How are we evolving now? Lieberman asks this question in his book, The Story of the Human Body.
Natural selection and human evolution used to be slow and steady. It occurred over generations. Over the last few centuries cultural evolution has caused more pressure on humans than the typical environmental/natural shifts. We eat differently, are exposed to more and novel chemicals, we are exposed to different infectious agents, we work more passively, and so on.
The cultural evolution is changing the environmental signals that we receive at a light speed pace. It is no longer purely Darwinian and natural.
These cultural developments are affecting us metabolically and epigentically, positively and negatively. They are heritable by being passed on to future generations through the environment. For example, pesticides and petrochemicals can get into ground water and affect the drinking water for a whole family over time. We have not evolved genetic techniques to sufficiently evade such chemical toxicity.
These cultural influences can go both ways. Let us look at two examples that Dr. Lieberman cites: scurvy and cavities.
Scurvy is a disorder of dietary vitamin C deficiency that affects our collagen causing bleeding, neuropathy, fatigue and in extreme cases death. Cavities, tooth enamel and dentin destruction, are the consequence of bacterial acid production through the fermentation of food on the teeth.
Culturally, we have evolved to cure scurvy by fortifying foods with vitamin C and also make natural vitamin C foods like citrus more available. Good thing right! Now look at sugar and cavities. Ever since the farming revolution, humans have consumed increasing quantities of refined foods and sugar that promote cavity development. We have passed on the cultural evolutionary knowledge to cure one disease while starting another.
What we end up with is a mismatch of our genome and the current environment. This is occurring more and more over the last three hundred years. As the pace of technological advance takes off exponentially, the questions of how we can handle them genetically are growing. Scurvy and cavities are minor issues in comparison to the emerging science of engineered foods, chemicals in the environment, nanotechnology...., we are starting to see data emerge that we are losing the battle and developing more disease.
To be continued.....
