Wednesday, December 01, 2010

Blood of the mammoth

ResearchBlogging.orgCatastrophists love frozen woolly mammoths. It doesn't matter what their preferred catastrophe is--Atlantis sinking, falling ice moons, the Noachian flood, abrupt changes of the Earth's axis, or a near miss by a pinballing planet disguised as an ancient Near Eastern god--at some point, they will trot out the frozen mammoths as proof positive of their theory. Frozen mammoths have already been spotted milling around 2012. What is it about mammoths that make them so attractive to catastrophists? The answer is an odd failure of imagination on their part. The mammoth, they say, is an elephant and elephants don't belong in the Arctic. It makes more sense, to them, for continents to go tumbling across the face of the earth than for an elephant to adapt to a cold climate. Two hundred years ago, the elephant in Arctic was a valid problem, but, since then, we have acquired evidence after evidence of the mammoth's cold weather adaptations. Now, we have one more.

When faced with the mammoth's obvious cold weather adaptations, the standard defense of the catastrophist is simply to say that the adaptation does not necessarily mean mammoths lived in the cold. Scientists say a mammoth's stockier build, shorter tail, and smaller ears are to conserve body heat. The catastrophist’s response is that animals can be found in all climates with stocky builds, short tails, and small ears and some Arctic animals do not have those features. Mammoths' bodies are covered with a thick layer of fat. The catastrophist response: fat animals can be found in all climates; that just means there was plenty of food. Woolliness is the defining trait of woolly mammoths and most people believe that makes it obvious that mammoths were adapted to a cold climate. The catastrophists respond, furry animals can be found in all climates, therefore woolliness is not necessarily a cold adaptation. The latest news will be a little harder to dismiss with that argument. Mammoth blood worked differently, and better, at cold temperatures than does elephant blood.

In most mammals, slight temperature increases cause hemoglobin, the oxygen-carrying protein found in red blood cells, to release oxygen. This mechanism assures that the oxygen goes where oxygen is being burned, such as in exercising muscles. However, this mechanism means oxygen is bound more tightly to hemoglobin at lower temperatures and releasing it is more costly. Animals that have adapted to cold climates usually allow their extremities to get cooler than their cores, but still need to deliver oxygen to those tissues. To do that, they have evolved an oxygen delivery system that is equally efficient at highter and lower temperatures. Kevin Campbell, of the University of Manitoba, and an international team hypothesized that woolly mammoths needed a similar adaptation to survive in the far North. To test their theory, they needed to build their own mammoth blood.

The sequencing of the genomes of animals during the last decade has opened up new horizons of research. Because the Arctic does such a good job of preserving things, mammoths were one of the first extinct species to be sequenced. In 2006, a team used genetic material recovered from a 43,000 year old mammoth femur found on the banks of the Bolshaya Kolopatkaya River to determine what color mammoths' hair was. Campbell and his team used reconstructed hemoglobin DNA from that same femur for their project. The DNA was converted into mRNA and injected into E. coli bacteria, which in turn manufactured mammoth hemoglobin. They then performed tests on the mammoth hemoglobin.

The reconstructed hemoglobin functioned over a much wider range than the hemoglobin of living Asian and African elephants. Most significantly, it delivered oxygen at low temperatures. The team then used molecular modeling to figure out why the hemoglobin functioned differently than the hemoglobin of living elephant species. What they found were three amino acid substitutions on the surface of the hemoglobin. To confirm that these substitutions were the cause of the better functionality at cool temperatures, the team spiced the three changes onto the hemoglobin of an Asian elephant, injected it into E. coli bacteria, manufactured the hemoglobin, and subjected it to the same tests as the reconstructed mammoth hemoglobin. It was indeed the source of the cool climate adaptation.

Illustration by ExhibitEase LLC - Steven W. Marcus. source

This research has a number of exciting implications. Obviously, it allows us to better understand mammoths themselves and how they managed their environment. The technique suggests many avenues of research to explore, not just for mammoths, but for any extinct species that we can recover DNA from. By determining the genetic origin of the mammoths' adaptation, the researchers gained a valuable insight into the evolutionary steps that led to the adaptation. And the implications of the research are not limited to extinct species. Better understanding the mechanism behind oxygen release in hemoglobin, mammoth blood could conceivably lead to new therapies for heart attack and stroke victims.

Finally, this research gives those of us who watch pseudo-science new facts to add to our armory. Catastrophism is a failure of the imagination. Catastrophists cannot handle the concept of mountains rising and oceans opening one centimeter at a time over tens of millions of years. They refuse to accept that complex processes could cause enormous ice sheets to creep across the landscape and then fade away. They cannot accept the idea of elephants in the Arctic. By insisting that one world magically turn into another with no intermediate stages, they voluntarily reel in their horizons and deprive themselves of the depth and grandeur that the past really held. Their mammoths are far less interesting than the ones that science is still discovering piece by tiny piece. Their world is far less interesting by not including real mammoths of woolly flesh and cold adapted blood.

Campbell, K., Roberts, J., Watson, L., Stetefeld, J., Sloan, A., Signore, A., Howatt, J., Tame, J., Rohland, N., Shen, T., Austin, J., Hofreiter, M., Ho, C., Weber, R., & Cooper, A. (2010). Substitutions in woolly mammoth hemoglobin confer biochemical properties adaptive for cold tolerance Nature Genetics, 42 (6), 536-540 DOI: 10.1038/ng.574

This post is my entry in the National Evolutionary Synthesis Center (NESCent) Science Online 2011 travel award competition.

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