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Who would argue that of all nature’s creatures, the evolutionary process of natural selection achieved its most stunning success when it brought Homo sapiens onto the world stage, about 200,000 years ago. You can imagine nature’s pride as she announced,  “here is my best work, 7 million years in the making” (the first human (hominin) ancestor in the fossil record is Australophithecus afarensis, who walked erect, but lived in trees, ate fruit and nuts and was preyed upon by the numerous predators of that era, like giant hyenas, saber-tooth tigers and many others. A. afarensis was an edge species, the size of a small ape, who  lived in the trees and on the ground. Perhaps 6-10 per cent of A. afarensis fell victim to these large, fast predators, based on the fossil record of  A. afarensis showing predator skull punctures and tooth marks on other bones). The guiding light for evolutionary change is natural selection operating on mutations that result in improved means of survival and procreation.

As humans, there is much that we can celebrate about ourselves. While we don’t have the greatest body plans and we are not the fastest or the most agile or the strongest species, we do have a brain worth bragging about, a modern marvel, and perhaps the pinnacle of the evolutionary process. Although big brains per se may be worth noting, it is far more important to understand what part of our brains have evolved in such a way that we manage to dwarf the achievements of all other species with our rich linguistic skills, a powerful sense of logic, a prolonged period of social learning  and the creation of a vast culture that has led to a sea change in the earth around us.  Our  language facility  keeps our social evolution on a continuous staircase of change and adaptation, one in which each new generation adds its own cultural layer on top of those of its predecessors.The central question is whether we can continue on the staircase we are currently on or whether we need to backup and start over on a new trajectory. As far as I know, there is no evidence in the fossil record that suggests Homo sapiens was ever confronted with something as threatening as what we might face with global climate change and its potential impact on our culture. Are we smart enough to make the kind of adaptation that may be required to meet this new uncertain future?

Cortical surface of human, cat and rat brain (NEUROSCIENCE: EXPLORING THE BRAIN, Bear et al, Fig 7-27; not to scale)

The figure above illustrates the cortical surface of thee different mammalian brains, including human, cat and rat. These are not drawn to scale, but magnified as required to illustrate how different regions of each brain are functionally divided into visual, auditory, motor and somatic sensory partitions (the olfactory bulb in humans is  tucked under the frontal lobes of brain and can’t be seen using this view). Most of us understand that the cerebral cortex (neocortex), the outer, undulated surface  of our brains, is the real envy of the neighborhood. It’s what has our competitors swooning. This convoluted outer surface of our brain is so vast that it has to be folded into peaks  (gyri) and valleys (sulci) to squeeze  its huge surface area into  our skull; within the skull, the brain is suspended in a fluid-filled shock absorber system, surrounded by cerebrospinal fluid (CSF) and suspended by strands and layers of concentric, fibrous collagen, through which blood vessels penetrate to nourish and oxygenate the brain: an impressive engineering marvel with natural selection at the control center. You can appreciate that the cortex of the rat has very few folds, whereas the number and complexity of them increase as one moves from cat to human.

The three pound universe that resides in our skulls, constitutes  a small percentage of our body weight, but requires 25% of the oxygen we consume. Our brains do not store energy, so blood supplied glucose provides the main nutrient and must be continuously available.  Every region of the brain is within 90 µm of a capillary, reflecting this supreme dependency on continuous access to oxygen and nutritional support. Our brains have created a miraculous way of regulating their own blood supply: the blood flow within the brain is not uniform, but varies according to the tissue demands. Brain regions where neuronal activity is high receive more blood flow compared to brain areas which have lower levels of activity. So, blood traffic in the brain is under neighborhood regulation. It’s like the street gets wider if the traffic gets heavier.  It is the change in blood flow, based on neuronal activity (maybe glial cells too (see below)), that serves as the signal detection basis  for the technique of functional Magnetic Resonance Imaging or fMRI. The cellular  mechanisms which regulate this regional blood flow  are still poorly understood, but appear to involve glial cells, the non-neuronal cells that were once thought to merely be the “glue” that keeps the neurons together.

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While the new swine flu epidemic is causing an appropriate level of alarm, more subtle aspects of environmental failure are beginning to surface, that, in the long run, will pose a more serious problem to our food supply and very likely escalate the cost of food. Europe is far more advanced than the United States in regulating the chemical industry and several herbicides that are toxic, such as Atrazine, have been banned from use in Europe, but are still used  widely in the United States. It’s ironic that the research showing Atrazine’s toxicity (it gets in the ground water and causes feminization of male frogs–if it does that to frogs what does it do to our own reproductive functions?) was done here in the United States. But, under the Bush administration, the EPA approved the use of Atrazine for United States agriculture.
As I was scanning the paper this morning, mostly focusing on reports about swine flu, I came across a more obscure but troubling article. A report in the New York Times today points out that Europe, like the United States, has a major bee problem. The currently high level of bee mortality in Europe could permanently wipe out bees in that region within 8-10 years, according to Apimondia, an international bee organization. Last year alone about 30%, or more than 13 million of Europe’s bee hives died out. The loss of bee hives was much higher in some regions, reaching 80% in southwest Germany. This problem is potentially far more serious than swine flu, since about 35% of Europe’s food supply depends on pollination and no one pollinates as effectively as bees.
We have already heard about the bee crisis in the United States where mobile bee hives have been used for farm pollination for many years. In this brave new world of our farm economy, farmers pay for massive numbers of bees brought to their farms in trucks, where they are released, sting a few people, and then serve as pollinators for the region for a set period of time before the bee keeper moves on to his next contract.  The near complete absence of local bees makes this arrangement a necessity. No magic bullet seems to explain the mounting decline of bee hives, either in Europe or the United States.  The cumulative effects of mite infestation, pesticides and herbicides have been blamed for this crisis, but no simple solution or cure is available. The bees leave the hives to forage and pollinate, but they don’t come back. A colleague of mine working on the problem of bee vitality  here at the University of Minnesota has concluded that the bees are simply stressed by too many excesses and over stimulation from their environment. One popular idea is that the stimulation by the chemical environment leads them to spend too much energy reliably identifying their to and from path and this stress leads to infestation with mites and an early death. But, stress is one thing, early death is another.

It is alarming to see that Europe is suffering from the same problem that we have here in the United States, since they have been better about regulating their chemical industry. Indeed representatives from Europe have appeared in this country giving lectures to major manufacturing establishments to tell them what chemicals they can and cannot use if they expect to export their products to Europe. And, they are all taking careful notes, because they can’t lobby their way into avoidance, like they do here. Fortunately for us, we are still enjoying benefits of a free market economy approach to the chemical industry–if it doesn’t smell too bad, go ahead and use it. I suppose what we need are large numbers of robotic bee colonies that only have to come back to their hives to get their little lithium batteries recharged.  Would a robotic bee project be a suitable challenge for the summer students at MIT? Or, should we take a stab at a biological approach? Where is the genome of the  honey bee when you need it most?

RFM

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It was too tempting not to get one. Imagine during the course of evolution, to have so many photons in the environment, regulated on a cyclical plan, with a trillion fold difference in photon emission rates from day to night. Imagine all that available light and then imagine a species that could survive without any ability to detect light or its absence. It would surely be an evolutionary crime. Most animals of which I am aware, that were once thought to be blind, turn out to have some form of light detection.  Even bacteria, such as halobacteria have the same rhodopsin in their membranes that we have in our eyes to detect light: they just do something a little different with the signal (they use it to make ATP). Light and sound provide us with the great distance receptors talked about by the Nobel laureate Lord Adrian. Vision allows every animal to detect images that are far away so that protective or survival mechanisms can be implemented long before the threat arrives. But the cyclical nature of light, from the noon day sun to the darkest shimmer of a moon, also provides a means for timing, and timing for some things, like reproductive behavior in an ocean that dilutes eggs and sperm, can be as critical for survival and propagation of the species as making a timely dash away from a predator. Every year it seems we discover something new driven by light.

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