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BIOLOGY ILLUSTRATED May 2011
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EVOLUTION
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EVO-DIVA
“Molecules are fossils too! They Persist over time. They have shapes and sizes and are beautiful like bones. Indeed they have form and function...” - Peggy Ostram
I
t all began with a dig at the Hell Creek Formation. Far, deep in the dry, desolate, lands of Garfield County, Montana, lay beds of rock that preserve history dating back 1.3 to 2.5 million years old. This formation is a ‘Hot Spot’ for many digs due to its once very lively, green environment millions of years ago. What happened during this time to create such a graveyard is still theorized today, but first to understand the land, Dinosaurs must be discovered and analyzed. Jack Horner, a remarkable Paleontologist known for his prolific discoveries, and his team had found what is known today as B-Rex. On June 28th, named after the discoverer, Bob, B-Rex was uncovered which will forever mark the beginning of an evolutionary change within the science field.
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Jack Horner
Although Horner does not have a formal college degree, he has still successfully discovered several new dinosaur species. He was also the first Paleontologist to obtain and prove evidence of colonial nesting.
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he discovery of this very large Tyrannosaurus Rex was a very exciting feat. The location of the discovery although was not as exciting per say. Located at the base of a 40ft cliff, climbers had to belay down the rocky wall as well as jackhammers and other supplies. As per excavating these finds, helicopters with plaster jackets were needed to lift the hind legs, both femurs, one tibia, and a fibula. Only fifty percent of the B-Rex was actually excavated. The Femurs were so large that they had to be broken down and transported in two pieces. This may sound like a terrible happening, but it was because of these conditions that new advancements in the paleontology, biology, and chemistry field were able to take place.
MARY AND THE FULL EFFECT
Mary Schweitzer, looking for well-preserved, untreated, fossil bones was ecstatic at hearing about the news of this break. She took the fragments back to North Carolina State University where she was currently undergoing her first semester as an assistant professor. She and her technician Jennifer Wittmeyer opened up the packaged fragments and instantly they discovered that B-Rex was a pregnant female! They found presence of medullary bone, which means two things, Ovulation, and birds. Medullary bone is a reproductive tissue that can only be found in ovulating birds. Further more, Mary begins slicing very thin sections of bones, dipping them in demineralizing baths, and then washing the acid off with distilled Mary Schweitzer
Contamination is one of the top concerns among many during the testing process. No one test can prove a definite answer. This is comparable to proving a specific scenario with a series of yes or no answers. The more tests will better strengthen theories, but will also raise concern for contamination. By running all the tests needed to prove one theory, a significant amount of fossils may be destroyed in the process.
Even though what was thought to be found were blood vessels, over these thousands of years, it is hard to prove that all the particles of these findings are true to it’s once lively state. In order to withstand time and uphold structure minerals during the fossilizing process replace the decomposing matter.
Schweitzer’s discovery of the medullary bone in B-Rex has lead to her current research in the reproductive system of dinosaurs. She is also working with NASA looking for traces of past life on other planets.
Key Facts n Paleontology is evolving beyond the traditional realms of shovels and chisels, and digging deeper into biology and chemistry field.
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n Technology today can help decode proteins and sequence them to pin point evolutionary change in a specific species.
n Evolutionary Developement is an emerging study linking several areas of science that typically did not coincide.
n Studying development of a living organism can help prevent and cure diesases as well as allow scientist to understand evolution and history.
water. After this bathing process the cortical bone, tissue that can be found in all four-legged vertebrae, is then placed under a dissecting microscope and analyzed. First, they noticed a bouncy, flexible, collagen-like, quality about the material. And after several different attempts and baths, this quality remained. “It was the most bizarre thing I’d ever seen…”, Mary stated. Finally, they began looking through the microscope and found gummy, hollow, tube-like structures. This too was very bizarre, because with the information at hand shows evidence to sixty-eight million year old blood vessels. Since the discovery of the medullary bone in B-Rex, Jennifer had been working on comparing B-Rex’s material with demineralized ostrich bone. The results yielded that both materials contained small, round, red, structures and a black dot that resembled a nuclei. Under the scanning electron microscope, they found many similarities as well as osteocytes –cells that promote growth. Osteocytes secrete minerals that form a matrix, which enable the rigid, strong qualities of bone. The cells themselves lay on the ‘in’side of these structures and use filidopia or tendrils that extend from out from the central body and connect to other filidopia of other cells. These workings create a “bucket brigade” network used to transport nutrient and waste material. To check her results, Mary used the same demineralizing method on other tyrannosaurs and hadrosaurs. She found vessels and structures that looked like osteocytes but not all of the bathed materials were flexible like the findings in B-Rex.
Ostrich & Osteocytes
By comparing ostrich bone tissue to B-Rex’s bone tissue, Mary was able to use the known living material from bird as a control to base her findings. The similarities between the two specimens not only helped identify fossilized dinosaur material, but strengthened the dinosaur-bird theory.
NOW WHAT ?
The existence of these findings is very exciting but now lets take this new, found knowledge and dig deeper into the realm of molecular paleobiology. Jack Horner describes is as a “second excavation” where they hope to identify and break down different proteins to better understand species as well as their evolution. The potential of the specimens found actually being collagen is of a relevant percent. Twenty-five percent of proteins found in mammals are collagen. This protein is an important material in bones and in the connective bone tissue. All proteins are made up of amino acids and all amino acids are made up of carbon, nitrogen, hydrogen, oxygen, and sometimes sulfur. As animals evolve, so does their make up. With this in mind, Collagen can be taken from modern animals, tested then broken down as well into elements and finally measured out and then appropriately sequenced. By doing so, Mary can then see and pinpoint molecular differences in this protein which then can act as a “benchmark in evolutionary change.” There are also several different kinds of tests that can help utilized this protein as an evolutionary decoder. First, is the scanning electron microscope which is used to identify the sixty-seven nanometer repeat banding that gives collagen that very strong, durable flexibility. The transmission microscope can give an elemental analysis and the atomic force microscopy can give a quantitative measure of elasticity. Next, is gas chromatography paired with the mass spectrometer. The gas chromatography can break down elements into gases those of which is then be drawn through filters at different speeds which finally is measured by the mass spectrometer providing the amount of different elements found. Now this test cannot prove if a protein is present, but can disprove. Last, is the immunoassay test. Here antibodies of a protein are injected into a modern animal and followed by another injection fused with fluorescent dye so the antibody can be tracked. If the antibody can bind, the fluorescent dye will show up on under a fluorescent microscope. Meaning the protein is recognizable within
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the gene structure, which in turn means share similar genetic make up, and again meaning they are a descendent of the dinosaur and can be used as a benchmark in evolution. All these tests cannot prove a specific answer, but more take a triangulation effect in slowly honing in on the answer by disproving any theory that may contradict the hypothesis. With that stated in order to prove a solid statement there will be a lot of testing on prehistoric material that must be “destroyed” in order to seek the conclusion we hope to find. Jack Horner explains it best when he speaks of the direction paleontology, paleobiology, and biogeochemistry should take in order to further evolutionary studies in a more effective manner, “…at a certain point we are left with dust in our hands, wondering where to dig next. The answer is: the genes of living animals, because a record of evolution is to be found there. For our purpose the most important record is in the gene of the only remaining dinosaurs-the birds.” EVOLUTIONARY DEVELOPEMENT
From paleontological digs with Jack Horner and his team, to molecular biology with Mary Schweitzer and Jennifer Wittmeyer in the lab, Jack Horner has now progressed to Hans Larsson with the intent to find answers in a new direction. Hans Larsson is at the forefront of evolutionary developmental biology also known as evodevo. This new growing field of science combines molecular biology
and paleontology with the intent to connect evolutionary changes to specific genes and understand their regulation. Embryology is seen as the future of evolutionary development. Since the bird is the closest living relative of the dinosaur the chicken egg is the perfect specimen for further research on dinosaur evolution. Over time due to “accident and opportunism” genes have been silenced and regulators have been altered which has resulted in shape change. Hans is working to reactive dormant genes and change gene regulation to bring back ancestral traits present in the modern day animal. The first step in this process is to observe embryonic growth, next is to pin point growths and retractions during development. At these stages it is important to figure out what is occurring at these events at the molecular level to cause these changes. These changes are of the workings of evolution. Since genetic development occurs in a cascading effect Hans dyes proteins at different stages in development to track and monitor activity. Different proteins yield different growth spurts. The presence of different proteins at growth sites helps define triggers that inhibit or permit growth to that specific area. With this knowledge Hans can bypass activation of certain sites or inject a protein called Sonic Hedgehog that induces growth, which commences the embryo to develop ancestral traits. There is much reversal that needs to take place in order to recreate a dinosaur, but step-by-step, gene by gene, it can be done n
More to Explore CBS’ s 60 Minutes aired a very informative overview of Jack Horner’s research and direction. The special described himself, his work, his direction, and introduced the astonishing findings of Mary Schweistzer.
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Jack Horner and James Gorman come together and write an fascinating book detailing the beginnings of these controversial studies and explain the journey they have taken thus far and where they hope this developing field to lead them.
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Jack Horner has spoken and can be watched online. Here he briefs his discoveries of parental involvement in dinosaurs, nesting grounds, and the developement of a dinosaur embryo and how to rebuild a dinosaur.