|About Rhythms (cont'd)
I suggest that variations in patterns of thyroid hormone secretion (thyroid hormone rhythms) are key to evolutionary change. Thyroid hormone controls a huge variety of body characteristics and functions - from foetal growth and hair color to the fight-or-flight response; thyroid function is what keeps each individual body adapted to conditions of light, temperature and food supply that vary with the seasons Ė such as co-ordinating mating times, increasing metabolic rates in winter, triggering hibernation, etc. My work suggests that the same group of genes that control thyroid rhythms also allow populations of individuals - species Ė to adapt to changing environmental conditions over evolutionary time. Moreover, since thyroid hormones are so critical to daily maintenance functions of the entire body, this hormone system also strongly affects the day-to-day health of each individual.
Itís such a new way of looking at evolution that it promises to change the way you look at life - evolution seen from this perspective suddenly becomes personal. Unravelling the conundrum of how wolves became dogs turns out to be essential for understanding the evolutionary flexibility of the natural world, for explaining why each of our bodies function in slightly different ways as we grow and age, and for comprehending the increasing incidence of a plethora of health problems that includes obesity, infertility, birth defects (including foetal alcohol syndrome), high cholesterol and depression, among others.
This revolutionary and provocative new idea is simple enough in principle to enlighten those with a high-school education but complex enough in detail to inspire post-doctoral research. The theory offers the first comprehensive explanation for how species are able to stay the same over long stretches of time but can change rapidly when necessary. Itís a true scientific theory in every sense of the word: itís eminently testable and provides a plausible explanation that fits available facts extremely well. The concept, while not yet proven, has been extensively peer-reviewed and is generating significant excitement within the scientific community because it provides several essential components that have long been missing from the story of life.