Undeniable (22 page)

Our bodies, like those of every other living thing on Earth, reflect the physiology of successive generations of ancestors who were built well enough to reproduce. That's all they had to be: good enough. People who have or had trouble accepting the process of evolution, often point (but not poke) at a human eye and marvel at its construction. They express stern skepticism that such an efficacious and wonderful structure could come to be without an all-powerful designer running the show. Really, this is another variant on the “half a wing” argument, and it's just as easy to refute.

If you take a little time with it, you'll find countless examples in nature of organisms that have light-sensitive cells. It's easy enough for us to imagine cells that sense heat. Light and heat are the same energy, just at different wavelengths and often at different intensities. In nature we find light-sensitive cells on a flatworm, say. We find light-sensitive cells lining a hollow or pit on the shell of a mollusk; eyes that work well enough for them. We find light-sensitive cells in nautilus eyes that are illuminated through a very small opening, just like the pinhole camera my father rigged up while interred in a prisoner-of-war camp. You find spider eye lenses that give them a sense of where the light is coming from. You find repeated-pattern compound eye lenses in insects, and so on.

Our eyes are derived from millions of years of trial and elimination of error. You'll find organisms with transparent cells. In other words, there are a great many examples of the intermediate steps required to get from a flatworm's “light patches” to a giant squid's manhole-cover-sized eyeball, to the eyes of a bald eagle that can resolve images about eight times better than we can. It's as though they have eight times the megapixels in their smartphone cameras. The intermediate steps are still extant. Each of the steps I mentioned exists in nature today, because each of these eyes is good enough to keep each animal and its genes in the game, the game of life.

Speaking of being in the game of life, who, in your estimation, is the most dangerous animal on Earth? Who is the baddest badass? It's you, of course. It's us. We are the dominant entity around these parts. If you're a cow, humans will breed you, milk you, kill you, and eat you. If you're a mouse, you can run around underfoot, but humans will exterminate you, if you get in our way. Heck, you can be a whale in the middle of the ocean, and humans will build ships big enough to sail on the open sea, hunt you down, and kill you. Humans are serious business because we have big brains (even if we don't all use them fully—again I'm reminded of my old boss). So let me take you down a peg by pointing out that the human brain, the exalted thing that elevates us above all other species, is just one more example of evolution's good-enough standard.

Our brains are radically bigger relative to our body weight than the brain of a horse, for example. I believe that's part of the reason horses can shy and act a little wild and, by human standards, irrationally and dangerously. Our brains are enormous compared to a dog's, even a sympathetic, happy, smart dog such as yours no doubt is. Our brain-to-body-weight ratio is somewhat bigger than that of our genetic cousins the chimpanzees. But our brains are not especially much bigger in proportion to our body weight than that of our former neighbors the Neanderthals. We outcompeted them and perhaps two dozen other almost-modern-human, or “hominid,” ancestors. We are just the next step. Our brains, compared with our bodies, are just a little bigger than the other guy's or gal's. Nor are our brains unique in the way they work. Have you ever watched a dog when he or she is asleep yet still a little active? They move and shake very much the way we do. You don't have to be a neuroscientist to figure out that our best friend is dreaming. Their brains are hooked up just like ours.

We are just the latest version of a brain good enough to conduct our lives in competition with so many other organisms in our ecosystem. As a consequence, we can communicate in ways that, at least from our point of view, seem to be far more complex than our next of genetic kin, the chimpanzees, bonobos, and gorillas. We can write books, and thank our readers for reading them. Thank you. We can understand patterns in nature, record them, and make predictions based on those patterns. We can discover calculus, write plays, develop movie projectors, and make moving-picture stories about a future that may or may not come to pass. This very discussion about evolution would not be possible if we did not have the uncanny ability to step back and be aware of our situation here on Earth and in the cosmos. A better brain is just not the same thing as a perfect brain.

Although our brains enable us to envision a remarkable future, it's not clear that we'll be able to fly around the galaxy or universe, beam down to a planet, and chat it up with beings who speak English (for example). And who knows? Some future, far-more intelligent species may look back at us as the transitional form with “half a brain.”

Bear with me for a little more delightful evidence of good-enough design in our brains. Studies have shown that not only does your brain direct your movements, your movements can affect what you think and how you feel. When test subjects are induced to move toward a stranger, the subjects tend to like the stranger more than when the subjects are induced to move away. This may be why shaking hands and bowing forward became traditions. By moving toward the other person, we feel, at some level, that we accept the other person. Psychologists and neuroscientists have coined the phrase, “embodied cognition.” When your brain directs your body to do something, your body, in a sense, directs your brain to feel something. I mention this, because it is, for me, yet another sign that our brains are derived from our ancestors' brains. In comedy writing, we would call us a derivative bit. We're just like those other hominids only updated to be funny (or tall, or smart, or cute, or charming) today.

And the brain, like every part of the body, is mortal. Right now, all manner of research and medical work is being done to try to prolong our lives. This may work out for future generations, but I've got a feeling that even if people live to be two hundred years old, it won't make that much difference in the evolutionary scheme of things, because what matters is getting one's genes into the future. It's as true for you and me as it is for lobsters. A human's reproductive period is probably going to remain only about thirty years long, even if that person goes on to live and pay taxes for many more decades. That we age, that we wear out, is not of much consequence in the evolutionary scheme of things so long as we reproduce. Having thirty years of reproductive time was good enough for our ancestors, and for better or for worse it has to be good enough for us, too.

It is reasonable to me that the length of a human's natural life is also the result of natural trial and error. If we lived too short of a life, we would not come of age and be sexually able to make more of us. If we live too long, it is reasonable that it would take too much out of our immune systems to keep fighting the next generations of germs and parasites. Instead our seven, eight, or nine decades are the right amounts of time naturally to be productive without being a burden, either to our own immune systems or our tribe. It's a troubling thought or an empowering one, depending on how you look at it.

Suppose you knew that you were going to live to be two hundred. Would you hustle as much? Would you work to better your life? Would you bother to learn algebra, or would you assume that you could just learn it later? Would your reproductive time be any different? Would women be able to conceive children after the age of sixty? Would a man's sperm not degrade with age? Extending life might be fun, but it probably wouldn't make too much difference in our reproductive ability and our evolution in the long run.

All of us, everyone reading these words, have made it this far in life. None of us would be here if we weren't genetically good enough. That's a rather encouraging thought. We celebrate certain people's appearance or their wit, but we are all so much more alike than we are different. The proof is in the living: We all made it. No matter how ugly you think someone else is, he or she got here just like (as) you did. There's a lid for every pot, as the saying goes.

 

22

EVOLUTION IS WHY WE DON'T BELIEVE IN EVOLUTION

From time to time, I meet someone who will say something like, “I am not afraid of dying.” I don't buy it.
Everyone
is afraid of dying. It's part of the instinct that helps us survive as a species. It's a crucial feature of human evolution. It's also, I strongly suspect, a crucial reason why so many people have trouble believing evolution is true. Life can be ironic like that.

It doesn't take much to trigger the fear of death. Just try to picture these scenarios. You're standing on a very high bridge, like we might have near the campus of Cornell University in New York State. The gorges there are 50 meters deep (about 150 feet). You are scared—because of your fear of something going catastrophically wrong, that you might lean to have a look, and lean too far, etc. Or, you're crossing the street, and a driver who's texting almost hits you. Perhaps he slams on his brakes at the last possible moment. The tires squeal, the horn blares, your heart almost stops. You are scared out of your mind because he almost killed you. We are all scared of things that go bump in the night, because it may be a sound made by something dangerous, e.g. a lion, tiger, or bear—that could kill you.

Our ancestors who did not have a fear of heights, who did not have a fear of eating something poisonous, who did not have a fear of venomous snakes and spiders, who were not afraid of drowning, well—they're dead. They did not have the instinct to keep themselves from getting killed. It's deep within us, and it had better be. I thought a lot about the fear of death after I debated creationist Ken Ham. There is a deep-seated reason why intelligent, sensible people suddenly recoil from objective evidence when the topic turns to evolution. I think the fear of death has a lot to do with it.

As you may know, a group of wags on the Internet issue what they call the Darwin Awards. These are largely just news stories about people who behave in extraordinarily stupid and dangerous ways. Many of the stories seem to be apocryphal, but they sure make for good reading. For example, a guy may find some old dynamite, bury it, and then tamp it down real well to make sure the soil fills in around the old sticks. Well, during the stamping and tamping, the pile explodes, and the man essentially vaporizes, leaving almost nothing for the police to examine. Or, there's a story about a guy, who tied jet-assisted takeoff (JATO) rocket tubes to the roof of his car. When the rockets were lit, the whole assembly became airborne and flew into a high mud cliff, flattening car and experimenter alike. Each of these people is given a Darwin Award, albeit posthumously. The moral is that they did not have sufficient fear of death, and it killed them.

There's a scientific message here, too. Evolution does not influence only physical attributes like height, number of knuckles, eye color, and earlobe shape; it also acts on emotions. What we feel is a result of evolution. This is true, no doubt, of your fear of death. It certainly seems to be true about our drive to reproduce. When we're thinking about sex, what we're really thinking about is what it would take to engage in activities (sex) that would lead to reproduction (babies). It goes on all day, all the time for most of us. I encourage you to place your own sex joke here, and notice how readily it came to mind. Sex is there, just below the surface, all the time!

If our genes drive us to remain alive and reproduce, and we are unconsciously driven all day and night by this impulse, what does that mean about the rest of creation—about all of nature? I like to compare us, or me at least, to dogs. I've watched them. They dream. They have fears. They certainly can be charming, and they can be quite difficult to be around, just like people. But, it's not clear to me that my dog friends get quite as caught up in the nature of our existence as my human colleagues and I do. I have seen dogs very afraid—of a mean or angry owner, or another, bigger dog. But I don't think I've ever seen a dog paralyzed by self-doubt, as
I
have been from time to time. I am open-minded, but I don't think dogs, even dogs I've spent a lot of time with discussing these things, ponder the origin of the universe and the fundamental meaning of life. Leastways, not the way you and I do.

Apparently, a consequence of having a human brain that can do all these other remarkable things like play the violin, invent a trick in calculus, or pole-vault over walls and thin striped bars, is being able to ponder our very existence. No other organism on Earth does that. Yes, yes, I understand that dolphins are very smart, but I don't think they build libraries or even contemplate such a project. Along with our special ability to think and reason, we just can't believe it's all going to end, that we are all going to die. But near as I can tell, everyone that's ever lived is either dead or is going to be. What about this house you designed? What about the poem you wrote? What about the feeling you had, when you fell in love? Those things are not going to go on without you; generally they'll disappear in a flicker. It is the miserable nature of our existence.

If you live to be eighty-two years old plus about seven weeks (it depends on leap years), you get thirty thousand days here on Earth. That's it! When I was a boy, thirty thousand of anything was hard to imagine. It sounded like a lot. I just think how many balsa wood airplanes and model rockets I could have flown and launched with thirty thousand dollars! Now, as an adult paying taxes and writing books, it hardly seems like a big number at all. Try this way of picturing a human lifespan. The National Football League's Dallas Cowboys' stadium holds 105,000 people. Now, imagine that you're watching life go by down on the field, and every day you watch that life go by from a different seat. You don't even get a third of the way around. Before you've settled into a third of the seats, you'd be dead. And, that's if you had a good run, eighty-two-plus years. Yikes!