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It Begins…

March 30, 2009 on 1:22 pm | In Blog info, Evolution | 316 Comments

Well, it’s happening this week, folks! I’m going to make the move over to ScienceBlogs this week, and I will have a special good-bye video post this Wednesday.

In the meantime, to help you cope with your sadness, Ian O’Neill at AstroEngine has this week’s Carnival of Space, and I have an example of artificial selection for you, duck-style:

The ones who are good at navigating metal grates survive to adulthood; the others, not so much. Yikes.

Between Bird and Mammal Lies the 6th Sense…

March 23, 2009 on 1:45 pm | In Evolution, Life | 58 Comments

This Australian “mammal” is one of the most bizarre creatures on Earth, having many of the characteristics usually reserved for either birds only or mammals only:

Ladies and gentlemen, the duck-billed platypus! Its most notable features are as follows:

1. It lays eggs. This is usually reserved exclusively for birds, reptiles, dinosaurs, etc. And these eggs are tiny! Mammals gestate with the eggs inside of them, giving birth to live young, but here’s a mammal that lays eggs!

2. It’s furry. Like mammals are — no feathers for this guy — the platypus is not only covered in fur, it’s got such a nice coat that it has historically been hunted for its fur!

3. It is venomous! This is extremely rare for mammals, and the platypus itself has three venomous compounds in it that are unique in all of nature to the platypus itself. The venom is emitted through a spur in the platypus’ foot, right around its ankle. And speaking of feet…

4. It has otter-like feet. Totally mammalian, you got it. On the other hand…

5. It has a duck-like bill. Totally bird-like, of course. On the other hand…

6. It has a beaver-like tail. Mammalian, I got it. I suppose we can go on and on, listing all the ways this animal is neither bird nor mammal, all of which I find fascinating. But this animal can do something that you and I cannot, no matter how hard we try. Your skin, your epidermal layer, is fantastic for sensing temperature, pressure, and pain. These three types of sensor suit us remarkably well, and allow us to experience all sorts of interesting sensations, like itch and ticklishness. But the platypus has us beat, because in addition to these, the platypus can detect electricity!

That’s right, the duck-billed platypus has the most sophisticated sense of “electroreception” of any mammal, allowing it to track its aquatic prey by locating where an electrical stimulus resulting from muscle contraction came from. Normally, we only see this in predatory fish, like I’ll show you in the image below:

But here it is, in a platypus! How cool of a sense is that?! So the next time someone tells you about “the sixth sense,” don’t think of ESP and don’t think of Bruce Willis, think about the platypus, an animal with a real sixth sense: the ability to detect electricity!

Because I want a sense like that…

How Quickly do Humans Evolve?

February 16, 2009 on 2:35 pm | In Evolution, Life | 30 Comments

One of the worst arguments out there against evolution is that we can see micro-evolution, in simple organisms, but not macro-evolution, or evolution in large plants and animals with long lifetimes. Therefore, the faulty argument goes, since we haven’t observed it directly, there’s no evidence for it. Let’s take a look at the obvious flaw in this argument:

Scientific studies have only been around for a few human generations. Evolution takes many generations to have visible effects. Something like a bacterium can reproduce so quickly that in just a few months you can have in excess of a hundred-thousand generations! So it’s very easy to observe evolution for microorganisms, since we have so much generational time to see change over time. This is much harder in longer-lived organisms. In humans, for instance, a typical generation is about 25 years. So while you get millions of generations for a microorganism, you only get one for humans and only a handful for even small mammals. So that logic is completely faulty.

Nevertheless, perhaps we can, if we’re clever enough, find evidence for the evolution of humans in our history. Human history goes back a long time, and if we study it properly, perhaps we can find something that shows how human characteristics change over time. As reported on MSNBC, changes in human DNA (as shown from human skeletal remains) have occurred about 100 times more quickly in the past 10,000 years than at any time in human history:

John Hawks, a professor at UW-Madison (shout-out!), rejected the assumption that human evolution ceased roughly 50,000 years ago, and working off of a sample of 35,000 years of skeletons from all around the world, uncovered the following:

In Europeans, the cheekbones slant backward, the eye sockets are shaped like aviator glasses, and the nose bridge is high. Asians have cheekbones facing more forward, very round orbits, and a very low nose bridge. Australians have thicker skulls and the biggest teeth, on average, of any population today.

“It beats me how leading biologists could look at the fossil record and conclude that human evolution came to a standstill 50,000 years ago,” Hawks says.

By his account, Hawks’ theory of accelerated human evolution owes its genesis to what he could see with his own eyes. But his radical view was also influenced by newly emerging genetic data. Thanks to stunning advances in sequencing and deciphering DNA in recent years, scientists had begun uncovering, one by one, genes that boost evolutionary fitness. These variants, which emerged after the Stone Age, seemed to help populations better combat infectious organisms, survive frigid temperatures, or otherwise adapt to local conditions. And they were popping up with surprising frequency.

The general rule here, that I love, is “adapt to local conditions“. What’s one of the simplest adaptations to local conditions in any living organism? The ability to blend in with their environment. The most stunning example is probably the chameleon, which can even adapt to change its color to match whatever it’s up against:

Does this work in humans? Could our huge variety in skin color be due to local adaptations? And if so, could we use this as evidence for human macroevolution?

Well, as reported by NPR, the answers are yes, yes, and yes! According to their research, changes in human pigmentation take only 100 to 200 generations, which is as few as 2,500 years. They specifically cite India as their example, that a few thousand years ago, when they lived farther to the North, their skin was much lighter, and has darkened dramatically over the past few millennia as they’ve migrated back to the south, to warmer climates.

Now, here’s a kicker: we already know why changing pigment is important for humans! From the NPR article:

“Humans started in Africa,” Jablonski says, the part of Africa near the equator where it is intensely sunny with lots of ultraviolet light.

Ultraviolet light, or UV, in high doses can age the skin and damage the DNA molecule, which makes it harder to build a fetus. Not to mention that ultraviolet light can sometimes cause skin cancer.

On the other hand, if a human is plopped down in, say, Norway, where the days can be short and there is precious little ultraviolet light, this creates problems, too. All vertebrate animals need ultraviolet light to help produce vitamin D. Vitamin D helps us absorb calcium from our food to build strong bones. If we don’t get enough ultraviolet light, we’re less likely to survive to reproductive age to produce strong-boned babies.

Thus the dilemma: People who live in sunny climes around the equator have too much UV. People who move away from the equator eventually have too little UV.

In fact, take a look at this map of UV radiation on Earth. How well do you think it will match the native population of that area?

Breathtaking, isn’t it? According to UV data alone, Australian Aboriginals and Africans should be the darkest, people from northern Europe, Asia and Canada should be the lightest, and Native Americans, those from the middle east (like me, ancestrally), and equatorial Asia should be in between. Sound like any world that you live in?

But science is even cooler than just this. Because we can make a computer model to simulate how the evolution of something like pigment works. We don’t need to simulate melanin or anything that complex, we can do it for a single-celled organism. If you have 10 minutes (and if you’re at work, feel free to turn the sound off; it’s just music), have a gander at how this works:

And while you’re here, I’d like to point out two things. First, I was asked a while ago where to go for educational science information on physics, astronomy, the natural world, etc. The National Geographic Channel has been putting out some good stuff recently. It seems like practically every Sunday night, starting at 8 PM ET/PT, they have a really interesting new science program on. This past Sunday, they had a 3-part program called Known Universe, where they talked about some of the biggest, smallest, fastest, and most extreme things we’ve ever discovered or created in the known Universe. This is great and rare, because it actually addresses things we know for certain, not only speculative theories or those for which there’s insufficient evidence. Yes, they have discussions about what may come next, but they’re well-done and reasonable, and it’s the things we already know that’s the (well-deserved) focus of the show. I’m really happy about it, and I regret not advertising it sooner. But look for it; it’s worth watching.

And second, the new Carnival of Space is up, just in time for… uhh… next year’s Valentine’s Day? Happy Monday, folks.

Q & A: How to Fight Global Warming

December 26, 2008 on 1:08 pm | In Evolution, Life | 54 Comments

People often write in wanting to know the answers to big questions. Earlier this week I got a message from kampfgestfj asking me about global warming. More to the point, he wanted to know the following:

Why are there still those that don’t believe global warming is affected by man’s input into the environment?

Now, I don’t have a good answer for this, because I don’t understand the reasoning behind denying mankind’s influence on global warming. For me, the scientific evidence is pretty straightforward: industrialization is at an all-time high, there are more pollutants in the atmosphere now than at any point in all of human history, and global average temperature has followed the trend of CO2 in the atmosphere over hundreds of thousands of years according to all reasonable tests of scientific rigor. (And yes, you have to include an appropriate time-lag of about 50-100 years for the full effects to be felt.)

But there is a new finding that I find absolutely delightful. Ever hear about the little ice age in Europe? A few hundred years ago, the temperature in Europe decreased by a little less than 1 degree Celcius, and remained that way for about 200 years. Have a look:

Well, we think we know why this happened. When the Europeans came over to America, the Aztec and Incan civilizations crumbled. This was due to many factors, including (and perhaps especially) disease. From when the Europeans came over in about 1500 to about 1600, the populations of the Incan and Aztec empires dropped by about 90%. This was about 9% of the world’s population, and it meant that about 500,000 km2 of land went from being used by humans to wilderness. At those latitudes, that means there was about 500,000 km2 of reforestation that occurred.

Now, as everyone knows, trees breathe in Carbon Dioxide and breathe out Oxygen. The researchers estimate that 10 billion tonnes of Carbon Dioxide was removed from the atmosphere by this reforestation, significantly contributing to the fall in global average temperature.

Even with accounting for volcanic activity and the Sun’s variation in intensity, the impact of humans, according to the study, was undeniably important. So if we want to fix our global warming problem now, what’s the answer?

Well, it’s simple. RE-forestation. This is a surefire way to remove significant amounts of CO2 from the atmosphere. But this is a huge policy problem: how can we not only keep humans out of habitable areas, how can we get humans to leave areas where they’re already living? We know the problem. We know how to fight it. We even know how to fix it. The big question is how do we make it happen?

And that’s one I don’t have an answer for, just hope that we’ll get it right, and soon.

Q & A: Why don’t Woodpeckers get Brain Damage?

December 10, 2008 on 12:50 pm | In Evolution, Life, Q & A | 9 Comments

Everyone knows how much fun it is to get repeatedly hit in the head. Just ask Oscar de la Hoya after his defeat against Manny Pacquiao last weekend:

Ouch. It isn’t just boxers, either. Every animal that experiences head trauma is susceptible to the following symptoms:

  • Abnormal level of consciousness
  • Differences in pupil size
  • Rigid limbs
  • Flaccid limbs
  • Unusual eye movement
  • Bleeding from the nostril
  • Bleeding from the ear canal
  • Seizures
  • Head tilt

But the worst thing imaginable to me that results from head trauma is brain damage. It’s our minds that make us who we are, and the idea of living without mine is completely horrifying. Look at how different a normal brain can be from a damaged one:

Out of all the animals I know of, there’s only one that repeatedly slams its head into a block of wood, over and over, day in and day out, for its entire life: the woodpecker.

A woodpecker moves so quickly that its tiny, 50 gram head absorbs 1,300 pounds of force every time it smashes into a tree! So why don’t woodpeckers get brain damage? There has to be something that prevents its brain from rattling around in its head and slamming against the skull around it, right? No, there isn’t. The woodpecker’s brain does rattle around in its head and smash into its skull. Yet it still emerges brain-damage-free. There are three special adaptations of a woodpecker that allow this to happen; let’s take a look.

1. Spongy skull bones — while humans have spongy bones mostly on the interior of large bones, woodpeckers’ skulls are extremely spongy. This means they can compress and help absorb the impact of the brain jostling around. It’s like smashing a brain into memory foam instead of into solid bone, and it reduces the force on the brain tremendously.

2. Large surface area — a woodpecker’s brain is tiny. This is actually a positive thing, because the smaller something is, the larger its surface-area-to-volume and surface-area-to-weight ratios are. If something has a bigger surface area, it means that even if the force is large, the pressure gets smaller, and this helps protect the woodpecker’s tiny bird-brain.

3. Woodpeckers peck in a straight line — this one is hugely important. If everything’s in a straight line then there’s no rotating or torquing of the brain, and therefore no tearing of the nerves in the brain. Hence, no brain damage the way that car crash victims experience it.

And those three things combined allow a woodpecker to escape from all their daily pecking activities without so much as a hint of head trauma. Isn’t evolution neat?

What, you were expecting some astronomy/physics today? Go check out the latest Carnival of Space to get your fix, done by Dave Mosher in a new video format, and I’ll see you all next time!

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