Carnival of Evolution #25 (July 2010)
Hey, all! Welcome to the 25th edition of the Carnival of Evolution. I’m honored to get to host the carnival this month – and, as you’ll see, I’ve got a lot of great posts to share. So grab some cotton candy, wander around, and stop to try the rides and exhibits I’ve organized (and illustrated) for you from 21 fabulous blogs.
There were several interesting posts this month about symbiosis – long-term interactions between two different species for the benefit of at least one.
Labrat explains the genomic changes that take place when a bacteria forms a symbiotic relationship with a eukaryotic cell – that’s right, it doesn’t only lose its “free will” (whatever that is), but also part of its genome. Read her post to find out how and why!
In contrast to Labrat’s harmonic story of mutual symbiosis, Psiwavefunction tells a grand story of intrigue, karma, and theft. (The jokes are all her’s.) Over at Skeptic Wonder (one of my new favorite blogs), you can read the saga starring a cryptophyte, a ciliate and a dinoflagellate. Seriously: head over and read the whole fascinating (and hilarious) post yourself.
Corals are well-known symbionts: they are inhabited by zooxanthellae, which undergo photosynthesis and produce energy for the coral in exchange for comfort. I usually think of corals as colonial organisms, living together in large groups in reefs. However, this is not always the case, as Lucas Brouwers explains in his Research Blogging Editors’ Selection at Thoughtomics on how solitary corals evolved.
As we know, the process of evolution takes an incredibly long time. How do evolutionary biologists study the process of natural selection just in their lifetimes? Two posts this month feature experimental methods to test traditional theories of natural selection.
At Denim and Tweed, Jeremy Yoder wrote about an experiment testing density compensation: the observation that islands have fewer species but a greater density of each species. By netting off or introducing predators to small islands, the scientists were able to draw conclusions about whether competition or predation was a more important factor in the natural selection of anoles.
In a similar vein, Marc Cadotte of The EEB and Flow wrote about Darwin’s naturalization hypothesis, which posits that the struggle for survival is most severe between closely related species. Thus, species introduced to an ecosystem are more likely to thrive if they did not share a common ancestor recently. He explains a recent experiment using bacteria species of varying “closeness” (i.e. phylogenetic distance) in variable communities.
Mimicry in the natural world is usually easily explained by natural selection. For example, if predators recognize the coloring of a poisonous organism and avoid it, genes coding a similar pattern will be selected for in a non-poisonous organism due to its release from predation. But sometimes we observe mimicry even where the distributions of the two organisms do not overlap. At NeuroDojo, Zen Faulkes provides some potential reasons why these “mimics without models” exist.
We humans often like to think of ourselves as free from the processes of evolution. And although selective pressures have been reduced in some parts of the world, natural selection is still at work. (My high school biology teacher told me that C-sections are currently relaxing selection against bigger heads – but don’t cite me on that.) At Why Evolution is True, Jerry Coyne wrote about a recent article supporting the current selection of the EPAS1 gene in humans living at high altitudes.
Here at Culturing Science this month, I wrote about the global distribution of microbial species in the face of the traditional idea that, due to mechanisms for wide dispersal and vast numbers, in the microbial world “everything is everywhere.” But if all microbes are everywhere at all times, waiting for the right conditions for their success, are they affected by selection pressures?
The growing and controversial field of social evolution tries to explain why we evolved social behaviors, many of which initially seem against our benefit. It’s particularly interesting when features we commonly attribute as unique to humans – such as empathy, morality, or culture – are found where we don’t expect them.
Let’s take empathy, for starters. It’s often assumed that humans alone are capable of empathy, since an awareness of others and ourselves (a.k.a. consciousness) is necessary to make the kinds of comparisons and conclusions to feel another’s pain. At Living the Scientific Life, GrrlScientist reviews an interesting study about empathy in crows, which console one another after a fight. After I get into a fight, I know that all I want is someone to preen my feathers!
Similar to empathy, adoption is something we think of as unique to humans. After all, why would a creature interested in the spread of its own genes take care of another? At This Week In Evolution, R. Ford Dennison discusses a paper on adoption in red squirrels, weighing the risks of taking on an additional baby with the relatedness of the orphan to the adoptive mother.
Many arguments in the field of social biology seem to be based on differing definitions of terms: what is empathy? morality? culture? Over at Biotunes, Dr. Henneman discusses a recent finding that human babies have a grasp of morality, although it has been traditionally taught that morality, an idea too abstract for a child, is something taught by parents and culture over time.
Additionally, a recent finding that chimpanzees are affected by their social culture was contested by French anthropologist Dan Sperber. At The Primate Diaries, Eric Johnson goes through the definitions of culture proposed by each side, and concludes that Sperber’s problem is not in the methodology, but rather “his objection comes from the definition of culture that he prefers.”
At The Thoughtful Animal, Jason Goldman writes about how sexual preferences affect brain size in his hilariously entitled post “Polygamous Males Have Larger… Hippocampi!” It’s a really lovely study: the scientists studied two populations of very closely related voles (within the same genus), one of which has polygamous males while the other has monogamous. Presumably a polygamous male, requiring a larger home range (to meet many lucky ladies) would need a bigger brain to store the information. Is it true? Click here to find out
Zen Faulkes wrote up a study at NeuroDojo about … well … cricket sex! The scientists were very dedicated to this topic: they set up 2 video cameras for 2 summers in a row capturing all the activity of 200 or so crickets. And then they watched the footage. After all that hard work, they deserve to have their findings known – so go ahead, read it.
Over at 360 Skeptic, you can read a tale by Andrew Bernardin about testosterone in dark-eyed juncos, those cute little winter birds found on the East Coast of the USA. While testosterone in birds can increase mating success through increased territory defense and mating displays, the authors wanted to know if there is such thing as too much testosterone. Maybe that’s why I’ve never seen a really jacked junco…
In a lovely post on Evolving Thoughts, John Wilkins goes through the arguments for different definitions for the word “homology.” He argues that “homology” does not necessarily refer to common descent (although that’s how it is often used), but rather simply to a part of one organism “agreeing” with a part of another organism, with no explanation built in. In the process, he goes through the history of cladistics in perfect detail (with some beautiful illustrations to boot).
You know how I feel about cephalopods – so I was very excited to get a submission from Cephalove on the evolution of octopus brains. In order to assess the evolution of the nervous system generally, Mike Lisieski takes us a few steps back to our closest common ancestor with octopuses: the Urbilaterian (or “original bilaterian”). He suggests that to learn about neural evolution generally, we should look at how cephalopod and human brains evolved separately from this common ancestor.
At Byte Size Biology, Iddo Friedberg explains the beautiful paper comparing the genomic makeup of E. coli and the operating system Linux, revealing how evolved and created systems differ. Does this put us a step closer to developing cyborgs?
The finding that we Homo sapiens share genes with Neanderthals and possibly bred with them was big news this month – and, over at The Atavism, David Winter does a great job explicating some of the issues that have been brought up. Just because we interbred does not mean we are the same species as Neanderthals; but it does bring up some issues of how we define a species. (Ahh, the species problem, one of my favorite things to think about…)
At The Voltage Gate, Jeremy Bruno wrote up some research on the biogeography on Flores, where the famous small fossils of Homo floresiensis were found. (“A hobbit’s contemporaries,” in Jeremy’s words.) The authors compared the distribution of other species on the island of Flores to that of other islands to see if similar patterns of evolution occurred, and ultimately to draw conclusions about the size of H. floresiensis. A great read.
Jason Goldman takes a look at risk-taking in primates, and whether it is related to foraging strategy at The Thoughtful Animal. The study looked at bonobos, which will chance upon an abundant food source and gorge, and chimpanzees, which are constantly gathering smaller foods. Which one is more likely to take a gamble on its snack quantity?
Over at Pleiotropy, Bjorn reports on the discovery of a fossils of multi-cellular precursors older than we’ve ever found, pushing back the evolution of multicellularity back 200 million years. These fossils do not represent specialized structures as we normally think of metazoans – but there is evident of cell-to-cell signaling, suggesting that these guys are not simply bacterial colonies.
Everything you ever wanted to know about tunicates – seriously! Check out this great, informative post at Fins to Feet, describing how vertebrate life may have evolved from these sessile sponge-like organisms. The answer lies in their larval form, which has a notochord. Through the process of neotony (which Lucas also discusses in his coral evolution post), when an organism continues to exist in its larval form into adulthood, these larvae could have evolved into early vertebrates. Check out the whole post here.
Evolution Shop Talk
Two posts this month try to clear up common mistakes or assumptions made about evolution. At Darwin’s Bulldogs, Madhusudan Katti writes about the common misconception of an “evolutionary ladder.” “EVOLUTION IS NOT A LADDER” is his battle cry; there are no pinnacles is his argument. Similarly, Andrew Bernardin at 360 Degree Skeptic responds to wording in a paper implying purpose in evolution. He explains that there is no goal in evolution, and more complex does not mean better or more evolved.
Some bloggers tried to debunk creationists this month. At Evolution is True, Jerry Coyne criticized a group that tried to reconcile evolution with the Adam and Eve story, and over at Pleiotrophy, Bjorn explains why some creationist promotional material he received is not truth in two parts: II and III.
Thanks for stopping by, and I hope you enjoyed the Carnival of Evolution. Next month will be hosted by Jason Goldman at the Thoughtful Animal. So write up your blog posts about evolution, and submit them here by August 1, 2010.