The Origin of Life on Earth

Based on many years of data and observations, scientists approximate the Earth to be around 4.5 billion years old. The earliest evidence of life that has been found exists in Greenland, and consists of fossilized remains of cyanobacteria, otherwise known as stromatolites. These fossils date back to 3.7 billion years ago, and even still, scientists believe that life may have gone back even further, due to rocks in Australia that contain high levels of carbon--an element that is majorly involved in most biological processes. This evidence raises the question of how life actually formed all those years back, and many different scientists propose different theories. Some of these include life coming from outer space, finding its way to Earth by means of an asteroid or comet. Others believe that there are several origins of life, and that life formed on Earth through a series of chemical reactions. These reactions are hypothesized to have led to the creation of self-sufficient systems that formed organisms. Whether one theory is correct or not, scientists still do not know for sure. However, by looking at the existing evidence, such as the cyanobacteria that is still around today, and by examining RNA and DNA qualities, they have a better idea of what very well might have been.

Scientists have widely accepted the idea that the primary molecule for life was RNA, a molecule made up of nucleotides that aids in protein synthesis and works as an on/off switch for many genes. However, upon the emergence of DNA, RNA was replaced due to the more stable and better performing nature of DNA. Since DNA is the basis of all life in organisms today, we can study it and gain multitudes of knowledge from studying its structure and functions. Perhaps we will never know the exact origins of life on Earth, but by continuing research on these molecules that we know have been around since the start, there is a much better chance at getting there. I think that the fact that we do not know the exact origin of life on Earth is very interesting because there are so many different explanations that can account for it. However, the fact that we know that RNA was the primary molecule is a step in the right direction because we have a lot of knowledge about it, and continue to study it nowadays. Perhaps one day we will make a discovery that answers how exactly life began on Earth, but until then we can only wonder.


Link: http://www.livescience.com/1804-greatest-mysteries-life-arise-earth.html

H.I.V. Arrived in the U.S. Long Before ‘Patient Zero’

There is a legend that Patient Zero, Gaetan Dugas, a French Canadian flight attendant supposedly picked up H.I.V. in Haiti or Africa and spread it to many men before he died in 1984. He is also sometimes blamed for almost all AIDS cases in the United Sates, from Zaire to Haiti to New York in 1969-1971. A new genetic analysis of blood samples that were stored declared that Dugas is innocent. The analysis showed that Digas’s blood that was sampled in 1983 contained a viral strain that was already infecting men in New York before he went to gay bars in New York in 1974.  Dugas was originally the focal point of the epidemic because he kept a diary about his travels and he gave names to investigators. The researchers also reflected on the fact that they originally believed that the epidemic could be blamed on just one person, but now looking at it, it seems like it is not plausible because the epidemic was too widespread in Africa.

            Dr. Jacques Pepin is an infectious disease specialist at the University of Sherbrooke in Quebec showed that H.I.V. was carried from Kinshasa to Haiti in the 1960s. It was probably carried by one the Haitian civil servants that was recruited by the United Nations to work in the Beglian Congo. He also explained that Haiti was a sex-tourism destination for gay men, which is another way that the virus could have travelled to New York. More blood samples that were stored away in 19798 and 1979 from New York and San Francisco were analyzed. They showed that all of the New York samples all derive from one Haitian strain and the San Francisco strain were so closely related that they probably both derived from one person, or multiple people introducing the strain in New York. The myth of patient zero is being put to an end because of the new genetic studies that have been under analysis. Before reading this article I was confused on who Patient Zero actually was, and it came to a surprise that it was all blamed on one person, because as mentioned above, the researchers on this case thought that was absurd as well. It is crazy to think that the researchers are coming across this information now after so much time has passed after the discovery of H.I.V. and after publishing all of the data that they already had about Patient Zero. 

How the Brown Rat Conquered New York City

The brown rat has managed to populate New York city by the millions, with billions more in other cities across the world. They contaminate crops and food supplied and destroy wires, walls, and cars, while spreading bacteria and disease. However, scientists are not entirely sure as to how Rattus norvegicus became so rampant. Dr. Munshi-South and colleagues finished a study of brown rats that began to answer the question of what is a New York city rat and where did it come from? They found that these rats began spreading slowly for thousands of years, but in the past three centuries they spread much more rapidly. Dr. Munshi-South contacted researchers from around the world and obtained DNA from hundreds of brown rats, from Japan, New Zealand, Brazil, and the Galapagos Islands to name a few,  to compare to that of the rats of NYC. The study revealed that brown rats originated in northern China or Mongolia and fed on wild plants and small animals, until farming in China began, during which rats found a reliable food supply and moved from open plains to farms and villages. The rats then began to expand to other parts of Asia, and eventually west to Europe. It is these rats that are the ancestors of the inhabitants of New York today. As European countries colonized the Western world, they took the rats with them.

Dr. Munshi-South thought that he would find that New York's rats have a mix of genes from ancestors from all over the world, but he found little evidence of genetic mixing in New York or any other city. It seemed that there was not many migrants that arrived and reproduced after a city was already populated with rats. This could be because brown rats are territorial and simply mean, as noted by missing eyes and scars observed by Dr. Mushi-South in many rats. The theory is that the first rats to arrive in a city reproduce rather quickly, so when new rats come along, they are no match for the residents that have already inhabited the city. This is a good thing because it is unlikely that new diseases on new rats can come into a city that is already populated with rats.
Based on the results of the study, I think that we should not take action to eliminate brown rats. Although they do spread bacteria and destroy wires and walls, they are keeping out lots of potential disease because of their territorial nature.

How We Got Here: DNA Points to a Single Migration From Africa

The question of where humans came from has been one of the biggest in science for years. Three separate teams of geneticists from different places, all sampling different people, sequenced the genomes of 787 people from hundreds of different populations and found that all humans came from a single population from Africa between 50,000 and 80,000 years ago. The genomes were taken from a variety of people from every continent and were examined separately to finally come up with the same conclusion as to where people came from. Before now, there were very few sequenced genomes from people outside of population centers like China and Europe, but this new data with genomes from indigenous populations adds great value to our understanding of human DNA. 

The first team was Dr. Willerslev and a few colleagues who first sequenced the genome from a century-old lock of hair of an Aboriginal Australian. The results raised many questions, so the group joined David W. Lambert and the University of Oxford to obtain DNA from people from Papua New Guinea and from Aboriginal Australians to sequence. Mait Metspalu from the Estonian Biocentre sequenced genomes mostly from populations from Europe and Asia.  David Reich and his team from Harvard Medical School formed their database of genomes from people from all six inhabited continents. All coming up with the same results, the teams each established that there was an exodus from Africa 80,000 to 50,000 years ago, resulting in the populations we have today. There is also evidence of other groups migrating from Africa much earlier than 80,000 years ago, but these groups have since disappeared, having been wiped out by others who came after them who were stronger in number or in technology. 

The Lost Identity of Man's Best Friend

We believe that the origin of Earth was caused by the Big Bang 13.7 billion years ago, but what can we say about the origin of dogs?

Comparing the two, the origin of dogs may seem minuscule and unimportant but just how much do we know about our best friend? Some people agreed on the fact dogs came from wolves, aside that we only know dogs appeared around 15,000 to 100,000 years ago somewhere in Asia or Africa.

According to Dr. Greger Larson at University of Durham, England, it is currently improbable to trace when and where dogs originated from the DNA of modern dogs. Larson and twenty other authors have been working on a paper about the origins of dog domestication. Currently the team has analyzed 49,024 locations on dog DNA; working with 1,375 DNA samples from 121 breed, and 19 wolves.So far they have only been successful tracing back to about a hundred years.

Larson and his colleagues concluded on how modern dog breeding is making it more difficult to locate when or where dogs were first domesticated. In fact, dog breeding had been so mixed, that the genetic history for dogs became very obscured; with the exception of basenji, shar-pei, Saluki, Akita, Finnish spitz, and Eurasier bring slightly less mixed.

What Larson and his team found out was that, dogs that are most genetically distinct were not from the places where the oldest dog fossil was found. Larson expected if these breeds were closer genetically to the first domesticated dogs, they would be geographically closer to sites of early dog fossils or ancient dog breeds. However, their studies shows the more genetically distinct dogs had been geographically isolated quite recent in the history of domestication. For instance, dingoes, basenjis, and New Guinea singing dogs came from southeast Asia and southern Africa about 3,500 and 1,400 years ago.

Larson concluded that there is still hope to learn about the origin of dogs. People have burying their dogs for a long amount of history, thus somewhere, there really is a fossil of an ancient dog--we just have to find it.

I think dog breeding is one of the things we, as humans take for granted. We decide on the breed that we want for our own purposes, not knowing the consequences of our selfishness. In order to create a companion to cuddle and be dog show material--we have made our best friend lost his identity. Everyone kept saying how much they love their dogs, but just how much do we know about their history?

Original article: http://www.nytimes.com/2012/05/22/science/dogs-genetic-roots-remain-obscure.html?_r=0

Related article: http://www.npr.org/2013/07/10/200498354/barking-up-the-family-tree-american-dogs-have-surprising-genetic-roots