Read Online Undeniable by Bill Nye - Free Book Online

big-shouldered family stops working as blacksmiths, they still have big shoulders. Lamarck’s ideas did not stand up to scientific scrutiny.
    We know now that a giraffe’s neck, like all its physical attributes, is controlled by genes, and living things in nature cannot alter their genes. All organisms—sea anemones, fireflies, giant squid, miniature poodles, and humans—have to play the genetic hand they’re dealt. What Darwin realized, and what Lamarck missed, is that the complexity emerges slowly through a whole population, not quickly within a single person or animal. With that said, researchers have recently discovered an intriguing twist to the story. Under the right conditions, and up to a point, inheritance can work the way Lamarck believed it did. Although genes themselves do not change on their own, the way that those genes are activated can change within a single individual’s lifetime. This phenomenon is called epigenetic change—changes coming from the outside.
    In the not-so-distant future, there may be another way that your genes can change. Scientists are working on gene therapy—ways to alter your DNA to eliminate or obviate a disease, to make adjustments, or to incorporate what we hope are improvements to our genes. Someday it may be possible to make modifications in the so-called germ line, which would result in that new DNA being passed on to your kids. Creepy or fabulous? Crazy or ethical? The possibility of genetic modification reminds me of the need for a scientifically literate electorate. Please stay tuned and vote!
    Keeping all of this in mind, let us once again consider the giraffe in its natural habitat. Having traveled in Africa a couple of times and observed giraffes in nature, I can tell you that you don’t have to be the world’s foremost authority to see that giraffes eat leaves on branches pretty high off the ground. They use their necks to get to vegetable matter that other animals would have to work quite a bit harder to get to. If you were a cat, you could climb out on those branches and gnaw away. But it would be a lot more work. Oh, and cats generally eat other animals rather than delicious acacia tree leaves. Giraffes have another fascinating feature that I didn’t notice, until it was pointed out to me. They have very tough tongues and lips. They can just grab onto the thick part of an acacia tree limb and slide their mouths right down the limb to the thin end, stripping all the leaves off as they go. Here’s the thing: African acacia trees are loaded with thorns. You and I cannot grab an acacia branch with our bare hands, let alone our bare tongues. Yee-ouch! But giraffes can.
    Thinking as Lamarck had thought, you might conclude or presume that the giraffes that we see today got their long necks by just reaching. You might think that just by stretching their necks to get food, giraffe necks would naturally get longer—and so would the necks of their offspring. But no. Darwin reached the correct answer: The ancestors of our modern giraffes, who happened to have slightly longer necks than their contemporaries, were able to reach just a little bit higher on acacia trees than the other members of their giraffe herd, or no kidding, other members of their tower. (It’s like school, as in a school of fish. Only this is a tower of giraffes.) The giraffes with longer necks were better—just a little bit better—at getting enough nutrition. So, they were just a little bit better at having babies, too.
    The evolutionary pressure to have longer necks was probably stronger when food supplies were scarce. Imagine a drought on the savannah, the African landscape that a European or American might describe as somewhere between a forest and prairie. During the drought the trees that survive probably have fewer, smaller leaves that don’t carry as much water as they do when there’s been plenty of rain. In this situation, all of the