ScienceAnd Blog

As a young scientist in the 1950′s I was introduced to thermodynamics by Turner and Verhoogen’s book [Igneous and Metamorphic Petrology¹] which was the basis a course given at Sheffield University, England. I was intrigued by Bowen’s Reaction Series which related minerals to pressure-temperature and chemical environment, and how so many things in nature seemed to depend on one or more of these three variables.

At the same time I was deeply involved in palaeontology, palaeo-geography, human zoology and mathematics. As a student stratigrapher it was apparent that climate and the atmosphere were major controls on evolution. A course in mathematical climatology offered in the Geography Department integrated many of the ideas of thermodynamics into weather prediction and early forms of climate modelling – ideas that I was able to utilise in an expanding view of palaeo-geography as it extended through time as historical geology. These were all things that were bombarding my mind during my undergraduate years at Sheffield and it was not until later as I began reacting with P. C. Sylvester-Bradley on questions of the concept of a species and evolutionary theory that I understood the real importance of P-T-C in the history of life. Climate and the atmosphere played an immense role in the the development of Earth and it’s living systems: from the setting of the vast latitudinally controlled coniferous forests to the adaptation of the Tibetans to life in the Himalayas.

Articles like that of Dr. Barry Sinervo, professor of ecology and evolutionary biology at the University of California, Santa Cruz, on the widespread extinction of lizard populations as a result of climatic change are part of the continuous documentation of the importance of P-T-C on Earth’s development [Science, May 14^th, 2010]. Accumulating an extensive database Dr. Sinervo’s group was able to document that extinction amongst lizard’s was due not to habitat loss but to climate warming [since 1975] that is driven by increased atmospheric CO₂. The essential factor is well known to those who study the rattle-snake in that rattle-snakes use heat to warm up their body temperature but cannot stay in the heat too long – it will kill them. Rattle-snakes, once sufficiently warmed, move into the shade. It is the same with other amphibians and Dr. Sinervo notes that with lizards, once they retreat into the shade there is less food to hunt. The implication is that heat pushes the lizards into a cooling location and they die of starvation! “These lizards need to bask in the sun to warm up, but if it gets too hot they have to retreat into the shade, and then they can’t hunt for food. At the extinct sites in the Yucatan, we found that the hours per day they could be out foraging had collapsed. They would barely have been able to emerge to bask before having to retreat……We thought we’d see evolution occurring in response to climate change, but instead we’re seeing extinctions. Beyond a certain point, the lizards can’t adapt.“

Science is definite in that factors other than temperature, pressure and chemical environment, come into play in the evolutionary process: catastrophic habitat loss for example. However, more and more research is showing the classical controls on adaptation, especially temperature and chemical environment, are major driving forces effecting Earth’s biocoenoses today AND these forces are a direct result of humankind’s activity.