Physics of the Future: How Science Will Shape Human Destiny and Our Daily Lives by the Year 2100

enhancing and improving them.
    The desire to have superhuman ability is an ancient one, rooted deeply in Greek and Roman mythology and our dreams. The great hero Hercules, one of the most popular of all the Greek and Roman demigods, got his great powers not from exercise and diet but by an injection of divine genes. His mother was a beautiful mortal, Alcmene, who one day caught the attention of Zeus, who disguised himself as her husband to make love to her. When she became pregnant with his child, Zeus announced that the baby would one day become a great warrior. But Zeus’s wife, Hera, became jealous and secretly schemed to kill the baby by delaying his birth. Alcmene almost died in agony during a prolonged labor, but Hera’s plot was exposed at the last minute and Alcmene delivered an unusually large baby. Half man and half god, Hercules inherited the godlike strength of his father to accomplish heroic, legendary feats.
    In the future, we might not be able to create divine genes, but we certainly will be able to create genes that will give us superhuman abilities. And like Hercules’ difficult delivery, there will be many difficulties bringing this technology to fruition.
    By midcentury, “designer children” could become a reality. As Harvardbiologist E. O. Wilson has said, “ Homo sapiens,
the first truly free species, is about to decommission natural selection, the force that made us. … Soon we must look deep within ourselves and decide what we wish to become.”
    Already, scientists are teasing apart the genes that control basic functions. For example, the “smart mouse” gene, which increases the memory and performance of mice, was isolated in 1999. Mice that have the smart gene are better able to navigate mazes and remember things.
    Scientists at Princeton University such as Joseph Tsien have created a strain of genetically altered mice with an extra gene called NR2B that helps to trigger the production of the neurotransmitter N-methyl-D-aspartate (NMDA) in the forebrain of mice. The creators of the smart mice have christened them Doogie mice (after the TV character Doogie Howser, MD).
    These smart mice outperformed normal mice on a variety of tests. If a mouse is placed in a vat of milky water, it must find a platform hidden just beneath the surface where it can rest. Normal mice forget where this platform is and swim randomly around the vat, while smart mice make a beeline to it on the first try. If the mice are shown two objects, one an old one and one a new one, the normal mice do not pay attention to the new object. But the smart mice immediately recognize the presence of this new object.
    What is most important is that scientists understand how these smart mice genes work: they regulate the synapses of the brain. If you think of the brain as a vast collection of freeways, then the synapse would be equivalent to a toll booth. If the toll is too high, then cars cannot pass through the gate: a message is stopped within the brain. But if the toll is low, then cars can pass and the message is transmitted through the brain. Neurotransmitters like NMDA lower the toll at the synapse, making it possible for messages to pass freely. The smart mice have two copies of the NR2B gene, which in turn helps to produce the NMDA neurotransmitter.
    These smart mice verify Hebb’s rule: learning takes place when certain neural pathways are reinforced. Specifically, these pathways could be reinforced by regulating the synapses that connect two nerve fibers, making it easier for signals to cross a synapse.
    This result may help to explain certain peculiarities about learning. It’s been known that aging animals have a reduced ability to learn. Scientists see this throughout the animal kingdom. This might be explained because the NR2B gene becomes less active with age.
    Also, as we saw earlier with Hebb’s rule, memories might be created when neurons form a strong connection. This might be true, since activating the NMDA receptor creates a strong connection.
    MIGHTY MOUSE GENE
    In addition, the “mighty mouse gene” has been isolated, which increases the muscle mass so that the mouse appears to be musclebound. It was first found in mice with unusually large muscles. Scientists now realize that the key lies in the myostatin gene, which helps to keep muscle growth in check. But in 1997, scientists found that when the myostatin gene is silenced in mice, muscle growth expands enormously.
    Another breakthrough was