A Discussion of GCC and Evolution

26 March 2008

The next step in our service learning project was to synthesize the aims of the grid computing project we’ve been contributing to with some of the major aspects of evolution covered in class. To this end, our professor, Dr. Walker, gave us five questions to address. Our responses to these questions are based upon our previous interview with Dr. Scholes and some recommended writings of Dr. Anthony Barnosky, a paleontologist serving as curator of the Museum of Paleontology at UCLA.

Two pronounced possibilities of climate change are extinction and speciation. We were first asked whether or not we think human-induced GCC could lead to speciation. Before our interview with Dr. Scholes or our review of Dr. Barnosky’s research, we would have thought that possible, as were a population adapted to a particular climate to see that climate disrupted, it might migrate to two or more different regions similar to the climate they’ve adapted to and, in time, become reproductively isolated. However, in an interview with the American Institute of Biological Science, Dr. Barnosky stressed that the key to addressing such a question is in the scale of time considered (Barnosky 2005). His specific approach was to define the scale of time into four categories. The first is ‘historical time’, which contains the previous thousand years of human record. ‘Deglacial/millenial time’, which corresponds with the cycles of glacial advance and retreat, are approximately 50000 years in duration. ‘Orbital time’, which corresponds with cycles of cooling and warming caused by Milankovitch oscillations, change climate across one to two hundred thousand years. Finally, ‘tectonic time’, the largest cycle, describes geologically induced climate change associated with the movements of the tectonic plates. Tectonic time spans millions to tens of millions of years (Barnosky 2001).

Barnosky and his team then set about testing what scale of climate change mammalian speciation requires, beginning with samples related to the smallest scale, historical time. They correlated the fossil record of a large, specimen-rich range of Montana, Wyoming and Idaho with relevant paleoclimactic data. Their results suggest that sustained climate change greater than the Milankovitch scale (~100000 years), extending into the average mammalian species lifespan (~1 to 2 million years) is required for speciation where climate change is the cause (Barnosky 2001). Based upon this, we think that human-induced GCC is an improbable mechanism of speciation, due to the scale Barnosky found necessary.

Secondly, in what other ways can GCC affect evolution? Some observed responses to climate change in terms of range, density and reproductive rates of various species have been noticed (Barnosky 2001). Regarding the range of a given species, populations will migrate to regions more suited to their adaptations when climate changes. As Dr. Scholes pointed out, when a given region loses a species due to extinction or changing range, the interactions it had with other species is left unfulfilled. While the exact results are difficult to predict, the colonization of an area by another species is almost certain.

Also, when a population changes its range, it may be prone to novel selection pressures it isn’t adapted to, such as parasites and predators (Barnosky 2005). Another factor related to range is whether or not a species is widely dispersed or tightly grouped. Widely dispersed species generally have better odds of survival than tightly grouped ones due to the gene flow allowed through greater dispersal. Human-induced GCC may not be sufficiently extreme or prolonged to cause speciation, but it will cause populations to change range, adapt in terms of phenotypic frequency within a population or, become extinct.

We were also asked to think deeply about how the project we’re contributing to through climateprediction.net relates to paleontology, and vice versa. Often times one approach to understanding a question is insufficient to answer it, unless augmented by another. One example of this was in the first descriptions of the fossil record itself. Initially, there was no known way to independently determine the age of a rock containing a fossil. A fossil-bearing rock could only be dated with respect to others – by superposition – younger than a lower layer yet older than a higher layer. Ultimately, radio isotope dating allowed a fossil-bearing rock to be dated concretely and without relation to other rocks. In this example, geologists and paleontologists put cutting edge developments in physics to great use.

Both the fossil record and grid-computing are, in isolation, flawed guides in predicting actual consequences of GCC. While paleontology can tell us what existed and for approximately how long, it can’t tell us what existed, yet hasn’t been found or, wasn’t a good candidate for fossilization to begin with. Thus, in the fossil record, we have a limited range of data. Similarly, yet in reverse, grid-computing projects can offer us approximations of a vast range of climatic data. While one offers us certainty without totality, the other offers totality, without certainty. We think that the efforts of Dr. Barnosky and others to combine paleontology with paleoclimatic, current and predicted climatic data is the most likely to predict actual consequences.

And as human activities are the cause of these consequences, we should address the question Dr. Barnosky answered in the affirmative; have humans changed evolution? While humans haven’t changed the mechanisms of evolution itself, we think our species offers at least three unique challenges to the balance that evolution has established. The first such challenge is that, unlike all other species, which are adapted to what their environment has been, we are capable of adapting to what it is and may be in the future … perhaps even what we wish it to be. One example of this can be seen in weaponry. Many adaptive weapons can be seen in other species – the poisonous weapons of snakes, the piercing and sawing weapons of many insects, the crushing weapons of crabs, the slicing weapons of reptiles and mammals and many more besides. Humans can not only mimic the adaptations we see in other species, adaptations that took many generations to develop, we can also develop novel weapons which have no natural precedent, such as chemical defoliants, lasers, even psychological weapons.

The second way we think humans offer a unique challenge to evolutionary balance lays in the fact that we can transplant genes between species which would never exchange them naturally. There are many examples of this, although one of the strangest was in the design of a plant which glows at night when growing in soil rich in explosive agents. This plant, designed to warn Vietnamese farmers of hidden landmines, combined genes from a plant and an insect in a way that certainly would never have occurred through any known mechanisms of evolution. Virology presents a third challenge. While all other species are constantly in a state of coevolution with the viruses that infect them, humans are capable of seeking out future antigens, yielding them inactive and distributing them for the production of predictive antibodies in the immune systems of others. In a sense, humans are unique in having a ‘collective’ immune system. Such advantages allow our species to grow far beyond its natural capacity, which brings us back to the causes of human-induced GCC.

Finally, we were asked to determine why the “Red Queen” and “Court Jester” hypotheses, coined by Dr. Barnosky, are named so. “Red Queen” posits that the primary force of evolution is the competition between members of a species and its predators, prey and parasites. This ongoing state of coevolution was named for a character from Lewis Carroll’s Through the Looking Glass. Therein, the Red Queen described her hopeless game with the words “It takes all the running you can do, to keep in the same place” (Carroll, 1871). Otherwise said, a species must continually adapt to maintain survivability with respect to the species it interacts with. Alternatively, “Court Jester” posits that interactions between members of a species and environmental conditions are primary. This name is probably a reference to a medieval court jester, whose task it was to do whatever he could to appease any member of the royal court, where jester is species and the whims of the court members are the ever-changing environment.

Barnosky, A. 2001. Distinguishing the effects of the red queen and court jester on Miocene mammal evolution in the Northern Rocky Mountains. Journal of Vertebrate Paleontology 21(1): 172 – 185.

Barnosky, A. 2005. Climate change and speciation of mammals. Interview with American Institute of Biological Sciences. March 2006.