Read Online Undeniable by Bill Nye - Free Book Online Page B

end up with this arrangement, which seems quite odd at first. After you mull it over, it’s just what you’d expect from fish, from yourself, and from giraffes.
    The same must be true of a giraffe’s tongue and lips. Each generation of proto-giraffe, the ancestors of modern giraffes, had successively tougher tongues. A tough tongue enabled you, as a proto-giraffe, to get a little more to eat from the leaves of high branches. Eventually, a generation of giraffes was born that could eat high and thorny acacia leaves.
    To drive this idea home, join me in a little thought exercise. Imagine a bicycle. Now, imagine a two-wheeled hand truck or a two-wheeled cart, the kind you see city dwellers bring to the grocery store. Now, imagine making changes to the cart or hand truck so that it becomes a bicycle—but making those changes step-by-step, in accordance with evolutionary principles. You would have to stretch the cart into a parallelogram shape or something similar, so that the wheels were one before the other rather than side-by-side. The wheels would have to be bigger. The tires would have to hollow out and become filled with air. You might have to modify the axle to become a chain. Maybe the handle that goes over the top would somehow have to become the top tube of a bike frame. And every bit of the cart would probably have to be thickened to become a bike frame able to support the weight of a human bouncing over a rough road.
    The crucial evolutionary requirement is this: At every stage, with every change you make, the whole thing has to still be functional. It has to still roll. It has to still be drivable or take-to-the-store-able. Otherwise, the cart or hand truck would die out. If at any point it didn’t roll, or couldn’t be steered in some fashion, or if there were no practical way to keep it in balance, you’d have to abandon it. You’d just leave it by the side of the road to rust to dust, and try again with one of your other related designs. Inevitably, you’d have to keep a lot of the original design and make changes in an incremental way. That’s how things are in nature, where there is no deliberate designer who can take things apart, redesign them, and put them back together if they don’t work. Instead, every step has to be “good enough.” Every generation has to survive lest that species or type of organism will disappear from our world.
    That is why giraffe necks are so similar to our necks and to dog necks and to horse necks. If we look closely, our necks are similar to fish necks. We are descendants of a common ancestor way back in Earth’s history. Configuring necks this way is almost certainly not how a designer or engineer would build the world. But the details all make perfect sense once you embrace the idea that evolution does not work the way a human designer or engineer would.
    Evolution happens as each generation of living things interacts with its environment and reproduces. Lamarck got at least that part of it right. Those natural designs that survive to reproduce pass on their genes. Those that don’t successfully reproduce disappear; their genes disappear as well. It’s survival of the hang-in-there’s, or the made-the-cuts, or the just good-enoughs.

 
    8
    MY PROM AND SEXUAL SELECTION
    Being a nerd, I did not anticipate going to my high school prom. Nevertheless, I did. I was driven to do so, apparently, by the shape of Leith’s legs, a (clearly) female classmate. This fascination with sex is, near as anyone can tell, not something we get to choose. Our ancestors bequeathed it to us. It’s another one of those deeply shared evolutionary traits. It’s a drive we cannot disengage.
    Along this line, I cannot help but recall a day at a beach in Delaware, when my mother’s first cousin Monique showed up to sun herself. I was about seven at the time. My mother’s mother was French, so my first cousin once-removed