Brain Plasticity—And the Problem It Poses for Evolution
For many people, he was known simply as “Superman”—a role that he began playing in 1978. Sadly, on May 27, 1995, we learned that Christopher Reeve was, in fact, human. The accident occurred during a three-day equestrian competition in Culpepper County, Virginia. Dressed in a protective vest and helmet, Reeve was riding his trained thoroughbred horse, Eastern Express. As his horse went over the third jump, it stopped suddenly, causing Reeve to go flying over the horse and land on his head, breaking his neck between the first and second vertebrae. He was knocked unconscious, and when he woke up, he was paralyzed from the neck down. Little did anyone ever expect that “Superman” would be confined to a motorized wheelchair. However, few realized that this same man one day would be the featured speaker at the 2000 Society for Neuroscience Convention, and that he one day would carry the banner for neuroscience research. His accident and subsequent injuries immediately propelled him into the spotlight for that type of research. Since that day, an enormous amount of money and man-hours have been spent researching the brain and the neurons that compose it. A great deal of interest has been given to the events surrounding traumatic injury in the brain and spinal cord—obviously in response to Reeve’s urgent appeals. Interestingly, one of the many findings that mushroomed out of this latest body of knowledge may prove to be kryptonite for the evolutionists.
The human brain is unique in that the human body is relatively small when ratios are compared among mammals. According to Science journalist Ann Gibbons, researchers have long known that an animal’s overall body size plays a critical role in brain size (1998, 280:1345). In animals such as whales and elephants, large brains are compensated for by an increased size in other organs that can provide energy (e.g., larger heart and lungs provide more oxygen). But humans do not follow this rule. In the context of simian primates, for example, the human brain is approximately “three times larger than the value predicted for an ‘average’ monkey or ape with our body size” (Jones, et al., 1999, p. 116). If evolutionists are correct, then the human brain has tripled in size since “Lucy” (Australopithecus afarensis) walked this Earth, while our bodies have yet to even double in size.
Since the brains of animals and humans differ, some explanation for the observed disparities obviously is required. Frequently, the causative factors for these changes in the brain are attributed to environmental changes (e.g., apes leaving the confines of the trees) or dietary changes (increasing meat and protein intake). Researchers speculated that each new branch of the evolutionary “tree of life” represented a progressive change within the brain, with humans currently residing at the pinnacle of development. However, according to evolutionists, such changes did not occur overnight. Millions and millions of years were required to evolve from the “simple” brain of an earthworm to the complex circuitry we now know exists within the human brain. These changes, we are assured, are simply the result of animals trying to advance themselves (“survival of the fittest”). Evolution not only embraces these changes, but is dependent on them. What would happen, however, if scientists discovered that the brain always has possessed the ability to change? What if the brain held the capacity to rapidly adapt, so that new environments and new food sources simply required a “reorganization” of brain circuitry? What if the brain possessed the ability to change and regulate itself literally on a day-to-day basis, so that changes to make the animal “more fit to survive” took place in mere minutes rather than millions of years? We no longer need to ask “what if.” It does!
AND THE PROBLEM IT POSES FOR EVOLUTION
Known commonly as plasticity, this concept simply means that the brain is not as “hard-wired” or permanently fixed as was once believed. One of the properties of plastic is flexibility—many jars and containers are formed from plastic so that they will not shatter when dropped. In a similar manner, the brain once was considered to be rigid, like the well-known Ball® jars used for home canning of foods. But we now know the brain is “plastic” (i.e. flexible), and can “reorganize” itself. Research has shown that the brain is able to remodel its connections in order to adjust the organism’s response to changing conditions. Previously, scientists considered the brain to be fixed or “hard wired”—that is, that it could not change, and once connections were in place, everything remained that way. However, we now know differently. Shepherd noted in his book, Neurobiology:
The inability to generate new neurons might imply that the adult nervous system is a static, “hard-wired” machine. This is far from the truth. Although new neurons cannot be generated, each neuron retains the ability to form new processes and new synaptic connections (1994, p. 222).
Interestingly, since this text was printed, additional research has documented the regeneration of neurons within certain areas of the brain. The cortical rearrangements that occur are not as simple as unplugging a lamp and plugging it into another socket. The changes observed by researchers indicate that if the brain were represented by a home electrical system, then many of the wires within the walls would be pulled out, rewired to different connections in different rooms, new outlets would appear, and some even would carry different voltages. Due to the colossal connectivity that takes place within the brain, any “rewiring,” by its very nature, is going to have an effect on several areas. Shepherd went on to note:
These rearrangements have several interesting and important features. First, they show that thalamic inputs to the cortex are both extremely precise and also significantly plastic. Second, these changes take place over varying time scales; in some cases the shifts in representations are slow, developing over weeks, but in other cases they may be surprisingly rapid, beginning within a day or so, or even a few hours. Third, these changes are not limited to the primary cortex (p. 290).
In the 1970s, William Greenough and his colleagues initiated a multidisciplinary study of the cellular effects of raising animals in visually or motorically enriched environments (Greenough and Chang, 1989). This research group, which continues to monitor changes, identified that synapses can form, and dendrites can grow, well beyond the period of brain development. While this observation certainly is not unique to Greenough, he and his coworkers have shown most forcefully that the adult mammalian brain can add not only dendrites and synapses in response to behavioral demands, but also supportive tissue elements such as astrocytes and blood vessels. Many of these studies have been carried out in rodents and primates, which clearly demonstrates that plasticity is not a trait that humans “evolved” after branching off the alleged evolutionary tree. In fact, the very presence of plasticity in lower animals begs the question of why there would be further brain evolution, since these animals already possessed the ability to rewire and reorganize brain circuitry.
At first glance, as one ponders the creation/evolution controversy, plasticity might seem almost trivial. However, one should not overlook the importance of the ability for cortical rewiring and reorganization. But what, exactly, does this mean for evolutionists? Quite simply, it means that they now must explain why an animal that can change or reorganize its own brain would need to “evolve” a different brain. Why did Neanderthal man or Australopithecus afarensis need to evolve a “bigger and better” brain—if the one he possessed already was capable changing? Plasticity allows animals to adapt within minutes or days, not millennia.
For years, evolutionists have used animal specializations as the factor that promoted and demonstrates evolution. However, they no longer can legitimately use such examples, because these adaptations and specializations can be understood in the context of plasticity. This means that if the monkeys were forced to “crawl down out of the trees” to pursue food on the ground, the brain would have made the necessary changes within days—in that very generation, rather than over thousands or millions of years. Neuronal changes would allow an animal to survive on the new diet, and associated changes likely would even help the animal locate the new food source.
Neuroscience has experienced tremendous growth in the last ten years due to increased funding and increased interest in the brain. One of the most exciting developments that has come from this increased study is the discovery of brain plasticity. We now know that the brain is not as “hard-wired” and static as was once thought. But this discovery places a tremendous burden on evolutionists, who must now explain why brains that are plastic and capable of change in the first place would ever “evolve”? Additionally, evolutionists always have assumed that it took animals millions of years to change and adapt to a new environment or new diet. Yet according to recent data, this easily could occur in mere days. Quite simply, brain “evolution” does not fit the evidence. Brains are able to rewire themselves; thus evolution is unnecessary. Brains were created by an intelligent Designer, and always have possessed this incredible ability to change and reorganize.
Gibbons, Ann (1998), “Solving the Brain’s Energy Crisis,” Science, 280:1345-1347, May 29.
Greenough, W.T., and F.F. Chang (1989) “Plasticity of Synapse Structure and Pattern in the Cerebral Cortex,” Cerebral Cortex, ed. A. Peters, E.G. Jones, 7:391-440 (New York: Plenum).
Jones, Steve, Robert Martin, and David Pilbeam, eds. (1999), Cambridge Encyclopaedia of Human Evolution (New York: Cambridge University Press).
Shepherd, Gordon M. (1994) Neurobiology (Oxford: Oxford University Press), third edition.