Evolution Awesomeness Series #3: Convergent Evolution

Meet the Emerald Tree Boa and the Green Tree Python, two different species from two different genera.

Emerald Tree Boa, Corallus caninus via Wiki

Green Tree Python, Morella viridis, via Wiki

What’s that you say? Those are the same snake?

Are you calling me a liar?!

Welcome to convergent evolution! When two species develop similar traits and are not related or only distantly related, it’s called convergent evolution, and it is freaking awesome.

The Emerald Tree Boa lives in the Amazonian rainforest of South America, while the Green Tree Python can be found in parts of Australia, New Guinea, and Indonesia. Boas and pythons are totally different groups of snakes but share characteristics in the way they look and live.

What’s that you say? You want another example? Okay, you don’t have to twist my arm.

Euphorbia obesa, via Wiki

Astrophytum asterias, via Wiki

The top plant is Euphorbia obesa, while the bottom plant is Astrophytum asterias. Both are succulent plants, meaning that their thick skins retain water and they can survive drought conditions. Euphorbias are prolific and found all over the world, while Astrophytums are found only in Mexico and Texas. Each belongs to a separate genus but has evolved to be short, squat, and divided into eight “segments.” Cool, huh?

So why does this happen? Essentially because there are certain adaptations that work in certain environments. Obviously, the conditions of New Guinea and the Amazon Rainforest were similar enough while the two afore-mentioned snakes were evolving that they developed into two separate species that look like twins. Same for the succulents.

According to PBS, “there are a finite number of effective solutions to some challenges, and some of them emerge independently again and again.” My Ph.D-in-Evolutionary-Biology-holding boss agrees; he says there are some traits that would be really effective, but that can’t evolve due to physical constraints. His example: that humans haven’t evolved wheels. Even though having wheels would make getting around a hell of a lot easier and potentially provide for better survival, we can’t make them. (Let’s all take just a moment to ponder what life would be like if we had wheels. Thanks.)

So basically there are some things that are pretty hard to code for genetically, and other things that are easier to code for and therefore show up more. Either way, the environment works together with evolution to shape the animal.

Another example of this awesomeness is the relationship between marsupials (animals that have pouches where the babies hang out after birth) and placentals (that’s you and me): although they occupy different parts of the planet and have different styles of reproduction, a lot of marsupials look like placentals and vice versa. Have a look:

(The site for this image has long since perished so I have no author info – if you know it, please contact me so I can give proper credit!)

Here’s a marsupial predator, the now-extinct Thylacine. Does it look like any placental predators you’re familiar with? Maybe canine in nature? (It’s a shame the Thylacine is extinct because they look pretty badass and I wouldn’t mind watching video footage of them on Discovery. Taking down kangaroos and shit.)

via Wiki

via Wiki

Look at this PBS page on convergent evolution for a great image comparing four anteating-animals found across the planet. (Click on the image for the full-size.)

I hope you’ve enjoyed today’s EVOLUTION AWESOMENESS SERIES on convergent evolution. I challenge you to find another example of convergent evolution and post it in the comments section! Thanks for reading!

Posted on August 7, 2010, in Biology/Ecology and tagged , , , , , , , , , , , , , , , , , , . Bookmark the permalink. 17 Comments.

  1. One must note that there is a difference between convergent and parallel evolution.

    Parallel evolution occurs when ancestors of a set of given descendants, who have similar traits, also have similar traits. Convergent evolution occurs when the ancestors did not have similar traits but the descendants do.

    Anywho…I dig the birds, so….Old World and New World vultures both eat carrion and thus have bare, featherless heads and necks. However, from their ancestry, Old World vultures still find food thanks to their eyes (it’s easy to see long distances on the Savannah), while New World vultures, like the turkey vulture, use their noses (it’s hard to see food on the forest floor beneath the canopy).

  2. Thanks ScienceGuy! I had actually been having a little bit of trouble understanding the differences between convergent and parallel, but you’ve just summed it up perfectly for me. I too, am a giant fan of vultures and I did NOT know that Old World Vultures relied on their eyes more than a sense of smell. I love asking a group of people if birds can smell, which of course they mostly can’t, but using the chance to make a plug for how awesome the turkey vulture is.

    If I may ask, how did you find the blog? And thanks again for your input!

    – t r n

  3. No problem. I found you on the wordpress global tag section and this series looked rather interesting.

  4. I am laughing my butt off at “Taking down kangaroos and shit!”

    I can’t think of any examples of convergent evolution off the top of my head, but your post reminded me of the last book of His Dark Materials. There was a species (in another universe or something) that had evolved to have a lubricated hook thing, which they used to attach to a giant tree nut that effectively worked as a wheel. After rolling around on this super hard nut for however long, the nuts eventually cracked open, allowing more of the giant nut trees to take root and grow. The wheel creatures depended on the trees for mobility, and the trees depended on the creatures for reproduction.

    If you haven’t heard of His Dark Materials, it’s pretty much the pro-evolution skeptic version of The Lion, The Witch, and The Wardrobe. It’s quite fantastic!

  5. one of my favorite examples of convergent evolution is the Desert Horned Viper of Africa (Cerastes cerastes) and our own native Desert Sidewinder (Crotalus cerastes) – They are both sand-dwelling desert snakes that have both developed sidewinding locomotion, pronounced scales over the eyes, and a very similar shape. So cool how evolution works!!!

    Jamison

    P.S. I found your blog by searching WordPress for “rattlesnake”.
    Feel free to visit my blog here as well if you’re at all interested in snakes.

    • Hi Jamison! Thanks for all your great comments! I agree with you on the phobic thing concerning legs – the more the scarier – but I find that I tend to be most skittish around things that move fast. I don’t REALLY mind spiders, but if one startles me and it’s all scampering about, I’ll squeal like a little girl. Thanks for the awesome example of convergent evolution! Glad you found me, I hope you keep reading! I will definitely be checking out your blog. Thanks again for the comments!

      -t R N

      • No problem! I love your articels and writing style! Your blogs look so much more professional than my own. I’m new to this still , but aspire to have my blogs look half as nice as yours.

        I’m with you in regards to speed as well. I don’t mind a little spider hanging out in its web, but when I spot a Wolf Spider hauling across the carpet (ugh), it makes my skin crawl. Have you ever seen the Giant Desert Centipedes we have in Arizona? They can get over a foot long, and are FAST!!! I was taking a photo of one last year when it literally raised up and grabbed a flying Preying Mantis right out of the air. Mantids are formidable predators, but this one oly lasted about 1 second against the venomous centipede. I’ll have to post pics on my blog sometime.

        Nice meeting you!

        Jamison

  6. I really wish you could have seen my face as I read your story about the centipede (seriously, 12 inches? that pretty much ensures I’ll never be visiting Arizona) – that’s definitely something I would have paid money to see. Post those pics!!!

    Also, I think your blog looks great! The only thing I would change is making the title and subtitle more about what you want the blog to be. Other than that, it looks great – I really like the photo bar at the top!

  7. Very nice example. I found your blog while searching for examples of convergent evolution. I’ll plug you on my own (http://eatmorecookies.wordpress.com/) where you might find some nature-y evolution-y stuff of interest.

  8. my name is guy and i study biology.

    first- i think have a very strong evidence for design in nature

    a) we know that a self replicate robot that made from dna need a designer

    b) from a material prespective the ape is a self replicate robot

    a+b= the ape need a designer

    or even a self replicat watch.the evolution side always say that a watch need a designer because it cant self rplicat. so if we will find a self replicat watch we need to say that is made by itself

    plus: if a self replicate car cant evolve into an airplan, how can a bacteria can evolve into human ?

    the evolution say that small steps for milions years become a big steps. but according to this a lots of small steps in self replicat car (with dna) will evolve into a airplan.

    but there is no step wise from car to airplan

    evolution say that common similarity is evidence for common descent. but according to this 2 similar self replicat car are evolve from each other

    according to evolution a car can evolve in a close room, beacuse a human can evolve in a close room and make a car

    check this interesting site

    http://creation.com/are-look-alikes-related

    what you think? yours sincerely

    • Hi Guy. I’m not sure I totally understand the entire argument here, but what I will say is that comparing non-living things to living things in terms of evolution doesn’t make much sense. A car can’t self replicate because a car isn’t alive, and doesn’t fall in line with any of the 7 requirements for being “alive.” Cars, airplanes, and watches don’t have DNA. Replication has to happen through multiple genetic lines coming together – or from asexual reproduction, which is cloning and the genetic material is identical through each generation.

      I hope that makes sense! Thanks for writing!

  9. Hi Nicole,

    Just found this page, brilliant and clear explanation of convergence!
    I think Guy might benefit from reading Richard Dawkins’ wonderful book ‘The Blind Watchmaker’, which deals with all the points he raises very clearly.
    Keep up the good work, Nicole!

    Matt

    • Thanks for reading and commenting Matt! :) I still have yet to read any Dawkins, isn’t that shameful? I’ll get there some day.

      -Nicole

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