The study of life’s evolution is a complex genre and one that Paper Masters can help with. Recent work from our writer in this field has yielded theories on evolutionary atmospheric conditions, recreating evolutionary microcosms, and the geographic origin of homo sapiens. While scientists have uncovered a vast amount of certainties regarding evolution, technological advances allow scientists to embark on explorations of theories and questions that remained elusive even just ten years ago.
In order to locate signs of the earliest life forms, astrobiologists are studying banded iron formations in sedimentary rock 3.7 billion years old. Finding signs of life in these samples will place life on Earth 200,000,000 million years before the earliest proven fossils. NASA scientists hope to prove that lower heavy isotope iron-56 levels indicate bacterial levels in the banded rock. These methods will allow scientists to develop methods to create an evolutionary timeline.
Researchers are also developing methods to identify life forms. Geochemist Roger Summons has discovered that bacteria and eukaryotes have molecularly different cell membranes. Bacteria cell membranes contain organic molecules with a five ring carbon backbone, while eukaryotes have a four ring backbone. Analysis of shale dated to 2.5 billion years ago shows that bacteria and eukaryotes were both present 300 million years before the earliest accepted eukaryotic fossils.
Astrophysicists have discovered some startling evidence about Earth’s early atmospheric conditions. They surmise that when the planet formed, 4.5 billion years ago, the sun provided 30% less warmth than today. Under today’s atmospheric conditions, such a reduction in temperature would force the Earth to freeze. Evidence of erosion, running water, photosynthesis and the discovery of alga Grypanai (the first fossil eukaryote) indicate that the planet was not frozen for long periods of time.
Planetary climatologist James Kasting of Pennsylvania State University theorizes that a methane greenhouse created by the planet’s organisms trapped heat in the atmosphere. Kasting asserts that extremely low levels of oxygen allowed methane to exist for approximately 20,000 years without being oxidized into carbon. Carbon dioxide would have prevented the methane from forming a haze that would cool the Earth. In support of this argument, most researchers agree that all of the oxygen produced by photosynthesis were used for oxidizing iron and volcanic omissions.
Geologist Roger Buick can account for evidence of Earth’s periodic deep freezes. About 2.2 billion years ago, oxygen levels rose at an astonishing rate, probably due to reduction of volcanic omissions using oxygen for reactions. This rise in oxygen would have oxidized the methane and eradicated the greenhouse gases. Periodic rise and fall in oxygen levels accounts for the intermittent frozen periods scientists encounter in studying early Earth.
While scientists have not recreated early Earth’s atmospheric conditions, they have been able to reproduce microcosm’s reenacting bacterial evolution. Richard Lenski and a small group of evolutionary biologists have grown 24,000 generations of e. coli bacteria in flasks of glucose formula. The bacteria are subjected to boom and bust cycles, supposedly mimicking the struggles of early life, are recreated with 6 hours of plenty followed by 18 hours of famine. Each of the 12 lines have responded to this, continuing to grow despite these challenges.
Paul Rainey adjusted this experiment by leaving the glucose flasks unshaken, which forms three different physical and chemical layers. Three different forms of bacteria were found to develop to fill these niches, which indicates that bacteria evolves according to environment.
Julian Adams also found speciation in his experiments, proving that diversification can occur even without an outside catalyst. Adams found that the bacteria secretes acetate when metabolizing glucose. As acetate levels rose in the microcosm, an acetate-scavenging strain evolved to devour the byproducts.
Recent advances in DNA technology have enriched the debate regarding the origins of homo sapiens.
- One camp of evolutionary theorists believes that live evolved from one small African population that migrated and spread through interbreeding.
- The opposing camp believes that several populations of homo sapiens existed at the same time.
- DNA study has not resolved this conflict, as information supporting both claims has been found.
- Study of mitochondrial DNA shows that sub-Saharan Africans have more variations in their DNA.
- Those supporting the single group theory assert that this proves African DNA existed longer than any other did.
- In addition, this DNA is genetically different from DNA found in other groups, supposedly proving Africa’s longer period of evolution.
Claiming that mitochondria go through frequent changes, some researchers have begun to test the slowly altering beta-globin gene. These experiments indicate that the difference between African and Asian beta-globin is very similar, indicating interbreeding. Study of mitochondria and the Y chromosome indicates that genetic differences are more marked in populations existing farther apart. Because these differences are minimal, scientists theorize that separate human races with different biological traits never existed.
Recent advances in scientific technology have allowed scientists to test startling theories, from recreating evolutionary microcosms to locating the origin of human life. However, the increase in tools has also created an increase in theories to be tested. Although we have come quite far, we are still miles away from developing definitive answers on evolution.