This Nature Walk edition continues from #4.1 - Arthopods.

I've broken this post up into four parts due to the large number of images:

• 4.1 - Arthropods
  
• 4.2 - Birds (this post)
• 4.3 - Reptiles, Amphibians, & Mammals
  
• 4.4 - Plants & Fungi
  

The images are highly compressed for bandwidth's sake, but you can click on the images for larger versions (and a few are much deserving of an extra click).

As always feel free to give me any species identifications where I have failed to do so or done so incorrectly.

Birds

Other than all the other scurrying, fluttering, swimming, and pulsing critters of the world, birds are my favorite.

I've managed to snap quite a few good bird images over the past few days (though more eluded me, such as the dastardly killdeer that continually thwarted my focusing attempts). Here are some of them.

First, the Eastern Bluebird (Sialia sialis). This bird was hanging out over by the Environmental Protection Agency (near the NIEHS). It was quite a distant shot, but turned out pretty well, considering. I am rarely able to get close enough to bluebirds around here. They're just so skittish.

Eastern Bluebird (Sialia sialis)

Eastern Bluebird (Sialia sialis)

This next is my favorite bluebird image ever. Today I just happened to walk by this birdhouse nestled in in the woods at the treeline (the NIEHS campus is covered with them), and I saw this single eye staring out at me.  Priceless!

"Please don't eat me, please don't eat me, please don't eat me!"

And the cutest thing I've seen this spring: a Mallard (Anas platyrhynchos) mother with eleven ducklings.

Mallard (Anas platyrhynchos)

Swimming among the algal mats - Mallard (Anas platyrhynchos)

Check out the front baby's face! - Mallard (Anas platyrhynchos)

And to top it off, I even have some video:

As I've mentioned before, one of the great things about the National Institute of Environmental Health Sciences (and the EPA) is the large lake in the middle of campus. We are a stopping ground for all sorts of migratory water fowl, with several species appearing and dissappearing throughout the year. (see the ruddy ducks from a previous Nature Walk)

One bird that I've seen alot of this year is the Double-crested Cormorant (Phalacrocorax auritus).

Double-crested Cormorant (Phalacrocorax auritus)

So regal!

"Do I look fatter to you?"

Of course, our campus is infamous for the gazillion Canada Geese (Branta canadensis) that stalk the grounds.  Right now the females are mostly nested, with the males hovering nearby - both ready to start a hissy fit (literally) if you get near the nests.

Canada Goose (Branta canadensis)

"Back off!"

"And you think we don't have teeth"

To truly appreciate their menacing display (more hiss than bite) you must see the video:

Don't worry - this goose was not overly stressed by me.  They nest about 3 feet from the walking trail. This female makes this display probably about a hundred times per day as each jogger strolls by.  It's quite hilarious actually. One has to admire their ability to keep up the front (I know of quite a few people who find them dangerous and terrifying - trust me, they are neither once you've figured out their game. It's the same as a defensive opossum: open your mouth and hiss alot - that's it).

As I was walking along, a Great Blue Heron (Ardea herodias) plopped down right next to me.

Great Blue Heron (Ardea herodias) coming in for a landing

Great Blue Heron (Ardea herodias)

Back at the homestead, I captured another priceless avian expression: an American Goldfinch (Carduelis tristis) suddenly noticing that I had snuck up behind the feeder.

American Goldfinch (Carduelis tristis)

Nearby, a White-breasted Nuthatch (Sitta carolinensis) skittered up the huge poplar tree in my front yard:

White-breasted Nuthatch (Sitta carolinensis)

A Northern Mockingbird (Mimus polyglottos) perched as well.

Northern Mockingbird (Mimus polyglottos)

Finally, I managed to capture a far away American Kestrel (Falco sparverius) scoping the farmland below for tasty treats. I grew up calling these "Sparrow Hawks," which is apparently a common misnomer - they are actually falcons (not hawks).

American Kestrel (Falco sparverius)

American Kestrel (Falco sparverius)

Who says the dinosaurs went extinct?

See the rest of this Nature Walk:

• 4.1 - Arthropods
  
• 4.2 - Birds (this post)
• 4.3 - Reptiles, Amphibians, & Mammals
  
• 4.4 - Plants & Fungi

Our self-aware cousins

This weekend I heard an incredibly interesting story on NPR's This American Life titled "Almost Human Resources" (Act 3). The story was all about the issues surrounding chimpanzees in the human world surpassing their usefulness and how we should care for them. Apparently this now includes retirement homes with TVs.

This story, along with a recent tangential debate over at Southern Fried Science and PETA's "sea kittens" campaign, sent my mind down a familiar path - one that anyone working in biology inevitably travels from time to time: the ethics of animal research for science.

There have been myriad writings, books, movies, discussions, and laws surrounding the practice of using animals for research. I'm sure most of us in the science world have come to very similar conclusions on the subject, though we may vary widely in the details.

Nonetheless, I'm very interested to hear where YOU, my readers and my fellow scientist peers, currently stand on the subject. I would like this post to be interactive.

First, I'd like to give my own thoughts.

In general, I view all living things as uber-complex organic robots (humans included). All life is amazing, precious, and beautiful - from bacteria to humans - but I still see us all as robots, running our nearly unfathomable genetic programs, developmental processes, and higher-level emergent programs of conscious and sub-conscious thought.

Mirror Test

At the same time, I feel - for no rational reason really - that consciousness and self-awareness inherently grant those that harbor them the right to live relatively free from human induced suffering. This is a feeling. We all feel it, at least for humans. We feel the immorality of conducting experiments on other human beings (though this was not always the case). Why? Because it's...just...wrong.

It's for this reason that I'm completely opposed to any medical research on chimpanzees or any great apes. There is no doubt that our great ape cousins share many if not most of our own emotional and sensory perceptions, as well as similar intellectual abilities (similar in type - not necessarily degree). For all intents and purposes, I see them as people. Not human people. Not anthropomorphized animals. But sentient to semi-sentient beings.

It's hard to measure degrees of self-awareness and know whether another creature has it. But the classic mirror test is one simple way to find when the answer is a clear yes. As of right now, great apes, dolphins, elephants, and at least one bird species, the magpie, have passed the test and shown that they have some understanding of "self."

If a creature can have any understanding of what is being done to "them," I am completely against it. Recently Orac at Respectful Insolence posted on the discontinuation of using dogs for teaching surgery techniques. He caught some flak from a few commenters for showing an emotional relief that dog use was being halted - at least partially because he loves dogs. As if any decisions on the use of other beings for our own benefit could be arrived at using only reason!

No - we as humans place some inherent value on consciousness, on self-awareness. Dogs may or may not be "self-aware" as defined by behavioral scientists. They can't pass the mirror test, but anyone who has had a dog knows that they clearly experience something akin to guilt, and a whole host of emotions similar to those of our own (I'm being careful here not to anthropomorphize). They know when they have done something wrong.

As any behavioral biologist, psychologist, or cognitive neuroscientist knows, there is no clear dividing line between conscious being and automaton. What about rhesus monkeys and the other more "primitive" primates? I personally feel that much monkey research - particularly those studies on the cutting edge of such diseases as A.I.D.S. - are critical right now. However, I also know that I could never be one to perform such studies. There is a mental hypocrisy here in my own mind. I would feel wrong performing primate research. But I support it to a limited extent.

But for some animals, it seems clear when they are well beyond that gray fuzzy line. Xenopus frogs, as far as any observation or measurement can tell, are much too dumb to have any sort of self-awareness. The same can be said of mice or rats. They simply do not have the cognitive capacity - the hardware - to generate emergent properties like self-awareness as we know it. It seems more than clear to science, I believe, that these creatures are fuzzy automatons. I have performed studies (using incredibly regulated and humane methods) using these creatures, and I have no qualms about it, so long as the use of animal models are absolutely critical to the study at hand. Hundreds of thousands of lives have been saved or vastly improved by such studies. Few people alive today (in America at least) can imagine what the state of human health would be without mice and rat studies.

And just to go one level further "down" the evolutionary ladder, consider fish.

Fish are NOT "sea kittens." We understand at least at a basic level what overall types of brain structures and neural pathways are required for higher cognition. Fish do not have these structures. They are insanely complex, from a genetic standpoint. They are beautiful. They are unimaginably important to the ecosystems of the earth. But they are still slimy scaly robotic automatons incapable of "suffering" in any human sense.

And invertebrates? Well, they're clearly organic machines. Would any of you really argue otherwise?

However, with all of the above being said, I often think about how barbaric people were only a generation ago (or sometimes less), and I wonder which of my beliefs will be considered equally barbaric by the next generation. As Richard Dawkins mused in "The God Delusion," perhaps animal rights is the issue upon which our generation will be judged to have sinned. Perhaps our ancestors will cringe at our actions (while praising the 500 year lifespans our research has given them - kidding).

What do you think? Take these polls and leave your comments below.

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Therein, in symbiotic relationship number one, sat a photograph that I found utterly astonishing:

"Plovers and Crocodiles"

According to the WebEcoist website which published this list of "symbiotic wonders."

"It looks like something out of a storybook - and in fact it can be traced back to accounts told thousands of years ago - a crocodile opens its mouth, invites a bird in before … what?  ::Chomp:: it swallows the sap alive? Amazingly, the crocodile remains still while the plover picks meat from its mouth. This cleans the crocodile’s teeth and prevents infection while providing a somewhat scary meal for the hungry bird."

The image stewed in my head for a couple of days, and I mentally bookmarked it as an excellent adaptation to cover in my Adaptation of the Week series. The story began to write itself as I drove to and from work.

It's quite easy to see how such a relationship, once begun, would be reinforced over successive generations, with the daring plovers becoming well-fed and the tolerant crocodiles' pearly whites gleaming like Smilin' Bob's.

Egyptian Plover (Pluvianus aegyptius)

But how would such a symbiotic relationship begin, I wondered?

Regardless of the incremental steps that naturally must have occurred, at some point a single dumb, brave, or incredibly hungry bird had to have been the pioneer to first brave the feast-laden crocodilian death-trap. Imagine being the first bird to firmly plant talons on that massive reptilian tongue. No doubt others had come to this place before - but none had survived unscathed.

And what of the first crocodile. Was he just so stuffed that he couldn't bear the thought of shoving one more feathered morsel down his gullet ("it's only wafer thin"). Or perhaps he was the Einstein of the ancient crocodiles, somehow sensing the advantage of letting the little plover do its thing.

In reality, I thought, the relationship probably came in many fits and starts, with the birds initially pecking around the crocs, grabbing whatever leftover bits they could. The crocs tolerated them, much as cattle do with egrets. Perhaps a fair number of plovers did end up as croc snacks. But over time, the crocs most friendly to the plovers gained a slight advantage, with the "friendly alleles" slowly increasing in frequency throughout the population. The birds, of course, now had to compete with one another, becoming bolder and more adventurous.

Nile Crocodile (Crocodylus niloticus) with Human Hand (Lucas skywalkerus)

In the end, this beautiful relationship was forged and stabilized, to the benefit of both parties (though I imagined that crocodiles who break the contract probably continuously cropped up).

I had my article, plainly written right there in my brain. But of course, as with any good article dealing with science..er...well, anything, I first had to do a little bit of research. What species of bird is it? How common is the relationship?

I make my way back to the original "7 Symbiotic Wonders" article and click on the above image to get the image credits.

The photography website (Warren Photographic) immediately opens to the same image with the following caption:

"WP00955. Nile Crocodile (Crocodylus niloticus) with Egyptian Plover or Crocodile Bird (Pluvianus aegyptius) - digital reconstruction of popular myth attributed to Herodotus, 5th Century BC." [emphasis mine]

Wait...what?!

That's not a real image, but a photoshopped one?  I immediately googled the bird (Pluvianus aegyptius), which pulled up this Wikipedia article:

"It is also sometimes referred to as the Crocodile Bird because it is famous for an unconfirmed symbiotic relationship with crocodiles. According to a story dating to Herodotus, the crocodiles lie on the shore with their mouths open, and the plovers fly into the crocodiles' mouths so as to feed on bits of decaying meat that are lodged between the crocodiles' teeth. The crocodiles do not eat the plovers, as the plovers are providing the crocodiles with greatly-needed dentistry. Two prominent ornithologists have supported this story anecdotally,^[who?] but the behaviour has never been authenticated (Richford and Mead 2003)." [emphasis mine]

You mean to tell me that after all of this thought, the whole thing is only an ancient myth?!

Apparently the author over at WebEcoist didn't do his research for the article (sorry Ecoist). I mean, c'mon! The original image they used as the lede explicitly states that it's only a myth.

So much for my Adaptation of the Week...

What a croc!!

In the end, I decided to do some research and find a REAL symbiotic relationship:

And in return?

(I photoshopped this)

Update: I found a great post on SkepticWiki that discusses this exact supposed phenomenon, and it even talks about how some creationists  use the "crocodile bird" (erroneously) as an example of a behavior that could not have evolved naturally. Right...

Previous Adaptations of the Week:

1. Timber Rattlesnake Camoflage
2. The Aye-Aye’s Freaky Finger (I’ve Been Cursed by an Aye-Aye!)
3. Flatfish Eyes & Recapitulation Theory

Unfortunately, I did not see the otters, though I will most certainly be attempting to capture them on digital film next week... I did see the following... (FYI: I am not an experienced birder - if I misidentify, feel free to let me know. Also: these are highly compressed images to limit bandwidth - click for higher res).

Beautiful lake between the NIEHS and EPA campuses

First up, a flock of ruddy ducks (Oxyura jamaicensis):

Sleepy...

so my tail's stiff...what of it?

Get back to work...

And of course, our ubiquitous Canada Goose (Branta canadensis). We literally have hundreds of these birds all over campus year round, covering every surface with green refuse. I look forward to nesting season when they develop severe huffy attitudes that involve a lot of loud hissing (but they're really all talk).

A while back they hired a company to capture most of them and relocate them...yeah...that didn't work (too many geese leads to many problems, environmental and otherwise).

Bring it on Cobra Kai

Walk on by...

And the less exotic, but still wonderful American Robin (Turdus migratorius) far away and HIGH up in a tree (I was surprised this photo even turned out at all.

Fluffed in the wind

After my walk around the lake, I went for a burger at Wendy's (I know - horrible - but they're so tasty). All of the following were taken from my car in the parking lot and at my parked eating spot.

Every year about this time, a huge flock of Ring-Billed Gulls (Larus delawarensis) shows up in this fast-food district. You coastal folks may bore of them, but we are pretty far inland, and I grew up in landlocked Arkansas, so I still find gulls utterly fascinating.

Give me fries!!

Call me Narcissus...

Beautiful Eyes (mature vs. immature)

One sad bird had a severely gimpy foot. But it seemed to be surviving...thanks to fast-food throw aways. I must say that it looked to be in some pain walking.

Victim of a fisherman (tangled line and rig)

And finally, I retreated to my favorite natural spot to eat, parked near a tiny copse of pines. Despite the fact that I always pay attention to nature, I somehow had never managed to see the following bird. I could tell it looked like a nuthatch - I'm very familiar with the White-Breasted Nuthatch (Sitta carolinensis) as we had hundreds on my property in Arkansas - but I had no clue what it was and had to look it up when I got home.

It's a Brown-Headed Nuthatch (Sitta pusilla). He was pretty cute - he would look in the hole and poke around, then jerk his head around to make sure no one was watching, then do it again and again.

The Paranoid Nuthatch

The Brown-Headed Nuthatch in action...

Shortly thereafter it was back to the lab...

Previous Nature Walks:

• Nature Walk #1 - Hawks, Epiphytes, Woodpeckers and Orchids

The point is: I love nature. Paying attention to it is first-nature to me, having been raised as a country boy in the Ozark mountain forests. It is for this reason that I also consider this a "nature blog." In fact, I recently joined the Nature Blog Network - THE community for nature bloggers - which was created by the wonderful Mike Bergin of 10,000 Birds and I and the Bird fame (note: Mike is in Guatemala at a birding conference right this minute - be sure to look out for what is sure to be an amazing photography collection and story when he returns).

In tribute to  my own inclusion in the Nature Blog Network, I give you the first in a series of posts consisting of my own observations from taking walks into nature. I've been posting similar things for a while now (check out the SWEET footage I got of a Great Blue Heron with a catfish recently), but I'd like to make this a formal posting event for me - especially since spring is looming and I will no doubt be making many forays into the natural world.

Although it is still very wintery here in North Carolina and wildlife is relatively sparse (I miss the bugs and other invertebrates...) there is still much to see if one looks closely enough.

Red-Shouldered Hawk (Buteo lineatus)

In fact, I had barely stepped outside my front door when I saw one of my all time favorite creatures: the red-shouldered hawk (Buteo lineatus). When I was a small child I read some tale of a now-forgotten Native American and his spirit or guardian animal - the red-tailed hawk (Buteo jamaicensis). Ever since then the hawk has been one of my favorite animals. If I had a "spirit animal" it would be a hawk. Yes, it's insanely silly, but I always pretend like it's a good luck sign when I see one - the key word here is pretend. Really, I love all raptors.

As I walked down my driveway, I heard a squawking sound coming from my neighbors yard. When I looked up, I saw two red-shouldered hawks - one in a nest and the other in a nearby tree. I quickly tried to photograph them, though they were still about 40 yards away. I have a great digital camera, though it is NOT a professional DSLR. However, the 12X optical zoom and decent manual options are more than good enough for me until I have cash to burn.

As soon as I snapped the pic above, both of them took flight. I tried to get an in-flight shot, but the one below was the best I could do in the 1.5 seconds I had before they were gone. Luckily, it was good enough for me to identify it as a red-shouldered rather than a red-tailed. My neighbor (Flyzeyes, who has some pretty awesome nature photography himself) and I both hope that the nest is theirs and that they will return - we shall see.

Red-shouldered Hawk in flight - barely got it.

I mosied on past my neighbors house and through the woods behind it, where a small pond lies hidden within the forest. The pond is surrounded by beaver-chopped trees from last spring. Here are two shelf fungus-laden remnants of the beaver's work:

To my mycologist friend, Southern Fried Scientist: Please identify...

Years of growth, felled by one small furry creature.

The pond overflows over a small levy into a large swamp below it.

Swamp

Flitting throughout the trees, flocks of tiny birds surround the entire marsh. I managed to get one decent picture (they tended to keep a good distance between them and me), and through my trusty bird guide I'm almost certain they were Swamp Song Sparrows (Melospiza melodia) Note: I had it wrong initially - so much for my bird ID skills... thanks to Mark Shields! The lateral eye-mark and streaked breast with dark spot in the middle is the give-away sign.

Song Sparrow (Melospiza melodia)

The swamp was also surrounded by one type of bush (I have no idea what kind) covered with cool looking pollen pods (see my non-existent botany lingo and knowledge?).

Pollen pod? I'm sure there's a proper word for this... Update: their called "catkins" - thanks to Inoculated Mind (see comments)

One of my favorite things about wet areas (like swamps and marshes) are that there tend to be various epiphytic species everywhere (epiphytes = things that live on other things - usually on plants. Most are not generally parasitic, but just use plants for structure, though parasites like mistletoe are still considered epiphytic in habitat. Small plants, algae, fungi, and lichens are among the most common - or visible anyway - epiphytes).

I believe this is a lichen - I could totally be wrong.

Amazing structure...

I also managed to snap two different woodpecker species - both from fairly great distances, so the images aren't superb. I'm almost 100% certain of both of their identities. The first is a Yellow-bellied Sapsucker (Sphyrapicus ruber), and the second is a Red-bellied Woodpecker (Melanerpes carolinus).

Yellow-bellied Sapsucker (Sphyrapicus ruber)

Red-bellied Woodpecker (Melanerpes carolinus)

After watching the birds for a while, I made my way to my own back yard, where I found a returning Lamb's Ear (Stachys sp.)

Lamb's Ear (Stachys sp.)

And finally, I took a few photographs of one of two native North Carolina orchid species I've found on my property. The first is the Cranefly Orchid (Tipularia discolor). What's interesting about this species is that they only bear one leaf - and only in the fall/winter. Once flowering season arrives in the summer, the leaf dies and they send up a shoot filled with tiny flowers. In the fall, the flower stem dies back, to be replaced by the single lone leaf, which has a bright purple underside.

Cranefly Orchid (Tipularia discolor)

Purple underside

Unfortunately, after a while of searching I was unable to find any of the second orchid - which I know I had several of last year. This second native orchid is quite a beautiful plant - and it has an awesome name: the Rattlesnake Plantain - or Rattlesnake Orchid (Goodyera pubescens). We've had 2 years of pretty bad drought, and an unseasonably cold winter - so I am hoping they have not all died. Perhaps I will find more in the spring. Here's a picture of some I took last September. Pretty amazing foliage pattern, no?

Rattlesnake Plantain (Goodyera pubescens). Extinct on my property?

And with that, my first nature walk of the year is concluded. I cannot wait for everything to start blooming and for all the insects and other crawly critters come out of the woodwork. Keep an eye out here for more nature photos and stories to come...

If you know the identity of anything above, or if I've misidentified something, please let me know.

So set aside some time over the coming days to peruse through the avian wonders. My own post on the Great Blue Heron and the Catfish is included in this 94th edition (with pretty cool videos).

Happy 200th birthday, Charles Darwin!
Happy 200th birthday, Abraham Lincoln!
Happy 150th anniversary, On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life!
And here's to a happy Darwin Day and upcoming Valentine's Day to everyone else.

As a part of my own contribution to the Blog for Darwin campaign, I present to you "Darwin and the Heart of Evolution."

What do all four of the above events have in common, other than being events of celebration? The answer will become obvious, but as a clue, I will begin with an appropriate Valentine's question:

A Frog's Heart

Why do humans have hearts?

I can see it already – you’re rolling your eyes thinking, “Well duh…because we need a way to circulate oxygen, hormones, immune cells and other signals, and transport waste compounds and gases.”

Ahh, but you would be wrong. For the above describes only what a heart does – not why we have one. As I wrote a few days ago, evolution pays no attention to "needs." Species don't evolve because they "need" to adapt or change some trait. Natural selection is blind to all intention and desire.

Before Charles Darwin (and his buddy Alfred Russell Wallace) gave us the theory of natural selection, the above "necessity" explanation would have sufficed – with an added “because God designed it that way” just for good measure.

The genius, beauty, and simplicity of Darwin’s big idea was in how it utterly reshaped the manner in which all “why” questions about reality are posed and how their answers are understood. The Origin of Species laid the foundation for the complete upheaval of the very word “why.” In fact, when it comes to describing biology, astronomy, physics, geology, and every other empirical look into reality, the word “why” now means nothing more than the word “how.” The how is the why.

So again, I ask - why (how) do humans have hearts?

To answer this question we need to jump back about 500 million years ago into the ancient ocean. Based on the fossil record, this is a good date to pick, considering that worms don’t make great fossils; however, the exact date is not at all important for this discussion. Nor does it matter the exact species of worm-like creature we consider, or the exact details of the hypothetical time-traveling adventure upon which we will now embark.

Imagine it - we’re swimming now in the ancient ocean sometime after the massive explosion in the evolution of all sorts of strange ocean-dwelling invertebrate body forms (the Cambrian explosion). One of the many advantages that certain individuals of various species find is that their larger body sizes makes them better able to compete – up to a point. Once a small early worm-like species reaches a certain size, it finds that it cannot grow any bigger with its current body plan. This is because at this point, our hypothetical creatures do not have circulatory systems. They must absorb all their oxygen from the surrounding water. Any individuals born larger than a certain size can no longer get enough oxygen due to the oxygen not reaching deep enough into their tissues, and so they die (or are our-competed).

The Vertebrate Family

Now imagine an individual of this species is born with what others of its species would consider a defect (if they had brains with which to consider such a concept). This individual has certain cells that have formed a small simple tube-like structure. Perhaps it is only a vague cavity – or some extra space between its cells. Now when this individual swims around, contracting its primitive muscles, the fluid within its body spreads a little bit more and a little bit faster through this cavity or space.

Our little worm leads a happy life, finding mates (or perhaps reproducing asexually) and leaving an ocean full of cavity-containing offspring. It seems self-evident to us now, but Darwin found himself surprised at the amount of variability in traits throughout the animal kingdom. All populations vary; thus, some of our worm’s children are a little bit bigger than their siblings. And some of these worm children will have inherited papa worm’s fluid cavity, which meant that they could survive with a slightly larger body than those without the primitive vessel, due to the oxygen distributing power of the fluid filled vessel.

Thus began the evolution of the heart. By a series of easy to imagine steps through thousands or millions of generations, the cavity became slightly more developed, eventually forming an actual tube. I would like to note here that the above scenario is strongly supported by much embryological, anatomical, and genetic data. However, I would like keep this simple and vague for the layperson.

Now, we move forward in time, though how far is unclear. Our little worms are now bigger worms, insect ancestors, and a myriad other small invertebrate species. Some of these species have evolved their tubes to have contractile regions - that is, a region of the tube than can actually squeeze and pump. Some, like our modern earthworm, have seven of these pumping “hearts”. Others, like the Drosophila fly, have only one heart - called a "dorsal vessel" (see the Drosophila larvae movie below).

The Fish Heart

We swim forward to 525 million years ago, just as the first fish appear in the fossil record. A lineage of the invertebrates has slowly morphed through primitive chordates (organisms with a nerve cord) to become the most primitive fishes. Along with the changes in many other body structures, the basic contractile heart and vessel system has itself become more complex. Instead of one contractile chamber, the fish heart has divided into two chambers: an atrium and a ventricle (and a stretchy region called the conus that isn’t contractile). The fish themselves then radiate over time, each lineage slowly accumulating many small changes, resulting in the gradual evolution of an ocean teeming with fish species – all with two-chambered hearts (see image at right).

Eventually, some fish species start shacking up near shorelines or in shallow ponds and lagoons. Some are born with thicker fins, which allow them to push along the bottom of the pools a little more quickly or lithely than others. They mate, and the process continues. Finally, one of them decides to just get it over with and leaps out of the water to land as a frog on four fully-formed legs.

The Amphibian Heart

Not really, but you get the picture.

We now see amphibious creatures roaming the shorelines like beastly salamanders. Their hearts have changed even further as other aspects of their bodies evolved to take in oxygen through lungs. Why did this happen? Because the changes that make it possible did happen. These shallow water-dwelling creatures began to develop vessel-filled outpockets on their esophagus, giving them the advantage of pulling oxygen from the air. In addition, the individuals with slightly better circulatory systems found their bodies better at all sorts of other things, such as regulating their bodies with hormones and getting rid of cellular wastes.

At this point, a series of further changes occurred in the amphibian heart. The atrium became two separate atria, either through a physical division of the one atrium, or through a duplication of the vessels coming into the heart. Thus, the frog ancestors developed three-chambered hearts, which were subsequently passed down to every frog currently inhabiting the earth (see image).

The Reptile heart

As time passed, the frogs began drying off their slime, sprouting scales and forked tongues, and inspiring instinctive reptilian nightmares in their prey. They became lizards. As the lizards moved fully to land and grew even larger, certain inherited variations in their hearts naturally worked a little better – thus natural selection continued the continuous sculpture of life. The ventricle began to separate into two chambers, much like the atrium had done in the amphibians. However, the ventricles didn’t fully divide. As one can see in almost every reptile on earth today, the ventricular division is incomplete – almost like a four-chambered heart, but with a hole between the ventricles (see image). However, I said that almost all reptiles have the pseudo four-chambered cardiac morphology; in fact, one branch of the reptiles went on to develop a fully-featured, true four-chambered heart: the crocodile - but that's a side story.

From some of the lizards the dinosaurs then sprung forth, populating the land from the small dark corners to the open plains. A short while later (a paltry 170 million years) most of the dinosaurs died off. Along with their distant crocodilian, lizard, and snake cousins, at least one dinosaur lineage and one reptilian lineage survived. We now call them birds and mammals, respectively.

Both the bird and mammalian lineages mirrored the path of the crocodile, completing the division between the ventricles (probably prior to their divergence). Natural selection has continued to sculpt our own mammalian hearts, resulting in marvelous structures such as the multiple different valve types, chordae tendenae ("heart strings"), and trabeculae (fibrous strings in the ventricle's interior).

The Bird and Mammal Heart

And with that, we have answered our initial question, in a massively oversimplified fashion. We have hearts because each change leading to our hearts conferred some small advantage to the individuals that inherited them (or at the very least, were not disadvantageous).

Of course, all of these cumulative small changes in the shape of the vessels and hearts, ultimately involved millions of small changes in the genes that controlled the behavior, shape, and functions of the circulatory cells. Scientists have now discovered an incredibly large and complex network of such genes controlling development of the heart.

One of the most astonishing yet completely expected facts we have garnered through studying organisms from Drosophila to the African clawed frog (Xenopus) to humans is the discovery that every organism on this planet with some version of a heart contains the same or a similar set of genes to control heart development.

That’s right. Read it again.

Many of the genes involved in the formation of the relatively primitive “dorsal vessel” in a fly are versions of the same genes that initially form our own hearts. Think about that! Think about how massively more complex we are compared to flies (which are themselves insanely complex in their own rights). Think about the hundreds of millions of years that separate us from our most recent common ancestor with a fly. Yet your heart still uses many of the same genes and in the same ways during early heart development. Of course flies and humans have continued to evolve in parallel ever since our lineages split those hundreds of millions of year ago – we have both made countless changes and tweaks to our own cardiac programs and networks. Nonetheless, our hearts remain related.

In fact, if you watch heart development in an embryo, such as in the Xenopus movie below, you can almost see the course of heart evolution itself. Of course this isn't really ontogeny recapitulating phylogeny - but some of the evolutionary history behind cardiac development is at least evident.

Tbx20 expression in a frog larva heart

One example of a cardiac gene that I’m particularly familiar with, having received my doctorate studying it, is a gene called “Tbx20”. For this discussion, its exact function does not matter. Suffice it to say that when I began my studies, we had a clue that this gene was important in heart development. Why? Because flies have a copy of this gene, as do humans, mice, and every other heart-bearing organism we’ve looked at; furthermore, in each of these organisms this gene is “turned on” in the developing heart tissue.

I went on to show that when you prevent frog larvae from making the Tbx20 protein, they develop incredibly malformed hearts (see the videos below). This means that the Tbx20 gene is indeed important in making a heart. Other researchers later went on to show similar results in mice and flies. Finally, about two months before I finished graduate school, another group of researchers found that some humans born with congenital heart defects have mutations in the Tbx20 gene.

Normal African Clawed Frog (Xenopus) heart

African Clawed Frog (Xenopus) heart lacking Tbx20 protein

So here we have found in only a few years of research a single gene that supports the entire model of evolutionary theory. To rephrase the famous quote from Theodosius Dobzhansky, the existence of Tbx20 in controlling the development of the heart in organisms from flies to humans does not make any sense – except in the light of evolution.

Due to the rich evolutionary history behind the development of this complex organ, the genetic network has become incredibly complex, involving hundreds of genes in thousands of cells all working, moving, and functioning in precise coordination. The higher the complexity, the more things that can possibly go wrong. Unsurprisingly, congenital heart defects are among the most prevalent of all inherited diseases, resulting in about 9 babies out of every one thousand being born with some sort of cardiac abnormality.

I’m sure many of you were wondering how I would manage to tie Abraham Lincoln tie into all this. Although still hotly debated and unproven, at least some researchers believe that Abraham Lincoln may have been afflicted with a disease called Marfan Syndrome, a connective tissue disorder affecting the heart and many other organs. Other researchers believe that he had an unrelated disease. Regardless, it remains at least possible that President Abraham Lincoln was the inheritor of one of the billions of less advantageous variances in heart development that have presented themselves throughout the heart’s evolutionary history.

In summary, the heart of Darwin's theory of natural selection is the idea that evolution comes not through the "why." It comes through the how - through the accumulation of minute individual variations that spread like wildfire when they contribute an advantage.  There remains no better demonstration of this principle than the myriad heart morphologies and functions we can trace today.

Each of you has most certainly inherited a cardiac variation, whether it be a major mutation in a gene, or a tiny change in one letter of your genetic code (a "single nucleotide polymorphism").

Who knows...perhaps yours is the one upon which an entirely new evolutionary history will be built.

So here’s to your own personal variation, and to the man who made our understanding of it all possible. We would have gotten there without him – but I doubt anyone could have rivaled the combination of his incredible intellect and beautiful prose.
Happy birthday Darwin!

_____________
Image credits

Frog heart photograph: Me
Phylogenetic tree: McGraw-Hill and Biology Corner (links to original source broken)
Drosophila heart tube movie: unknown
Heart diagrams: Oracle ThinkQuest Education Foundation
Cardiogenesis animation: Me
Frog heart movies: Me
Lincoln photograph: Visiting DC

Lincoln photo:

My cousin, Steven Garrison, has been an accomplished sculptor and artistic engineer for as far back as I can remember. My favorite of his types of work is his series of nautiloid carvings. Be sure to check them all out at his website, www.stevengarrison.com.

Update: (2/9/09) Steve has informed me that he managed to get his work in del Mano Gallery in Los Angeles (considered the premier gallery in the nation for woodwork - you'll find his work there sometime this summer). Congratulations Steve!

Eastern Red Cedar Shell - Steven Garrison

Fiddleback Nautiloid - Steven Garrison

Aromatic Red Cedar Nautiloid - Steven Garrison

He also makes all sorts of other crazy sculptures, the accomplishment and engineering of which can boggle the mind.

You MUST check out his elliptical gears about halfway through this clip.

And one of his latest pieces: wooden gear driven window blinds!

And finally, his own favorite piece:

"All Screwed Up" - Steven Garrison

Obviously, I've always harbored a bit of jealousy at Steve's talent.  But that's ok - the artistic thread runs cleanly through his lineage. My Uncle Bill and Aunt Gloria are both highly accomplished artists as well, with Bill focusing on oils and Gloria on watercolors (and oils).

"Leatherwood Creek" - Bill Garrison

"A Fine Pair" - Gloria Garrison

What a day! A two post day for sure.

The morning started off with an entertaining and educational tour of the Duke Lemur Center in Durham, NC (blog post to follow).

Next, my wife and I were off to the Sarah P. Duke Gardens, where I had a birding opportunity heretofore unprecedented for me.

Duke Gardens is a massive cross between city park and botanical garden, sprawling with trails and ponds and happy people. My goal was to simply find some interesting natural wonders to photograph, as it's been a while since the weather has allowed me to partake in my outdoor hobby.

We began at a nice looking little pond where my eyes became drawn to a set of cypress knees under a beautiful sun.

For oxygen or support? The jury is still out...

After snapping a few shots, I looked way across the pond and saw a Great Blue Heron patiently fishing. I've photographed many herons - in fact, I had previously considered my coolest heron spotting as last summer when one let me get within about 15 feet. Normally in the wild, I've found that blue herons get rather irritated when a human passes too closely, letting you know quite vocally before taking flight that you've mucked up their fishing.  If you've heard their loud angry squawk, then you know exactly what I mean. If you use your imagination you can almost hear the word "asshole!" escape their beaks as they take off.

If only I could get closer...

I have a decent (non-professional) camera - so the above image was taken with 12x optical zoom - further than it looks.

Immediately after getting this shot, a couple of kids approached the heron and started throwing bread at it.

"Damn," I think, "now they're gonna scare it away."  I look over at my wife, shaking my head. "They don't even eat bread!"

But the big bird doesn't move. In fact, he gets closer to the the kids and begins staring at the water where the bread floats by. The heron had become completely acclimated to people! (note: I'm using "he" but herons are not sexually dimorphic, so I have no idea its gender)

"I've got to get over there to get some pictures - mind if I run ahead?" I ask my wife, as I begin sprinting down the trail around the far side of the pond - just knowing that the bird will be gone by the time I get there.

It was my lucky day - it was still there!

I immediately (and slowly) perched about 15 feet away and started shooting.

closer...

See the arrow? (S)he let me get that close!

I decided to test his comfort zone limits and slowly moved to the arrow in the above image.

He still remained statuesque. In fact, the kids continued to thrown bread into the water, even pelting him a couple of times. At this point it became quite clear that this bird had learned to use human behavior as fish bait.  He stared intently directly over the floating bread, waiting for any fish to nibble.

This went on for ten minutes (no fish), so I just began taking as many cool shots that I could.

No sexual dimorphism?

Baby got back!

You know I can stab you with this, right?

Next I took a quick video of this beautiful bird.

And then - for the climactic ending.

I was in the middle of setting up for another shot when the heron lunged into the water in about a third of a second! I immediately tried to switch to video mode as quickly as possible, which took about two seconds.

THIS is what followed:

Truly amazing!

I was a bit sad to have missed recording the actual capture - but hey - how much can I really complain after witnessing it myself AND getting all these cool shots.

As an aside, after this event we went to watch "Coraline 3D" (an insanely creative movie by the way). This required wearing special polarized glasses.

Which got me thinking - any fisherman knows the value of a good pair of polarized glasses for reducing surface glare. Do herons and other fishing birds have polaroid filters in their eyes? I found one mention that this is the case in the abstract of a paper from 1973, but I haven't absolutely confirmed this.

And finally - check out this video of a green heron actually fishing with a piece of bread - utterly astonishing behavior!

I was just outside the lab sitting under this short tree. I was kneeling down leaning against the tree. There was a chipmunk (Alfonzo – I’ve seen him about once a day for two years) digging for nuts and whatnot about 15 feet away. All of a sudden a robin flew down about five feet away, and while cautiously watching me proceeded to catch an earthworm from the mulch around the tree. There was a large crust of bread about ten feet away that had been there all morning (between the bird and the chipmunk) and the Robin flew straight to it and, I shit you not, he began making an earthworm and bread-crust sandwich. Actually, it was more like a salad. But he would break up the bread, then tear the worm, then pick up a piece of the worm with a piece of the bread and eat it. I was just sitting their mouth agape at this freaking bird reinventing the sandwich.
It was disturbing I tell you.

But there is more.

About five seconds later Alfonzo the chipmunk stands on his hind legs (as they are wont to do) and looks directly at me. He then runs to about 2 feet away from me, stops and looks at me again. I tried to be relatively still to see how close he would come (I assumed he didn't realize I was there). After staring at me a few seconds he walks up to my foot (keep in mind I am kneeling close to the ground) and he puts his front paws on my shoe, flattens his body to the ground, looks up at me, and begins waving his tail in this methodic left-right fashion while staring right at my face. He does this for about five seconds before slowly sauntering off to look for more nuts. I swear to god he was trying to tell me something (probably something like "hey you - I know you", or "why the hell are you always hangin’ round my crib?" or maybe he was saying "damn you're one large fine-ass specimen of a man - for a chipmunk"). He could have been saying that - really - maybe he's retarded and doesn't know the difference.

I'm still not sure if all this really happened or I'm just going insane. Or maybe God is just screwing with me. It would be a pretty funny joke. I'd be doin' all sorts of crazy shit like that if I were God.

Imagine walking around a corner to find three raccoons playing jump rope.

Anyway, I hope you've enjoyed my tale.

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