguing my own view as forcefully and as cogently as possible, but always trying to be completely receptive to opposing views when they are even more compelling — all while doing my best not to attach my own ego to any of the argumentation. The idea for me is that I am seeking to falsify the strongest logic that I can muster up, because then the resulting logic is even stronger.

    I know that this is in complete accordance with what you’ve just said. I enjoy these times when I can harmonize my thoughts and feelings with others, but the times that we exchange views that are at loggerheads are also genuine learning opportunities, no matter whose logic prevails (or not) in the end.

  49. OEL M says:

    I don’t pretend to know everthing. But friend…the truth is out there. We are being goberned by the riches. I am right? life is organized in this planet to do business. I am right? Our president Obama knows about aliens and knows NASA deceive people. NASA is not to be trusted. NASA uncovered the famous incident of Roswell, the crash and alien bodies recovery. Our president know about it. NASA uncover what our astronauts saw on the moon and Mars. But he is not going to make a fool of himself talking on the tv about the aliens and what governent knows because the 75% of people living in the EU are men of faith and they only believe in Christ Savior. The polls shows too many idiots and zaelots live in the EU. No way our president are going to talk about the aliens and making a fool of himself. When the day come like the movie INDEPENDENCE DAY, only then our president pressed by some strange event that took place and the thousands of witnesses who witnessed….only then may be our president obliged will disclose the truth long time uncover.

  50. Thomas Kang says:

    This is a long-winded repeat of the above, but I just had the following conversation with another friend on g+ yesterday. I may as well share it here for anyone who bothers to read it because I try to make this my primary, and perhaps my sole, reason for exchanging differing opinions with anyone.

    For me it’s a matter of muddling through, trying to work out the difficulties or contradictions in my own thoughts and the thoughts of others as I see them, then mulling over the ideas some more until I have greater clarity.

    One thing I have noticed is that people who have great clarity because they have deep expertise in their field have the ability to express the ideas more simply and more coherently than those who are still muddling through. I continue on with the muddling because I know that’s the road that ultimately leads to greater clarity.

    It helps when others with similar goals can provide the stimuli that offers up more food for thought, and it doesn’t matter much to me whether the ideas are generally in agreement or wholly opposed, as long as the dialog is conducted with mutual respect and the recognition that the goal is not so much to win an argument as it is to express the arguments as forcefully as possible, coupled with a complete willingness, and even desire, to abandon such arguments when confronted with a stronger argument.

    One may not appear to be seeking to falsify one’s own logic when one is arguing so forcefully in favor of that particular logic, but in my opinion that should be regarded as an invitation to generate more compelling logic rather than simply an indication of a willingness to accept anything that drifts by.

  51. Thomas Kang says:

    LEONEL MAZA I’m curious what you think about this video of Bertrand Russell, particularly the first half of his response about the need to determine what the facts are:


    The reason that I ask is that you seem to be making many claims that need to be substantiated with evidence before they can be accepted as being true.

  52. Thomas Kang says:

    LEONEL MAZA Please feel free to call me Thomas. Thank you for the compliment, but I’m struggling through life just like everyone else trying to learn as I go along.

    I do believe in caution when it comes to drawing conclusions, though; that’s why I was wondering what was the basis of some of your conclusions.

  53. OEL M says:

    Mr Kang, with the due respect we are being governed by the riches and we only can bark like a dog. Huau, huau! Bertrand can’t change the world because this planet is organized to do business. People can only bark. Some bark more loudy than others. It is all about. Leave the world alone. No worry for mankind since I know humanity is damned. The only form you can change the world is using nuclear warheads. All our wars, masacres, brutalities came from those that wanted to establish love over the face of earth. In consecuence we have set in motion destructives forces that not power can stop. That destructives forces originated from the thinking of that man that talk about love…… from that religious man that practice kidness like a fine art. 

  54. Thomas Kang says:

    LEONEL MAZA I can understand your concerns about wars, rampant greed, and so on. Human civilization may have made great advances, technologically speaking, but we still have the brute in us, and keeping this harnessed so that we can convert some of this destructive energy into more positive aims is not easy to do. Perhaps it’s impossible to keep it suppressed forever, given our animal nature; our greed and aggression are, after all, a product of our biology.

    Even so, I think it’s an extreme statement to assert, for example, that the ” only form you can change the world is using nuclear warheads.” When I enjoy an afternoon out in the country with my children, and teach them to respect and be kind to others, I am helping to change the world in my own small way. People here on g+ are helping to change the world, for good or for bad, simply by living their lives and by sharing their knowledge and wisdom and joy (or fears and disappointments and sadness) with others. You are helping to change the world, again for good or for bad, by living your life as you do and sharing your thoughts with us here.

    I understand that this is not the kind of world change that you are talking about, but in the end every human being is limited by their biology, by their own thoughts of what they can or cannot do, and by the powers they have been given, either through natural constitution or through our societal institutions.

    It is frightening to see that many people who have the power to rule often abuse that power, but that to me cannot be a complete explanation. For if that were the case, humanity would be faring much more poorly than it is now.

    With the threat of international conflicts, global warming, still rampant poverty and all the ills associated with that poverty, unforeseeable natural disasters and general pestilence all around, I understand your concerns. Even so, you must share a smile with your friends and loved ones, and to me that, too, helps to change the world. If it didn’t, I wouldn’t be here.

  55. Susan LaDuke says:

    Excellent post! Thanks, Rajini!

  56. Besitiful colors,awsome.

  57. Prasad T says:

    natural macthing

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