Undeniable (21 page)

It was quite a deal in my little world of military airplane design (I had security clearance for a while, and so on) to design a plane with no tail sticking up. Obviously for a bird to go without one is easy, a day in the office … or nest for them. Humans, at great expense, designed a flyable plane without a vertical tail, and we did so perhaps 150 million years after birds did. It took us years of research and the development of flight-control computers that could work fast enough to continually adjust the other control surfaces like ailerons inboard and outboard to pull it off. Perhaps
Archaeopteryxes
had no such trouble, because they had the feathers and the brains for it.

With all this, it's reasonable to infer that
Archaeopteryx
could fly a little bit, or perhaps well enough to ride the wind and columns of rising hot air (thermals) the way so many modern birds do. It's fun to consider. Even if they really couldn't lift their wings in modern bird fashion, even if their feathers weren't really long or strong enough to spread their weight out sufficiently, even if their brains couldn't pilot them over a warm sea or through a thick forest, well, they still must have
almost
flown.

However you cut it,
Archaeopteryx
basically had half a wing.
Velociraptor
had something more like one quarter of a wing, or one eighth of a wing. And you know what? Those intermediate steps worked just fine; they were just adapted to slightly different functions than the wing of a hawk. Perhaps
Archaeopteryx
could glide from limb to limb. Maybe he or she had the ability to jump off a high branch or cliff and land slowly, without breaking a leg or neck. Maybe they could just barely fly. If that was the case, it would be as though they had just half a wing. What if all those feathers did nothing more than keep these animals warm? What if all my musings about their aerodynamic performance was just that—thinking out loud without a strong basis for doing so? Then what if the feathers were just adornment for making time with others of their kind? That would be good enough, in the evolutionary sense, and very useful. Half a wing was all an
Archaeopteryx
needed to survive.

Archaeopteryx
was, in our modern evolutionary way of thinking, a transitional animal. Its fossils are transitions from feathered dinosaurs to birds. And, if you haven't heard, our birds flying around today are indeed direct descendants of ancient dinosaurs. We see it in their feet, their fossils, and their feathers. Darwin speculated quite reasonably about this relationship long before X-ray analysis was available or quarter-chord points were postulated. He was a thoughtful young man.

But here's a crucial point: At the time when
Archaeopteryx
lived, it wasn't a transitional
anything
, or a half anything. It was a creature well adapted to its environment. To a human designer,
Archaeopteryx
looks perhaps like an incomplete version of what we expect a bird to look like, because our expectations are set by the birds of today. In its time,
Archaeopteryx
was a perfectly complete competitor in its ecosystem.

If these ancient protobirds were like our modern birds, and they used feathers to keep warm just like modern birds and we do, it is quite reasonable to presume that the ancient dinosaurs were able to generate their own heat, just like us. How about that? Instead of slow-moving, sun-basking snakelike animals, they were quick like a hummingbird or a hawk. The scary-fast dinosaurs of the
Jurassic Park
movies were inspired by these fossil discoveries. And the science keeps getting richer. Some of the newest studies suggest the dinosaurs were not entirely warm-blooded but weren't cold-blooded either. They may have been something in between: Half-warm blooded, which (like half a wing) evidently suited them just fine for many millions of years. I'll use a new term:
mesothermic
, meaning “heat from somewhere in between in and out.”

Feathered dinosaurs are one among a series of recent discoveries that are filling in the story of evolution by illustrating the transitions between one kind of organism and another. The exact transitional moments may be almost impossible to find (a characteristic feature of punctuated equilibrium), but in many cases it's possible to track down the more general intermediate forms—with persistence and some smart strategy.

For many years, evolutionary scientists were frustrated that they could find no transitional animal between fish and land animals, like lizards, crocodiles, and alligators. That is, until they got to thinking about it. They figured such a creature would live in a swamp or a marsh and he or she would have had to be living about 375 million years ago. When people discovered a fossilized swamp that tectonic plate movement had carried north to what is now eastern Canada, they went looking. That is how Neil Shubin managed to find the remarkable
Tiktaalik
, a fish with transitional features between fins and legs. In the context of our current discussion, you might say
Tiktaalik
had half-limbs. But from the creature's perspective, there was no such thing as a half anything. What it had was something that enabled it to crawl onto land, to escape predators, perhaps, or to get a better look at potential prey.

I cannot emphasize enough the significance of this discovery. What we want as scientists, and as non-geek people who use the scientific method, is prediction. We want to come up with theories that allow us to make predictions about the future. It's in our nature. Our ancestors, who did not bother to make predictions about the future, no doubt got very quickly outcompeted by other ancestors who could predict seasons, the movements of herds of prey, and the growth of food plants. Scientists predicted that an animal like
Tiktaalik
would be found, and they found it. I drove this point home to my creationist adversary in the Kentucky debate. Creationism, unlike science, can predict nothing. Along with it being obviously wrong, it is obviously not useful. And of course, an appendage that serves as both foot and fin was no doubt extremely useful to animals like
Tiktaalik
. It's how they got around, hunted, escaped predators, and reproduced.

The efficacy of half a wing is an old question that has a clear, compelling answer in the context of evolution. Here's another fantastic example of how evolution produces intermediate forms. In the 1990s, a group of fossil hunters found the remains of a whale that once walked. No kidding.
Ambulocetus
(walking whale) fossils were discovered in what is now Pakistan. It is an animal that has whalelike flippers, and feet with toes.

Ambulocetus
must have roamed the shallows, where, judging by its teeth, it ate other animals. Through chemical analysis of those teeth, investigators have determined that
Ambulocetus
was able to make the transition from salty water to freshwater. They lived in the estuaries, where rivers meet the seas. They probably had no trouble finding food in these nominally productive areas. And they had hair, enough of it to be apparent in their fossils. These animals evolved into our modern whales. They had both half a flipper and half a hoof. You can be certain that they made outstanding use of both.
Ambulocetus
lived in large enough numbers, and retained reproductive capacity long enough, for us to find their fossils 50 million years later.

Half a wing, half a foot, or half a fin, they were well suited enough to outfit their descendants who are flying, walking, and swimming among us to this day. Each feature had to work well enough in its time. And each one did—well enough.

 

21

HUMAN BODIES ARE WALKING, TALKING, AND GOOD-ENOUGH

You don't have to dig into the past to see examples of good-enough design. You don't even need to visit the zoo. May I respectfully suggest you just walk up to a mirror? You and I, and our parents, and their parents, and your kids are the walking, talking, dancing (sometimes) result of evolution's principle of “good enough.” You and I will wear out. You might already have aches, pains, eyeglasses, and dental fillings. But your generation, no matter which one it is, was good enough to make it this far. This is another consequence of being shaped by natural selection. In our evolutionary world, good enough is as good as it gets. There is no reason for nature to work any other way. There's no evolutionary pressure to produce designs that are better than they need to be.

Every single feature of an organism takes energy to produce. Your hands, your eyes, your brain—all of these require chemical energy from somewhere, and the plan or design for them came or comes from your DNA. No entity at the top of the Human Being Design Shop is anticipating what feature we will need in the future. Whichever organisms, with their (our) randomly generated and sexually selected mutations, happen to come out better suited to the world they're born into—those are the ones, like you, that have a shot at reproducing. Either your features, such as your eye color, fingernail thickness, elbow joints, and emotional disposition, enable you to live long enough to reproduce, or they don't. Nature's good designs outcompete her not-so-good designs.

This fundamental feature of natural selection explains something we all worry about. Or if we're not exactly worried about it, we are at least keenly aware of it: We are all going to die. I know, it sucks, but it is the way of our world. From an evolutionary point of view, or from the point of view of your genes (if they have points of view, as such), what difference does it make? That you have this great big brain and you can worry about it is, in a charming sense, your problem. Evolution, with its 16 million species of animals, plants, microbes, and viruses, continues whether or not you or I express concern. All of us living things, from sea jellies to zebras, have to play the genetic hand we're dealt.

What really puts this in perspective for me is the fictional world of superheroes. Everyone is aware of characters like Superman, Spider-Man, and Wolverine. They have superpowers. O, would but that we could fly! How cool would that be? Or what if we had superhuman strength? Wouldn't it be nice to be able to outwit every villain you can think of? For me, these comic book heroes help us imagine what we'd change about our biological selves. They are also a means to nurture logical thinking. I'm not kidding. What if you, like Green Lantern, could move objects all over the place with your ring … unless the object is yellow? On one level it's silly. On another level, it's a mental exercise that helps you notice a detail in the world around you that many of us might otherwise overlook.

Batman is important in this discussion. Wait, hear me out. He doesn't have superpowers. He's just a brilliant man and a superb athlete, who never loses his cool, and is astonishingly wealthy. Oh man, I want to be that guy! But even Batman is replete with human features that a thoughtful designer—an intelligent designer, in the term favored by some creationists—would improve.

One of the most obvious human design puzzles is that our waste disposal plumbing is immediately adjacent to our reproductive and pleasure producing plumbing (even for Batman, I assume; though that information is not generally available). Your anus is right next to either your penis or your vagina. Would you have put the urethra right there in the middle of the whole business? If you were in charge, wouldn't you have separated those a bit? How hard could that be? (A car's air intake and its exhaust pipe are on opposite ends of the car, aren't they?) Seems like a simple problem to correct. Speaking of air intakes: why is yours right next to, actually right on top of, your fuel input system? Your windpipe (trachea) is right next to your food tube (esophagus), making it easy to choke. What's up with that? Couldn't that have been improved?

Why does anyone need to wear glasses with corrective lenses? Wouldn't you, as the designer, have just specified perfect vision for everyone? Why do so many of us get sunburn? Why isn't our skin more sensitive and tougher all at the same time? Same with hips, knees, and anterior cruciate ligaments: Why not make them a lot more durable? We wouldn't be having all these replacement and repair surgeries.

Next time you look an octopus in the eye, respect her or him, because her or his eye is a better design than yours. We have a blind spot near the middle of our retinas where our optic nerves connect. Your brain has to fill in the missing piece of the picture so you don't notice it. Moreover, the human eye's light-sensing cells are tucked behind other layers of tissue, which creates a slight distortion. That's not an optimal optical arrangement, but that's how we evolved. Octopus eyes don't have either of these problems. The eyes of octopuses and humans came to be by way of different evolutionary paths; and here we all are.

Every third pitcher in Major League Baseball in the United States has what has come to be called “Tommy John” surgery (after the first player to undergo the procedure). The ulnar collateral ligament, which runs around everyone's elbow, wears out. Surgeons harvest a ligament from somewhere else in your (a pitcher's) body, drill little holes in your bones, and tie the replacement part into your arm. The procedures work very well. Modern surgeons literally can't count how many of these operations they've done. If you were designing the elbows, wouldn't you make the elbow ligaments a good deal better or tougher? Or, wouldn't you make it so humans didn't want to play baseball? Perhaps better still, make it so that our brains were able to stop us from continuing to play before our elbow ligaments were worn out? Nope. Pitchers play the arm they're dealt. Nowadays, a third of them rely on other humans to fix their overuse problems.

Now that I think on it, I believe the brain is the biggest problem here. First of all, why do we need to sleep? For cryin' out loud (as babies are wont to do), couldn't we design a brain that can just keep going 24-7? Our computers run day and night with little difficulty, and they have not had the better part of a billion years to get things right. Why not us? Why do we get confused (in my case, more confused)? Why don't we have brains that just figure everything out, just like that? How hard could it be? If a few of us can figure out how to do arithmetic problems in a flash, why not everyone? Why can't we all be born able to work calculus problems? With the right designer in charge we would all come fully loaded, as we say at the car dealership. But we don't, and evolution is why.